Blood parasites in sympatric lizards: what is their impact on hosts’ immune system?

Assessment of parasites and their pathogenicity is essential for studying the ecology of populations and understanding their dynamics. In this study, we investigate the prevalence and intensity of infection of haemogregarines (phylum Apicomplexa) in two sympatric lizard species, Podarcis vaucheri and Scelarcis perspicillata, across three localities in Morocco, and their effect on host immune response. We used the Phytohaemagglutinin (PHA) skin testing technique to relate the level of immune response with parasite infection. Prevalence and intensity levels were estimated with microscopy, and 18S rRNA gene sequences were used to confirm parasite identity. All parasites belong to the haemogregarine lineage found in other North African reptiles. There were differences in prevalence between localities and sexes. Overall, infected lizards were larger than uninfected ones, although we did not detect differences in parasitaemia across species, sex or locality. The swelling response was not related to the presence or number of haemogregarines, or to host body size, body condition, sex or species. We found no evidence of impact for these parasites on the circulating blood cells or the hosts’ immune system, but more data is needed to assess the potential impact of mixed infections, and the possibility of cryptic parasite species.

Effect of body size, age and timing of breeding on clutch and egg size of female Eastern Gray Treefrogs, Hyla versicolor

Information on how organisms allocate resources to reproduction is critical for understanding population dynamics. We collected clutch size (fecundity) and egg size data of female Eastern Gray Treefrogs, Hyla versicolor, and examined whether observed patterns of resource allocation are best explained by expectations arising from life history theory or by expected survival and growth benefits of breeding earlier. Female Hyla versicolor showed high between-individual variation in clutch and egg size. We did not observe maternal allocation trade-offs (size vs number; growth vs reproduction) predicted from life history theory, which we attribute to the large between-female variation in resource availability, and the low survival and post-maturity growth rate observed in the study population. Rather, clutches are larger at the beginning of the breeding season, and this variation in reproductive investment aligns with seasonal variation in ecological factors affecting offspring growth and survival.

Improving kettle holes as habitat and reproduction areas for amphibians – a case study in organic farms in north-eastern Germany

Kettle holes are found in young moraine landscapes and serve as an important habitat for amphibians. The loss of amphibians has been dramatic in recent decades, mainly because of the increase in land use intensity and deterioration of habitats e.g., kettle holes in agricultural landscapes. We monitored amphibian species on three organically managed farms in north-eastern Germany to get an overview of their occurrence and proof of reproduction to develop effective protection strategies. From 2016 to 2020, we investigated 50 kettle holes in cultivated fields. In 2018, we implemented the nature conservation measure ‘cutting back dense wooded belts’ in six of these kettle holes. Here, we focused on seven species considering four highly endangered species. We found six to seven species in up to 17 kettle holes in the 44 kettle holes without the measure ‘cutting back dense wooded belts’. Bombina bombina occurred at the most kettle holes (57%). The number of kettle holes where amphibians reproduced differed strongly. On average, at least one species reproduced at 58% of the kettle holes. Many kettle holes become overgrown with negative effects for amphibians due to the reduction in solar irradiation and higher water consumption. The nature conservation measure increased the number of species on average from two to four and the number of species with reproduction from one to three. It is one of more than 100 measures in the ‘Farming for Biodiversity’ project that farmers can choose to receive a nature conservation certificate, which can be used for marketing purposes.

Repeatability of water loss and gain rates of Plethodon cinereus

Water loss and gain rates of amphibians are important to understanding their ecology, especially for plethodontid salamanders. We report the first estimates of repeatability of relative water loss and gain rates of the two major colour morphs of the Eastern Red-backed Salamander, Plethodon cinereus, in the fall and spring seasons. Repeatability of relative water loss in P. cinereus was >0 in the fall but not in the spring. Repeatability of relative water gain was significant for all salamanders pooled in the fall, and was not repeatable in the spring. There were no apparent differences in repeatability of relative water loss or gain between the two colour morphs. Our results suggest that the repeatability of relative water loss and gain rates varies by season, but not by colour morph.

Distribution of tiger salamanders in northern Sonora, Mexico: comparison of sampling methods and possible implications for an endangered subspecies

Many aquatic species in the arid USA-Mexico borderlands region are imperiled, but limited information on distributions and threats often hinders management. To provide information on the distribution of the Western Tiger Salamander (Ambystoma mavortium), including the USA-federally endangered Sonoran Tiger Salamander (Ambystoma mavortium stebbinsi), we used traditional (seines, dip-nets) and modern (environmental DNA [eDNA]) methods to sample 91 waterbodies in northern Sonora, Mexico, during 2015-2018. The endemic Sonoran Tiger Salamander is threatened by introgressive hybridization and potential replacement by another sub-species of the Western Tiger Salamander, the non-native Barred Tiger Salamander (A. m. mavortium). Based on occupancy models that accounted for imperfect detection, eDNA sampling provided a similar detection probability (0.82 [95% CI: 0.56-0.94]) as seining (0.83 [0.46-0.96]) and much higher detection than dip-netting (0.09 [0.02-0.23]). Volume of water filtered had little effect on detection, possibly because turbid sites had greater densities of salamanders. Salamanders were estimated to occur at 51 sites in 3 river drainages in Sonora. These results indicate tiger salamanders are much more widespread in northern Sonora than previously documented, perhaps aided by changes in land and water management practices. However, because the two subspecies of salamanders cannot be reliably distinguished based on morphology or eDNA methods that are based on mitochondrial DNA, we are uncertain if we detected only native genotypes or if we documented recent invasion of the area by the non-native sub-species. Thus, there is an urgent need for methods to reliably distinguish the subspecies so managers can identify appropriate interventions.

