Size at Maturity and Partial Parasitic Castration

Male specimens with a carapace length of less than 9 mm invariably have a petasma with the various lobes and crochets incompletely developed. The immature petasma illustrated (Fig. 4) is from a specimen with a carapace length of 8 mm and represents an even earlier stage than that figured by Holthuis (1952). Those specimens with carapace lengths of 10 mm and more always have, with certain exceptions mentioned below, mature petasma. Thus males, and we must assume, females, usually mature at a carapace length between 9 and 11 mm.

Many specimens have small or large larval nematode worms loosely coiled in the posterodorsal portion of the cephalothorax immediately beneath the carapace. Collection VUZ 25 had one so parasitised out of 14, collection VUZ 52 had 6 parasitised out of 20 and collection VUZ 84 had 5 out of 15, making a total of 12 of these 49 specimens parasitised (approx. 24%). Specimens with such a nematode in the area of the gonads have the dorsal mid-line of the carapace characteristically weakly convex, and males, at least, show partial parasitic castration. Thus no parasitised male seen had a mature petasma, even specimens with carapace lengths of 14 mm had this organ small and still relatively undeveloped.