What kind of fish are these?

This should be pretty easy. We have a tropical fish tank, and among a few other species we have an adult pair of these guys. The female is a live-bearer, and seems to be giving birth to two young at a time. However, I can't for the life of me remember what kind of fish they are.

The male is in the foreground, and the female in the background. Any ideas?

I believe it is a Red Wag Platy (Xiphophorus maculatus)

This looks like a Red Wag Platy (Xiphophorus maculatus). Apparently it is a common tropical aquarium fish. Wikipedia does not show a picture of this variant. However a google image search with this will return the images of fish that you have shown.

40 Different Types of Fish Species In World and Their Facts

Fish is a member of the paraphyletic group of organisms. This consists of gill-bearing aquatic craniates animals with limbs and digits. Most of the fishes are hagfish, cartilaginous, bony fish and lampreys. Fishes are ectothermic, which means cold-blooded. Fish are abundant in most of the bodies of water. Fishes are an important resource for humans worldwide, especially as food because it consists of a lot of minerals, vitamins, and proteins as it stays in water bodies. These are served as religious symbols.

They breathe through the gills, which serves the same function as our lungs. Bony fishes have only a single gill. Fish has a closed-loop circulatory system. They are an omnivorous group because they feed on plants and other small sea animals of water bodies. Fishes excrete nitrogenous and ammonia. Fishes reproduce highly in the open water column only. The eggs have an average diameter of one millimetre only.

Take a look at some of the list of types of fishes that are pretty common around the world. They are all unique yet share the beauty of being one.

Table of Contents:

All Types of Fishes Names:

Some of the wide varieties of fishes which are available in the world are as followed:

1. Siamese Fighting Fish:

Scientific Name:

The scientific name of Siamese fighting fish is known as betta splendens.

Family and History:

This fish is classified under the classification of betta. It is an aquarium fish. It belongs to a family of the Gourami family. Other names of this fish are pla-kad and trey krem. They can mingle with other fish. The body length of the fish is seven centimetres and it appears in colours of red, green, opaque, albino, orange, yellow and blue, etc.


The Lifespan of this fish is about 2 years only. Water temperature must be around 23 degrees– 27 degrees.

2. Common Carp:

Scientific Name:

The scientific name of common carp is Cyprinus Carpio. This kind of fish is found in a flaming gorge reservoir, Lake Mohave, Aral Sea, and more places.

Family and History:

It is classified under Cyprinus. The body mass of this fish is about 2-14 kilograms. These are grown in freshwater lakes. Mostly found in water bodies in Asia and Europe. They can tolerate low oxygen levels.

These are omnivorous. It can lay up to 300,000 eggs in a single spawn. This fish is taken as food by humans all over the world.


The lifespan of common carp is until 47 years.

3. Goldfish:

Scientific Name:

The scientific name of goldfish is Carassius auratus. It is classified under the higher classification of Carassius. It is mostly found in Utah Lake.

Family and History:

It is an aquarium fish. This fish native is in East Asia. It was domesticated in China and later breeds have developed. Size of this fish is 19 inches.

Goldfish has an ability of strong learning, social learning skills. Goldfishes are gregarious. They feed on insects and plants. Goldfish eggs hatch within 48-72 hours.


The lifespan of goldfish is about 30 years. Haven’t we all seen one?

4. Oscar:

Scientific Name:

The scientific name of Oscar is Astronotusoscellatus. It is classified under the higher classification of Astronotus. Other names of Oscar are tiger Oscar, marble cichlid and velvet cichlid.

Family and History:

These species are found in South America, Australia, the United States and China. It is seen as aquarium fish. The body length of Oscar is about 36cm and the mass of the body is 1.4 kg. They grow quickly and are carnivores.


These have territorial behaviour. The lifespan of this fish is about 10-13 years.

5. Wels Catfish:

Scientific Name:

The scientific name of Wells catfish is Silurusglanis. It is classified under the classification of Silurus. It is also called as sheatfish.

Family and History:

This fish is mostly found in Lake Constance. These also found in basins of Baltic, black and Caspian Sea. Size of this fish is about 13 ft that is of 4m. Maximum weight is about 400kg. These are mostly found in freshwater places. They feed on other animals which live in water bodies.

These are taken as food by humans. It is rich in proteins and nutrients.


Lifespan of this fish is about 60 years.

6. Zander:

Scientific Name:

The scientific name of Zander is Sander lucioperca.

Family and History:

This fish is classified under the classification of Sander. It is mostly found in the Aral Sea and Lake Constance. It is also called as pike-perch. Species of Zander fish from freshwater and brackish habitats in western Eurasia.

It is eaten by humans and is rich in nutrients. Mass of the body is 20 kilograms. These fishes can be hybrid.


The lifespan of this kind of fish is usually very less.

7. European Seabass:

Scientific Name:

The scientific name of European seabass is Dicentrarchuslabrax.

Family and History:

It is classified under the higher classification of Dicentrarchus. These are primarily ocean-going fish. These are seen in brackish and fresh waters as well. It is also known as sea dance. These are marketed by loup de mer, robalo, spigola, brinzino, Mediterranean seabass and Branzino. It is regarded as table fish. It is mostly night hunter and feeds on small fish like crustaceans, cephalopods and polychaetes.


It has a lifespan of about 25 years.

8. Northern Pike:

Scientific Name:

It is known simply as a pike in Britain, Canada, Ireland and some parts of the United States.

Family and History:

This fish is classified under the classification Esox. It is considered as a symbol of North Dakota. It is founded in Fort Peck Lake, Lake George, and Lake of the Woods and many more. They feed on big prey of animals that live in water bodies.


Lifespan of this fish is about seven years in the wild.

9. Sword Fish:

Scientific Name:

The scientific name of swordfish is Xiphias gladius.

