Stanley, Falkland Islands
Stanley, Falkland Islands

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Arkhipkin A.,Bypass Road | Boucher E.,Bypass Road | Gras M.,Bypass Road | Brickle P.,South Atlantic Environmental Research Institute SAERI
Journal of the Marine Biological Association of the United Kingdom | Year: 2014

Common rock oysters Saccostrea cucullata (Bivalvia) were sampled from intertidal volcanic rocks at five sites around Ascension Island (central-east Atlantic) in austral winter 2012–2014. Their left valves were sectioned to reveal annual growth increments. Their periodicity was validated by the presence of specific growth marks in the increment sequence visible in consecutive years of sampling. No significant differences in shell height-weight relationships were revealed between sites. Marginal analysis of the increment width showed that S. cucullata accelerated their growth in cooler winter months and decelerated the growth in warmer summer months. Rock oysters in Ascension Island lived up to 14–16 years with maximum age of 26 years. Young oysters (1–5 years old) had the same growth rates both in shell height and weight in all sites. However, their starting point (size and weight of 1-year-old animals) was different in various sites, with largest animals occurring in the most protected site Northeast Bay with sheltered inlets and smallest animals inhabiting exposed to surf site of Letterbox. Growth in shell height was best described by von Bertalanffy growth function with the largest L ∞ in animals inhabiting the windward side and smallest animals occurring in the leeward side of the Island. In summary, S. cucullata around Ascension Island lived longer but had slower growth than those from tropical regions of Southwest Asia probably due to comparatively low productivity observed in the central part of the equatorial tropical Atlantic. Copyright © Marine Biological Association of the United Kingdom 2014


Arkhipkin A.,Bypass Road | Weis R.,National Museum of Natural History | Mariotti N.,University of Rome La Sapienza | Shcherbich Z.,Bypass Road
Journal of Molluscan Studies | Year: 2014

The anatomy and development of the tails at the posterior part of the mantle were studied in several groups of Recent and extinct coleoid cephalopods; substantial differences in their formation were revealed. Males of the Recent loliginid squid Alloteuthis spp. form their tail by increased growth of the anterior part of the gladius with simultaneous growth of the posterior mantle. As a result, the gladius rolls longitudinally in the tail forming a pseudoconus. The attenuated tail in males of the squid Lycoteuthis springeri (Lycoteuthidae) is supported from inside by the special rod-like apical vacuolated cartilage. Adults of both sexes of recent Onykia robsoni and O. robusta form a carrot-shaped flexible chitinous rostrum supporting the attenuated tail. Adults of several Jurassic belemnites formed an elongated epirostrum posterior to their orthorostrum; the structures differed in growth and microstructure. Counts of growth microincrements within the orthorostrum and epirostrum were used to date their formation and estimate the age of belemnites. The development of the long rigid tail and the corresponding shift of the fin to the middle part of the mantle streamline the body and possibly facilitate the animal's movement in the water by gliding. The analogous tail formation in several independent groups points to its adaptive nature for the development of a more mobile adult phase in species of coleoid cephalopods. © 2015 The Author 2015. Published by Oxford University Press on behalf of The Malacological Society of London, all rights reserved.

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