Technical development and calibration of lipofuscin quantification for the potential use as an age estimate in snow crabs Chionoecetes opilio (Decapoda: Oregoniidae)

• Main Authors: ALLAIN, Renée, MORIYASU, Mikio, CRAWFORD, Bryan, COURTENAY, Simon
• Format: Text
• Language: unknown
• Published: Station Biologique de Roscoff (SBR) 2011
• Subjects: Chionoecetes opilio; Snow crab
• Online Access: https://dx.doi.org/10.21411/cbm.a.352973f6; http://application.sb-roscoff.fr/cbm/doi/10.21411/CBM.A.352973F6

This study demonstrated the presence of lipofuscin granules in the olfactory lobe cell mass (OLCM) of snow crab Chionoecetes opilio and examined whether granule quantification results are subject to methodological bias. Lipofuscin quantification in histological sections of the OLCM were compared between: 1) snow crab categories (sex and two indicators of age: size and condition of carapace (evaluated by the coloration of the carapace, presence/absence of scars and epizootic and epiphytic growth); 2) sample preparation methods; and 3) microscopic image collection parameters. No significant difference was observed in lipofuscin levels between mature males and females of similar size and carapace condition. Lipofuscin was more abundant in crabs with a decalcifying (presumably, older) carapace condition. However, larger clean-shell males did not have higher lipofuscin levels than smaller old-decalcifying-shell males. Autofluorescent intensity of granules was significantly higher in brain samples post-fixed in decalcifying solution compared to formalin fixed samples; however, lipofuscin levels did not differ. Increased exposure times to laser light of up to 120 seconds significantly decreased autofluorescent intensity of lipofuscin granules. No significant differences were observed in lipofuscin levels when varying optical section thickness or when comparing single confocal planes and stacks. Lipofuscin granule size frequency histograms showed possible image analysis limitations in terms of minimum lipofuscin granule size. These results raised concerns regarding the applicability of histological lipofuscin quantification in the OLCM of snow crabs.