No abstract

Tetrastemma Ehrenberg, 1828, is one of the most speciose (~110 spp.) genera within the phylum Nemertea, comprising marine monostiliferans generally having four eyes. Monophyly of Tetrastemma remains open to question, having been tested to date only with 18S rRNA gene sequences targeting 13 species. Here, we examine the clade Tetrastemma with additional gene markers (18S rRNA, 28S rRNA, histone H3, 16S rRNA, and cytochrome c oxidase subunit I genes) and OTUs (66 specimens representing 53 species in Tetrastemma), along with a taxon sampling covering the entire Eumonostilifera. Our analysis revealed that Tetrastemma (a) as non‐monophyletic (as were Tetrastemmatidae) (b) contains a major clade consisting of four geographically cohesive subclades, whereas (c) Tetrastemma arcticum Uschakov, 1926; Tetrastemma bilineatum Coe, 1904; Tetrastemma vittigerum (Bürger, 1904); Tetrastemma wilsoni Coe, 1943; and two specimens tentatively identified as Tetrastemma sp. occur outside this major clade, and iv) the three species of Psammamphiporus Gibson, 1989, and Quasitetrastemma Chernyshev, 2004, nest within in the major Tetrastemma clade. Thus, we (a) synonymize Psammamphiporus and Quasitetrastemma with the senior name Tetrastemma and (b) establish Arctostemma gen. nov. for T. arcticum to yield Arctostemma arcticum (Uschakov, 1926) comb. nov.

No abstract

Both odd-and even-year pink salmon populations were sampled during the spawning runs in Firsovka and Bakhura rivers on Sakhalin Island. Four collections of 30 fish spaced at 2-week intervals were taken from each river in 2 consecutive years. Four restriction endonucleases were used to examine 2·15% of the mitochondrial genome. Eighteen variable sites and three types of insertion defined 37 haplotypes among 449 fish. Heterogeneity tests showed highly significant differences among temporal collections taken in the odd year from Bakhura River, and no significant differences among temporal collections from the other three spawning runs. However, probabilities of homogeneity among temporal collections were low in all tests, and an integral estimate of the probability of homogeneity for the total set of tests was less than 0·001, indicating highly significant overall temporal heterogeneity. Analysis of molecular variance (AMOVA), revealed that a small portion of the variance was distributed among temporal collections, and small ST values that differed significantly from zero only in the odd-year population in Bakhura River. Temporal differences in spawning are probably adapative, and allow greater productivity in areas of high spawning densities. 1999 The Fisheries Society of the British Isles

A new species of the genus Tetrastemma Ehrenberg, 1831, T. freyae sp. nov., is described and illustrated from Hawaii and India. The description is based on light microscopy examination of the external and internal morphology, as well as on two gene markers (cytochrome c oxidase subunit I and histone H3 DNA).