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1000
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Abstract/Summary
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Statolith ageing techniques provide a useful tool in the study of age, growth, and population structure of several marine organisms. Previous investigations on scyphozoan statoliths demonstrated increased statolith numbers and size with increasing medusa size, as well as taxon-specific variations in statolith shape. Thus, statoliths are potentially useful for age determination and taxonomic studies on medusae. Unfortunately, studies on statoliths are difficult because of the fragile structure of the numerous tiny crystals and their hygroscopic nature. We evaluated the potential of various modified study techniques for scyphozoan statocysts and statoliths applied to early medusa stages of Sanderia malayensis Goette, 1886. Light microscopy was suitable to follow the increase of statolith numbers and sizes with age and allowed differentiation of various statolith shape types, which were confirmed by scanning electron microscopy. The use of the fluorescent marker calcein provided direct evidence for measurable statolith growth. Our results indicated that statoliths stopped growing after reaching a certain size while additional statoliths developed in the basal region of the statocyst. Micro-computed tomography data allowed visualization and morphometric measurements of statoliths, revealing interspecific differences that may be useful for phylogenetic studies. Statolith numbers were positively correlated with medusa age and bell diameter. Thus, statolith analyses could provide information on medusa age or size, both of which are important parameters for population structure analyses that are difficult to assess with currently applied techniques. Our study provides methodological bases for future studies to reveal further potential of scyphozoan statolith investigations for phylogenetic and ecological studies.
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