Parental care behavior in the wood-boring isopod Sphaeroma terebrans

Several wood-boring crustaceans engage in parental care, i.e., juveniles remain in the parent’s dwelling after having hatched from the female’s brood pouch. It has been hypothesized that small juveniles are not capable of burrowing into wood, and therefore rely on parental assistance during their early life. In this study, I examined parental care in the wood-boring isopod Sphaeroma terebrans, which inhabits burrows in aerial roots of the red mangrove Rhizophora mangle. Offspring remained in the maternal burrow for up to 40 days after hatching from the female’s brood pouch. The female remained in her burrow throughout this time. Most juveniles started burrowing to the outside from within the female’s burrow but some left the mother’s burrow. The latter started to build their own burrows in the immediate vicinity of the natal burrow on the maternal root rather man emigrating from it. Small orphan juveniles that were experimentally separated from their mothers were able to build their own burrow on aerial roots. However, they required several days to establish a burrow, whereas small sub-adults that had already reached independence built a new burrow within 48 hours. These results suggest that parental care in wood-boring crustaceans provides protection for small offspring during their early life stages when they cannot efficiently bore themselves. Thus, woody substrate may have contributed to the evolution of parental care in two ways: 1) It constitutes a stable microhabitat allowing for a moderately long (~ 40 days) persistence of parent-offspring groups, and 2) These isopods, as well as other crustacean borers, become efficient borers late in life, therefore requiring parental protection during the early phase of their life..