Family and History:

It is classified under the higher classification of Xiphias Swordfish are well known as broadbills in some of the countries. These migrate from one place to another and are mostly found in tropical and temperate parts of Indian Oceans, Pacific Ocean and the Atlantic Ocean. They are found under the depth of 550m. They reach a length 9.8 ft and mass of 650-kilo grams. It is called as swordfish because it has a sword-like spear to kill prey and make it is easier to eat. These are vigorous fighters.

Use and Lifespan:

It is hunted by humans and taken as food and lives for about nine years.

10. Tench:

Scientific Name:

The scientific name of Tench is Tincatinca. Tench is called Schlei in Germany. This fish is classified under a higher classification of Tinca. It is mostly found in Lake Constance and Lake Garda. It is found majorly in fresh and brackish water only.

Family and History:

It is a family member of cyprinid. Its family is mostly seen in Eurasia and Western Europe. It is even found in Lake Baikal. These are the best resources for the recopies for humans. It is used for a better economy.


It lives up to 15 years and can live for 30 years in captivity.

11. Atlantic Cod:

Scientific Name:

The scientific name of Atlantic cod is Gadusmorhua. It is well known as benthopelagic. It is classified under the classification Gadus.

Family and History:

It is a family member of Gadidae. This fish is widely found in Bay of Biscay, north of Arctic Ocean, North Sea and Baltic Sea etc. and It can grow up to 2 meters in length and mass of the body is 96 kilograms.

Use and Lifespan:

It is widely consumed by humans. Commercially it is called as codling or cod. The lifespan of cod is about 25 years. It attains sexual maturity in between the ages of two and four. Their colour will vary from brown to green.

12. Atlantic Mackerel:

Scientific Name:

The scientific name of Atlantic mackerel is Scomberscombrus. It is classified under the classification of scomber.

Family and History:

These are found on both sides of the North Atlantic Ocean. Species of Atlantic mackerel are called as mackerel or Boston mackerel. Almost ten species of a family were caught in British waters. This fish migrates towards the coast for a feed of small fishes and prawns in summer. It forms large schools near the surface of cold and temperate shelf areas. They move to shore when water temperatures range between 11-14 degrees.

Lifespan and Use:

The lifespan of mackerel is about 20 years. It will become the best food for humans.

13. Common Bream:

Scientific Name:

The scientific name of the Common bream is Abramisbrama. It is widely known as carp bream, bronze bream, freshwater bream and Abramis bream.

Family and History:

This is classified under the classification of Abramis. It belongs to a family of Cyprinidae. It is found in Aral lake and Lake Constance. The length of bream is about 30-55cm and mass is about 2- 4 kg. Recorded length is 0cm and weight is 9.1 kg. It is an omnivore. It eats larvae and plankton of the sea. Generally, they spawn in April to June.

Use and Lifespan:

This kind of fish is used for both purposes of sport and commercial purposes and lives for about 29 years.

14. Basa Fish:

Scientific Name:

The scientific name of the basa fish is Pangasiusbacourti. It is classified under the classification of Pangasius.

Family and History:

This is the species of catfish. It belongs to a family of Pangasildae. The native of basa is at Chao Phraya and Mekong basins in Indonesia. These are labelled in Australia and North America as basa, panga, swai and bocorti etc. The body of basa fish will be heavy and stout. Length of the body is 120 centimetres. They feed on plants. They spawn on the flood season in June which has an average of 5 cm.

Use and Lifespan:

It used as frozen food in some countries. They are rich in proteins and is a river fish and have a long lifespan, which is yet to be determined.

15. European Fish:

Scientific Name:

The scientific name of European fish is Percafluviatilis. It is known as redfin perch, English perch, and perch. It is classified under the higher classification of Perch.

Family and History:

These are seen in northern Asia and Europe. The body length of the fish will be 60cm and weight will be of 2.8 kg. Perch spawn deposits egg at the end of the month April and beginning of May on water plants. Eggs are migrated through birds to other waters as eggs stick to the bird’s legs.


These are mostly the aquarium fishes and live for over 22 years.

16. Rainbow Trout:

Scientific Name:

The scientific name of this type of fish is rainbow trout is Oncorhynchus mykiss. It is classified under the classification of Oncorhynchus.

Family and History:

These are species of salmonid. It is represented as symbol Washington. It is found Flaming Gorge Reservoir, Watauga Lake, and Lake Mohave and many more. They live in oceans for two –three year and move to spawns. Spawns of these fishes are called as steel head. Maximum mass of a body is about 9 kg.

Use and Lifespan:

It is introduced as food and sport for almost 45 countries in the world. Their lifespan is usually about 11years and is one of the healthiest food to include in your diet.

17. Ocean Sun Fish:

Scientific Name:

The scientific name of Ocean sunfish is Mola mola. It is classified under the classification of mola.

Family and History:

It is the heaviest bony fish in the world. Sunfish diet consists of mainly Jellyfish the reason is it is nutritionally poor. These will become food for predators like a sea lion, killer fishes etc. These are native to tropic waters and temperate to every ocean in the world. They swim up to 26 km per day.

Use and Lifespan:

Yummy dishes can be made out of sunfish and they, usually live for about 10 years in captivity, while their lifespan in their natural habitat is not known.

18. Blob Fish:

Scientific Name:

Scientific name of blobfish is Psychroulutesmarcidus.

Family and History:

The fish is classified under the classification of Pdychrolutes and is a deep-sea fish. It is a family member of Psychroulutidae. It is found in the seawater of Australia, New Zealand and Tasmania. Length of blobfish is typically shorter than 30 cm. They live in depths between 600 to 1200 m. It feeds on crustaceans.


Their lifespan is not determined.

19. Blue Fish:

Scientific Name:

The scientific name of bluefish is Pomatomussaltatrix.