Is it heterochrony? Populational differences in tadpole of Corythomantis greeningi Boulenger, 1896 (Anura: Hylidae)

Corythomantis greeningi is a hylid widely distributed in the xerophilic and sub-humid morphoclimatic regions of northeastern Brazil. The morphology of C. greeningi tadpoles were described from specimens collected in the Bahia, however, we observed some differences in morphology of individuals from Piauí, northeastern Brazil. The tadpoles were collected during the 2019 rainy season and 14 individuals were used to compare the larval characters. We observed differences in external, internal oral and chondrocranial morphology in relation to specimens previously described, especially in oral disc, number and shape of oral cavity papillae and some chondrocranium structures, suggesting a heterochrony in the development of the species. Further studies involving a greater number of tadpoles at different stages, combined with genetic, acoustic, and morphological factors of adult may establish the variation degree of C. greeningi in different regions of northeastern Brazil.

Foraging and scavenging behaviour of the prairie rattlesnake (Crotalus viridis): no evidence that envenomation cues facilitate kleptoparasitism of struck prey

Most viperids are ambush predators that primarily use venom to subdue prey, employing a strike-release-trail hunting strategy whereby snakes follow the unique scent of envenomated prey to locate carcasses they have bitten and released. In addition to killing prey, rattlesnakes (like most carnivores) will also opportunistically scavenge carrion. This scavenging strategy likely includes the occasional consumption of carcasses killed by other snakes (i.e., kleptoparasitism). In areas with high densities of other pitvipers, utilizing the unique scent of animals envenomated by other snakes might be a viable alternative foraging strategy. We evaluated this possibility experimentally using a series of captive behavioural trials on prairie rattlesnakes (Crotalus viridis) to determine whether conspecific or heterospecific (C. scutulatus, C. ornatus) envenomation cues might increase the likelihood of kleptoparasitism. Rattlesnakes did not prefer envenomated prey over nonenvenomated prey, nor did they prefer venom cues of one species over another. Although they did frequently scavenge carcasses, in the absence of striking, snakes generally located carcasses using random searching movements instead of scent trails. Additionally, the amount of time rattlesnakes spent investigating carcass trails did not differ significantly among treatments, suggesting that striking, and the resultant formation of a chemical search image of prey, is more crucial to trailing behaviour than venom cues. Moreover, a high degree of behavioural variation among individuals was observed, suggesting that scavenging and kleptoparasitism in rattlesnakes is more complex than previously realized, and making generalizations about these behaviours is challenging.

The distribution and biogeography of slow worms (Anguis, Squamata) across the Western Palearctic, with an emphasis on secondary contact zones

The slow-worm lizards (Anguis) comprise five species occurring throughout most of the Western Palearctic. Although these species are relatively uniform morphologically – with the exception of A. cephallonica, which exhibits a quite unique morphology – they are genetically deeply divergent. Here, we provide detailed distribution maps for each species and discuss their biogeography and conservation based on updated genetic data and a robust distribution database. We pay particular attention to the so called ‘grey zone’, which typically represents secondary contact zones and in some cases confirmed or presumed hybrid zones. Four of the five species live in parapatry, while only two species, A. cephallonica and A. graeca from the southern Balkans occur in partial sympatry. Further research should focus on the eco-evolutionary interactions between species in contact, including their hybridization rates, to reveal deeper details of the slow-worm evolutionary and natural history.

Tolerance and osmotic response to food deprivation and salt loading in the herbivorous non-drinking Moroccan Spiny-tailed lizard Uromastyx nigriventris (Sauria: Agamidae)

Animals inhabiting arid environments use a variety of behavioural and physiological strategies to balance their water and salt budgets. We studied the effects of dehydration and salt loading on osmoregulatory capacities in a large herbivorous desert lizard, the Moroccan Spiny-tailed lizard Uromastyx nigriventris, the family Agamidae. These lizards select plants with a high K+ to Na+ ratio of 15 to 20, and like other herbivorous lizards, effectively eliminate the extra electrolyte load, mainly via a pair of active nasal salt glands, which exude the extra ions from blood. Here we present results of a series of laboratory experiments, which tested a five-week food and water deprivation and the excretory response of nasal salt glands, during a short period of five days, following salt loading by two separated injections of KCl or NaCl at a 5-day interval (4th and 9th days). During food-water deprivation, hypohydrated lizards lost 32% of their initial body mass with a substantial decrease of their Body Condition Index and the tail volume as an index of energy (fat and then potential metabolic water) storage. Plasma osmolality significantly increased by 20%. There were also significantly increased plasma sodium, chloride, and total protein concentrations. On the other hand, there was no significant decrease in the plasma glucose level. Most of the salt loaded lizards secreted far more K+ than Na+ via the nasal glands, even after NaCl loading. The K+/Na+ ratio decreased only after two to three repetitive NaCl injections but insufficient Na+ was eliminated. Two successive KCl injections were successfully eliminated, but daily natural average K+ administration induced progressive hyperkaliemia. These experimental data agreed with previous observations showing variations of plasma Na+ and K+ concentrations in free-living lizards. The nasal gland constitutes the main route of Cl− excretion but the Cl−/(Na+ + K+) ratio may vary according to observations in other herbivorous species.