Some life-history parameters of the non-native amphipod Platorchestia platensis (Talitridae) in a warm temperate South African estuary

Density, population structure, growth, mortality and aspects of reproduction of the non-native amphipod Platorchestia platensis were studied for 20 consecutive months (October 2008 to May 2010) in the supralittoral wrack of the Knysna Estuary, South Africa. Amphipod density varied over the sampling period with the lowest numbers recorded in summer (January and February). Ovigerous females with embryos, and juveniles were found in most months with peaks in recruitment found in both April and October, suggesting that in Knysna this species is a biannual breeder. Average female size was significantly greater in winter, with larger females tending to brood more embryos. The largest adults (13.5 mm total length) were always male although the monthly sex ratio was nearly always female biased. Growth rate estimated from a cohort analysis was about 1 mm per month and monthly survival about 69%. The ability to reproduce all year round may be one reason why this introduced species has become established within this warm temperate estuary

Comparative gastric anatomy of Cricetomys gambianus and Saccostomus campestris (Cricetomyinae) in relation to Mystromys albicaudatus (Cricetinae)

The gastric anatomy of two African cricetomyines is described and compared with that of the only African cricetine. The stomach of C. gambianus is more specialized than that of S. campestris and shows many parallels with that of M. albicaudatus. Both cricetomyines possess an oesophageal groove system which is absent from the cricetine, while C. gambianus and M. albicaudatus have forestomach papillae supporting vast colonies of symbiotic bacteria that are not found in S. campestris. Specializations in gastric anatomy are discussed in relation to phylogeny, using taxonomy to distinguish between apomorphic and plesiomorphic characters, convergence and divergence. Complex gastric adaptations can be explained only by increased digestive efficiency, while the symbiotic association with numerous autochthonous bacteria implies-revolutionary adaptation