Host-parasite interactions in perpetual darkness:Macroparasite diversity in the cavefish Astyanax mexicanus

Astyanax mexicanus has repeatedly colonized cave environments,displaying evolutionary parallelisms in many troglobitic traits.Despite being a model system for the study of adaptation to life in perpetual darkness,the parasites that infect cavefish are practically unknown.In this study,we investigated the macroparasite communities in 18 cavefish populations from independent lineages and compared them with the parasite diversity found in their sister surface fish populations,with the aim of better understanding the role that parasites play in the colonization of new environments.Within the cavefish populations,we identified 13 parasite taxa,including a subset of 10 of the 27 parasite taxa known for the surface populations.Parasites infecting the cavefish belong to five taxonomic groups,including trematodes,monogeneans,nematodes,copepods,and acari.Monogeneans are the most dominant group,found in 14 caves.The macroparasites include species with direct life cycles and trophic transmission,including invasive species.Surprisingly,paired comparisons indicate higher parasite richness in the cavefish than in the surface fish.Spatial variation in parasite composition across the caves suggests historical and geographical contingencies in the host-parasite colonization process and potential evolution of local adaptations.This base-line data on parasite diversity in cavefish populations of A.mexicanus provides a foundation to explore the role of divergent parasite infections under contrasting ecological pressures(cave vs.surface environments)in the evolution of cave adaptive traits.

Mitochondrial phylogeography and molecular evolution of the rhodopsin visual pigment in troglobitic populations of Astyanax mexicanus(De Filippi,1853)

Cave-adapted animals provide a unique opportunity to study the evolutionary mechanisms underlying phenotypic,metabolic,behavioral,and genetic evolution in response to cave environments.The Mexican tetra(Astyanax mexicanus)is considered a unique model system as it shows both surface and cave-dwelling morphs.To date,at least 33 different cave populations have been identified,with phylogenetic studies suggesting an origin from at least two independent surface lineages,thereby providing a unique opportunity to study parallel evolution.In the present study,we carried out the most exhaustive phylogeographic study of A.mexicanus to date,including cave and surface localities,using two mitochondrial markers(cytochrome b(cyt b)and cytochrome c oxidase subunit I(COI))and nuclear rhodopsin visual pigment(rho).Additionally,we inferred the molecular evolution of rho within the two contrasting environments(cave and surface)and across three geographic regions(Sierra de El Abra,Sierra de Guatemala,and Micos).In total,267 individuals were sequenced for the two mitochondrial fragments and 268 individuals were sequenced for the rho visual pigment from 22 cave and 46 surface populations.Phylogeographic results based on the mitochondrial data supported the two-lineage hypothesis,except for the Pachón and Chica caves,whose introgression has been largely documented.The Sierra de El Abra region depicted the largest genetic diversity,followed by the Sierra de Guatemala region.Regarding the phylogeographic patterns of rho,we recovered exclusive haplogroups for the Sierra de El Abra(Haplogroup I)and Sierra de Guatemala regions(Haplogroup IV).Moreover,a 544 bp deletion in the rho gene was observed in the Escondido cave population from Sierra de Guatemala,reducing the protein from seven to three intramembrane domains.This change may produce a loss-of-function(LOF)but requires further investigation.Regarding nonsynonymous(dN)and synonymous(dS)substitution rates(omega valuesω),our results revealed the prevailing influence of purifying selection upon the rho pigment for both cave and surface populations(ω<1),but relaxation at the El Abra region.Notably,in contrast to the other two regions,we observed an increase in the number of dN mutations for Sierra de El Abra.However,given that a LOF was exclusively identified in the Sierra de Guatemala region,we cannot dismiss the possibility of a pleiotropic effect on the Rho protein.

Genetic identification and reiterated captures suggest that the Astyanax mexicanus El Pachón cavefish population is closed and declining

The sizes of Astyanax mexicanus blind cavefish populations of North-East Mexico are demographic parameters of great importance for investigating a variety of ecological,evolutionary,and conservation issues.However,few estimates have been obtained.For these mobile animals living in an environment difficult to explore as a whole,methods based on capture-mark-recapture are appropriate,but their feasibility and interpretation of results depend on several assumptions that must be carefully examined.Here,we provide evidence that minimally invasive genetic identification from captures at different time intervals(three days and three years)can give insights into cavefish population size dynamics as well as other important demographic parameters of interest.We also provide tools to calibrate sampling and genotyping efforts necessary to reach a given level of precision.Our results suggest that the El Pachón cave population is currently very small,of an order of magnitude of a few hundreds of individuals,and is distributed in a relatively isolated area.The probable decline in population size in the El Pachón cave since the last census in 1971 raises serious conservation issues.

Could Grasshoppers Be a Nutritive Meal?

The nutritive value of 25 edible Orthoptera in Mexico is shown. Protein content ranges from 43.93% to 77.13% (mix of Edible Acrididade of Puebla). Fat percentage goes from 4.22% to 34.21%. Richest species in ashes were Arphia fallax S., Sphenarium histrio G. and Sphenarium purpurascens Ch. with 16.5%. Energy contribution varies from 14.05 kJ to 21.88 kJ. Their amino acids profile was compared with the WHO/FAO/UNU Pattern (1985). The total quantity of es-sential amino acids that all insects species provides was superior to those signaled in the pattern. The highest quantity (53.60 g) was for Sphenarium histrio G. Chemical score goes from 50% to 88%. In vitamins, the highest value in Thiamine and Riboflavine was for Sphenarium magnum M., in Niacine for Sphenarium borrei B., in vitamin C and for vitamin D Acheta domestica L., and in Vitamin A for Periplaneta americana L. In minerals, all species were very rich in magnesium. All the edible orthopterans results were compared with those of the most conventional mexican foods used to obtain proteins. The quantity and quality of the nutrients that these edible orthopterans allows, provides a significant contribution to the nutrition of the peasants who eat them.