Family and History:

This fish is classified under the classification of Pomatou and belongs to a family of Pomatomidae. Illawarra Lake, Black sea and Lake Macquarie are the places to see this fish. It is marine pelagic fish found in temperate and subtropical waters. It is also known as a tailor in Australia. Bluefish is moderately proportioned fish with a forked tail. Length of the body ranges from 20 -60 cm and mass of the body will be of 14 kg. They live in groups and are fast swimmers.


The lifespan of this fish is about nine years.

20. Doctor Fish:

Scientific Name:

The scientific name of doctor fish is Garrarufa.

Family and History:

It is classified under the classification of Garra. Other names of doctor fish are bonefish, Kangal fish and nibble fish. The species are bred in Turkish river systems.

Use and Lifespan:

These are used in a spa treatment for skin patients to cure psoriasis. They occur in river basins of Central Middle East and Northern part of Syria, Turkey, Oman, Iran and Iraq. This kind of fish lives for about 6-7 years.

21. Zebra Fish:

Scientific Name:

The scientific name of zebrafish is Danio rerio.

Family and History:

It is classified under the classification of danio. Zebrafish is found in tropical freshwater and belongs to minnow family of the order Cypriniformes. It native is from the Himalayan region. This is a popular aquarium fish. It is sold under the trade name zebra danio. Zebrafish is widely used as a model organism in scientific research. It is the first vertebrate to clone. It is found in regions like India, Bangladesh, Nepal, Burma and Pakistan. These are mostly seen in the Ganges regions. These are omnivorous. It means their prey includes plankton of Phyto and zoo. These are seen in the aquarium.


Their lifespan is usually 5.5 years and shows signs of ageing over time.

22. Sand Steenbras:

Scientific Name:

The scientific name of sand Steenbras is Lithognathusmormyrus.

Family and History:

It is classified under the classification of Lithognathus. It is a marine fish and belongs to a family of Sparidae. Sand steenbras is found in shallow water in the Mediterranean Sea and in the Eastern Atlantic Ocean from France to South Africa. It is even observed in the Red Sea and the coast of Mozambique in the Indian Ocean. Length of the body will be about 55cm and, the weight will be around 1 kg.


Their lifespan is not known yet.

23. Nile Tilapia:

Scientific Name:

The scientific name of Nile tilapia is Oreochromis niloticus.

Family and History:

It is classified under the classification of Oreochromis. It is found in the Lake Victoria. Its native is from Africa and Gambia. It is also called as mango tilapia. Length of the body will be 6o cm and weighs up to 4.3 kg. It is an omnivore. It feeds both plankton and harmful gases like carbon dioxide, ammonia and hydrogen sulphide. The red hybrid is taken as plathaptim in Thai. It means it is a pomegranate fish or ruby fish. In different types of fish in India, it will be one.


Their lifespan is usually for nine years.

24. Flathead Grey Mullet:

Scientific Name:

The scientific name of flathead grey mullet is Mugil Cephalusi. It comes in the list of different types of freshwater fish.

Family and History:

It is classified under the classification of Mugil. Flathead grey mullet found in the Red Sea and Lake Awoonga. It is found in coastal tropical and subtropical waters worldwide. Body length is about 30-75 centimetres. It is well known as bully mullet, grey mullet, common mullet, mullet and sea mullet. They feed on algae in the freshwater.

Use and Lifespan:

It is special food for humans across the world. In Egypt, it is salted, dried and pickled to make feseekh. Their lifespan is about 11-16 years.

25. European Eel:

Scientific Name:

The scientific name of European eel is Anguilla Anguilla.

Family and History:

It is classified under the higher classification of Anguillidae. It is a fish like a snake and catadromous fish. Length of the body reaches up to 1.5 m and rarely reaches 1m. Mass of the body will be of 3.6 kg.

Use and Lifespan:

It is eaten by a human as a rich source of food. Its species are being extinct and live for about 60 years.

26. Neon Tetra:

Scientific Name:

The scientific name of Neon tetra is Paracheiodoninnesi.

Family and History:

It is classified under the classification of Paracheirodon. This is freshwater fish which belongs to a family of characin family. Its native is in black waters. It is seen in some of the countries like Peru and Brazil etc. Tetras are omnivores. It is kept in the same tank as the shoaling effect is enjoyable when they swim around the tank.


It is an aquarium fish and lives for about five years.

Here Fishy Fishy

Fish have had an evolution all their own. When you think of a fish today, you are actually thinking about an advanced organism. They started their development over 500 million years ago as fish-like organisms without jaws. Over many years they developed bones and skeletons. There are four main types of fish.

(1) Jawless fish: Like we just said, the first fish didn't have jaws. It is tough to eat and even harder to survive in the long run. Even with a mouth and a series of teeth to cling to their food, it's still hard to compete with fish that have jaws and mouths. Some species made it to the modern world. One good example is a Lamprey. These fish suck on the sides of other fish. Not a very exciting life.

(2) Fish with cartilage: In our opinion, though not as advanced as fish with real bones, fish with cartilage are the coolest fish out there. Cartilaginous fish include species of sharks, rays, and skates. Sharks are the ultimate hunters of the ocean. They are big, fast, and have very sharp teeth that rip their prey apart. Skates and rays are a lot more docile or non-aggressive. They are usually bottom feeders. The bodies of rays and skates have developed large wings that allow them to glide through the water using their tail as a rudder.

(3) Bony fish with lobe fins: And then the fish with real bones came along. No longer was cartilage the skeleton of choice. Bony fish were able to out-compete most of the fish that had cartilage for skeletons. Scientists classify them into two groups - the LOBE-finned and the RAY-finned. Lobe-finned bony fish include examples such as lungfish and coelacanthus. Until about 30 years ago, scientists thought the coelacanthus was long extinct. One day a fisherman found one in the net and voila!

