Excerpts from Jim Conrad's
Naturalist Newsletter

Smoothtail Spiny Lobster, PANULIRUS LAEVICAUDA

from the March 15, 2015 Newsletter issued from Río Lagartos, on the north-central coast of Yucatán, MÉXICO

At low tide Rayo and I were exploring in and around an old, metal, decaying dredging pipe left over from when the canal in front of Río Lagartos was dug. From inside an open-topped part of the pipe, Rayo plucked from the water the crayfish-like creature shown on his wrist above.

Rayo was excited because lobster fishing is big business around here, but normally you see them much larger than this one, and in much deeper water beyond the estuary, out in the Gulf of Mexico. Rayo assumed he was seeing a juvenile of that species, and learning that young ones live in the estuary. Soon the lobster curled into a shrimp-like pose, shown below:

Smoothtail Spiny Lobster, PANULIRUS LAEVICAUDA, tail curled

A close-up of the creature's oval eyes and the forward-projecting spines around them is shown below:

Smoothtail Spiny Lobster, PANULIRUS LAEVICAUDA, head

You might guess that many kinds of lobster exist, if only because you know that lobsters eaten in restaurants up north bear big claws, while the one on Rayo's wrist doesn't. Taxonomically, big-clawed ones belong to the Lobster Family, the Nephropidae, while Rayo's is a member of the Spiny Lobster Family, the Palinuridae. So, technically, Rayo's lobster isn't a lobster; it's a SPINY lobster. The Spiny Lobster Family embraces about 60 species worldwide, and are recognized by being shaped like crawfish, bearing no big claws, and by having very long antennae armored with low spines.

Sipse.Com reports that during the 2014-2015 lobster season, 395 metric tons (435 US short tons) of spiny lobster were harvested in the waters off Yucatán State. This is reported, in Spanish, here.

The lobster species the Yucatan's fishermen catch is Panulirus argus, known as the Caribbean Spiny Lobster. You can see what that looks like on its Wikipedia page at http://en.wikipedia.org/wiki/Panulirus_argus.

When I compared Rayo's spiny lobster with pictures of Caribbean Spiny Lobsters, there were mismatches. For one thing, Caribbean Spiny Lobster tails display a different arrangement of spotting from ours. More strikingly, Caribbean Spiny Lobster legs bear long, narrow, dark lines on tan backgrounds, while our spiny lobster's legs bore broad bands and blotches.

It turns out that only 99% of the Yucatan's spiny-lobster catch consists of Caribbean Spiny Lobsters. 1% of the catch consists of a species called the Smoothtail Spiny Lobster, PANULIRUS LAEVICAUDA, and that's the lobster Rayo plucked from the decaying dredging pipe in the estuary that day. Caribbean Spiny Lobsters occur farther out to sea in deeper waters. The habitat of our Smoothtail Spiny Lobster is described as coastal waters, down to 165ft deep (50m), on rock or coral. To that we can add that they cluster around man-made structures such as collapsing metal pipes.

The feeding habit of Smoothtail Spiny Lobsters is described as "predatorily opportunistic," meaning that they feed mostly on easy-to-catch crustaceans, annelids, echinoderms and mollusks more or less randomly encountered. They feed mainly at night.

Smoothtail Spiny Lobsters occur in the western Atlantic from Bermuda and Florida south through the Caribbean to Brazil. They can reach a body length of over a foot long (32cm) but most are about eight inches long (20m). They're not regarded as especially desirable for eating, and seem to be caught incidentally during the harvest of Caribbean Spiny Lobsters.

The IUCN Red List of Threatened Species doesn't rate our Smoothtail Spiny Lobster because there's not enough information about the species to decide. Now we've added a tiny bit more to that limited knowledge.