Apseudes nipponicus, Shiino, 1937

Kakui, Keiichi & Hiruta, Chizue, 2023, Differential masculinization of the chelipeds in two simultaneously hermaphroditic Apseudes tanaidaceans (Crustacea: Malacostraca), Zoologischer Anzeiger 305, pp. 23-27 : 25

4.1. Apseudes nipponicus is simultaneously hermaphroditic

Our study confirmed that Apseudes nipponicus is an SH species; it is the fourth tanaidacean for which the SH condition has been confirmed both externally and internally. It is unknown whether this species can self-fertilize, as does Apseudes sp.

In A. nipponicus , we found increases in the widths of the chelipedal carpus and chela relative to body size to be diphasic, with larger individuals showing a higher rate of increase. These allometric changes started at a body size roughly equivalent to that of the smallest preparatory individual.

Large individuals showed both ventral spiniform processes on the chelipedal carpus and a dorsal triangular process on the fixed finger, but these structures did not appear simultaneously: the process on the fixed finger appeared first, followed by the processes on the carpus. All ovigerous individuals bore processes on both the carpus and fixed finger.

Masculinization of the cheliped in A. nipponicus occurred in approximately three stages: (1) formation of the process on the fixed finger, (2) widening of the carpus and chela, and (3) formation of four processes on the carpus ( Fig. 3 ).

Figures

Fig. 3. Schematic drawings showing stages of chelipedal-masculinization and the corresponding reproductive stages in A. nipponicus and Apseudes sp. Arrows, formation of the process on the fixed finger; bidirectional arrows, widening of articles; arrowheads, formation of four processes on the carpus. OL, oostegite lacking. *, including preparatory individuals that ovigerous individuals molted and again became.