(3) Bony fish with ray fins: You probably think of these fish when you think of a classic fish. The bony fish with ray shaped fins include goldfish, tuna, and trout, all tasty fish you can eat. Goldfish are for the college guys. They have complex skeletons and are built to move. Some move really fast and are very strong. Something like a tuna can move extremely quickly through the water.

What kind of fish are these? - Biology

Fish are some the most interesting and varying types of animals in the animal kingdom.

What makes a fish a fish?

All fish are cold-blooded animals that live in the water. They have backbones, fins, and gills.

Fish come in more varieties than any other group of vertebrate animals. There are 32,000 different species of fish. There are three major types or classes of fish including jawless, cartilaginous, and bony fish. An example of a jawless fish is the lamprey eel. Sharks are cartilaginous fish and the blue marlin is a bony fish.

Fish vary in all sorts of colors and sizes. Fish can be as large 40 ft long to 1/2 inch long. There are some animals that live in the water and we may think of as fish, but really aren't classified by scientists as fish. These include whales, dolphins, octopus, and jellyfish.

All fish have gills that allow them to breathe water. Just like we use our lungs to exchange oxygen for carbon dioxide from the air, the gills of a fish perform a similar function from water. So fish still need oxygen to live, they just get it from the water instead of the air.

Fish live in nearly every large body of water in the world including streams, rivers, ponds, lakes, and oceans. Some fish live on the surface of the water and some live in the very depths of the ocean. There are fish that live in fresh water and others that live in salt water.

Some fish eat plant life. They may scrape algae off rocks or eat plants that grow in the ocean or sea. Some fish, called predators, prey on other fish and animals. The shark is a noted predator that hunts for prey. Other predators lay in wait for their prey by hiding in the sand or rocks in order to ambush their prey.

A group of fish is called a school. Some fish gather in schools so they are harder to catch. A predator will get confused when attacking a school and sometimes can't catch any fish at all. A loose grouping of fish is called a shoal.

  • The biggest, or heaviest, fish is the ocean sunfish which can weigh as much as 5,000 pounds.
  • The longest fish is the whale shark which has been known to grow to over 40 feet long.
  • The fastest fish is a sailfish which can swim as fast as 68 miles per hour.
  • The smallest fish is the dwarf goby at only 9mm long.

A lot of people like to have fish as pets. There are special aquariums and food you can get to take care of your fish. They can be fun to have and also beautiful to look at. Although they are fairly easy to take care of as pets, you will need to do some work. You need to keep the aquarium clean and make sure to feed your fish the proper amount each day.

Stingray Species

Stingrays include ten different families of fish and there are about 220 different species of these fish in oceans, freshwaters, and lakes around the world.

One of the most common freshwater stingrays is the river stingray, and the mother will give birth to live babies, which are called pups. In the Atlantic Ocean (as well as in the Mediterranean and Black Seas), the common stingray thrives, though only in habitats with depths of no more than 200 feet. They prefer to reside in muddy or sandy regions.

In general, none of the species are aggressive without being threatened. The blue-spotted stingray, however, will attack with their venom, which can be fatal when the victim is stung in their abdomen or heart. If the sting occurs in other areas of the body, the outcome will not likely be fatal.

Types of Animal Partnerships

Imagine life without your best friend. Who would you hang out with and talk to about your problems? Life would be so lonely! You rely on your friends for companionship, fun, and support. Animal species rely on each other, too. Some have lifelong relationships with other organisms, called symbiotic relationships or symbiosis. There are three different types of symbiotic relationships in the animal kingdom: mutualism, commensalism, and parasitism.

  • Mutualism: both partners benefit. An example of a mutualistic relationship between the Egyptian plover and the crocodile. In the tropical regions of Africa, the crocodile lies with its mouth open. The plover flies into its mouth and feeds on bits of decaying meat stuck in the crocodile?s teeth. The crocodile does not eat the plover. Instead, he appreciates the dental work. The plover eats a meal and the crocodile gets his teeth cleaned. Coincidentally, the Egyptian plover is also known as the crocodile bird. It's a win-win!
  • Commensalism: this is an animal behavior where only one species benefits while the other is neither helped nor harmed. For example, remora fish are very bony and have a dorsal fin (the fin on the back of fish) that acts like a suction cup. Remora fish use this fin to attach themselves to whales, sharks, or rays and eat the scraps their hosts leave behind. The remora fish gets a meal, while its host gets nothing. Selfish, sure, but neither gets hurt.
  • Parasitism: One organism (the parasite) gains, while the other (the host) suffers. The deer tick is a parasite. It attaches to a warmblooded animal and feeds on its blood. Ticks need blood at every stage of their life cycle. They also carry Lyme disease, an illness that can cause joint damage, heart complications, and kidney problems. The tick benefits from eating the animal's blood. Unfortunately, the animal suffers from the loss of blood and nutrients and may get sick.

Think about other relationships you see in your local ecosystem. Bees are pollinators they help flowers reproduce with pollination, and in turn they get food.

Animal Life Cycles

Most animals including fish, mammals, reptiles and birds have very simple life cycles:

These animals have three stages -- before birth, young and adult. The young are typically similar to the parent, just smaller. The young slowly "grow" to become adults.


Amphibians, like frogs and newts, have a slightly more complicated life cycle. They undergo a metamorphosis (a big change):

  • they are born (either alive from their mother or hatched from eggs)
  • they spend their childhood under water, breathing with gills
  • they grow into adults and move to the land, breathing with lungs

Animals that Undergo a Complete Metamorphosis:

These insects have four stages in their life cycle:

  • egg: unborn stage.
  • larva: young stage -- this is when most of the feeding is done.
    (they usually look like worms)
  • pupa: inactive (no feeding) stage between larva and adult stages.
    (usually well camouflaged)
  • adult: final, breeding stage.
    (they usually grow wings)

Animals that go through a complete metamorphosis are what my daughter Kaitlyn calls "Wow!" animals -- they go to bed looking one way and wake up a completely different creature. Wow!

