Shelter preference in Macrobrachium spp. with reference to aquaculture

Abstract

Macrobrachium malcolmsonii, M. nobilii, and M. lamarrei were used to investigate their preferences among three substrate colors (dark brown, black, and light brown), shelter type (black tile and black PVC pipe), color (black and brown tile), and diameter, and regarding intra- and inter-species habitation. Both M. lamarrei and M. malcolmsonii preferred dark-brown substrate, while M. nobilii preferred black. The choice of shelter type was monitored by time spent by each species in a black PVC tube or in a black tile. Within a 24-h period, M. malcolmsonii spent a greater amount of time (60.5%) within the black tile, while M. nobilii spent more time (71%) inside the black PVC tube. M. lamarrei always occupied an open area and thus was discarded from further experiments. If we consider daytime and nighttime separately, both species spent more time within the black tile during the day than during the night. Choice of shelter color was tested with black and brown shelters of identical size; both species exclusively preferred the black. Between the species, despite the smaller body size both male and female M. nobilii succeeded in evicting M. malcolmsonii, suggesting a stronger shelter affinity. When competing for shelter within the same species, a male was more dominant than a conspecific female and juvenile. Similarly males of both species allowed conspecific juveniles to cohabit for about 16% of the time. Male M. malcolmsonii also allowed cohabitation of a female for 31.2% of the time, unlike the male M. nobilii, which did not allow female cohabitation at all. Both species preferred shelters that were adjusted to their meral spread as opposed to their carapace width. The possibility of taking meral spread as a taxonomic character was also indicated. The study also found a linear relationship between exuvium weight and shelter affinity among the three species. A lower ratio indicated a higher shelter affinity. The exuvium/total body weight ratio confirmed the shelter affinity, which was ranked as M. nobilii (0.275) < M. malcolmsonii (0.312) < M. lamarrei (0.426).