Elephantulus Myurus Research Articles

Repeatability of daily profiles of baseline glucocorticoid metabolites measured in the urine and faeces of eastern rock sengis (Elephantulus myurus)

Repeatability of hormone concentrations is of great interest for studies investigating the evolution of hormonal traits. Particularly the repeatability of glucocorticoids (GCs) in response to a stressor is frequently investigated, but often only point (initial and/or response value), or single measures are used. A new method takes into account the entire individual hormone profile and generates an individual profile repeatability (PR) score. The method was developed for response profiles, but it may also be valuable for baseline values in species with diurnal changes in hormone concentrations. GCs are determined in a variety of matrices, and repeatability can vary considerably depending on the matrix. We investigated the repeatability of baseline GC metabolite (GCM) concentrations measured in urine (uGCM) and faeces (fGCM) of captive eastern rock sengis (Elephantulus myurus) using the more traditional linear mixed model approach and the PR method. GCMs were assessed over 24 h and measurements were repeated twice with two weeks between replicates. A diurnal rhythm in GCM concentrations associated with the activity period of the sengis was found in urine, but not in the faeces. Urinary GCM concentrations exhibited a moderate repeatability, whereas the repeatability of fGCM concentrations was low. Urinary GCM concentrations and their repeatability differed between the sexes; with higher concentrations and lower PR scores in females. No such sex differences were apparent for fGCM concentrations and the PR score was not able to characterise repeatability of fGCM concentrations, which were lacking a distinct profile. The PR score enabled a successful quantification of the repeatability of the diurnal uGCM profiles. Hormone profile, sex and sample matrix can affect hormonal traits considerably and the results may be obscured if these factors are not carefully considered.

Sex and dose-dependent responses of urinary and faecal glucocorticoid metabolite concentrations following an ACTH challenge in eastern rock sengis (Elephantulus myurus)

Non-invasive methods for measuring glucocorticoids and their metabolites are frequently used in ecological, behavioural and physiological studies of mammals. Using faeces, urine and other matrices for such a measurement has considerable advantages in comparison to more traditional methods, but also requires thorough validation of the methods used. Eastern rock sengis (Elephantulus myurus) are fascinating African mammals and the non-invasive monitoring of the adrenocortical activity opens up new opportunities to study their biology. We were able to validate two assays for measuring urinary (uGCM) and faecal glucocorticoid metabolite (fGCM) concentrations in this species using a dose-dependent challenge with adrenocorticotropic hormone (ACTH). A higher concentration of ACTH elicited higher uGCM and fGCM concentrations in both males and females. Interestingly, uGCM and fGCM concentrations and the responses to ACTH were higher in females than in males and small changes in faecal glucocorticoid metabolites could not be reliably detected in males. In contrast to ACTH, a saline injection did not result in an increase in uGCM or fGCM concentrations. The study also provided insight into when responses to a stressor are likely to be detected in the urine and faeces of sengis and opens up new opportunities to study the stress physiology of this and other sengi species. It further emphasises the importance of thoroughly validating non-invasive methods for measuring hormones in both sexes of a species and for incorporating dose-dependent approaches.

Space use and the evolution of social monogamy in eastern rock sengis

AbstractLimiting resources often differ between males and females. Reproductive success in females is constrained by resources such as food and shelter, while the availability of receptive females determines male reproductive success. In addition to limiting resources, low intra‐sexual tolerances among females can affect their spacing. High intolerances coinciding with low population densities have been suggested as a cause for the evolution of monogamy in mammals, but the evidence for female intolerance is limited. We investigated long‐term space use patterns (measured as home range sizes and centers of activity) in a wild population of eastern rock sengis (Elephantulus myurus) from Limpopo, South Africa. Between March 2012 and March 2016, we recorded capture locations for 93 sengis and home range size for 22 sengis and evaluated the contributions of study year, sex, and season on these measures. Sex had no significant effect on home range size, but ranges were significantly greater during the breeding compared to the non‐breeding season, consistent with the increased energetic demands during reproduction. We found corroborative support for the role of energetic demands on home range size fluctuations. The activity centers of female–female dyads were further apart than those of male–male or mixed‐sex dyads, suggesting lower female–female tolerances in the study species. Our results offer evidence that intolerances may affect female spacing behavior and may have contributed to the evolution of monogamy in sengis.

Redescription of Maupasina weissi (Seurat, 1913) (Nematoda: Ascaridida) from sengis, Elephantulus spp. and Macroscelides proboscideus (Shaw) (Macroscelidea), in Africa.

Maupasina weissi (Seurat, 1913), is redescribed from the eastern rock sengi, Elephantulus myurus Thomas & Schwann, from Limpopo Province and compared with material collected from Free State and North West Provinces, South Africa, as well as the description of the type-material from South Tunisia. Distinguishing features of the species include a corona radiata of 12 pointed leaflike elements, a complex bipartite buccal capsule with 3 large bicuspid denticular lobes and 4 smaller club-shaped lobes and 11 (occasionally 10) pairs of cloacal papillae in the male. The complex taxonomic history of the genus Maupasina Seurat, 1917 is discussed. The probable misidentification of Macroscelides proboscideus Shaw, the short eared sengi, from North West Province, South Africa, as a host of M. weissi is explained, indicating that M. weissi occurs only in species of the genus Elephantulus Thomas & Schwann. The widely separated geographical regions, stretching the length of the African continent, in which M. weissi has been found are indicative of a conservative species with a broad geographical distribution. Tenebrionid beetles, up to 50% of stomach contents of E. myurus in Limpopo Province may act as intermediate hosts in the life-cycle of M. weissi.

