No abstract

We report the discovery of an enigmatic, small eel-like fish from a 35 m-deep fringing-reef cave in the western Pacific Ocean Republic of Palau that exhibits an unusual suite of morphological characters. Many of these uniquely characterize the Recent members of the 19 families comprising the elopomorph order Anguilliformes, the true eels. Others are found among anguilliforms only in the Cretaceous fossils, and still others are primitive with respect to both Recent and fossil eels. Thus, morphological evidence explicitly places it as the most basal lineage (i.e. the sister group of extant anguilliforms). Phylogenetic analysis and divergence time estimation based on whole mitogenome sequences from various actinopterygians, including representatives of all eel families, demonstrate that this fish represents one of the most basal, independent lineages of the true eels, with a long evolutionary history comparable to that of the entire Anguilliformes (approx. 200 Myr). Such a long, independent evolutionary history dating back to the early Mesozoic and a retention of primitive morphological features (e.g. the presence of a premaxilla, metapterygoid, free symplectic, gill rakers, pseudobranch and distinct caudal fin rays) warrant recognition of this species as a ‘living fossil’ of the true eels, herein described as Protanguilla palau genus et species nov. in the new family Protanguillidae.

No abstract

No abstract

Barfin flounder and spotted halibut have been selected as target species for stock enhancement in Japan. Understanding the genetic condition of the wild stock is a principal requirement in any stock enhancement program. The genetic variability of barfin flounder and spotted halibut, and the population structure of spotted halibut were evaluated using microsatellite DNA markers (msDNA) and the control region of the mitocondrial DNA (mtDNA). Barfin flounder and spotted halibut showed high genetic variability at the msDNA level. Barfin flounder A was 16.7 and H e was 0.860; spotted halibut A n ranged from 7.7 to 10.2 and H e ranged from 0.710 to 0.774. At the mtDNA level, high haplotype (h = 0.922) and low nucleotide (π = 0.002) diversities were observed for barfin flounder; however, low haplotype and nucleotide diversities (h = 0.603-0.620 and π = 0.001-0.002), and very low haplotype and nucleotide diversities (h = 0.193 and π = 0.0003) were observed for spotted halibut in the north and south locations, respectively. Slight genetic differentiation among spotted halibut sampling locations was observed from the msDNA. MtDNA analyses showed genetic differentiation between north and south locations, but not within them. The designation of north-specific and south-specific management units in the future stock enhancement activities of spotted halibut is recommended.

The importance of the surf zone as a nursery ground for larval and juvenile fishes has been widely recognized, however the zone has yet to be studied in Mauritius. Recently, the coastal area of the island has been increasingly affected by human activities, especially by tourism. We collected fish samples with a hand pulled seine net during the period of August 2001 to March 2003 to clarify the fish fauna and the dynamics of fishes in the surf zone. Two sampling sites adjacent to river mouth areas and one sampling site adjacent to a mangrove area were selected for comparison of fish fauna in relation to environmental conditions. A total of 9,429 fish larvae and juveniles, representing at least 112 species from 48 families were collected. The abundant species were hardyhead silverside, Atherinomorus lacunosus, bluespot mullet, Valamugil seheli, and Ambassis spp., each contributing 16.2, 12.4, and 11.8% of the total number of individuals, respectively. Estuarine species dominated in the surf zone adjacent to the river mouth areas. Species composition and diversity changed seasonally. The number of fish increased during the rainy season. Species diversity increased at the turn of the seasons from the dry season to the rainy season. We conclude that species composition in each site was affected by environmental factors, such as the scale of the flux from the rivers, which is related to the precipitation. The results indicated that freshwater from the river is a trigger to aggregate larvae and juveniles in the surf zone.

The Sebastes Cuvier, 1829 subgenus Pteropodus Eigenmann and Beeson, 1893 includes six species from the northeastern Pacific Ocean (NEP) and four species from the northwestern Pacific Ocean (NWP). Several NEP species assigned to other subgenera are similar to NEP Pteropodus species. Restriction site variation in the mitochondrial NADH dehydrogenase subunit 3 and 4 genes and the 12S and 16S ribosomal RNA genes were used to evaluate their relationships. Phylogenetic reconstruction showed that six NEP species of Pteropodus formed a monophyletic group that also included three NEP species currently assigned to other subgenera: Sebastes atrovirens (Jordan and Gilbert, 1880) (subgenus Mebarus Matsubara, 1943) and Sebastes auriculatus Girard, 1854 and Sebastes dalli (Eigenmann and Beeson, 1894) (both subgenus Auctospina (Eigenmann and Beeson, 1894)). The small average nucleotide divergence (0.0124 per nucleotide) observed among members of this group of species was similar to that observed among species of the monophyletic subgenus Sebastomus Gill, 1864 (0.0089 per nucleotide). The NWP species of Pteropodus did not cluster with their NEP consubgeners but, generally, were similar to other NWP species. We recommend that S. atrovirens, S. auriculatus, and S. dalli be included in subgenus Pteropodus with the other NEP species and that the NWP species of Pteropodus be removed from the subgenus. Our results indicate that the morphological characteristics used to distinguish species often may not be useful for phylogenetic analysis.

No abstract