When we think of spiny lobsters, many of us will conjure up images of their sweettasting, meaty tails draped on a grill, drizzled in garlic and lemon butter. However, there is more to these spiny creatures than just their value as an expensive menu item. Spiny lobsters (family Palinuridae), as their common name indicates, can be recognized by their spines and extremely long, thick antennae. It is these antennae
and lack of large claws that set them apart from their clawed crustacean counterparts, the true lobsters of the family Homaridae. These two families are not as closely related as you might think, even though they share morphological similarities. The Palinuridae family is a highly successful group of crustaceans which includes about 49 species that are spread around the world. We are, however, more interested in the one species that creates such a sensation in the Caribbean and adjacent waters, the Caribbean or Florida spiny lobster (Panulirus argus)
This iconic species is no stranger to divers and snorkelers alike, nor to people who partake in the annual lobstering frenzy. Spiny lobsters can be recognized by the two sharp, black-banded horns above their eyes and a reddish body that is pale below. They can reach a respectable size of two feet (60 cm), and are a familiar sight in crevices and under ledges during the day, where they peek out at you with their long antennae prominently displayed. You will often find more than one lobster sharing the safety of a crevice, but a recent study found that this social habit is easily disrupted if one of the individuals is sick. Healthy lobsters will move away from infected ones, leaving them to fend for themselves. At night they become braver and venture out to forage, targeting a variety of prey such as crabs, shellfish, mussels, worms, sea urchins and sand dollars. They rely on two smaller antennae, called antennules, to locate their prey. These sensory organs are super sensitive to
chemicals and movement in the water.
The large antennae are used for fighting and defense. If intimidation does not work, they will apply these antennae in another way to deter the enemy. They can produce a loud screech by rubbing the spiny antennae against a smooth part of their exoskeleton, a sound that would-be predators do not seem to appreciate.
If caught unawares in the open, spiny lobsters do have another escape method up their sleeve, one many of you might have witnessed: speed. They have a wonderful ability to travel backwards at such great speeds that, once in motion, they are hard to catch. Forward motion, however, is a more sedate process achieved by walking on their many legs.
Adult spiny lobsters use their walking skills in a unique way: their tendency to migrate in great numbers. What makes it more fascinating is that they migrate in single file, keeping in contact with each other with their long antennae. Migration is usually triggered by changes in water temperature, such as the arrival of a big storm, causing them to head for deeper offshore waters where the temperatures are more stable. They navigate by using smell, taste, and the Earth’s magnetic field. I have only seen this behavior in documentaries—imagine what a spectacular sight it must be to witness it for yourself!
Caribbean spiny lobsters mate from March through June, or, depending on their geographic location, from June through November. The female carries the orange eggs on her underside until they turn brown and hatch, a process that takes about three weeks. During this period she is considered gravid or berried, a fact that enforces the need for closed harvesting seasons during this crucial time in the lobster’s life cycle. Spiny lobsters begin their lives as free-swimming, microscopic phyllosoma larvae that settle after about one year among mangrove roots or in Thalassia testudium seagrass beds. Here they undergo several molts before migrating to the coral reefs. Conservation of these habitats is thus essential to the maintenance of Caribbean spiny lobster populations and their continued utilization as an economic resource. Size restrictions on this heavily harvested species are also important, as it takes an individual lobster more than two years to reach its full adult, legal harvesting size with a three-inch carapace. Minimum size limits allow them to reach adulthood and spawn at least once before being harvested.
The Caribbean is also home to a true beauty that you can keep an eye out for, the spotted spiny lobster (Panulirus guttatus), a reclusive species recognized by the distinctive white spots that dot its dark red to brown body. Another close but unique relative of these two spiny species is the elusive Spanish slipper lobster (Scyllarides aequinoctialis). They get their common name from their flattened outer shell which resembles a slipper, but their most outstanding feature is their second pair of antennae that is expanded and flattened into large plates which help them dig in the sand to find prey. The Spanish slipper has a rounded, brown-to-orange body with distinctive purple antennae. These nocturnal critters remain well hidden on the reef during the day and are not as commonly encountered as their spiny
cousins. They do not have the same speed and intimidating antennae as the spiny lobsters, and therefore rely on other methods to evade predators. Their flattened bodies and ability to cling to rocks, combined with their mottled coloring, allow them to blend in very well with their environment. Even on sandy substrates, if they lie very flat passing predators have a hard time spotting them.
