Remipedia

Dorsal view of a remipede from the Bahamas.

Remipedes, a rare group of marine crustacean first described in 1981¹, occur only in anchialine karst systems in Central America, the Caribbean, the Canary Islands, and western Australia. Anchialine caves are generally dolomite or limestone in composition and contain a marine layer that flows beneath a fresh or slightly brackish layer.

Morphological and genetic evidence has led many phylogeneticists to classify remipedes as ancestral crustaceans². However, the well-developed brains and sensory organs of these organisms have convinced other researchers that remipedes stem from more derived lineages³. These disagreements reflect our restricted knowledge of remipede natural and evolutionary history.

The living representatives of this group, of which there are only 17 known species, are the Nectiopoda. Remipede adults feed with three pairs of raptorial mouthparts unique to the group¹. Remipede bodies are divided into a cephalon (head) and elongate trunk with up to 32 similarly shaped segments. All known living remipedes except Enantiopoda lack eyes (see next paragraph). The appendages on the trunk segments are paddle-like and directed out to the side. This appendage orientation is unusual in crustaceans, and it makes them superficially similar to polychaete worms (Annelida). Remipedes swim on their backs similar to the Anostraca (fairy shrimp). All known species of the Remipedia are hermaphroditic, simultaneously containing both female and male sexual organs⁴. Yet, little else is known about their reproductive cycle or their ability to disperse. There remains much to learn about the biology of these unusual animals.

Click on any of these photos to see an enlargement. Top left: Several species of Speleonectes are known from the Bahamas, Cuba, the Yucatan Peninsula, and the Canary Islands. Top center: A claw on the maxilla of Speleonectes. Top right: Lasionectes entrichoma is found in the Caicos Islands, British West Indies. Bottom left: Cryptocorynetes haptodiscus has been found in anchialine caves on two islands in the Bahamas. Bottom center: A close-up of a grasping disc on Cryptocorynetes haptodiscus. Bottom right: A ventral view of the head of Godzillius robustus showing the raptorial mouthparts —this remipede is known only from North Caicos Island in the Caribbean.

The extinct group of Remipedia are the Enantiopoda, represented by two fossil forms: Tesnusocaris goldichi, described in 1955⁵, and Cryptocaris hootchi⁶, described in 1991. Tesnusocaris was found in the lower Pennsylvanian Tesnus Formation of Texas. Cryptocaris is from the famous middle Pennsylvanian Mazon Creek faunas of Illinois.

Mouth area of a typical remipede.

Resources

1. Yager, J. 1981. Remipedia, a new class of Crustacea from a marine cave in the Bahamas. Journal of Crustacean Biology 1:328-333.
2. Carapelli, A., P. Liò, F. Nardi, E van de Wath, and F. Frati. 2007. Phylogenetic analysis of mitochondrial protein coding genes confirms the reciprocal paraphyly of Hexapoda and Crustacea. BMC Evolutionary Biology 7(suppl 2):S8.
3. Strausfeld, N.J., C.M. Strausfeld, R. Loesel, D. Rowell, and S. Stowe. 2006. Arthropod phylogeny: onychophoran brain organization suggests an archaic relationship with a chelicerate stem lineage. Proceedings of the Royal Society B 273(1596):1857-1866.
4. Koenemann, S., F.R. Schram, M. Hönemann, and T.M. Iliffe. 2006. Phylogenetic analysis of Remipedia (Crustacea). Organisms Diversity & Evolution 7(1):33-51.
5. Brooks, H.K. 1955. A crustacean from the Tesnus Formation of Texas. Journal of Paleontology 29:852-856.
6. Emerson, M.J., and F.R. Schram. 1991. Remipedia, part 2: paleontology. Proceedings of the San Diego Society of Natural History 7:1-52.
    

Original page created by Ben Waggoner 1995 with further modifications by Amy Lesen 8/2002; updated text content by Joey Pakes and design modification by David Smith 6/2008. Bahamas remipede photo © Dennis Williams and Jill Yager; all other remipede photos © Jill Yager, Antioch College.