Shell tubules in Condylocardiinae (Bivalvia: Carditoidea)

摘要

Shell tubules are microscopic canals in the shells of various molluscs. In polyplacophorans and fissurellid gastropods, the canals form by shell growth around multicellular extensions of the mantle epithelium (caeca). Bivalves have unicellular caeca which etch tubules into prefabricated shell ( Reindl & Haszprunar, 1996). These occur in numerous independent bivalve lineages, although more frequently in Pteriomorphia and Carditoida ( Taylor, Kennedy & Hall, 1969, 1973). Tubules are a taxonomically constant feature of all postlarval Arcoida and most likely of all Carditidae, Pisidiidae, Sphaeriidae and Corbiculidae ( Araujo, Ramos & Bedoya, 1994; Araujo & Korniushin, 1998; Malchus, 2006; Taylor et al., 1973; Waller, 1980; this study). Unionidae (Palaeoheterodonta) seem to be the only taxon with shell tubules in the larval, glochidial shell ( Lima et al., 2006; Roe, Simons & Hartfield, 1997; Malchus personal observation).