Monday, July 17, 2017

18/07/2017: Lobster expert topic

by Zasha Whiteway-Wilkinson, International Aquafeed magazine

The spiny lobster, or alternatively known as the rock lobster or crayfish, are a family of around 60 species of achelate crustaceans, in the Decapoda Reptantia within the class Malacostraca

Although they superficially resemble true lobsters in terms of shape and having a hard carapace and exoskeleton, the groups are not closely related. Spiny lobsters can be identified by their long, thick spiny antennae, by their lack of claws on the first four pairs of walking legs (although the females of most species have a small claw on their fifth pair) and by a specialised larval phase called phyllosoma.

The species typically have a slightly compressed carapace, lacking any lateral ridges. Their antennae lack a scaphocerite, the flattened exopod of the antenna. This is fused to the epistome (a plate between the labrum and the basis of the atenna). The flagellum, at the top of the antenna, is stout, tapering, and very long. The ambulatory legs (pereopods) end in claws (chelae).

The lobsters are found in almost all warm seas, including the Caribbean and the Mediterranean, although they are particularly common in Australasia. They tend to live in crevices of rocks and coral reefs, only occasionally venturing out at night to eat.

Sometimes they migrate in very large groups in long files across the ocean floor, the lines could be up to 50 lobsters long. The spiny lobsters navigate using the smell and taste of natural substances in the water that can change in different areas of the ocean.

It was also recently discovered that spiny lobsters could navigate by detecting the Earth’s magnetic field. They contact each other using their long antennae and deter potential predators also using their antennae by rubbing it against a smooth part of their exoskeleton, creating a loud screech.

This noise is produced by frictional vibrations – sticking and slipping, similar to rubber materials sliding against hard surfaces, while a number of insects use frictional vibration mechanisms to generate sound, this particular acoustic mechanism is unique in the animal kingdom.

Notably, this system does not rely on the hardness of the exoskeleton, meaning that they can continue to produce deterrent noises even in the period following a moult when they are at their most vulnerable.

Read the three page section on Lobsters in International Aquafeed's July edition, HERE.

The Aquaculturists
This blog is maintained by The Aquaculturists staff and is supported by the
magazine International Aquafeed which is published by
Perendale Publishers Ltd

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