Godišnje promjene u građi jajnika Europske srdele (Sardina pilchardus Walbaum) iz sjevernog Jadranskog mora.

Annual oscillation of ovarian morphology in European pilchards (Sardina pilchardus Walbaum) caught in the period July 2001 to June 2002 in the region of the Northern Adriatic (Croatia) was studied. Fifty females were taken in the middle of each month and determining body mass they were dissected, ovaries extracted and weighed, and the centre of each ovary was sampled for histological analysis. Samples were fixed in Bouin’s solution, mounted in paraffin and cut into 6 μm-thick slices which were stained with hematoxylin and eosin (HE) and using the Periodic-acid Schiff method (PAS). During oogenesis the oocytes passed through four developmental phases: peri-nucleolus stage (phase I), yolk vesicle stage (phase II), yolk stage (phase III) and mature stage (phase IV). Oocytes in phase I were present during all months, forming more than 40% of all oocytes. Their percentage increased from May to August (P<0.05) and was the highest in August (84%). Percentage of oocytes in phase IV increased from October to April (P<0.05) and was the highest in November (36.3%). An increase in percentage in phases II and III of oogenesis was noticed in September and remained at an almost equal level until May. The developmental cycle of oocytes began in September and October, coinciding with an increase in the ovarian mass, which achieved its maximum level in October, remaining at an almost equal level until April. During this period the mass of ovaries reached more than 4% of body mass, and the GSI (gonadosomatic index) was significantly different (P<0.05) from other months.Istraživane su godišnje promjene u građi jajnika srdela (Sardina pilchardus Walbaum) ulovljenih u periodu od srpnja 2001. do lipnja 2002. na području sjevernog Jadrana (Hrvatska). Sredinom svakog mjeseca uzimano je po 50 riba ženskog spola. Nakon određivanja mase tijela ribe su secirane i odvojena su im oba jajnika. Jajnici su izvagani i od sredine svakog jajnika uzet je uzorak za histološku analizu. Uzorci su fiksirani u Bouin’s otopini, uklopljeni u parafin i izrezani na 6 μm debele rezove. Rezovi su obojeni hematoksilinom i eozinom (HE) te perjodnom kiselinom- Shiff metodom (PAS). Za vrijeme nastanka oocite prolaze četiri razvojne faze: faza I (faza izvan jezgrice), faza II (faza mjehurića), faza III (žumanjčana faza) i faza IV (faza zrenja). Oocite u fazi I prisutne su tijekom svih mjeseci i čine više od 40% svih oocita, a njihov broj povećava se od svibnja do rujna (P<0,05) te je najveći u kolovozu (84%). Udio oocita u fazi IV povećava se od listopada do travnja (P<0,05), a najveći je u studenom (36,3%). Povećanje broja oocita u fazi II i III oogeneze zapaža se u rujnu i ostaje gotovo na istoj razini do svibnja. Razvojni ciklus oocita počinje tijekom rujna i listopada te se podudara s povećanjem mase jajnika koja dosiže svoj vrhunac u listopadu i ostaje na gotovo istoj razini do travnja. U tom razdoblju težina jajnika dosiže više od 4% tjelesne mase, a gonadosomatski indeks (GSI) je značajno različit (P