Animals that Undergo an Incomplete Metamorphosis:

About 10% of insects go through an incomplete metamorphosis. They do not have a pupal form -- these include dragonflies, grasshoppers and cockroaches.

These insects have three stages in their life cycle:

  • egg: unborn stage.
  • nymph: young stage -- this is when most of the feeding is done.
  • adult: final, breeding stage - including wings.


How were fast-growing GMO salmon created?

Canadian researchers created the fast-growing genetically engineered salmon with a growth hormone gene from Chinook salmon and a gene promoter from ocean pout. They microinjected the transgene into fertilized eggs of wild Atlantic salmon, and characterized the insertion.

The resulting genetically engineered fish are

99.99986% Atlantic salmon, with the addition of just 4,205 base pairs in a genome of 2.97 billion bases. Further, the growth hormone proteins from Chinook and Atlantic salmon are 95% identical. This leaves the ocean pout promoter as the only “new” element. The developers chose this promoter because genes it controls are continually expressing – always on – as opposed to the salmon promoter for growth hormone, which is only on in certain environmental conditions.

Even though the inserted growth hormone gene is always on, it doesn’t have much of an effect unless the fish have access to food. When allowed to eat as much as they want (fed to satiation), juvenile AquAdvantage salmon can grow nearly 3 times longer than conventional juvenile Atlantic salmon. But in a simulated natural environment with limited food, juvenile AquAdvantage salmon grew only a little larger than juvenile conventional salmon.

While AquAdvantage salmon grow faster, they do not grow larger overall – adult AquAdvantage salmon and adult conventional Atlantic salmon are the same size. The genetically engineered fish just get to that size faster and with less feed. As FDA describes, “the overall total amount of feed required to produce the same fish biomass was reduced by 25%” for AquAdvantage salmon.

Juvenile AquAdvantage salmon and juvenile wild salmon raised under different conditions. Image from Gene-environment interactions influence ecological consequences of transgenic animals.

Multi-celled animals (Metazoa)


5 pages with photos of echinoderms


There are 5 related classes in the phylum Echinodermata (the Latin name means "spiny-skinned"). For a detailed list with all classifications click here:

Characteristics of Echinoderms

Echinoderms are characterized by radial symmetry, several arms (5 or more, mostly grouped 2 left - 1 middle - 2 right) radiating from a central body (= pentamerous). The body actually consists of five equal segments, each containing a duplicate set of various internal organs. They have no heart, brain, nor eyes, but some brittle stars seem to have light sensitive parts on their arms. Their mouth is situated on the underside and their anus on top (except feather stars, sea cucumbers and some urchins).

Echinoderms have tentacle-like structures called tube feet with suction pads situated at their extremities. These tube feet are hydraulically controlled by a remarkable vascular system. This system supplies water through canals of small muscular tubes to the tube feet (= ambulacral feet). As the tube feet press against a moving object, water is withdrawn from them, resulting in a suction effect. When water returns to the canals, suction is released. The resulting locomotion is generally very slow.

Ecology and range of Echinoderms

Echinoderms are exclusively marine. They occur in various habitats from the intertidal zone down to the bottom of the deep sea trenches and from sand to rubble to coral reefs and in cold and tropical seas.

Behavior of Echinoderms

Some echinoderms are carnivorous (for example starfish) others are detritus foragers (for example some sea cucumbers) or planktonic feeders (for example basket stars).

Reproduction is carried out by the release of sperm and eggs into the water. Most species produce pelagic (= free floating) planktonic larvae which feed on plankton. These larvae are bilaterally symmetrical, unlike their parents (illustration of a larvae of a sea star below). When they settle to the bottom they change to the typical echinoderm features.

Echinoderms can regenerate missing limbs, arms, spines - even intestines (for example sea cucumbers). Some brittle stars and sea stars can reproduce asexually by breaking a ray or arm or by deliberately splitting the body in half. Each half then becomes a whole new animal.

Echinoderms are protected through their spiny skins and spines. But they are still preyed upon by shells (like the triton shell), some fish (like the trigger fish), crabs and shrimps and by other echinoderms like starfish which are carnivorous. Many echinoderms only show themselves at night (= nocturnal), therefore reducing the threat from the day time predators.

Echinoderms serve as hosts to a large variety of symbiotic organisms including shrimps, crabs, worms, snails and even fishes.

Sea stars (starfish)

Characteristics of sea stars (or starfish)

Sea stars are characterized by radial symmetry, several arms (5 or multiplied by 5) radiating from a central body. Mouth and anus are close together on the underside, the anus is at the center of the disc together with the water intake (madreporite). The upper surface is often very colorful. Minute pincer-like structures called pedicellaria are present. These structures ensure that the surface of the arms stay free from algae. The underside is often a lighter color.

There are a few starfish that have 6 or 7 arms, for example Echinaster luzonicus or Protoreaster, some even more like the elven-armed sea star (Coscinasterias calamaria). Others normally have 5 arms but now have more arms, because after an injury an arm divided and grew into two arms.

Ecology and range or sea stars

The starfish lives everywhere in the coral reef and on sand or rocks.

Behavior of sea stars

The ability of an organism to grow a body part that has been lost

The spontaneous self amputation of an appendage when the organism is injured or under attack. The autotomized part is usually regenerated.

Is asexual reproduction in which an outgrowth on the parent organism breaks off to form a new individual

Self-division into two parts, each of which then becomes a separate and independent organisms (asexual reproduction)

The majority of sea stars are carnivorous and feed on sponges, bryozoans, ascidians and molluscs. Other starfishes are detritus feeders (detritus = organically enriched film that covers rocks) or scavengers. Some starfish are specialized feeders, for example the crown-of-thorns that feeds on life coral polyps.

