CLAMP, J.C.; North Carolina Central Univ.: The phylogenetic position of Lagenophrys (Protista, Ciliophora, Peritricha) inferred from the sequence of the gene for 18S small subunit rRNA

Lagenophrys is a genus of peritrich ciliates in which the cell body and life cycle are highly modified to accommodate existence as ectosymbionts of a wide variety of crustaceans. On one hand, the morphology of the peristome (expanded oral area) of Lagenophrys suggests a phylogenetic relationship to the family Operculariidae; however, Lagenophrys is so different from operculariids with respect to other morphological characteristics that this relationship cannot be supported well on those grounds alone. On the other hand, sequencing genes of Lagenophrys spp. to obtain molecular data for phylogenetic analysis presents special challenges because the organisms are surrounded by a protective lorica that is cemented firmly to the exoskeleton of the crustacean host, making separation from the host almost impossible. Moreover, the cell body of Lagenophrys is extremely flat, which adds to this difficulty. Normally, Lagenophrys spp. abandon a host before its ecdysis by undergoing binary fission and then exiting their loricae, but individuals occasionally fail to react to the host�s impending molt and remain behind. A sample of the common grass shrimp Palaemonetes pugio, a frequent host of Lagenophrys eupagurus, was collected from the Pamlico River in eastern North Carolina during December, when they are heavily infested with the ciliates. This created a greater possibility that each freshly molted exoskeleton would harbor at least a few individuals of L. eupagurus. DNA was extracted from specimens of L. eupagurus on fresh molts of P. pugio and the 18S small subunit rRNA gene was sequenced successfully. The molecular evidence suggests that Lagenophrys is indeed most closely related to operculariid peritrichs, confirming morphological results.