Statolith shape and microstructure as indicators of ontogenetic shifts in the squid Gonatus fabricii (Oegopsida, Gonatidae) from the Norwegian Sea |
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Authors: | Alexander I Arkhipkin Herman Bjørke |
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Institution: | (1) Atlantic Research Institute of Marine Fisheries and Oceanography (AtlantNIRO), 5 Dmitry Donskoy Street, Kaliningrad, 236000 Russia, RU;(2) Institute of Marine Research, P.O. Box 1870 Nordnes, N-5024 Bergen, Norway, NO |
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Abstract: | Statolith shape and microstructure were studied in 151 specimens of the common arctic squid Gonatus fabricii (7.3–322 mm pen length) collected in the southern Norwegian Sea. Statolith development and growth both comprised two main
periods, which corresponded with the epipelagic and meso-bathypelagic ontogenetic periods of G. fabricii. During the epipelagic period (pen length range from 3 to 50–60 mm), statoliths quickly developed from the droplet-like form
in early paralarvae to the pre-definite stage in juveniles (30–50 mm pen length). Paralarval and juvenile statoliths grew
with high growth rates, and their microstructure contained narrow first-order growth increments. Three main growth zones (Z1,
Z2, Z3) developed during this period, being well distinguished from each other by specific patterns of microstructure and
separated from each other by distinct checks. During the meso-bathypelagic period (from 50–60 to 322 mm pen length), statoliths
hardly changed their shape and grew very slowly. Only one growth zone (Z4) was formed within the statolith microstructure,
characterized by disappearance of the first growth increments and formation of specific second-order bands. Each second-order
band consisted of approximately seven first-order increments. If the assumption “one increment-one day” is true for G. fabricii, the squid would then be a slow-growing animal with a life span for both sexes not exceeding 2 years.
Accepted: 25 May 1999 |
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