engleski

Morphology of the epaxial musculature and osteological development of the early developmental stages of softmouth trout (Salmothymus obtusirostris, Heckel, 1851)

Investigations were carried out on the early developmental stages of softmouth trout (Salmothymus obtusirostris, Heckel, 1851), taken from a hatchery in Proložac near the River Vrljika, Croatia. Samples were collected every two days 10-56 days post-hatching (dph), fixed in 10% buffered formalin, embedded in paraffin, cut into 10 μm thick serial longitudinal sections and stained with Hematoxylin and Eosin, Toluidin Blue, Alcian Blue-specific (pH = 2.5) and Alcian Blue and Alizarin Red. The number of myomeres in the dorsal epaxial musculature of the softmouth trout increased between 10-18 dph and 50-56 dph to either 42 or 59 myomeres, respectively. Total body length increased from a minimal value of 19.57 mm to a maximum value of 25.80 mm between 10-56 dph. The number of vertebrae in all investigated groups was 59. Through this follow-up of the period of development of softmouth trout to the stage of complete yolk sac absorption it was established that it takes about 24 to 26 dph when they start opening their mouth and when all the bones of the head and all fins are visible. In the period of 26-56 dph the number of myomeres was 55-59, and this could be used for taxonomic identification of the early developmental stages of softmouth trout. throughout whole investigation period no signs of ossification in the vertebral column, fins and head bones were observed or any skeletal malformations.

softmouth trout ; Salmothymus obtusirostris, heckel, 1851 ; early developmental stages ; epaxial muscles ; osteological development

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