Effects of dehydration on cardiovascular development in the embryonic American alligator (Alligator mississipiensis).

Effects of dehydration on reptilian embryonic cardiovascular function are unknown. Here, we present the first morphological and physiological data quantifying the cumulative effects of four acute dehydration events on the embryonic American alligator, Alligator mississipiensis. We hypothesized that dehydration would alter embryonic morphology, reduce blood volume and augment the response to angiotensin II (Ang II), a key osmotic and blood volume regulatory response element in adult vertebrates. Drying events at 30%, 40%, 50%, and 60% of embryonic incubation reduced total egg water content by 14.43 ± 0.37 g, a 3.4 fold increase relative to controls. However, embyronic blood volume was greater in the dehydration group at 70% of embryonic incubation compared to controls (0.39 ± 0.044 mLg(-1) and 0.22 ± 0.03 mLg(-1), respectively), however, both groups were similar at 90% of incubation (0.18 ± 0.02 mLg(-1) in the controls and 0.23 ± 0.03 mLg(-1) in the dehydrated group). Dehydration altered the morphological phenotype and resulted in an overall reduction in embryonic mass at both incubation time points measured. Dehydration also altered the physiological phenotype, resulting in embryonic alligators that were relatively bradycardic at 90% of incubation. Arterial Ang II injections resulted in a dose dependent hypertension, which increased in intensity over the span of incubation studied. While progressive incubation altered the Ang II response, dehydration had no impact on the cardiovascular responses to the peptide. Quantification of Ang II type-1 receptor protein using western blot analysis illustrated that dehydration condition and incubation time point did not alter protein quantity. Collectively, our results show that dehydration during embryonic development of the American alligator alters embryonic morphology and baseline heart rate without altering arterial pressure and response to Ang II.

Adaptive plasticity of killifish (Fundulus heteroclitus) embryos: dehydration-stimulated development and differential aquaporin-3 expression.

Embryos of the marine killifish Fundulus heteroclitus are adapted to survive aerially. However, it is unknown if they are able to control development under dehydration conditions. Here, we show that air-exposed blastula embryos under saturated relative humidity were able to stimulate development, and hence the time of hatching was advanced with respect to embryos continuously immersed in seawater. Embryos exposed to air at later developmental stages did not hatch until water was added, while development was not arrested. Air-exposed embryos avoided dehydration probably because of their thickened egg envelope, although it suffered significant evaporative water loss. The potential role of aquaporins as part of the embryo response to dehydration was investigated by cloning the aquaporin-0 (FhAqp0), -1a (FhAqp1a), and -3 (FhAqp3) cDNAs. Functional expression in Xenopus laevis oocytes showed that FhaAqp1a was a water-selective channel, whereas FhAqp3 was permeable to water, glycerol, and urea. Expression of fhaqp0 and fhaqp1a was prominent during organogenesis, and their mRNA levels were similar between water- and air-incubated embryos. However, fhaqp3 transcripts were highly and transiently accumulated during gastrulation, and the protein product was localized in the basolateral membrane of the enveloping epithelial cell layer and in the membrane of ingressing and migrating blastomers. Interestingly, both fhaqp3 transcripts and FhAqp3 polypeptides were downregulated in air-exposed embryos. These data demonstrate that killifish embryos respond adaptively to environmental desiccation by accelerating development and that embryos are able to transduce dehydration conditions into molecular responses. The reduced synthesis of FhAqp3 may be one of these mechanisms to regulate water and/or solute transport in the embryo.

Effects of temperature, salinity, desiccation and chemical treatments on egg embryonation and hatching success of Benedenia seriolae (Monogenea: Capsalidae), a parasite of farmed Seriola spp.

The effects of temperature and salinity on the embryonation period and hatching success of eggs of Benedenia seriolae were investigated. Temperature strongly influenced embryonation period; eggs first hatched 5 days after laying at 28 degrees C and 16 days after laying at 14 degrees C. The relationship between temperature and embryonation period is described by quadratic regression equations for time to first and last hatching. Hatching success was >70% for B. seriolae eggs incubated at temperatures from 14 to 28 degrees C. However, no B. seriolae eggs embryonated and hatched at 30 degrees C and <2% of eggs hatched when incubated at 24 degrees C after transfer to 30 degrees C for 48 h. Embryonation period was similar for eggs incubated in sea water at 25, 30 and 35 per thousand salinity, but increased for eggs incubated at higher or lower salinities. When incubated at salinities ranging from 25 to 45 per thousand, more than 70% of B. seriolae eggs embryonated and hatched. Hatching success was lower at 20 and 50 per thousand salinity and few or no eggs hatched at 10 and 15 per thousand. Hatching of B. seriolae eggs can be prevented by desiccation for 3 min, by immersion in water at 50 degrees C for 30 s or by treatment with 25% ethanol for 3 min.

Description of the fully mature oocyte of Drosophila melanogaster.

We detected fully mature undescribed oocytes in Drosophila melanogaster ovaries. The fully mature oocytes were rehydrate in ovaries. In the oocyte of stage 14, chromosomes make globular mass, while the chromosome shows meiotic metaphase I in fully mature oocytes. Both mature oocytes and stage 14 oocytes were activated by hypotonic treatment. When the mature oocytes or the stage 14 oocytes were activated, telophase II figures were observed in former oocytes but meiosis in latter oocyte stopped at late metaphase I, suggesting the stage 14 activated oocyte cannot pass the second checkpoint of meiosis.

Intraruminal rehydration of ovine fetuses.

During oral rehydration of adult mammals, oropharyngeal stimulation, the act of swallowing, and/or gastric factors contribute to a rapid decrease in plasma arginine vasopressin (AVP) that precedes plasma osmolality changes. To determine whether similar mechanisms are present in the developing fetus, six chronically prepared ovine fetuses were rehydrated with intraruminal (IR) distilled water infusions (1 ml.kg-1.min-1 for 60 min) after 43 +/- 3 h of maternal water deprivation. In response to maternal dehydration, significant increases were noted in maternal and fetal mean plasma osmolalities, sodium and AVP concentrations, and fetal urine osmolality. As estimated by hematocrit, fetal intravascular volume decreased by 11%. Fetal rehydration via IR distilled water infusion evoked a significant decrease in fetal plasma osmolality but no change in urine osmolality. Unexpectedly, fetal arterial blood pressure increased and arterial PO2 decreased while fetal hematocrit indicated a further 7% decrease in intravascular volume after the IR infusion. There was a nonsignificant trend toward increased fetal glomerular filtration rate, urine volume, and plasma AVP concentrations. Identical IR water infusions to five euhydrated fetuses resulted in significant decreases in fetal plasma osmolality and increases in glomerular filtration rate, urine flow, and osmolar excretion. The euhydrated fetuses also exhibited significant increases in mean arterial blood pressure and hematocrit and decreased fetal arterial PO2. These results indicate that IR water does not suppress AVP secretion in the dehydrated ovine fetus. Rather, both euhydrated and dehydrated fetuses exhibit an idiosyncratic vasoconstrictive response to IR water.