MORPHOLOGICAL CHANGES IN ASTACUS ASTACUS GONADS DURING THE REPRODUCTIVE CYCLE
The reproductive cycle of Astacus astacus was described by the external observation of the gonads, recording changes in the gonadosomatic index (GSI) and by the histological analysis of the reproductive organs. A total of 37 males and 13 females of Astacus astacus were collected from the Vukovina gravel pit located at northwest Croatia from May 2003 until January 2004. All crayfish were mature with total body lengths between 7.84 and 13.7 cm and weights between 16 and 125 g. There was a pronounced difference between the GSI values of the sexes. GSI fluctuated within a very small range (between 0.2 and 1.5%) in males while in females it increased up to 12.3% during the mating season. The external appearance of the testes and ovaries during the reproductive cycle was compared with the histological sections of germ cells in the testes, the vas deferens and ovaries. Besides the germinative cells, the morphological changes in testis and vasa deferentia of A. astacus extended also to the connective tissue and secretory epithelium. The maturation of germinative cells was synchronized, both in testes and ovaries.