Starfish have no hard mouth parts to help them capture prey. The stomach is extruded over the prey, thus surrounding the soft parts with the digestive organs. Digestive juices are secreted and the tissue of the prey liquefied. The digested food mass, together with the stomach is then sucked back in. This method can be observed, if you turn around a starfish, that sits on prey or sand - you will see the stomach retreating.

Starfish are well known for their powers of regeneration. A complete new animal can grow from a small fragment such as a arm. In some species (Linckia multifora and Echinaster luzonicus) one of the arms will virtually pull itself away, regenerates and forms a new animal. Autotomy (self amputation) usually is a protective function, losing the body part to escape a predator rather than being eaten. But here it serves as a form of asexual reproduction. In other species of sea stars (Allostichaster polyplax and Coscinasterias calamaria) the body is broken into unequal parts (= fission) then the missing limbs regenerate.

Predators of starfishes

Tritonshorn - Charonia tritonis

Harlequin Shrimp - Hymenocera elegans

Harlequin Shrimp is carrying a sea star - Hymenocera elegans

The crown-of-thorns (Acanthaster planci) is one of the largest and the most venomous starfishes. It can reach 50 cm diameter and has numerous (10 to 20) spiny arms with formidable thorn like toxic spines. Don't touch them! A species of small cardinalfishes (Siphamia fuscolineata) and a commersal shrimp (Perliclimenes soror) live among those spines. The crown-of-thorns feed on live coral polyps. They "graze" the corals which are left behind white and dead. Their predators are the giant triton shell (Charonia tritonis) and some puffer fish. Scientist have also found out, that some crown of thorns are deterred from eating the coral polyps by the small crabs living among the coral branches (Trapezia sp). These crabs defend their coral host by breaking them off at the pedicellaria. Other small crabs (Tetralia sp) only pinch the tube feets of the starfish. Crown of thorns prefer corals, that are not hosts to these crabs.

The cushion star (Culcita nouvaeguineae) doesn't look like a starfish at all, more like a large sea urchin without spines. Its pentagonal appearance gives only the slightest indication that this organism is related to other starfish.

Photos of sea stars (photo collection) click for enlargement

Crown-of-thorns starfish (Acanthaster planci)

Spiny Cushion Starfish - Halityle regularis

Necklace Sea Star - Fromia monilis

Starfish / sea star (Nardoa variolata)

Horned Sea Star - Protoreaster nodosus

Egyptian Sea Star - Gomophia egyptiaca

Thyca crystallina - this snail lives on sea stars

Starfish Shrimp - Periclimenes soror

Zenopontonia noverca - Starfish Shrimp

Regeneration of an arm: Luzon Sea Star- Echinaster luzonicus

Starfish Shrimp - Periclimenes soror

Comb Jelly on Starfish - Coeloplana astericola

Feather stars

Characteristics of feather stars

Feather stars also known as crinoids. They are characterized by radial symmetry. The body of a typical feather star is cup-shaped, their numerous feathery arms project from a central disc. Some have five arms, others as many as 200. The arms, called pinnules are coated with a sticky substance that helps to catch food. There are appendages known as cirri attached to the underside of the body with which they cling to to sponges or corals. Both their mouth and their anus are situated on the upper side.

Ecology and range of feather stars

Feather stars are primarily nocturnal but they are seen in the open during the day with their arms rolled up.

Behavior of feather stars

Feather stars can crawl, roll, walk and even swim but usually they cling to sponges or corals. Feather stars are very abundant in areas exposed to periodic strong currents, because they feed on plaktonic food.

Numerous animals live in close association with feather stars. Echinoderms are hosts to various symbiotic animals such as the crinoid clingfish (Discotrema crinophila), the elegant squat lobster (Allogalathea elegans) or the crinoid shrimp (Periclimenes sp.). These animals receive shelter and food (left over) and also feed on microorganisms living on feather stars.

Photos of feather stars (photo collection) click for enlargement

Feather star (Stephanometra sp.) - gallery

Feather star (Lamprometra sp) half open, holding on to sponge with its cirri (appendages)

Rolled up feather star (Himerometra robustipinna) by day

Central body of a feather star with mouth and anus

Pinnules of a feather star (Pontiometra) coated to help catch food

Pontoniopsis comanthi - Comanthus shrimp

Laomenes sp8 - Ffeather star shrimp

Diademichthys lineatus - Clingfish

Myzostoma sp - worm living on feather stars

Brittle stars
Basket star

Characteristics of brittle stars

Brittle stars are close relatives of sea stars. Characterized by radial symmetry with a central body from which five snakelike arms protrude. The arms are highly flexible. There is no replication of internal organs, just one set in the central disk. Compared to starfish, brittle stars have a much smaller central disc and no anus. Wastes are eliminated through the mouth which is situated on the underside center.

On the underside of the body disk there is a splitlike opening at the base of each side of each arm. These ten openings are breathing and reproductive outlets, taking in water for oxygen and shedding eggs or sperm into the sea.

The basket stars are a specialized type of brittle stars. They have a series of complexly branched arms which are used to catch plankton.

Serpent stars are seen coiled snakelike around branches of gorgonians.

Ecology and range of brittle stars

Brittle stars are very cryptic and hide in crevices under corals. Best seen at night time, when they emerge to feed on plankton. Usually at places exposed to strong currents.

Serpent stars feed mostly on small invertebrates like mollusks, worms and crustaceans and are generally found in crevices and beneath rocks or in holes in the sand.

Snake stars (for example Ophiothela danae) are found entwined in the branches of black corals or gorgonians where they feed on the rich mucus of their host, in turn performing cleaning functions.

Behavior of brittle stars

As the name suggests, the arms of the brittle stars are rather liable to break. This is actually an escape mechanism. Those arms regenerate quickly and an entire new organism can regenerate, if the broken arm is attached to a seizable portion of the disk. Brittle stars can reproduce asexually by self-division. Brittle stars are the most active and fastest moving echinoderms.

