New Jersey Scuba Diving

Marine Shellfish

crabby

These animals are lumped together here because they all have hard external shells. Crustaceans and Mollusks are not closely related at all. This is more of a restaurant classification than a scientific one.

American Lobster

Homarus americanus

Size: to 36" and 45 lbs. (record)

Habitat: subtidal to the edge of the continental shelf, in any sheltered spot

Notes:

Lobsters differ from shrimps in having three pairs of clawed legs, the first with very large claws. Southern "Spiny Lobsters" are only distantly related; freshwater crayfish are closer. Lobsters, or "Bugs", are mainly nocturnal, and feed primarily on living or freshly killed food rather than scavenging on carrion, as was once thought. Although they are predominantly solitary creatures, lobsters do have a sort of social life amongst themselves. Males are more aggressive than females and will form pecking orders among individuals in an area. Female lobsters apparently seek the protection of a male when molting, then mate afterward. Lobsters shed their shells once or twice a year, depending mainly on the temperature.

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Crabs

These are all so-called "true crabs".

Crab anatomy
Crab anatomy - Blue Crab

True crabs are crustaceans with extremely reduced tails, which are carried folded under the body. Males are generally larger than females. Presented here are just the most common of many local species. Sizes quoted below are body width. Hermit Crabs are listed elsewhere. They are not closely related.

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Snails

x-ray

These creatures are all of the order Gastropoda - having a single, often coiled, shell, as opposed to the bivalves, which have two matching shells. Most snails are hermaphroditic. Also, most snails have a right-hand twist to the shell, although there are exceptions.

Right:
X-ray image of a Channeled Whelk, showing internal structure.

Nudibranchs are a form of snail that has lost its shell, while Corollas and Sea Butterflies are snails that have abandoned not just their shells, but the snail-like existence entirely, swimming up into the water column as plankton.

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Bivalves

All of these bivalves are filter feeders. The other major group of mollusks is the Gastropods or snails. Squid and octopus ( cephalopods ) are mollusks too, but they don't behave like other mollusks, so I included them elsewhere. Teredos are bivalves that have evolved a worm-like wood-boring habit.

Clam Anatomy
Typical bivalve anatomy

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Why the Buddy System is Dangerous

by Paul Humann

I am confounded by the illogic of many of those who try to defend the buddy system, even the spokesperson for a training agency such as PADI - the same folks who preached the dangers of dive computers and Nitrox a few years back. Here is some of the nonsense I've heard and why it is just that:

The buddy system makes diving more fun and practical

Of course, neither has anything to do with the buddy system. Fun is touted as sharing the dive and the after-dive experience with your buddy. Practicality means helping your buddy lug around equipment, get suited up, and other niceties. These benefits can be enjoyed with any dive companion without that person being a "buddy" for whose safety you are legally responsible.

More: Why the Buddy System is Dangerous ...

Disclaimer:

I make no claim as to the accuracy, validity, or appropriateness of any information found in this website. I will not be responsible for the consequences of any action that is based upon information found here. Scuba diving is an adventure sport, and as always, you alone are responsible for your own safety and well being.

Copyright © 1996-2024 Rich Galiano
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