Unusual gonad structure in the paedomorphic teleostSchindleria praematura(Teleostei: Gobioidei): a comparison with other gobioid fishes.

The gonads of eight gobioid species were examined histologically, includingPandaka pygmaeaandSchindleria praematura, in order to investigate the manifestations of miniaturization and paedomorphosis in the gonads. Rearrangements of reproductive structures were found only inS. praematura, and included only the gonad tissues, not the gametes. Both sexes ofS. praematuramaintain basic germinal components: the spermatocyst composed of Sertoli cells and spermatogonia in the testis and the follicle and oocyte complex in the ovary. The stromal ovarian tissue and testicular interstitial tissue, however, is reduced compared to other gobies, and the number and location of gonial cells is restricted. This sequestered pattern of gonial cells is known as a restricted spermatogonial type in the testis, and has been reported only in atherinomorphs. The restriction of gonial cells in the ovary is extremely rare among teleosts, known only from one other species. These restricted gonial patterns inS. praematuraare probably related to the overall reduction of morphological complexity in this genus, due to its extreme paedomorphosis. [ABSTRACT FROM AUTHOR]