Dietary analysis of Homonota darwini (Squamata:Gekkonidae) in Northern Patagonia

Our study investigated the diet of the southernmost gecko in the world, Homonota darwini. Fifty-three specimens were captured during spring and summer in four locations in Patagonia, Argentina. The stomach contents of the specimens were identified, and we tbund that prey consisted of six main groups： Coleoptera, Hymenoptera, Homoptera and Araneae, and the adults and larvae of moth Lepidoptera. Lepidoptera was the major dietary component. The presence of ants and moths as common prey suggests an ambush feeding strategy. In spring, females consumed more ants than males although no other dietary differences between males and females were evident. We tbund nine geckos with empty stomachs and six parasitized by nematodes. Presence of empty stomachs corroborates previous observations of other nocturnal geckos and non-gecko lizards. Reduced foraging success of nocturnal lizards could be due to difficulty in prey detection due to dim light, reduced or erratic activity of insect prey at night, or shorter activity times of geckos relative to diurnal success. Sex and season were not associated with the incidence of empty stomachs. Principal component analysis showed that four food alternatives correlated with season. The constraint of nocturnality, coupled with low night-time temperatures restricting feeding to only a few hours after sunset, appear to have caused a generality of diet which may limit energy acquisition. We conclude that H. darwini is an arthropod generalist and likely an ambush forager, as are many other nocturnal gekkonids

Within-brood body size and immunological differences in Blue Tit(Cyanistes caeruleus)nestlings relative to ectoparasitism

Several ectoparasites parasitise nestlings decreasing their body condition,growth and survival.To minimise any loss of fitness due to ectoparasites,birds have developed a wide variety of defence mechanisms,potentially including hatching asynchrony.According to the Tasty Chick Hypothesis(TCH),the cost of parasitism would be reduced if ectoparasites tend to eat on less immunocompetent nestlings,typically the last-hatched chick in asynchronously hatched broods,as they are in poor body condition.Two predictions of the TCH are that immune capacity is lower in smaller nestlings than in larger ones and that parasites should provoke a more negative effect on smaller nestlings.Here,we test these predictions in a population of Blue Tits(Cyanistes caeruleus)whose broods are parasitised by Hen Fleas(Ceratophyllus gallinae)and Blowflies(Protocalliphora azurea).We recorded the presence of both ectoparasites and analysed the immunocompetence(number of leucocytes per 10,000 erythrocytes and cutaneous immune response to phytohaemagglutinin)and body condition of smaller and larger nestlings within individual broods.The leucocyte count was higher in smaller nestlings than in larger ones,whereas the cutaneous immune response did not differ between smaller and larger nestlings.Smaller nestlings,but not larger nestlings,had lower body mass when fleas were present.Blowflies,by contrast,had no detectable negative effect on nestlings.Overall,our findings provide partial support to the TCH.Lower immune capacity in smaller nestlings than in larger ones was not supported,but Hen Fleas seemed to negatively impact on smaller nestlings more than on larger ones.

Socio-spatial organization reveals paternity and low kinship in the Honduran white bat(Ectophylla alba)in Costa Rica

Ectophylla alba is a tent-making bat that roosts in mixed-sex clusters comprising adults and offspring.Our goal was to determine the genetic identity of individuals belonging to different roosting groups.We tested the hypothesis of kin selection as a major force structuring group composition.We used 9 microsatellites designed for E.alba to determine the genetic identity and probability of parentage of individuals.We analyzed parentage and kinship using the software ML-Relate,GenAIEx,and Cervus.The obtained relationship probabilities(0.5)revealed a clear maternal relationship between female adults and offspring with allele compatibility,and at least 5 relationships between male adults and pups.We found a low degree of relatedness within roosting groups.Between roosting groups at different sites,the mean probability of a half-sibling relationship ranged from 0.214 to 0.244 and,for full-sibling relationship,from 0.383 to 0.553.Genetically,adult individuals were poorly related within clusters,and kinship as an evolutionary force could not explain group membership.

Relationships between soil pollution by heavy metals and melanin-dependent coloration of a fossorial amphisbaenian reptile

Melanin is the basis of coloration in many animals,and although it is often used in communication,thermoregulation,or camouflage,melanin has many other physiological functions.For example,in polluted habitats,melanin can have a detoxifying function.Melanic coloration would help to sequester in the skin the heavy metal contaminants from inside the body,which will be expelled to the exterior when the skin is sloughed.Moreover,animals should have evolved more melanic colorations in more polluted habitats(“industrial melanism”hypothesis).We examined whether the fossorial amphisbaenian reptile,Trogonophis wiegmanni,is able to eliminate heavy metals,derived from soil pollution by seagull depositions,through sloughing its skin.Our results suggest a covariation between levels of soil pollution by heavy metals and the concentration of heavy metals in the sloughed skins of amphisbaenians.This suggests that amphisbaenians may expel heavy metals from their bodies when they slough the skins.We also tested whether amphisbaenians inhabiting soils with higher levels of heavy metal pollution had darker(melanin-dependent)body colorations.However,contrary to predictions from the“industrial melanization”hypothesis,we found a negative relationship between soil pollution and proportions of melanic coloration.This contradictory result could,however,be explained because heavy metals have endocrine disruption effects that increase physiological stress,and higher stress levels could result in decreased melanogenesis.We suggest that although amphisbaenians might have some detoxifying mechanism linked to melanin in the skin,this process might be negatively affected by stress and result ineffective under conditions of high soil pollution.