Distribution and size of a stalked barnacle (Octolasmis muelleri) on the blue crab, Callinectes sapidus

The objective of this research was to redescribe the spatial distribution o f Octolasmis muelleri on Callinectes sapidus in order to explore the relati onship between the spatial distribution and the size of O. muelleri on C. s apidus. Size distributions of O. muelleri were also investigated in order t o elucidate the mechanism of colonization by the cyprid larvae. The distrib ution of 1832 O. muelleri over the inside and outside surfaces and proximal , medial and distal regions of gills 1 to 8 of 17 C. sapidus was non-random and in agreement with previous studies. A weak relationship was found betw een the size of O. muelleri and their spatial arrangement on the gills of C . sapidus. The modest differences in the size of O. muelleri on different g ills and in different gill regions could be a function of different growth rates in different gill regions or colonization patterns that would place e arly arrivals in selected regions and thus give them a head start and a lon ger period of growth. An extended period of cyprid settling that occupies f rom 25 to 100% of the intermolt period of the adult instars of C, sapidus w as suggested by the size distribution patterns of O. muelleri.