The present study characterizes the embryonic development of Aegla platensis Schmitt, 1942 by means of optical microscopy and electron microscopy. The sequence of morphological changes observed in the egg allowed to describe ten embryonic stages: the unsegmented egg, cleavage, blastula, gastrula, nauplius, metanauplius, early zoea, late zoea, decapodid, and juvenile. Cleavage was centrolecithal and the blastula was regular. The nauplius stage was transient. The development of the gut could be observed during the zoea stages. At the late zoea stage the posterior midgut was well developed showing chromophobous cells. The dark eye pigmentation started to develop at the early zoea stage and was completed at the decapodid stage. Newly hatched juveniles exhibit some yolk incorporationin the cephalothoraxand do not need food during the rst days after hatching. The morphological changes observed during the development of this anomuran are discussed in relation to patterns of development reported for other allegedly allied decapods. ZUSAMMENFASSUNGIn der vorliegenden Arbeit wird die Embryonalentwicklung von Aegla platensis Schmitt, 1942 licht-und elektronenmikroskopischuntersucht.Aufgrund der Abfolge morphologischerVeränderun-gen im Ei können 10 Embryonalphasen unterschieden werden: ungefurchtes Ei, Furchungteilungen, Blastula, Gastrula, Nauplius, Metanauplius, frühe Zoëa, späte Zoëa, Decapodid und Juvenil. Die Furchung war centrolecithalmit regulärer Blastula und transitorischemNauplius. Die Darmentwicklung konnte während der Zoëa-Phase beobachtet werden. In der späteren Zoëa-Phase zeigte sich der hintere Mitteldarm gut entwickelt mit chromophoben Zellen. Die dunkle Pigmentierung der Augen begann während der frühen Zoëa-Phase und war in der Decapodid-Phase abgeschlossen. Bei frisch geschlüpften Juvenilen be ndet sich Dotter im Cephalothorax, so daß in den ersten Tagen nach dem Schlüpfen keine Nahrung benötigt wird. Die morphologischen Veränderungen im Verlauf der Entwicklung dieses Vertreters der Anomura werden mit denen bei anderen, vermeintlich verwandten Decapoden verglichen. © Koninklijke Brill NV, Leiden, 2003 Crustaceana 76 (1): 13-25

The sub-chronic (28-56 days) effects of exposure to low concentrations of cadmium (Cd; 0Á05, 0Á25, 0Á50 and 2Á50 mg l À1 ) shortly following fertilization on embryos, larvae and juvenile rainbow trout Oncorhynchus mykiss were examined. Premature hatching occurred at lower concentrations (0Á05 and 0Á25 mg l À1 Cd), however, delayed hatching was seen in the 2Á50 mg l À1 Cd group, with >90% of hatching occurring on the last day of the hatching period. Larval growth was negatively affected by Cd exposure in a concentration-dependent manner. Larvae exposed to 2Á50 mg l À1 Cd were 13Á9 AE 0Á8% shorter in total length (L T ) and weighed 22Á4 AE 3Á5% (mean AE S.E.) less than controls at the end of the exposure period. Plasma sex steroid concentrations (oestradiol in juvenile females and 11-ketotestosterone in juvenile males) were elevated (four-to 10-fold over controls) in exposed fish in both males and females, following 28 days of exposure to 0Á05, 0Á25 and 0Á50 mg l À1 Cd, respectively. These results suggest that environmentally realistic concentrations (in the mg l À1 range) of Cd can affect the development of O. mykiss impacting embryos, larvae and juvenile fish.

