Osmotic induction of stress proteins in nemerteans

DNA Taxonomy of Paranemertes (Nemertea: Hoplonemertea) with Spirally Fluted Stylets

Of the 14 nominal species that are now or have ever been assigned to the genus Paranemertes Coe, 1901 , four have been reported to have stylets with a spirally fluted or braided appearance. Although differentiation in color patterns has been documented among species/populations, these nemerteans share similar external characters. Using the sequence datasets of mitochondrial cytochrome c oxidase subunit I (COI), 16S rRNA, and nuclear 28S rRNA genes of specimens from 14 localities of Canada, USA, Russia, Japan, and China, we analyzed the genetic differentiation and reconstructed the phylogenetic trees for these nemerteans. In conjunction with the external characters, we discuss their taxonomy and species delimitation. An analysis based on COI dataset showed high genetic variations among populations and even among worms from the same geographic area. The analyzed 111 individuals were assigned into seven networks by statistical parsimony analysis. The inter-network uncorrected p-distances ranged from 0.044 to 0.172 and the mean intra-network uncorrected p-distances varied from 0.001 to 0.005. With the exception of two networks that contain specimens from the East China Sea, all networks were well-supported by the results of Bayesian and neighbor-joining analyses on the COI data. Phylogenetic trees based on 16S rRNA and 28S rRNA datasets were basically similar to the COI trees, but specimens in some networks were merged into larger clades. Present molecular analyses support the validity of P. sanjuanensis and the synonymization of P. cylindracea with P. peregrina. Nemerteans previously recorded as P. peregrina may contain several species and sympatric speciation might have been occurred in this nemertean group.

Preliminary Report of a Neurokinin-Like Receptor Gene Sequence for the Nemertean Paranemertes sp

Tachykinins (TKs) are a family of neurotransmitters that function as signaling molecules for such processes as maintaining homeostasis, regulating stress response, and modulating pain. TKs require the expression of at least one of three receptor subtypes: Neurokinin Receptor-1 (NKR-1), Neurokinin Receptor-2 (NKR-2), or Neurokinin Receptor-3 (NKR-3). We have isolated and cloned a portion of a gene coding for a tachykinin-like receptor from the nemertean Paranemertes sp. This 488-bp portion contains a short 101-bp segment that shares 85% similarity to the mouse substance-K receptor in Mus musculus and 83% similarity to the moth neuropeptide receptor A24 in Bombyx mori. Translated homology analysis aligning the coding sequence with the initial cytoplasmic carboxyl terminus of numerous G-protein coupled neuropeptide receptors also revealed 73% similarity to B. mori neuropeptide receptor A24. Our finding is the first report of a sequence amplified from Paranemertes sp. that may code for a small portion of a G-protein-coupled neuropeptide receptor with significant similarity to the TKR family, particularly the NKR-3 receptor isoform. This novel finding may open new avenues into exploring the role of tachykinin and its receptor in nemertean neurophysiology.