| 1. |
- Brande-Lavridsen, Nanna, et al.
(author)
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Effects of prochloraz and ethinylestradiol on sexual development in Rana temporaria.
- 2008
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In: Journal of Experimental Zoology. Part A. - : Wiley. - 1932-5223 .- 1932-5231. ; 309:7, s. 389-98
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Journal article (peer-reviewed)abstract
- A wide range of environmental xenobiotics that mimic hormones (endocrine-disrupting chemicals) may cause alterations in sexual development or reproductive function in aquatic organisms such as amphibians when exposed during early sensitive stages. We exposed tadpoles of the Common frog, Rana temporaria, from hatch to metamorphosis, to two different endocrine disruptors, the synthetic estrogen 17 alpha-ethinylestradiol and the fungicide prochloraz. The object of the study was to assess the effects of these two compounds on the sexual development of the tadpoles by investigating sex ratio, gonadal development, sex steroid concentrations and vitellogenin induction. Histology revealed that a large percentage of all groups were juvenile hermaphrodites at metamorphosis. Tadpoles exposed to 115 and 251 microg/L prochloraz showed a significant increased proportion of males. However, the testosterone concentrations were depressed in those groups. Ethinylestradiol in concentrations of 77 and 159 ng/L EE(2) increased whole-body calcium levels in a dose-dependent manner indicating induction of the egg yolk protein vitellogenin, verified also by gel electrophoresis. The study shows that ethinylestradiol may induce vitellogenesis and prochloraz may affect the sexual development in Common frogs.
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| 2. |
- Kotrschal, Alexander, et al.
(author)
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A Noninvasive Method to Determine Fat Content in Small Fish Based on Swim Bladder Size Estimation
- 2011
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In: Journal of Experimental Zoology. Part A. - : Wiley. - 1932-5223 .- 1932-5231. ; 315A:7, s. 408-415
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Journal article (peer-reviewed)abstract
- The presence of fat stores in fish is widely used as a correlate of fish health and fitness. Techniques to measure fat content with some accuracy are available for medium-sized and large fish, but apart from morphometric indices, a noninvasive method to determine fat content in small fish has hitherto been lacking. In this study, we introduce a novel method to measure the fat content in live fish that can be applied also to small fish of less than 0.5 g of body mass. This approach relies on a precise measurement of the swim bladder volume, from which fat content can subsequently be deduced. As fat is positively buoyant, fish with larger fat stores require a smaller swim bladder to attain neutral buoyancy. To determine swim bladder volume, we developed a measuring device, which makes use of the differential compressibility of air and water. A fish is placed in a pressure-tight chamber to which a standardized amount of water is added. The resulting change in pressure Delta p is inversely proportional to the volume of the swim bladder. Using juveniles and adults of Simochromis pleurospilus (Nelissen, '78; Pisces: Tropheini) a small cichlid fish, we show that Delta p is tightly related to structural size, mass, and body condition. Most importantly, this approach allows to predict the visceral fat content of small fish more precisely than the six most commonly used morphometric body indices.
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| 3. |
- Laska, Matthias, et al.
(author)
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Olfactory sensitivity for alkylpyrazines - A comparative study in CD-1 mice and spider monkeys
- 2009
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In: Journal of Experimental Zoology Part A: Ecological Genetics and Physiology. - : Wiley. - 1932-5223 .- 1932-5231. ; 311:4, s. 278-288
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Journal article (peer-reviewed)abstract
- Using a conditioning paradigm, the olfactory sensitivity of four CD-1 mice for six alkylpyrazines was investigated. With all six stimuli, the animals discriminated concentrations =0.1 ppm (parts per million) from the odorless solvent, and with three of the six stimuli the animals were even able to detect concentrations =0.1 ppb (parts per billion). Four spider monkeys tested in parallel were found to detect five of the same six stimuli at concentrations less than1ppm and with one stimulus they were able to discriminate concentrations =1ppb from the solvent. The results showed CD-1 mice to be more sensitive than spider monkeys with five of the six alkylpyrazines tested. There was a significant positive correlation between sensitivity and the number of alkyl groups attached to the pyrazine (Pyr) ring in both species. A comparison of the detection thresholds obtained here to those obtained in human subjects suggests that neither the number of functional olfactory receptor genes nor the absolute or the relative size of the olfactory bulbs reliably predict a species olfactory sensitivity. These threshold data may provide useful information for the choice of adequate stimulus concentrations in electrophysiological or imaging studies of the olfactory system or investigations of the discriminative abilities of mice and spider monkeys.
