Temperature and photoperiod effects on sex determination in Leuresthes tenuis (fish)

In some gonochoristic species, sex is influenced not only by genotype at conception but also by the environment that offspring experience during early ontogeny (termed environmental sex determination or ESD). ESD is thought to be adaptive when seasonal variations in environmental conditions provide a sex-specific fitness advantage. In vertebrates, temperature is the most common determinant of sex, and seasonal variation in temperature serves as a temporal cue of environmental quality such as length of the growing season. Some environments, however, lack strong seasonal temperature fluctuations and other cues, particularly photoperiod, may provide a more reliable indicator of the environment offspring enter. We tested this hypothesis by rearing the offspring of the California grunion (Leuresthes tenuis, Ayres), which experiences low seasonal temperature variation in nature, under common garden conditions at three temperature and two photoperiod treatments. Our experiments revealed that both temperature and photoperiod significantly affected sex ratios in L. tenuis. More females were produced at cooler temperatures and longer day lengths, which is consistent with female biased sex ratios early in the breeding season, and likely adaptive through increased female size and fecundity. To our knowledge, this is the first documented case of photoperiod-dependent sex determination in a gonochoristic vertebrate.

Effective acoustical monitoring tools for Mannophryne lamarcai

We performed the field-work during the dry (March 2014) and reainy season (May and June 2014) at the species type locality: Cerro Socopó, located at central-west region between Falcón, Lara and Zulia states, Venezuela. Socopó is a small and isolated mountain (1.571 m) belonging to the Ziruma mountains, and represents a relict of tropical mountain forest surrounded by semi-arid vegetation and grassland. This area is home to 312 species of vertebrates, including endangered and endemic amphibians species like Mannophryne lamarcai, Leptodactylus magistris and Dendropsophus amicorum. These forest and species are severely threatened by cattle ranch and illegal timber extraction, with forest formations only above 1000 meters. Despite this, no legal protected figure has been established in the area. We identified a 2.5 km secondary road transect within the study area based on the following criteria: 1) it cover different habitat types (streams and lagoons); and 2) it within the altitudinal gradient described for the specie (1,040 to 1,363 m). We identified three sampling points throughout the transect located in the vicinity of wetland habits: socopo1, socopo2 and socopo4. We did two types of recordings: 1) high quality recordings to characterize the advertisement call for M. lamarcai, non described to date (socopo4), and 2) recordings in different sampling points to evaluate call detectors performance in different acoustic scenarios (in all three localities).

Evolution of extreme stomach pH in bilateria inferred from gastric alkalization mechanisms in basal deuterostomes

The stomachs of most vertebrates operate at an acidic pH of 2 generated by the gastric H+/K+-ATPase located in parietal cells. The acidic pH in stomachs of vertebrates is believed to aid digestion and to protect against environmental pathogens. Little attention has been placed on whether acidic gastric pH regulation is a vertebrate character or a deuterostome ancestral trait. Here, we report alkaline conditions up to pH 10.5 in the larval digestive systems of ambulacraria (echinoderm + hemichordate), the closest relative of the chordate. Microelectrode measurements in combination with specific inhibitors for acid-base transporters and ion pumps demonstrated that the gastric alkalization machinery in sea urchin larvae is mainly based on direct H+ secretion from the stomach lumen and involves a conserved set of ion pumps and transporters. Hemichordate larvae additionally utilized HCO3- transport pathways to generate even more alkaline digestive conditions. Molecular analyses in combination with acidification experiments supported these findings and identified genes coding for ion pumps energizing gastric alkalization. Given that insect larval guts were also reported to be alkaline, our discovery raises the hypothesis that the bilaterian ancestor utilized alkaline digestive system while the vertebrate lineage has evolved a strategy to strongly acidify their stomachs.

The effect of repeated exposure to parasite genotypes of the eyefluke Diplostomum pseudospathaceum on infection rate and immunization in three-spined sticklebacks

Adaptive immunity in vertebrates can confer increased resistance against invading pathogens upon re-infection. But how specific parasite genotypes affect the transition from innate to adaptive immunity is poorly understood. Here, we investigated the effects of homologous and heterologous exposures of genetically distinct parasite lineages of the eye fluke Diplostomum pseudospathaceum on gene expression patterns of adaptive immunity in sticklebacks (Gasterosteus aculeatus). We showed that observable differences were largely attributable to final exposures and that there is no transcription pattern characteristic for a general response to repeated infections with D. pseudospathaceum. Final exposure did not unify expression patterns of heterologous pre-exposed fish. Interestingly, heterologous final exposures showed similarities between different treatment groups subjected to homologous pre-exposure. The observed pattern was supported by parasite infection rates and suggests that host immunization was optimized towards an adaptive immune response that favored effectiveness against parasite diversity over specificity.

Impaired learning of predators and lower prey survival under elevated CO2: a consequence of neurotransmitter interference

Ocean acidification is one of the most pressing environmental concerns of our time, and not surprisingly, we have seen a recent explosion of research into the physiological impacts and ecological consequences of changes in ocean chemistry. We are gaining considerable insights from this work, but further advances require greater integration across disciplines. Here, we showed that projected near-future CO2 levels impaired the ability of damselfish to learn the identity of predators. These effects stem from impaired neurotransmitter function; impaired learning under elevated CO2 was reversed when fish were treated with gabazine, an antagonist of the GABA-A receptor - a major inhibitory neurotransmitter receptor in the brain of vertebrates. The effects of CO2 on learning and the link to neurotransmitter interference were manifested as major differences in survival for fish released into the wild. Lower survival under elevated CO2 , as a result of impaired learning, could have a major influence on population recruitment.

Automated processing of zebrafish imaging data: a survey

Due to the relative transparency of its embryos and larvae, the zebrafish is an ideal model organism for bioimaging approaches in vertebrates. Novel microscope technologies allow the imaging of developmental processes in unprecedented detail, and they enable the use of complex image-based read-outs for high-throughput/high-content screening. Such applications can easily generate Terabytes of image data, the handling and analysis of which becomes a major bottleneck in extracting the targeted information. Here, we describe the current state of the art in computational image analysis in the zebrafish system. We discuss the challenges encountered when handling high-content image data, especially with regard to data quality, annotation, and storage. We survey methods for preprocessing image data for further analysis, and describe selected examples of automated image analysis, including the tracking of cells during embryogenesis, heartbeat detection, identification of dead embryos, recognition of tissues and anatomical landmarks, and quantification of behavioral patterns of adult fish. We review recent examples for applications using such methods, such as the comprehensive analysis of cell lineages during early development, the generation of a three-dimensional brain atlas of zebrafish larvae, and high-throughput drug screens based on movement patterns. Finally, we identify future challenges for the zebrafish image analysis community, notably those concerning the compatibility of algorithms and data formats for the assembly of modular analysis pipelines.

Handbuch der vergleichenden und experimentellen entwicklungslehre der wirbeltiere, bearb. von prof. dr. Barfurth [u.a.] hrsg. von Oskar Hertwig.

3, pt. 3

Handbuch der vergleichenden und experimentellen entwicklungslehre der wirbeltiere, bearb. von prof. dr. Barfurth [u.a.] hrsg. von Oskar Hertwig.

3, pt. 2

Handbuch der vergleichenden und experimentellen entwicklungslehre der wirbeltiere, bearb. von prof. dr. Barfurth [u.a.] hrsg. von Oskar Hertwig.

2, pt. 2