The embryonic development of freshwater triclads is mainly known from studies of species of Dendrocoelum, Planaria, Polycelis, and, more recently, Schmidtea. The present study characterizes the development of Girardia tigrina (Girard, 1850) by means of optical microcopy using glycol methacrylate semi-thin sections. 94 cocoons were collected in the period from laying to hatching, with intervals of up to twenty-four hours. The sequence of morphological changes occurring in the embryo permitted the identification of nine embryonic stages. At the time of cocoon laying, numerous embryos were dispersed among many yolk cells, with a rigid capsule covering the entire cocoon. In the first stage (approx. up to 6 hours after cocoon laying), yolk cells and embryonic cells showed random distribution. Stage II (between 12 and 24 hours after cocoon laying) is characterized by aggregates of blastomeres, which later aggregate forming an enteroblastula. Approximately 2 days after cocoon laying (stage III), formation of the embryonic epidermis and embryonic digestive system took place, the latter degenerating during the subsequent stage. Stage V (until the fourth day) is characterized by the formation of the definitive epidermis. Between 4 and 6 days after laying, organogenesis of the definitive inner organs starts (stage VI). Approximately 14 days after laying (stage IX), formation of the nervous system is completed. At this stage, the embryo shows similar characteristics to those of newly hatched juveniles. The hatching of Girardia tigrina occurs in the period between twelve to twenty-two days after cocoon laying.Keywords: developmental stages, morphology, optical microscopy, Dugesiidae, freshwater planarians. , 1850) (Platyhelminthes, Tricladida, Paludicola) Desenvolvimento embrionário de Girardia tigrina (Girard ResumoO desenvolvimento embrionário dos tricladidos é conhecido, fundamentalmente, por estudos realizados em espécies de Dendrocoelum, Planaria, Polycelis e, mais recentemente, Schmidtea. O presente estudo descreve o desenvolvimento embrionário de Girardia tigrina (Girard, 1850), a partir de análises realizadas em cortes histológicos seriados e semifinos de glicol-metacrilato, ao microscópio óptico. Noventa e quatro casulos foram coletados no período entre a postura e a eclosão, em intervalos de até vinte e quatro horas. A seqüência das modificações morfológicas no embrião permitiu a identificação de nove estágios embrionários. Na postura dos casulos, envoltos por uma cápsula rígida, observam-se numerosos embriões dispersos entre grande quantidade de células vitelinas. No estágio I (aproximadamente até 6 horas após a postura), as células vitelinas e as embrionárias mostram uma distribuição aleatória. O estágio II (entre 12 e 24 horas após a postura) caracteriza-se pela formação de agrupamentos de blastômeros, os quais posteriormente formam uma enteroblástula. Aproximadamente dois dias após a postura (estágio III), ocorre a formação da epiderme e do sistema digestivo embrionário, sendo que este último degenera ...

The disruption of endocrine system function in wildlife species, including teleosts, by contaminants such as metals is presently of major environmental concern. Recently, it has been shown that cadmium (Cd) exposure results in significant reductions in corticosteroid secretion by fish interrenal steroidogenic cells, likely through an inhibition of intracellular cortisol synthesis. In the present study, the effects of CdCl(2) on unstimulated and stimulated interrenal steroidogenesis in rainbow trout were examined with the intention of furthering an understanding of the site(s) of Cd toxic action. CdCl(2) alone reduced cortisol secretion in minced interrenal tissues to 59% and 55% of control values when exposed to 10 and 100 microM, respectively. Incubation of interrenal tissues with 0.01 IU/mL adrenocorticotropic hormone (ACTH), which activates rate-limiting steps in steroid synthesis, resulted in significant stimulation of steroidogenesis in controls. However, ACTH-stimulated steroidogenesis was reduced when tissues were previously incubated with Cd. Maximal rates of unstimulated cortisol secretion were achieved by augmentation using 5 microM 25-hydroxycholesterol (25-OHC) or 0.8 microL/mL synthetic cholesterol [SyntheChol(SC)]. Steroidogenesis augmentation by 25-OHC was significantly reduced in tissues incubated with Cd. Interestingly, cortisol secretion was significantly higher in SC-augmented tissue exposed to 1 and 10 microM Cd when compared to augmented control tissues. The results of this study show that Cd affects both stimulated and unstimulated steroidogenesis in rainbow trout, and that one major site(s) of action of Cd in the cortisol synthesis pathway is likely prior to cytochrome P450 side chain cleavage.

