Laser capture microdissection of gonads from juvenile zebrafish

<p>Abstract</p> <p>Background</p> <p>Investigating gonadal gene expression is important in attempting to elucidate the molecular mechanism of sex determination and differentiation in the model species zebrafish. However, the small size of juvenile zebrafish and correspondingly their gonads complicates this type of investigation. Furthermore, the lack of a genetic sex marker in juvenile zebrafish prevents pooling gonads from several individuals. The aim of this study was to establish a method to isolate the gonads from individual juvenile zebrafish allowing future investigations of gonadal gene expression during sex determination and differentiation.</p> <p>Methods</p> <p>The laser capture microdissection technique enables isolation of specific cells and tissues and thereby removes the noise of gene expression from other cells or tissues in the gene expression profile. A protocol developed for laser microdissection of human gonocytes was adjusted and optimised to isolate juvenile zebrafish gonads.</p> <p>Results</p> <p>The juvenile zebrafish gonad is not morphologically distinguishable when using dehydrated cryosections on membrane slides and a specific staining method is necessary to identify the gonads. The protocol setup in this study allows staining, identification, isolation and subsequent RNA purification and amplification of gonads from individual juvenile zebrafish thereby enabling gonadal gene expression profiling.</p> <p>Conclusion</p> <p>The study presents a protocol for isolation of individual juvenile zebrafish gonads, which will enable future investigations of gonadal gene expression during the critical period of sex differentiation. Furthermore, the presented staining method is applicable to other species as it is directed towards alkaline phosphatase that is expressed in gonocytes and embryonic stem cells, which is conserved among vertebrate species.</p

Structure by size, sex and maturity stage of the withe croaker (Micropogonias furnieri, Desmarest, 1823; Teleostei: Sciaenidae) in the bycatch of the artisanal fishery at Rocha Lagoon, Uruguay

The structure of the population of white croaker (Micropogonias furnieri), a bycatch species of the multi-specific artisanal fishery at the coastal lagoon of Rocha, was analyzed. This species is Uruguay's second fishery resource and it has been declared fully exploited. Few data are available on the artisanal fishery and the biology of this fish, which inhabits the Uruguayan coastal lagoons. The white croakers were obtained from the bycatch of five fisheries that target diverse species in different parts of the lagoon. The five net types studied (mesh sizes 1, 2, 4, 10 and 20 cm) caught different fractions of the structure per size, sex and maturity stage. Both the median and first quartile of the size composition retained by each net size were bigger than the size at first maturity. This work shows the effect of different kinds of artisanal fishery on the structure of the white croaker population and provides basic information for the conservation and management of one of the fishery resources whose habitat forms part of the national park within the MAB/UNESCO Bañados del Este Biosphere Reserve

Induction of oocyte maturation in the white croaker Micropogonias furnieri (Pisces: Sciaenidae) by human chorionic gonadotropin

The present work aimed to identify the best doses of human chorionic gonadotropin (hCG) needed to induce oocyte maturation of Micropogonias furnieri and to characterize ovarian dynamics during the periovulatory period. Adult M. furnieri females with fully developed ovaries were injected intraperitoneally with four different doses of hCG. The gonadotropin response was suceeded by analyzing morphologically gonadal biopsies and following the postinjection changes in follicle diameter. Oocyte maturation was induced by three doses used: 100, 300, and 500 IU of hCG kg bw-1, and was reached 48 h after treatment with 300 and 500 IU of hCG kg bw-1, and 72 h after treatment with 100 IU of hCG kg bw-1. Concerning ovarian dynamics, only 100 and 300 IU of hCG kg bw-1 mimicked the natural ones which have a synchronic group maturation. In conclusion, the dose mimicking natural ovarian dynamics and inducing oocyte maturation more quickly is 300 IU of hCG kg bw-1