What Do Lobsters Do?

A while back, we were out grocery shopping. My son really enjoys this (sometimes) because I let him get involved. He gets to pick out some of the fruit we buy, and he asks questions, and he gets to go look at the lobster tank. This last part is huge for him, because the lobster tank at the local grocery is a big cylinder sitting out in the aisle. And it has benches next to it, so you can sit and look at the lobsters. Or, if you’re five, so you can climb up and press your face to the plexiglass and stare at the lobsters in fascination. I’ve told him that they’re there so people can buy them and eat them, but he still regards it as a huge aquarium.

So we’re sitting and looking at the lobsters, taking a short break before we get back to the shopping. And he’s tapping on the glass, and staring at the lobsters, and asking questions. “Why are they in there?” “Why do they have rubber bands on their hands?” Things like that, easy questions.

“What do lobsters do?” he asks.

What? What does that even mean? So, I ask him. “What do you mean?”

“What do lobsters do?” he repeats, his voice incredibly patient.

“Like, what do they eat?”

“No, daddy,” he repeats, enunciating. “What do lobsters do?”

That’s a pretty heavy question. Let’s see if I can’t answer it.

What is a lobster?

Let’s start at the beginning. What, exactly, is a lobster?

lobster

This. This is a lobster.

Sure, I’ve seen pictures of them. And I’ve seen them in grocery stores, and at the aquarium. And that’s about as far as my knowledge goes. I think I’ve always assumed that they were oceanic bugs, maybe related to crabs, and then I went on with my day. They never really caught my attention the way dolphins or sharks or cuttlefish ever did.

The answeer is a bit tricky.

See, lobsters are crustaceans, a class of creature defined by the Encyclopedia of Life as belonging

to the phylum Arthropoda, as do insects, arachnids, and many other groups; all arthropods have hard exoskeletons or shells, segmented bodies, and jointed limbs. Crustaceans are usually distinguishable from the other arthropods in several important ways, chiefly:

  • Biramous appendages. Most crustaceans have appendages or limbs that are split into two, usually segmented, branches. Both branches originate on the same proximal segment.
  • Larvae. Early in development, most crustaceans go through a series of larval stages, the first being the nauplius larva, in which only a few limbs are present, near the front on the body; crustaceans add their more posterior limbs as they grow and develop further. The nauplius larva is unique to Crustacea.
  • Eyes. The early larval stages of crustaceans have a single, simple, median eye composed of three similar, closely opposed parts. This larval eye, or “naupliar eye,” often disappears later in development, but on some crustaceans (e.g., the branchiopod Triops) it is retained even after the adult compound eyes have developed. In all copepod crustaceans, this larval eye is retained throughout their development as the only eye, although the three similar parts may separate and each become associated with their own cuticular lens. In other crustaceans that retain the larval eye into adulthood, up to seven optical units may develop.
  • Labrum. Crustaceans have a lobe-like structure called the labrum anterior to the mouth that partially encloses it.
  • Head. Crustaceans are distinguished by a five-segmented head (cephalon), followed by a long trunk typically regionalized into a thorax and abdomen.
  • “Baby teeth.” Most crustaceans in their early larval stages chew their food with a unique structure called a naupliar arthrite, which is on the second antenna. This chewing tool is lost later in development, and chewing is taken over by the mandibular gnathobase.

Wikipedia adds that crustaceans include crabs, lobsters, crayfish, shrimp, krill, barnacles, and “all animals in the Pancrustacea clade other than hexapods” (with hexapods meaning insects). So, you really could argue that lobsters are bugs. They’re just not insects.

But wait! It gets even more complicated!

True lobsters are part of the Nephropidae family. They’re part of the Animalia kingdom (making them animals), the Arthropoda phylum (meaning they’re invertebrates with exoskeletons and segmented bodies), class Malacostraca, order Decapoda (meaning “ten-footed”). At present, fourteen different genera of Nephropidae are known, with a total of 54 different species. Out of those, if you’ve eaten one, it was most likely Homarus americanus (the American lobster, found on the Atlantic coast from Labrador to New Jersey) or Homarus gammarus (the European lobster, found along the eastern Atlantic coast of Europe, as well as the Mediterranean and Black Seas).

Related Decapodae are the spiny lobsters (family Palinuridae), the slipper lobsters (family Scyllaridae), furry lobsters (family Palinuridae), and squat lobsters (which are actually more closely related to hermit crabs). None of them are considered to be true lobsters.

Great. So what does a lobster [do?

There’s 54 different species, each of which does its own thing. In general they are benthic omnivores, meaning they live on the sea floor and eat whatever they can find. Fish and mollusks make up the majority of their diet, but they’ll eat algae, sea plants, and even other lobsters if they need food – although cannibalism appears to be a response to population pressures and is not believed to be a primary strategy. As benthic animals, they primarily walk (using eight of their ten legs for locomotion). They can swim as well – backwards – as an escape mechanism if needed. Swimming speeds of up to 11 mph (17.7 kph) have been recorded.

Lobsters, like most crustaceans, have to molt (shed their exoskeleton) in order to grow, something which is part of their reproductive cycle – males and females mate after the female has molted and while here carapace is still soft. The female stores the sperm for up to a year before fertalizing and laying eggs, which she will carry curled in her tail her tail for another 9 to 12 months before they hatch. At hatching, the female uncruls her tail and allows the surviving eggs to be exposed to the water so the larvae can float free.

Larval lobsters are planktonic, swimming near the surface as they go through three stages of development (named stages I through III). Stage III ends with the third molt, when the post-larval lobster finally resembles a lobster and settles down to the sea floor. The young adult lobster spends much of its time hiding and feeding at night, when predators are less likely to find and eat it. As they age and grow, they travel further to feed and begin to stake out a territory. Then, once they reach sexual maturity, the process starts over.

So, what do lobsters do? Pretty much what all other animals do: eat, sleep, grow, and breed.

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