Brittle stars feed on plankton but also on detritus, coral-shed mucus, bottom detritus (detritus = organically enriched film that covers rocks), mollusks and worms.

Photos of brittle stars (photo collection) click for enlargement

Brittle Star - Ophiothela sp

Many snake stars (Ophiothela danae) on gorgonian

Ophiothrix martensi - Martens brittle star

INFO - Serpent star (Ophiarachna incrassata)

Erna's basket star (Astroboa ernae)

Ophiothela danae - brittle star

Periclimenes lanipes - Basket Star Shrimp
Copyright Johanna Gawron

Periclimenes lanipes - Basket Star ShrimpGarnele

basket star (Astroglymma sculptum)

Sea urchin

Characteristics of sea urchins

Radial symmetrical body with a external chitinous skeleton and a centrally located jaw (called Aristotle's lantern) with horny teeth. The mouth consists of a complex arrangement of muscles and plates surrounding the circular opening. The anus is located on the upper surface. Some sea urchins have a spherical, bulb like cloaca (to store fecal material) that protrudes from the anal opening. It can be withdrawn into the shell.

Depending on the species, movable spines of various sizes and forms are attached to the body. These spines often are sharp, pointed and in some cases even venomous. Pincer like pedicellaria for grabbing small prey. Some pedicellaria are also poisonous.

Ecology and range of sea urchins

Rubble and sand. An abundance of sea urchins can be a sign for bad water conditions.

Behavior of sea urchins

Locomotion by tube feet but also by movement of the spines on the underside of the body. Sea urchins are generally nocturnal, during the day they hide in crevices. However some sea urchins such as Diadema sometimes form large aggregations in open exposed areas. Despite their sharp spines sea urchins are easy game for some fishes, particularly triggerfishes and puffers. A triggerfish grabs the sea urchin with its hard beak like mouth by the spines or it blows some water towards the sea urchin and turns it on its back. The underside of a sea urchin has much shorter spines and those are easily crushed. During the breeding season the body cavity is crammed with eggs or sperms. This is one of the main reasons urchins are so attractive to fish predators (Japanese also like them for the same reason).

Some sea urchins are camouflaged. They hold on with their tube feet onto some bottom debris like rubble or pieces of seagrass and carry them on their back. Some even carry live soft corals or anemones.

Most sea urchins are algal grazers but some feed on sponges, bryozonans and ascidians and others on detritus (detritus = organically enriched film that covers rocks).

The sexes are separate and the young are formed indirectly by the fusion of sperm and eggs released into the water.

Sea urchin cardinalfish

Aeoliscus strigatus - Centriscidae)

Sea urchin shrimp
Mandarinfish, dragonet

Many animals live in symbiotic relation with sea urchins. Even on the poisonous spines of the fire urchin (Asthenosoma varium) small shrimps (Periclimenes colemani) can be found. One shrimp (Stegopontonia commensalis) is striped black and white lengthwise and perfectly camouflaged and lives in spines of the long-spined sea urchin (Diadema setosum). Some cardinalfishes and juvenile shrimpfishes also like to take shelter in-between these spines, but even small cuttlefish hide there. It has been observed, that they change their coloring also to black and white. Some flatworms wrap around the thicker spines of the diadema sea urchin (Echinothrix calamaris).

The mandarin dragonet (Mandarinfish) lives close to congregations of sea urchins and hides among them if threatened.

There are two specialized types of sea urchins with an unusual appearance: the sand dollar is very much flattened with very small spines and the heart urchin which are oval and have bristle like spines. The both bury in sand. The heart urchin "jumps" out of the sand, when disturbed.

Photos of sea urchins (photo collection) click for enlargement

Heart Sea Urchin - Maretia planulata

Sea urchin (Prionocidaris verticillata)

Sea urchin (Astropyga radiata)

Sea Urchin - Diadema setosum

Toxic sea urchin (Asthenosoma pileolus)

Matha's sea urchin (Echinometra mathaei)

Zebracrab (Zebrida adamsii) on sea urchin

shrimp (Stegopontonia commensalis)

Coleman shrimp (Periclimenes colemani)

Comb yellies on seeurchin - Coeloplana sp

Shrimpfish (Aeoliscus strigatus)

Urchin clingfish - Diademichthys lineatus


Characteristics of sea cucumbers

Unlike other echinoderms, holothurians don't have a distinct radial symmetry but are bilateral (distinct dorsal and ventral side). Holothurians are also called sea cucumbers. As their name suggests, they are cucumber shaped with an elongated, muscular, flexible body with a mouth at one end and the anus at the other. Around the mouth there is a number of tentacles (modified tube feet) used in food collecting. Sea cucumbers come in many sizes, from small species only a few centimeter in length to long snakelike animals which may stretch up to 2 meter!

Ecology and range of sea cucumbers

Rubble, rocks and sand. Also seen on some sponges in large aggregations.

Behavior of sea cucumbers

Most species feed on the rich organic film coating sandy surfaces. The crawl over the bottom ingesting sand. The edible particles (organic matter such as plankton, foraminifera and bacteria) are extracted when passing through their digestive tract and the processed sand is expelled from the anus (as worm-like excrements).

Sea cucumbers move by means of tube feet which extend in rows from the underside of the body. The tentacles surrounding the mouth are actually tube feet that have been modified for feeding.

Other holothurians feed on current-borne zooplankton. They bury in sand extruding their featherlike tentacles (Pseudocolochirus violaceus, Neothyondium magnum or Pentacta crassa). The tentacles have the same shape as soft corals or some anenemones. Large congregations of some small species are found on sponges. They apparently feed on substances secreted by the sponges as well as detritus from the surface.

Some species of holothurians have separate sexes others are hermaphrodites. The sea cucumbers hold on to exposed rocks or corals, raise their body to a upright position, rock back and forth and release the sperm and eggs into the sea.