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| 4. |
- Strobel, Anneli, et al.
(author)
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Influence of Temperature, Hypercapnia, and Development on the Relative Expression of Different Hemocyanin Isoforms in the Common Cuttlefish Sepia officinalis
- 2012
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In: Journal of Experimental Zoology Part A. - : Wiley. - 1932-5231. ; 317:8, s. 511-523
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Journal article (peer-reviewed)abstract
- The cuttlefish Sepia officinalis expresses several hemocyanin isoforms with potentially different pH optima, indicating their reliance on efficient pH regulation in the blood. Ongoing ocean warming and acidification could influence the oxygen-binding properties of respiratory pigments in ectothermic marine invertebrates. This study examined whether S. officinalis differentially expresses individual hemocyanin isoforms to maintain optimal oxygen transport during development and acclimation to elevated seawater pCO 2 and temperature. Using quantitative PCR, we measured relative mRNA expression levels of three different hemocyanin isoforms in several ontogenetic stages (embryos, hatchlings, juveniles, and adults), under different temperatures and elevated seawater pCO 2. Our results indicate moderately altered hemocyanin expression in all embryonic stages acclimated to higher pCO 2, while hemocyanin expression in hatchlings and juveniles remained unaffected. During the course of development, total hemocyanin expression increased independently of pCO 2 or thermal acclimation status. Expression of isoform 3 is reported for the first time in a cephalopod in this study and was found to be generally low but highest in the embryonic stages (0.2% of total expression). Despite variable hemocyanin expression, hemolymph total protein concentrations remained constant in the experimental groups. Our data provide first evidence that ontogeny has a stronger influence on hemocyanin isoform expression than the environmental conditions chosen, and they suggest that hemocyanin protein abundance in response to thermal acclimation is regulated by post-transcriptional/translational rather than by transcriptional modifications.
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| 5. |
- Paredes, Ursula, et al.
(author)
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Low Incubation Temperature Induces DNA Hypomethylation in Lizard Brains
- 2016
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In: Journal of Experimental Zoology Part A: Ecological Genetics and Physiology. - : Wiley. - 1932-5223. ; 325:6, s. 390-395
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Journal article (peer-reviewed)abstract
- Developmental stress can have organizational effects on suites of physiological, morphological, and behavioral characteristics. In lizards, incubation temperature is perhaps the most significant environmental variable affecting embryonic development. Wall lizards (Podarcis muralis) recently introduced by humans from Italy to England experience stressfully cool incubation conditions, which we here show reduce growth and increase the incidence of scale malformations. Using a methylation-sensitive AFLP protocol optimized for vertebrates, we demonstrate that this low incubation temperature also causes hypomethylation of DNA in brain tissue. A consistent pattern across methylation-susceptible AFLP loci suggests that hypomethylation is a general response and not limited to certain CpG sites. The functional consequences of hypomethylation are unknown, but it could contribute to genome stability and regulation of gene expression. Further studies of the effects of incubation temperature on DNA methylation in ectotherm vertebrates may reveal mechanisms that explain why the embryonic thermal environment often has physiological and behavioral consequences for offspring.
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| 6. |
- Uller, T., et al.
(author)
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Sperm Storage and Sperm Competition Across Ovarian Cycles in the Dragon Lizard, Ctenophorus fordi
- 2013
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In: Journal of Experimental Zoology Part a-Ecological Genetics and Physiology. - : Wiley. - 1932-5223. ; 319:7, s. 404-408
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Journal article (peer-reviewed)abstract
- Female sperm storage can influence male reproductive success and may favour males that produce sperm that remain viable across several ovarian cycles. Here we show that sperm are viable in the female reproductive tract across ovarian cycles in the mallee dragon, Ctenophorus fordi. Based on experimental mating trials, we show that stored sperm were generally less likely to fertilize eggs than recently inseminated sperm. The fertilization success of stored sperm increased with male body size relative to rivals. This may be due to differences in ejaculate volume or sperm number transferred by males of different sizes. However, there was no evidence that copulation time, which is correlated with ejaculate volume, contributed to fertilization success. We suggest that sperm storage across ovarian cycles may be common in small, multi-clutched lizards and that its impact on selection on male phenotypes could contribute to the evolution of lizard mating systems.
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