Moulting and growth in Pagurus traversi and P. novizealandiae (Decapoda: Anomura: Paguridae): The effects of neighbours

Abstract

This study, of Pagurus traversi and P. novizealandiae, is the first to investigate moulting and growth of New Zealand hermit crabs. These 2 sympatric intertidal species exhibit a high degree of overlap in the type of shell they occupy. Moulting is a hazardous event in the life of a hermit crab and in both species it is asynchronous and occurs more frequently at night when animals are kept alone. However, in the presence of conspecific neighbours, P. traversi moulted more frequently during the daytime, although the probability of moulting was significantly reduced. Only the moulting of small (CL < 4 mm) P. novizealandiae was significantly reduced by conspecific neighbours. Moulting probability decreased with increasing size. Moult increments were independent of pre‐moult size for both species and ranged from 29% for small animals to 2.9% for large animals. Male and female moult increments of P. traversi and P. novizealandiae were not significantly different. Both species had similar moult increments. Growth curves were derived for each species and these suggest that P. traversi are fast‐growing, shorter‐lived, small hermit crabs, whereas P. novizealandiae are slower growing, longer‐lived, large hermit crabs. Median and maximum life spans are: P. traversi males — 1.5, 4.9 y, females — 0.4, 2.2 y; P. novizealandiae males — 1.6, 10.9 y, females — 1, 6.5 y.

Keywords:

• Pagurus traversi
• Pagurus novizealandiae
• moulting
• growth
• hermit crab