Courtship and sperm transfer in Charinus neocaledonicus Kraepelin, 1895 and Charinus australianus (L. Koch, 1867) (Arachnida, Amblypygi, Charinidae)

The Charinus australianus group is a well-defined species group characterised by rounded, cushion-like female gonopods. Before the present study, the morphology of the gonopods and their function have not been understood. This paper describes courtship behaviour, spermatophore morphology, and the morphology of the female genitalia of Charinus neocaledonicus Kraepelin, 1895 and C. australianus (L. Koch, 1867). Courtship behaviour, though different in details, is similar to that of many other species. The spermatophores are large and soft and carry very small sperm packages, each with a short stalk. After sperm transfer, the spermatophore may be eaten by the female. The spermatophore thus transfers not only spermatozoa but also nutritious paternal investment to the female. Each female gonopod is equipped with a seminal receptacle consisting of an atrium and a spacious inner receptacle. The cover of the atrium can be elevated by high blood pressure and pulled back by a group of muscles attached to the inner part of the receptacle. The female probably picks up the sperm packages with the atria of her receptacles. The observations are compared to those on other amblypygids, and the evolution of different types of spermatophores and of gonopods with seminal receptacles is discussed.