Reproduction of the deep-water shrimp Aristeus antennatus (Decapoda: Dendrobranchiata)

Abstract

Morphology, structure, and function of the reproductive system of the shrimp Aristeus antennatus (Risso, 1816) were investigated using light microscopy and scanning electron microscopy. Monthly samples were taken by trawling on the continental slope (400 to 800 m) of the northwestern Mediterranean during 1984, 1985, 1986 and 1989. Sexual characteristics, thelycum, petasma, genital apertures, appendix masculina, and rostrum were considered and possible functions in reproductive behaviour are suggested. The roles of tesis, proximal and medial vas deferens regions, and terminal ampulla in hemispermatophore formation were assessed. During mating hemispermatophores join and form a compound spermatophore. The sperm mass in the compound spermatophore was surrounded by 5 layers secreted along the vas deferens duct. Open-type thelycum species with external mating and fertilization such as A. antennatus need to develop a complex spermatophore to protect the sperm mass. The structure of sperm was examined for the first time in A. antennatus. The peculiar morphological features of this immobile sperm differ considerably from sperm cells of other decaphod groups. It is suggested that this spermatophore formation and sperm structure have taxonomic and phylogenetic value. Spermatogenesis and spermatophore formation divided male gonad development and functionality into 3 stages. Oogenesis can be divided into 6 stages taking into consideration cytological changes in the oocytes. A key to macroscopically identify sexual stages of gonad development which can be used externally on fresh or live specimens is proposed based on the study of gametogenesis and gonad and sexual characteristic development and function.