February 21, 2021 | 7:55 am

Are the Shellfishes come under fish?

Mostly Seafood is either considered into Fish or Shellfish, other animals too are there.

But, all are classified as either vertebrates or invertebrates.

Now, what is Vertebrates?

The animals that have a backbone inside their body are called Vertebrates. Likes fish, amphibians (small vertebrates that need water, or a moist environment, to survive. The species in this group include frogs, toads, salamanders, and newts), reptiles, birds, and mammals

What Are Invertebrates?

The animals don’t have a backbone. They either have a soft body, like worms and jellyfish, or a hard outer casing covering their body, like spiders and crabs.

In my last blog, we had discussed few important points on fish, in this blog we are discussing shellfish.

Shellfish are not actually fish but are simply water-dwelling animals. They come in Invertebrates.

There are two groups of shellfish: Crustaceans and Mollusks.

Crustaceans:

Two pairs of antennae such as Prawns, shrimp, crab, and lobster are called crustaceans.

Prawns and Shrimps: In terms of aquaculture and farming, shrimp are marine creatures, while prawns live strictly in freshwater. Both are decapods (Ten Legs).

Shrimp, have lamellar (or plate-like) gills, and claws on two pairs of their legs, whereas Prawns on the other hand have branching gills and claws on three pairs of their legs. Prawns have an almost straight body whereas Shrimps are curved. Shrimp belong to the sub-order Pleocyemata, while prawns belong to the sub-order Dendrobranchiata.

Sr.No	Shrimps	Prawns
1.	Shrimp, have lamellar (or plate-like) gills, and claws on two pairs of their legs,	whereas Prawns on the other hand have branching gills and claws on three pairs of their legs
2.	Shrimps are curved bodies.	Prawns have almost straight bodies.
3.	Shrimp are marine creatures.	While prawns live strictly in freshwater.
4.	Shrimp belong to the sub-order Pleocyemata (A taxonomic suborder within the order Decapoda – decapod crustaceans whose fertilised eggs are incubated by the female, and remain stuck to the pleopods).Broods eggs on the underside of their body.	Prawns belong to the sub-order Dendrobranchiata.( is a suborder of decapods, commonly known as prawns. There are 540 extant species in seven families, and a fossil record extending back to the Devonian). Release eggs into the water.
5.	They are smaller than Prawns	Prawns are larger than Shrimps

Crabs and Lobster:

Both are popular seafood and are marine invertebrates that belong to the class Crustacea under the phylum Arthropoda. Although both are crustaceans and mostly look alike, they don’t have much in common.

Crab:

Around 6800 species of crab habitats found in freshwater, marine water, and terrestrial ecosystems. Accordingly, they are found all over the world but are mostly found in tropical and subtropical geographical areas mostly at the time of rainy.

Their body covered with carapaces (hard upper shell) like tortoise and their eyes is located on the eyestalks. They have four pairs of legs and one pair of claws called chelae which they use to walk sideways. They have small tails. The female crabs have a round abdomen and the male crabs have a triangular abdomen.

Crabs can be small as a few millimeters and 12 to 13 feet. They can live up to 13 years. They are omnivorous (feed on algae, plankton, fungi, mollusks, small fishes, etc). They are said to be very cooperative creatures and work together to protect, feed, and find shelter for their family.

Lobster:

Around 85 species of lobster, except the Polar region, are found all over the world. Their body is covered with an exoskeleton like a crab with a muscular tail and long antennae. The eyes are present near the base of the antennae. They have 5 pairs of legs in which the first pair are modified into claws and bigger than the rest. Lobsters can dwell in saltwater, freshwater, and land. Lobsters can measure from 20 inches long and can live up to 70 years. They walk slowly on the seafloor and swim by curling or uncurling their abdomen. They are omnivorous creatures as they can feed on worms, seaweeds, seashells, small fishes, and other crustaceans. Furthermore, lobsters undergo molting to grow and also change their color when they shed their shell.

Sr.No	Crab	Lobster
1	They are smaller than lobsters.	They are larger than crabs.
2	Their eyes are located on the eyestalks.	Their eyes are present at the base of the antennae.
3	Their body is covered with large carapace and a smaller circular exoskeleton.	They have a longer and larger exoskeleton.
4	Their claws are smaller than that of lobsters.	Their claws are larger than that of crabs.
5	There are around 6800 species of crabs.	There are around 85 species of lobsters.
6	They usually walk sideways.	They move forward and backward.
7	They have short tails and antennae.	Their tails and antennae are longer than that of crabs.
8	They are social creatures.	They are solitary creatures.
9	They have four pairs of legs and one pair of claws.	They have five pairs of legs, out of which one pair is modified into claws.
10	They can live up to 3 to 4 years.	They can live up to 70 years.

Mollusks:

Mollusks is a soft animal such as clams, mussels, oysters, scallops, and octopus. A Mollusk is an animal with is univalve, it basically has one shell, or a Bivalve, which has two shells.

Cephalopoda, meaning “head-footed,” includes squids, octopods, cuttlefish, and nautiluses. The feet, or arms, of these creatures, are connected to their heads, not their bodies.

Cephalopods, like most mollusks, have a mantle, a mantle cavity, a radula, and a U-shaped digestive tract. and have two kidneys and three hearts, which pump blue blood.

The most obvious difference between most cephalopods and other mollusks is the apparent lack of a shell. Octopuses do not have shells at all, while squids have a small internal shell.

Cephalopods have a more developed nervous system than other mollusks like good eyesight use for finding prey and grasped firmly and eaten with a mouth (parrot-like beak) located at the base of the arms.

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