Evaluation of gladius dorsal surface structure for age and growth studies of the short-finned squid, (Illex) (illecebrosus)(Teuthoidea: Ommastrephidae)

Ontogenetic variation of δ13C and δ15N recorded in the gladius of the jumbo squid Dosidicus gigas: geographic differences

“…The strong positive linear relationship between ML and GL agree with previous studies (e.g. Jackson et al 1993, Perez et al 1996. The δ 13 C and δ 15 N values varied along the proostracum for all squid and sites with increasing δ…”

Gladius and statolith as tools for age and growth studies of the squid Loligo plei (Teuthida: Loliginidae) off southern Brazil

“…Moreover, because validation experiments performed in the Gulf of Mexico confirmed the daily deposition of statolith increments in the species (Jackson and Forsythe, 2002), it can be assumed that total increment counts obtained in squid caught off southern Brazil were approximations of individual age in days. The gladius structure undergoes structural modifications as ostracum layers are continuously added to the ventral surface of the gladius plate (Perez et al, 1996). Because this process tends to mask part of early deposited growth increments, increment counts underestimate total age.…”

“…In that sense, L. plei gladius showed a strong linear correlation with mantle length, a common measure of somatic growth in cephalopods. Because its length was less variable than ML, GL could be the best linear measurement of size (Kristensen, 1983), and gladius growth increments excellent indicators of size-specific somatic growth (Bizikov, 1991;Arkhpkin and Bizikov, 1991;Jackson et al, 1993;Bizikov, 1995;Perez et al, 1996;Arkhipkin and Perez, 1998). Assuming the gladius increment daily deposition, the structure seemed suitable for reconstructing individual daily growth histories in L. plei, which had recently provided important insights into other squid population ecology (Perez et al, 1996;Perez and O'Dor, 1998;Arkhpkin and Perez, 1998).…”

“…Because its length was less variable than ML, GL could be the best linear measurement of size (Kristensen, 1983), and gladius growth increments excellent indicators of size-specific somatic growth (Bizikov, 1991;Arkhpkin and Bizikov, 1991;Jackson et al, 1993;Bizikov, 1995;Perez et al, 1996;Arkhipkin and Perez, 1998). Assuming the gladius increment daily deposition, the structure seemed suitable for reconstructing individual daily growth histories in L. plei, which had recently provided important insights into other squid population ecology (Perez et al, 1996;Perez and O'Dor, 1998;Arkhpkin and Perez, 1998). Gladius increment s Statolith increments Preliminary age estimates obtained from the interpretation of statolith and gladius structures, have shown that L. plei life span was likely less that one year (large males, 230 mm ML, were found to be around 9 months old), contradicting previous estimates (Perez et al, 2002).…”

“…The gladius is the internal uncalcified chitinous shell present in squids and sepiolids. Periodic growth increments have been identified in all three shell layers (ostracum, hypostracum and periostracum) and shown to be suitable for age determination and principally to reconstruct squid individual growth (Arkhipkin and Bizikov, 1991;Bizikov, 1991;Jackson et al, 1993;Perez et al, 1996;Perez andO`Dor, 1998, 2000;Arkhipkin and Perez, 1998). Both structures have been used in loliginid squid age and growth studies (Jackson, 1990;Jackson et al, 1993;Balgos and Pauly, 1998 and others).…”