淡水産スジエビ(Palaemon paucidens)の小触角に見られる性的2型について

概要

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The outer flagellum of the antennule in the freshwater prawn, Palaemon paucidens, is bifurcated, with the inner branch bearing 8-13 sensory hairs, about 400μ long, arranged in two rows on the ventral side of each segment (Figs.1 and 2). The length of the inner branch, the number of its constituting segments, and the number of sensory hairs were compared among 582 specimens collected in September. It was found that both the length of the inner branch and the number of segments were larger in males than in females (Fig.3, A and B). The ratio of length of the inner branch to that of the carapace was about 30-35% in females of different sizes, whereas the value was about 55% in fully grown males(Fig.3, C). The number of sensory hairs increased as the animals grew (Fig.3, D); 408-456 hairs per antennule in fully grown males (13-14mm in carapace length), 146-194 hairs in females of the corresponding size, and 228-308 hairs in fully grown females (18-19mm in carapace length). The sexual dimorphism such as this welldeveloped sensory (possibly chemoreceptive) organ in mature males provides a circumstantial evidence for the existence of sex pheromone in this species.
1972-09-25