Larval growth, development and duration in terrestrial hermit crabs

We investigated patterns of larval growth and development in terrestrial hermit crabs of the family Coenobitidae (genera Coenobita and Birgus).Larvae of 5 species (C.cavipes, C. purpureus, C. rugosus, C. violascens, and B. latro) were cultured individually at ~28°C, and their moulting, growth and developmental duration were analysed in conjunction with published data for coenobitid species (C.brevimanus, C. cavipes, C. clypeatus, C. compressus, C. purpureus, C. rugosus, C. scaevola, C. variabilis, and B. latro).Coenobitid crabs metamorphosed into megalopae after 2 to 7 zoeal stages, and intraspecific variability in developmental pathways (number of zoeal stages) was observed in 6 out of 10 species.Interspecific variability in body lengths was large at hatching but reduced in megalopae.Linear growth equations (y = a + bx) between number of moults (x) and body length (y) in the zoeal stages were determined, parameters a and b representing body length at hatching and mean growth increment at moulting, respectively.The relationship between parameters a and b for the species examined suggested the existence of 4 larval growth and development patterns in coenobitids: (1) initially smaller larvae and smaller growth increments -longer pathway; (2) initially smaller larvae and larger growth incrementsshorter pathway; (3) initially larger larvae and smaller growth increments -shorter pathway; and (4) initially largest larvae and smallest growth increments -shortest pathway (abbreviated development).Total zoeal duration increased with decreasing water temperatures and increasing number of zoeal stages and was apparently unrelated to the geographical distribution of coenobitid species.