Abstract:
St. virei has been bred in the laboratory for many years (1960-1974). Most of the St.v.hussoni were captured in karstic waters, near the Moulis subterranean laboratory. Some St.v.virei from the Padirac sink-hole; St.v.buchneri from Cantabrian caves; St.v.boui and St.v.virei from phreatic waters; and St.buili and St.breuili have also been bred. Since Stenasellids are unable to swim, very low aquariums are used, with a bed of cave clay, some calcareous stones, dead wood and dead elm tree leaves. Little depth of water is necessary. Stenasellus was originally carnivorous, being able to capture and devour living prey, such as Chironomid larvae, but the populations of cave waters have developed a different diet: silt, guano, plant remains..., because they have been often insulated from their original phreatic biocenosis. Nevertheless, the existence of cannibalism among them points out that the predatory behaviour has not completely disappeared. Adult St.virei can be fed with Cerophyl. Some observations on the burrowing activity and on the reactions to light, temperature and salt water have been made. All postmarsupial molts of Stenasellus occur in two steps (isopodian molts). The intramolt is extremely long (from 83 h 30 mi for the first molt of the free young), to 8-12 days, for the adult male and female, 14 days for female reproductive molts and 16-21 days for the molts of aged or senile individuals). The intermolts last from 2 1/2 months (first intermolt of the free young), to 9-12 months (non-reproductive ones of the adult) and 12-18 months (average: 15-16), for reproductive 9 intermolts. The normal lifespan of karstic subspecies of St.virei and related species must be estimated as 12 years (males) and 15 years (females). All these values are 10-20 times longer than these of an epigean Asellid of the same size (Asellus aquaticus). The reproductive cycle has been studied. The adult female is larger than the male. There is no precopulatory pairing ("nuptial ride"d 6-7 years or more, fur the female. In the juvenile male, the morphogenesis of I and Il pleopods takes place normally on intermolts 4-9 and lasts 3 years or more. On intermolt 10, it seems that the male is able to mate.