Meeting Abstract

1.9  Jan. 4  Phylogeny and co-evolution in Carcinonemertidae (Nemertea), ecto-symbiotic egg-predators on decapod crustaceans. SANTOS, C.; ROE, P.; SADEGHIAN, P.; SUN, S.; NORENBURG, J.L.*; Smithsonian Institution National Museum of Natural History, Washington, DC; California State University � Stanislaus, Turlock, CA; Santa Barbara Museum of Natural History, CA; Ocean University of China, Qingdao; Smithsonian Institution National Museum of Natural History, Washington, DC norenburgj@si.edu

Carcinonemertid worms are Monostilifera, i.e., the proboscis is armed with a single stylet. Features of both proboscis and body structure, as well as of reproductive biology, can best be interpreted as evidencing significant modification that befits a quasi-parasitic, egg-sucking life-style. Eleven species were recognized until recently, from about 65 recorded host species. Our recent, relatively limited surveys have increased the number of known host species to about 100, including 20 brachyuran crab families, and yielded 10-20 presumptive new worm species. Previous diversity appears significantly underestimated. A phylogeny for carcinonemertids from 30 host species, based on about 2,300 nucleotides of sequence data from mt COI, mt 16S rDNA, and nuclear 28S rDNA, supports the hypotheses that Carcinonemertes s.s. is monophyletic and that of Thollesson & Norenburg (2003, Proc. Royal Soc., Lond. 270:407-415) that it is the sister group to the remaining approximately 400 known species of Distromatonemertea (Monostilifera minus the Cratenemertidae). The implication is that extant Carcinonemertes represent an ancient radiation. The maximum genetic divergence in the data is 23.4%, compared to about 30% for the Monostilifera. Some Carcinonemertes clades appear co-evolved with host clades, especially among the portunids, but there are significant exceptions. Surprisingly, the worm species that infests the largest number and range of host species also is among the most derived, rather than basal.