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Abstract PHYLOGENETIC STUDIES OF CARCINONEMERTES (NEMERTEA), EGG PREDATORS OF DECAPOD CRUSTACEANS. Cynthia Santos and Jon Norenburg Over the course of about 150 years 11 species of Carcinonemertes
were described, spanning about 60 decapod crustacean host species,
on which the worms live as obligate ectosymbiont egg-predators.
Over the last five years of fieldwork we have identified about another
60 decapod crustaceans as hosts, including well-studied species
such as the Florida spiny lobster and stone crab. We have described
three new species of Carcinonemertes and have several more
new species description in progress. Others recently found the first
Carcinonemertes from several deep-sea, vent-associated
crab species. Carcinonemertes worms, like many organisms
with highly specialized life-styles, are greatly simplified in anatomical
structure compared to other nemerteans; hence, distinguishing species
is very difficult and often based on feature that would be accorded
little significance for other nemerteans. The type species, C.
carcinophila, has been ascribed to 33 of the 60 host species
mentioned above, whereas C. epialti is known from 11 host
species, both spanning a wide range of crustacean families. Our
research program was motivated by a desire to understand the actual
diversity of these worms, including an assessment of how host specific
they are. Preliminary results based on phylogenetic analysis of
DNA sequence data from three genes for worms from about 40 host
species suggests either a very early or a very rapid radiation of
the carcinonemertid group with respect to other hoplonemerteans,
and much greater diversity than had been appreciated from morphology.
Some species appear to be relatively host specific and others quite
generalist. Sample size for host diversity still is relatively low.
There is a relatively weak bias toward lineage co-evolution of hosts
and worms. We suspect that elements of host life history are major
selective factors in the Carcinonemertes radiation, but
details of life history are unknown or obscure for many host species. PHYLOGENETIC STUDIES OF OTOTYPHLONEMERTES, MARINE INTERSTITIAL NEMERTEANS Sónia Andrade and Jon Norenburg Ototyphlonemertes is a group of 21 recognized species
and at least 30 more undescribed morphotypes that occupy the pore
space of coarse marine sediments and share a number of features
considered to be adaptations to that specialized mode of existence.
The most conspicuous of these features is a pair of cerebral statocysts,
which is a synapomorphy for the genus. There are two groups recognizable
based on coordinated features of the statocyst and proboscis stylets
– one group has oligogranular statoliths and smooth stylets,
the other has polygranular statoliths and spirally sculpted stylets.
However, monophyly of the genus or either of these groups had not
been convincingly tested. The genus also can be divided into 6 “phylomorphs”
based on combinations of morphological features. The probability
of convergent morphologies must be considered as significant, because
the features that characterize the putative lineages also can be
interpreted as having been strongly selected by the specialized
mesopsammic habitat. Our goal is testing monophyly of the putative
lineages, as well as examining species boundaries. Specimens were
collected from much of the world, with particular focus on the Western
Atlantic Ocean, Caribbean Sea and Eastern Pacific Ocean. We present
results of phylogenetic analysis of sequence data from three genes
for about 50 morphs, representing each of the 6 phylomorphs. Our
results support monophyly of the genus but not reciprocal monophyly
of the two groups defined by statolith structure. In addition to
a phylogeny, we have sufficiently fine-grained data for some morphs
to begin examining phylogeography.
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