Morfologija epaksijalnog mišićja i osteološki razvoj ranih stadija mekousne pastrve (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.Istraživanja su provedena na ranim razvojnim stadijima mekousne pastrve (Salmothymus obtusirostris, Heckel, 1851). Uzorci su prikupljeni u mrijestilištu u Prološcu u blizini rijeke Vrljike, u Hrvatskoj, i to svaki drugi dan od 10. do 56. dana poslije valenja (dpv). Uzorci su fiksirani u 10 %-tnom formalinu i uklopljeni u parafin te izrezani u serijama na 10 μm tanke rezove koji su potom obojeni hematoksilinom i eozinom, toluidinskim modrilom te alcijan plavo-specifičnom (pH = 2,5), alcijan plavom i alcijan crvenom metodom bojenja. Broj miomera u dorzalnoj epaksijalnoj muskulaturi mekousnih pastrva povećavao se s povećanjem njihove dobi te je između 10. i 18. dpv iznosio 42, a između 50. i 56. dpv 59 miomera. Dužina tijela u razdoblju od 10. do 50. dpv povećavala se od minimalno 19,57 do maksimalno izmjerene vrijednosti od 25,80 mm. Broj kralježaka u svih istraživanih uzoraka bio je 59. Praćenjem razvoja mekousnih pastrva do stadija potpune apsorpcije žumančane vrećice 24. - 26. dpv, kada su počele otvarati usta, utvrđeno je da su vidljive sve kosti glave i sve peraje. U razdoblju od 26. do 56. dpv broj miomera mekousne pastrve iznosio je 55 - 59 i taj bi podatak mogao poslužiti za taksonomsku identifikaciju ranih razvojnih stadija mekousnih pastrva. Tijekom cijelog istraživanja nisu utvrđeni vidljivi znakovi osifikacije na kralješcima, kostima glave ili na perajama niti su utvrđene vidljive malformacije kostura