Morphogenesis in hatchery-reared larvae of the black rockfish,Sebastes schlegeli,and its relationship to the development of swimming and feeding functions |
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Authors: | Michio Omori Yoshio Sugawara Hitoshi Honda |
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Institution: | (1) Department of Applied Bio-Science, Faculty of Agriculture, Tohoku University, 1-1 Tsutsumi-dori, Amamiya-machi, 981 Sendai, Japan;(2) Department of Biotechnology, Senshu University of Ishinomaki, 1 Shinmito Minamisakai, 986 Ishinomaki, Japan;(3) Present address: Nansei National Fisheries Research Institute, 61-21 Sanbashi-dori, 780 Kochi, Japan |
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Abstract: | The developmental sequence of morphological characteristics related to swimming and feeding functions was investigated in
hatchery-reared larvae and juveniles ofSebastes schlegeli, a viviparous scorpaenid. The fish were extruded at an early larval stage, when the mean body size was 6.23 mm TL.
Fin-ray rudiments became visible at 9.0 mm TL in the dorsal and anal fins, at 8.0 mm TL in the pectoral and pelvic fins and
6.0 mm TL (size at extrusion) in the caudal fin. Completion of segmentation of soft rays in the dorsal and anal fins was attained
by 14 mm TL and in all fins by 17 mm TL. Branching of soft rays in the respective fins started and was completed considerably
later than the completion of segmentation, as well as ossification of the fin-supports. Morphological transformation from
larva to juvenile was apparently completed by about 17 mm TL. Although the completion of basic juvenile structures was attained
by transformation at that body size, succeeding morphological changes occurred between 17 mm and 32 mm TL.
Newly-extruded larvae possessed one or two teeth on the lower pharyngeal and pharyngobranchials 3 and 4, but lacked premaxillary,
dentary, palatine and prevomer teeth. The fish attained full development of gill rakers and gill teeth by 15 mm TL, the upper
and lower pharyngeal teeth subsequently developing into a toothplate. Development of the premaxillary, dentary and palatine
teeth was completed at about 30 mm TL, by which time loop formation of the digestive canal and the number of pyloric caeca
had attained the adult condition.
The developmental sequence of swimming and feeding functions during larval and early juvenile periods appeared to proceed
from primitive functions to advanced or complex ones, from the ability to produce propulsive force to that of swimming with
high maneuverability and from development of the irreducible minimum function of passing food into the stomach to the ability
to actively capture prey via passive food acquisition with the gill rakers and gill teeth.
The relationship of morphological development to the behavior and feeding activity of artificially-produced hatchlings is
also discussed. |
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Keywords: | Rockfish morphogenesis larva swimming feeding |
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