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.

Interactions between intruders and residents in the mole vole Ellobius talpinus

We studied the behavioral and endocrine responses of the fossorial s ocial rodent, mole vole Ellobius talpinus Pall., to intrusions of strangers int o burrow systems that were occupied by intact families. Both in reproductive and non-reproductive seasons, all intruders disappeared from the burrow systems of residents within two days of introduction, whereas 4 of 7 individuals introduced into empty burrows remained there at least for two days. Introduction of strang ers led to the concentration of residents at the point of release and to an incr ease of plasma corticosterone in both residents and intruders. During the breedi ng season, introduction of strangers was also accompanied by an increase of plas ma testosterone of residents on the day of introduction. Thus, simulation of int rusion of strangers demonstrated the efficient social fence of resident mole vol es that seems to be an important mechanism of stabilization of size and structur e of mole vole families. Encounters of residents and intruders resulted in activ ation of physiological mechanisms of stress, especially during the breeding seas on .

Coping with drought? The hidden microhabitat selection and underground movements of amphisbaenians under summer drought conditions

Habitat selection is a dynamic process that depends on many environmental variables that can vary with weather conditions.This is important because,within a context of global change,extreme weather events,such as severe droughts,are predicted to become more frequent.We examined the patterns of microhabitat selection and underground movements(using PIT-tag telemetry)of a strictly fossorial reptile,the North African checkboard amphisbaenian Trogonophis wiegmanni,during the summer drought period.We aimed to test whether changes in strategies of habitat use and movements could allow this amphisbaenian to cope with unfavorable weather.We found that during the summer drought period,T.wiegmanni did not use the microhabitats in relationship to their availability,but particularly selected sites with high abundance of rocks but also areas under a high cover of bushes,where environmental conditions were more favorable.We also found,using PIT-tag telemetry,that the numbers of T.wiegmanni individuals located under rocks and their activity(number of days with movements)decreased largely in summer.However,the animals were not entirely inactive,but,especially males were active below the ground under bushes and made some relatively long underground hidden movements between favorable areas.

Ecological role of the giant root-rat(Tachyoryctes macrocephalus)in the Afroalpine ecosystem

Rodents with prevailing subterranean activity usually play an important role in the ecosystems of which they are a part due to the combined effect of herbivory and soil perturbation.This is the case for the giant root-rat Tachyoryctes macrocephalus endemic to the Afroalpine ecosystem of the Bale Mountains,Ethiopia.We studied the impact of root-rats on various ecosystem features within a 3.5-ha study locality dominated by Alchemilla pasture,which represents an optimal habitat for this species,in 2 periods of a year.The root-rats altered plant species composition,reducing the dominant forb,Alchemilla abyssinica,while enhancing Salvia merjame and a few other species,and reduced vegetation cover,but not the fresh plant biomass.Where burrows were abandoned by root-rats,other rodents took them over and A.abyssinica increased again.Root-rat burrowing created small-scale heterogeneity in soil compactness due to the backfilling of some unused burrow segments.Less compacted soil tended to be rich in nutrients,including carbon,nitrogen and phosphorus,which likely affected the plant growth on sites where the vegetation has been reduced as a result of root-rat foraging and burrowing.