Geometric morphometric analyses were conducted on cultured populations of five Micrasterias species (M. crux-melitensis, M. papillifera, M. rotata, M. thomasiana, M. truncata). The patterns in the morphological variation measured using the morphospaces spanned by a PCA of morphometric data for individual populations were compared. In addition, the 18S rDNA sequences of these species are reported. The phenetic comparisons demonstrated the overall great similarity of morphometric indicators extracted from isolated polar lobe data and 18S rDNA genetic distances, and also indicated that the morphometric data of complete semicells were less well correlated with 18S rDNA distances. The phylogenetic analysis revealed clustering of the Micrasterias sequences into two clades, which correspond to qualitative patterns in the morphological variation of isolated polar lobe data. We propose that patterns of variation in the polar lobes of Micrasterias should be used in phenotype analyses of morphologically closely similar or cryptic species.
Lake Biwa consists of a large, deep north basin and a small, shallow south basin, and the body weights of bluegill Lepomis macrochirus in the north basin tend to exceed those in the south basin. To elucidate the cause of this phenomenon, the physical characteristics of the fish in the two basins were compared. The fish in the north basin had larger gonads and stomachs than did the fish in the south basin, but the contributions of these organs to the body weight were very small. The body weights of the fish in the north basin still exceeded those in the south basin after the subtraction of the weights of the gonad and stomach. Bluegill in the north basin had deeper
bodies than those in the south basin. The heavier body tissues of bluegill in the north basin appear to be an adaptive response to the colder environment. Given the flourishing of largemouth bass Micropterus salmoides
in the littoral zone in the north basin, the deeper bodies of bluegill there may contribute to their increased survival rate by reducing their vulnerability to predation by largemouth bass.
The pimelodid fish Rhamdia quelen (Quoy et Gaimard, 1824) in South America harbours two species of proteocephalid cestodes, Proteocephalus bagri Holcman-Spector et Mañé-Garzón, 1988 and P. rhamdiae Holcman-Spector et Mañé-Garzón, 1988. These species are redescribed based on a detailed morphological study, supported by multivariate analysis (principal component analysis). Features distinguishing these species are: (1) the shape of proglottides, (2) the mean number of testes, (3) the topography of vitelline follicles, (4) the thickness of internal longitudinal musculature, (5) the mean number of uterine branches, (6) the ratio of cirrus pouch length to proglottis width, (7) the shape of ovary in mature and gravid proglottides and (8) the genital pore position in mature proglottides. The specific status of P. bagri and P. rhamdiae is confirmed and neotypes of both species are designated.