Sea cucumbers have a remarkable capacity for regenerating their body parts. When attacked they shed a sticky thread like structure which is actually parts of their guts. The so called Cuverian threads are toxic (the poison is called holothurin) and can dissuade many potential predators. These structures quickly regenerate. (see photos below)


Encheliophis homei and mourlani / Onuxodon margaritiferae

Holothurians host a variety of symbiotic organisms: crabs, shrimps, worms and even a very unusual fish. The pearlfish (Encheliophis homei and mourlani / Onuxodon margaritiferae) has a long slender, transparent body and lives in the gut cavity of the sea cucumber (Boshida argus, Thelanota ananas, Stichopus chloronotus). They also inhabit some starfish as well as pearl oyster shells. The fish leaves and enters (tail first) through the holothurian's anus. They probably feed on the gonads and other tissues of its host. It is said to leave at night to feed on small fishes and shrimps. Sea cucumbers are used in Asia as a base for soups.

Photos of sea cucumbers (photo collection) click for enlargement

Sea cucumber (Bohadschia argus) with Cuiverian threads

Sea cucumber (Bohadschia argus) with Cuiverian threads

INFO - Emperor Shrimp on Sea Cucumber - Periclimenes imperator on Opheodesoma australiensis

Black Sea Cucumber - Holothuria atra

Pineapple sea cucumber (Thelenota ananas)

INFO - Sea Cucumber - Synaptula media

Sea Cucumber details tentacles (Synapta maculata)

Sea cucumber skin (Thelenota rubrolineata)

Horrid Sea Cucumber - Stichopus horrens

Galathea sp1 - crab living on sea cucumbers

Imperator shrimp on sea cucumber - Periclimenes imperator auf Opheodesoma australiensis

Microbial Examination of Milk

It can be done by the following methods:

Standard Plate Count

It is also called “Viable Count Method“, which examines the viable count of bacteria present in the milk. It gives a rough and direct assessment of a viable number of bacteria and a very simple method to carry out.

Procedure: Take 1ml of milk sample. Then, prepare serial dilutions by transferring 1ml of a sample from each tube, i.e. 10, 100 etc. After that, transfer solid agar media into the sterile plates. Spread 0.5 ml of a milk sample over the solidified agar media. At last, incubate the prepared plates for 24-48 hours at 35-37 ֯C and finally count the number of colonies.

Interpretation of result: More than 300 colonies indicates the milk is unpotable.

If the solution is more diluted, then it will produce the highest number of colonies, i.e. milk becomes impotable, whereas a less diluted solution will produce less number of colonies.

Coliform Count

It is used to examine the presence of coliform bacteria, which can cause the fermentation of milk by the production of acid and gas. It becomes necessary to detect the presence of coliform, as these make the milk unpotable for human consumption.

Procedure: Firstly, take MacConkey fluid medium. Then, add milk of different concentrations in a fermentation tube. After that, dip a Durham tube and incubate the tubes for 24-48 hours at 35-37 ֯ C. In this test results are made, based on the fermentation property of coliforms.

Interpretation of result:
Positive: It is indicated by the colour change (purple to yellow) and formation of gas bubbles in the Durham tube.
Negative: If is indicated by the no acid and gas formation.

Methylene Blue Reductase Test

It is a rapid method to determine the microbial load. Using this test, we can identify the quality of milk depending upon the colour-retaining property. The speed of reduction of methylene blue colour is directly proportional to the volume of bacteria present in the milk sample.
In simple words, an increase in the number of bacterial flora will reduce the colour of methylene blue more rapidly due to the consumption of oxygen.

Procedure: Add a definite quantity of methylene blue to 10 ml of milk. After that, hold the sample at 37 ֯C until the colour disappears.

Interpretation of result:
Decolouration time —— Result
30min-2hrs —— poor quality
2-6hrs —— Fair quality
6-8hrs —— Good quality
Over 8 hours —— Best quality
Shorter the decolouration time, higher is the volume of the bacterial flora present in the milk and poor is the quality of milk and vice versa.

Resazurin Test

It is very similar to the methylene blue reductase test

Procedure: Firstly add resazurin to the milk sample. Then, incubate the tubes for 10 minutes and observe the shades of colour.

Interpretation of result:
Positive: Formation of pink colour indicates the presence of bacteria that reduce resazurin.
Negative: Colour remains unchanged, i.e. bacteria are not present in the milk, which indicates that milk is of good quality.

Phosphatase Test

It is used to check the pasteurisation process, to verify whether milk is pasteurised, or not. Phosphatase is an enzyme that is usually present in the milk. This enzyme becomes inactivated if pasteurisation is performed properly.

Procedure: Firstly, take 5 ml of milk in a sterile test tube. Then, add a few drops of sodium biphenyl phosphate. After that, incubate the tubes for 10-15 minutes.

Interpretation of result:
Positive: Blue colour appears, which indicates the presence of a phosphatase, i.e. milk is pasteurised appropriately.
Negative: No changes in colour, indicates the absence of phosphatase, i.e. milk is not pasteurised.

Turbidity Test

It checks the sterilisation process of milk, whether the milk is boiled correctly or not, to the temperature prescribed for sterilisation. In sterilized milk, all the coagulable heat proteins get precipitated.

Procedure: Firstly, take 5 ml of sterilised milk. Then, add a few drops of ammonium sulphate and boil it in a water bath for 5 minutes.

Interpretation of result:
: If turbidity appears, i.e. milk has been not sterilized properly.
Negative: No turbidity indicates that the milk is sterilized properly.

Direct Microscopic Count

It is a rapid method for the microbial examination to determine the cell type and morphology.

Procedure: Firstly, take 0.01 ml of raw milk in glass slide (hemocytometer) and air dry. Then, add one drop of methylene blue. At last, count the bacterial clumps in a colony counter.

It counts both viable and non-viable cells.

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