The Spanish slipper lobster is not the only slipper lobster that calls the Caribbean home. Its cousin, the sculptured slipper lobster (Parribacus antarcticus), is another reef resident that hides itself away during the day. I have not had the privilege of encountering this secretive creature whose main distinguishing features are the presence of tufts of hair and small spines on flat antennal plates, giving it that sculptured look. Its coloring differs from that of the Spanish slipper in being tan to yellow with dark blotches, and it has small black eyes.
But the crustacean universe extends far beyond lobsters. The variety of shapes and sizes that members of the different crustacean orders exhibit is truly remarkable, and none are more morphologically diverse than the isopods. These unlikely crustaceans might not always resemble each other, but all share the same basic body plan: a head, a thorax with seven segments, and an abdomen with six segments. They are typically dorsoventrally flattened and covered with overlapping plates. The marine environment alone is home to about 4,500 isopod species. Of greater interest are the isopods that are ectoparasites of fish—parasites that live on the outer surface of a host. In your diving and snorkeling adventures you might have noticed these bug-like creatures attached to a fish, typically the head. These permanent ectoparasites of fish are known as the Cymothoid isopods. Some prefer to attach to the skin, others attach to the gills, and some even replace their hosts’ tongues, such as the infamous Cymothoa exigua, or tongue-eating louse. Cymothoid isopods of the genera Anilocra and Renocila are common ectoparasites of Caribbean fish and attach to their hosts as juveniles, feeding on blood and possibly mucus and epithelium. During the juvenile stage they will change hosts, but once settled they will remain attached to their host for the rest of their life , unless they are dislodged or eaten. Studies have shown that infestation by Anilocra species such as the anilocra leach can impact breeding success, interfere with swimming dynamics, decrease fish size and reduce the number of red blood cells.
When it comes to unique crustaceans none can compete with the barnacles, the most unlikely of crustaceans—creatures who once were believed to be related to snails. These familiar little animals spend their life attached to the substrate, usually packed together densely, hidden within their hard protective shells. They are not very picky when it comes to the substrates they colonize. The array of substrates astound, from rocks, dock pilings, shells of clams and oysters, to whales, turtles, and manatees. Other favorite sites, to the horror of many a boat owner, are boat and ship hulls. In fact, barnacle glue is six times stronger than most synthetic glues. This adhesion ability of barnacles has actually inspired MIT engineers to develop a strong, biocompatible glue that can seal injured tissues and stop bleeding–another example of why we need to conserve and continue studying the amazing natural world around us.
Mussels and limpets are common neighbors of these sticky crustaceans, a situation that often results in a battle for space among them. As sessile animals they have no need for legs, so their legs have become modified into feeding appendages called cirri. They actively sweep the water column with these featherlike structures, catching passing food particles. When threatened, the cirri are hastily withdrawn into their protective shells, usually made up of six calcium plates. The opening is then closed with two to four plates that act as a door. This also helps to conserve moisture when the tide goes out.
Sexual reproduction can become somewhat problematic it you are immobile and trapped within a shell. To overcome this problem barnacles have evolved extraordinarily long penises. When it comes to having the largest penis to body size ratio in the animal world, the barnacles are the clear winners—a fact that fascinated the barnacle-obsessed Charles Darwin, who dedicated years of his life to studying them.
Not all barnacles attach themselves directly to the substrate; some use a distinctive fleshy stalk or peduncle. One such species is the stunningly beautiful grooved gooseneck barnacle (Lepas anserifera), found widely distributed in temperate and tropical seas around the world, a true cosmopolitan species. Their delicate, chalky white shells, edged in orange, make them stand out from their substrate-hugging family. Being a pelagic species, preferring the open sea, they tend to attach themselves in clusters to driftwood and other floating debris,
including whales. They are often found washed up on beaches, still attached to their floating perch.
I hope you found this glimpse into the lives of these incredible creatures and their astounding adaptations to survive in the marine world interesting. Crustaceans are truly the rulers of the sea.