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Cadmium (Cd) is a known endocrine disruptor with the ability to affect the production of hormones involved in the regulation of reproductive processes. In the present study, the effects of CdCl(2) on unstimulated and stimulated testicular steroidogenesis were examined with the intention of furthering the understanding of the potential site(s) of action in the signaling pathway for 11-KT synthesis in teleosts. In short-term (2-h) exposures, CdCl(2 )stimulated 11-KT production (29% and 28% over controls) in minced testicular tissues at concentrations of 10 and 100 microM, respectively. However, 11-KT production was significantly lower than in controls (54%, 62%, and 54%) when tissues were incubated for 18 h with 1, 10, and 100 microM Cd. Incubation of testicular tissues with 100 IU/ml human chorionic gonadotropin (hCG) and 5 mM dibutyryl-cAMP (dbcAMP), which activate rate-limiting steps in steroid synthesis, or 1.3 microM 25-hydroxycholesterol (25-OHC), which augments production, resulted in significant increases in steroidogenesis over controls. hCG-stimulated steroidogenesis was reduced to 54% and 62% that of stimulated controls when tissues were incubated with CdCl(2) at 1 and 10 microM, respectively. 11-KT production in dbcAMP-stimulated and 25-OHC-augmented tissues was not affected by Cd exposure. The results of this study indicate that one site of action of Cd in the signaling steroidogenic pathway is located prior to cAMP formation. This impairment could be overcome when higher concentrations of Cd were used in hCG-stimulated cells, suggesting the presence of a stimulatory site at, or following, hCG receptor binding.

The objective of the present study was to adapt techniques for the histological processing of Dugesiidae cocoons for the study of embryo development. The cocoons were fixed with formalin, SUSA, Bouin or paraformaldehyde/glutaraldehyde and subsequently embedded in Paraplast or glycol methacrylate (Historesin). Paraplast embedding yielded reasonable results only after the cocoon was perforated or fixed for a prolonged period of time using softening techniques with acid solutions. When the SUSA or Bouin fixative and Historesin embedding techniques were used the results were good for light microscopical analysis. Fixation with paraformaldehyde/glutaraldehyde and glycol methacrylate embedding resulted in better tissue preservation, and did not require prolonged fixation or softening techniques. Thus, we suggest this technique for light microscopical analysis of embryo development in Dugesiidae.Key words: embryo development, techniques, glycol methacrilate, Tricladida. RESUMOTécnicas de processamento histológico para estudos do desenvolvimento embrionário de Dugesiidae (Platyhelminthes, Tricladida, Paludicola)Este trabalho teve por objetivo adequar técnicas ao processamento histológico de casulos de Dugesiidae para a realização de estudos do desenvolvimento embrionário. Os casulos foram fixados em formol 10%, SUSA, Bouin ou paraformaldeído/glutaraldeído, e, subseqüentemente, incluídos em paraplasto ou glicol-metacrilato (Historesin). A inclusão em paraplasto forneceu resultados razoáveis apenas após fixação por tempo prolongado e utilização de técnicas de amolecimento por soluções ácidas ou perfuração do casulo. Utilizando-se fixação em SUSA ou Bouin e inclusão em Historesin, foram obtidos bons resultados para análise ao microscópio óptico. Porém, a fixação com paraformaldeído/glutaraldeído e a inclusão em Historesin resultaram, sob todos os aspectos, em uma melhor preservação dos tecidos, além de dispensar o uso de técnicas demoradas de fixação e amolecimento. Assim, sugerese a utilização dessa técnica para estudos ao microscópio óptico do desenvolvimento embrionário de Dugesiidae.Palavras-chave: desenvolvimento embrionário, técnicas, glicol-metacrilato, Tricladida.