Radiant  Squat Lobster, Iradonida refulgens

Radiant Squat Lobster, Iradonida refulgens. Lobster provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, January 2011. Length: 6.5 cm (2.5 inches); claws: 16 cm (6.3 inches).

Phylogeny:  The Radiant Squat Lobster, Iradonida refulgens (Faxon, 1893),  is a member of the Munididae family of Squat Lobsters. The genus Iradonida is one of thirty-three genera in this family, and there are six species in this genus. They are also known as the Long Claw Squat Lobster and in Mexico as Langostino Pinze Largo and Munida Radiante. This species has recently classified as Munida refulgens.

Morphology:  Radiant Squat Lobsters resemble lobsters in shape, though slightly flattened dorsoventrally. They have 5 head segments, 8 thoracic segments, and 6 abdominal segments. The head and thorax are combined as a cephalothorax. The head includes a pair of antennae, a pair of antennules, and mouth parts. They having short spines along the front edge of their carapace, two additional, longer spines over the eyes, and a central rostrum. They have five pairs of appendages that function as legs (pereiopods)and three pairs that function as mouth parts (millipedes). Radiant Squat Lobsters are characterized by their first set of legs (pereiopods), which are greatly elongated (three to five times longer than the shell) and armed with long claws. The fixed portion of the claw is about twice the width of the movable finger (dactyl). The forearm (propodus) is free of spines. The fifth pair of legs are often hidden within the gill chamber, under the shell giving them the appearance of having only eight legs. They have six pairs of biramous (dividing to form two branches) appendages along their abdomen. The first five pairs function as swimmerets (pleopods). The last pair is flattened to form a tail fan. They hold their long tail curled up under their thorax, which gives them a squatting or crouching appearance. They have a thick carapace, which is well marked with transverse lines (striae). Keys to identification include a very long and straight rostrum with adjacent supraocular spines that are short, sharp, slightly diverging and 20% of the rostrum in length with their tips reaching one-third the level of the eyes. They have large brown eyes with diameters that are approximately one half the length of the rostrum. They are reddish- brown in color, with darker blotches. Radiant Squat Lobsters reach a maximum of 9.1 cm (3.6 inches) in length. This species can be confused with the Squat Lobster, Munida debilis (large eyes that reach two-thirds of the rostrum).

Habitat and Distribution:  Radiant Squat Lobsters are found in rock crevices or sitting on top of coral reefs at depths between 18 m (60 feet) to within deep sea hydrothermal vents of 1,463 m (4,800 feet). They are highly territorial. They are a tropical Eastern Pacific species and in Mexican waters are found within the extreme southern portion of the Sea of Cortez and along the coast of the mainland south to Guatemala.

Diet:  Radiant Squat Lobsters are opportunistic feeders. They are primarily scavengers and supplement their diets with passing prey, including passing fish, with their long claws.

Predators:  Radiant Squat Lobsters serve as a vital food source for a wide variety of marine life including numerous fishes, the Humboldt Squid, Dosidicus gigas, turtles and whales.

Reproduction: Radiant Squat Lobsters are gonochoric (male or female for life). Reproduction is sexual with external fertilization. Mating is accomplished by the transfer of a sperm packet from the male to the abdomen of the female. The female scratches open the sperm packet as she releases her eggs. The female carries the fertilized eggs on her abdomen until they hatch after a few weeks. The eggs hatch into planktonic larvae. After several developmental stages the larvae molt into benthic juvenile lobsters.

Ecosystem Interactions:  Radiant Squat Lobsters are known to host the parasitic Bopyrid Iisopod, Mudidion princeps. The exact nature of this relationship is poorly understood. There is no documentation of commensal or symbiotic relationships of the Radiant Squat Lobsters.

Human Interactions: There is a small commercial fishery that catches Radiant Squat Lobsters by trap or trawl. They are sold commercially and sold in restaurants as “langostino lobster” or as “lobster” when incorporated into seafood dishes. From a conservation perspective they have not been formally evaluated however they are fairly common with a relatively wide distribution and should be consider to be of Least Concern.  Fossil records indicate that the Squat Lobsters date to 150 to 175 million years ago.

Synonyms:  Munida refulgens