Sensory neurons in the spinal cord of nominal female embryos in the marine turtle Lepidochelys olivacea respond to shifts in incubation temperature:implications for temperature dependent sex determination

Gonadal determination in marine turtles depends on incubation temperature. The mechanisms that spark off this process remain unclear. Previously, we proposed that sensory nerves reaching the gonadal primordium in nominal female embryos of Lepidochelys (L) olivacea may sense and signal incubation temperature. These nerves could later trigger ovarian determination by releasing neurotransmitters in a code constructed based on the thermal information (Gutierrez-Ospina et al., Acetylcholinesterase-positive innervation is present at the undifferentiated stages of the sea turtle Lepidochelys olivacea embryo gonads: implications for temperature-dependent sex determination, J. Comp. Neurol. 410 (1999) 90-98). The hypothesis briefly described, however, has been recently refuted under weak theoretical grounds and experimental misinterpretations (see introduction). Here, we present preliminary results that show that nominal female embryos have sensory neurons located in the dorsal horn laminae I and II of the lumbar spinal cord that display increased c-Fos-like immuno-staining after being incubated either at 15°C or 50°C. Because these spinal neurons are the primary central target of dorsal root ganglion neurons that innervate the urogential crest, these observations keep open the possibility that gonadal sensory nerves indeed signal thermal information that could later be used to trigger or instruct ovarian specification in marine turtles.

Increased serotonin concentration and tryptophan hydroxylase activity in reproductive organs of copulator males:a case of adaptive plasticity

Individual male rats may systematically display or not copulatory behavior when paired with receptive females. Although these phenotypes are associated with differences in brain organization and function, they might also do so at the level of the reproductive organs. We then used high performance liquid chromatography to quantify serotonin concentration and the activity of tryptophan hydroxylase in the reproductive organs of copulator and non-copulator males. Sexual behavior display was compared between groups and parameters of fertility and reproductive fitness were determined for copulator males. Copulator males had higher concentrations of serotonin in the epididymis, testicle and ventral prostate than their non-copulator counterparts, as it was found for epididymal and testicular tryptophan hydroxylase activity. However, preliminary data shows that serotonin elevation occurs in copulator males only until they have accumulated several sexual encounters, so it might be a response to genital gratification or sexual rewarding. Interestingly, only epididymal serotonin concentration correlated with reproductive fitness, offspring number, mating success and seminal plug volume in copulator males. Our results support that copulator and non-copulator male rats feature a phenotype-specific serotoninergic tone in the epididymis, testicle and ventral prostate gland. The observation documenting that epididymal serotonin concentration correlated with parameters that monitor male fertility and reproductive fitness in copulator males predicts that epididymal factors increase their chances of parenting offspring.

Exploring the adjustment to parasite pressure hypothesis: differences in uropygial gland volume and haemosporidian infection in palearctic and neotropical birds

Parasites are globally widespread pathogenic organisms,which impose im portant selective forces upon their hosts.Thus,in accordance with the A djustm ent to parasite pressure hypothesis,it is expected that defenses among hosts vary relative to the selective pressure imposed by parasites.According to the latitudinal gradient in diversity,species richness and abundance of parasites peak near the equator.The uropygial gland is an im portant defensive exocrine gland against pathogens in birds.Size of the uropygial gland has been proposed to vary among species of birds because of divergent selection by pathogens on their hosts.Therefore,we should expect that bird species from the tropics should have relatively larger uropygial glands for their body size than species from higher latitudes.However,this hypothesis has not yet been explored.Here,we analyze the size of the uropygial gland of 1719 individual birds belonging to 36 bird species from 3 Neotropical(Peru)and 3 temperate areas(Spain).Relative uropygial gland volum e was 12.52%larger in bird species from the tropics than from temperate areas.This finding is consistent w ith the relative size of this defensive organ being driven by selective pressures imposed by parasites.We also explored the potential role of this gland as a means of avoiding haemosporidian infection,showing that species with large uropygial glands for their body size tend to have lower mean prevalence of haemosporidian infection,regardless o f their geographical origin.This result provides additional support for the assum ption that secretions from the uropygial gland reduce the likelihood of becoming infected with haemosporidians.

Diversity and host assemblage of avian haemosporidians in different terrestrial ecoregions of Peru

Characterizing the diversity and structure of host–parasite communities is crucial to understandingtheir eco-evolutionary dynamics.Malaria and related haemosporidian parasites are responsible forfitness loss and mortality in bird species worldwide.However,despite exhibiting the greatest ornithologicalbiodiversity,avian haemosporidians from Neotropical regions are quite unexplored.Here,we analyze the genetic diversity of bird haemosporidian parasites(Plasmodium andHaemoproteus)in 1,336 individuals belonging to 206 bird species to explore for differences in diversityof parasite lineages and bird species across 5 well-differentiated Peruvian ecoregions.Wedetected 70 different haemosporidian lineages infecting 74 bird species.We showed that 25 out ofthe 70 haplotypes had not been previously recorded.Moreover,we also identified 81 new host–parasite interactions representing new host records for these haemosporidian parasites.Our outcomesrevealed that the effective diversity(as well as the richness,abundance,and Shannon–Weaver index)for both birds and parasite lineages was higher in Amazon basin ecoregions.Furthermore,we also showed that ecoregions with greater diversity of bird species also had highparasite richness,hence suggesting that host community is crucial in explaining parasite richness.Generalist parasites were found in ecoregions with lower bird diversity,implying that the abundanceand richness of hosts may shape the exploitation strategy followed by haemosporidian parasites.These outcomes reveal that Neotropical region is a major reservoir of unidentified haemosporidianlineages.Further studies analyzing host distribution and specificity of these parasites inthe tropics will provide important knowledge about phylogenetic relationships,phylogeography,and patterns of evolution and distribution of haemosporidian parasites.