Annual Shell Growth Increment Formation in the Deep Water Patagonian Scallop Zagochlamys Patagonica

Differences in shell morphology and internal growth pattern of the Patagonian scallop Zygochlamys patagonica in the four main beds across their SW Atlantic distribution range

“…In Z. patagonica the formation of "external rings" was coincident with higher temperatures (minimum ␦ 18 O isotopes) in all beds analyzed here , and a higher gonadal condition index (gamete proliferation, following Campodónico et al, 2001) observed in the Reclutas bed in winter that coincide with higher percentage of individuals forming a "cluster of translucent bands" (this study), showing that the energy input to gamete proliferation could be the cause of decreased in shell growth . This is likely given that food availability in this period is low (Rivas and Piola, 2002;Lomovasky et al, 2007).…”

“…= 0.4 • C) and minimum during springsummer (5.8, S.D. = 0.3 • C; Lomovasky et al, 2007). However, maximum annual sea-bottom temperature variation (4.5 • C) was observed on the Beagle bed (55 • 10 S, southern range of species distribution) with lowest values from September to December (5.7, S.D.…”

“…Translucent bands are narrow dark while opaque bands are wide white. To confirm during which season translucent and opaque bands (Jones et al, 1990) formed, and validate the external ring formation (annual formation confirmed by stable isotopes analysis; Lomovasky et al, 2007) with the internal bands formation, the stage of terminal growth in cross-section shells was identified within either the translucent band or the opaque band (see Arnold et al, 1998) and the correspondence with an external ring. At least 16 specimens per month were analyzed from the Reclutas bed, monthly growth stage data were pooled into seasonal groups and a proportion comparison test was performed (Zar, 1999).…”

“…The number of internal translucent bands and the corresponding shell height were recorded as age-shell height data (following Lomovasky et al, 2007) and fitted to the general von Bertalanffy growth model. For this purpose we used…”

“…= 0.7 • C) and maximum from January to May (8.5, S.D. = 0.4 • C; Baldoni and Guerrero, 2000;Lomovasky et al, 2007).…”