Phylogenetic Relationships of Five Species of the Amphipod Genus Gammarus

The phylogenetic relationships of five amphipod species of the genus Gummarus: G. oceanicus, G. locusta, G. salinus, G. zaddachi and G. duebeni are presented based on starch gel electrophoresis of 12 enzymes determined by 17 loci. The five species separate into three groups: G. locusta and G. duebeni each represent a distinct group while G. oceanicus, G. salinus and G. zaddachi together form a third group. This grouping results when the number of diagnostic loci, as well as when genetic distance between species pairs, are considered. The results compare well with morphological and, to some extent, ecological data.     

Origin and Differentiative Capacities of Cells in the Blastema of the Regenerating Salamander Limb

The salamander limb regenerate develops from a mesenchymatousbud of cells called the blastema. This review briefly considersthe local origin and major features of blastemal cells and thendiscusses their role in the histogenesis of the regenerate.The capacity of blastemal cells to form the various cell typesof the regenerate is first considered in general terms, withthe discussion focusing on three major alternatives: blastemalcells form (a) cartilage only, (b) connective tissues only,or (c) essentially all internal tissues of the regenerate. Thedifferentiative properties of blastemal cells originating fromknown cell types are then considered in detail. Cartilage isof particular interest in this regard, because it has been utilizedas a pure cell type. Results from the study of mixed tissues,including muscle and connective tissue of the fin, are alsopresented. Information gained from the study of known cell typesparticipating in regeneration is discussed in terms of the mechanismsresponsible for the stability of cellular differentiation andin terms of the flow of cells from stump tissues into the regenerate.     

Sex-specific provisioning behaviour in a monomorphic seabird with a bimodal foraging strategy

Sexual differences in foraging and provisioning behaviour have been observed in several size-dimorphic seabird species. These differences are usually thought to be driven by size-related mechanisms such as the ability to compete for food or defend the nest. However, recent studies on monomorphic species suggest that sexual differences in foraging may arise independently of size. Selective forces driving sex-specific patterns are poorly known but essential to understand parental strategies. In this study, we examine sex differences in the provisioning behaviour of a monomorphic species, the Little Auk Alle alle . Using automated recording systems during two consecutive seasons at two colonies, we found that both sexes used a bimodal foraging strategy in which they regularly alternated single foraging trips of long duration with a cycle of several short-trips. The duration of long-trips was substantially longer in females than in males, and the sexes differed in the number of short-trips they performed in between long-trips, resulting in male-biased provisioning rates in both years. In species with a bimodal foraging strategy, long-trips have been interpreted as self-feeding trips to replenish body reserves. Our results therefore suggest that female Little Auks allocate more time to self-maintenance at the cost of chick provisioning, possibly due to different energetic constraints of the sexes prior and/or subsequent to chick-rearing. Our findings contribute to accumulating evidence that sex-specific foraging patterns may be widespread in sexually size-monomorphic seabird species.