Analysis of gonadotrophin-releasing hormone-1 and kisspeptin neuronal systems in the nonphotoregulated seasonally breeding eastern rock elephant-shrew (Elephantulus myurus).

Of the 18 sub-Saharan elephant-shrew species, only eastern rock elephant-shrews reproduce seasonally throughout their distribution, a process seemingly independent of photoperiod. The present study characterizes gonadal status and location/intensity of gonadotrophin-releasing hormone-1 (GnRH-1) and kisspeptin immunoreactivities in this polyovulating species in the breeding and nonbreeding seasons. GnRH-1-immunoreactive (ir) cell bodies are predominantly in the medial septum, diagonal band, and medial preoptic area; processes are generally sparse except in the external median eminence. Kisspeptin-ir cell bodies are detected only within the arcuate nucleus; the density of processes is generally low, except in the septohypothalamic nucleus, ventromedial bed nucleus of the stria terminalis, arcuate nucleus, and internal and external median eminence. Kisspeptin-ir processes are negligible at locations containing GnRH-1-ir cell bodies. The external median eminence is the only site with conspicuously overlapping distributions of the respective immunoreactivities and, accordingly, a putative site for kisspeptin's regulation of GnRH-1 release in this species. In the nonbreeding season in males, there is an increase in the rostral population of GnRH-1-ir cell bodies and density of GnRH-1-ir processes in the median eminence. In both sexes, the breeding season is associated with increased kisspeptin-ir process density in the rostral periventricular area of the third ventricle and arcuate nucleus; at the latter site, this is positively correlated with gonadal mass. Cross-species comparisons lead us to hypothesize differential mechanisms within these peptidergic systems: that increased GnRH-1 immunoreactivity during the nonbreeding season reflects increased accumulation with reduced release; that increased kisspeptin immunoreactivity during the breeding season reflects increased synthesis with increased release.

Is reproduction of male eastern rock sengis (Elephantulus myurus) from southern Africa affected by photoperiod?

Many mammals use the change in day length to time physiological and behavioural activities on a seasonal basis. Particularly, mammals from temperate regions use photoperiod to regulate reproductive functions; however, information on the role of photoperiod in small mammals from the tropics and subtropics is scarce. We studied the response of the reproductive system of male eastern rock sengis (Elephantulus myurus Thomas and Schwann, 1906) from southern Africa to photoperiods of differing length. Elephantulus myurus breeds seasonally during the spring and summer months of the southern hemisphere despite its subtropical distribution. It is one of only three sengi species known to breed seasonally. Fourteen male E. myurus were subjected to either long-day (LD; 16 h light (L) : 8 h dark (D)) or short-day (SD; 8 h L : 16 h D) photoperiods and the photoperiodic effects on the testes, testosterone concentration, and body mass were examined. Testicular volume and mass, seminiferous tubule diameter, and body mass were not significantly different between LD and SD conditions. However, plasma testosterone concentration was significantly lower in males on LD photoperiods compared with SD photoperiods. Male E. myurus may not use photoperiod as a cue to control seasonal reproductive changes. Other environmental factors such as temperature, rainfall, food abundance, or social factors are possibly influencing seasonal reproduction in this species.

Characterization of 14 polymorphic microsatellite loci developed for an Afrotherian species endemic to southern Africa, Elephantulus myurus (Macroscelidea: Macroscelididae)

National Research Foundation of South Africa (BvV), the University of Johannesburg and the DST-NRF SARChi Chair of Behavioural Ecology and Physiology (NCB). Electrophoresis of microsatellite markers was done at the Analytical Facility based at Stellenbosch University.

Of feathers and fur: Differential pollinator roles of birds and small mammals in the grassland succulent Aloe peglerae

AbstractThe pollination syndrome of the genus Aloe, with gaudy inflorescences and orange–red flowers, suggests bird pollination. However, the diversity of flowering phenologies and structures suggests that generalizations within the group are currently uninformative because few studies have addressed the role of multiple pollinator guilds, especially mammals. Aloe peglerae, endemic to montane grassland of the Magaliesberg Mountains, South Africa, is primarily bird pollinated, although small mammals are recorded nocturnal visitors. We compared the independent contributions of diurnal and nocturnal visitors, i.e. birds and small mammals respectively, to reproductive success by assigning 12 flowering A. peglerae plants to each of four pollinator selective exclusion treatments: (i) no‐visitors; (ii) nocturnal‐visitors; (iii) diurnal‐visitors; and (iv) all‐visitors (control). Birds alone contributed more to fruit set (1.2–2.6 times), average seed/fruit (1.0–1.8 times) and total seed production (1.1–2.8 times) than both the all visitors (birds and small mammals combined) and the small mammal visitors respectively. The exclusion of all visitors resulted in no fruit set, suggesting that A. peglerae requires pollinators to set seed. Germination trials over six weeks and viability testing with tetrazolium staining identified no significant differences among the three treatments that produced fruit and seed. Germination success was 90–97%, indicating that seed quality of small‐mammal and bird‐pollinated plants are similar. Aloe peglerae inflorescences were visited continuously throughout the day and night, with the Cape rock‐thrush (Monticola rupestris) and dark‐capped bulbul (Pycnonotus tricolor) being the most abundant pollinators, accounting for 68.2% and 13.7% of all visits respectively in the control treatment. Small mammals, i.e. Namaqua rock mouse (Micaelamys namaquensis) and eastern rock sengi (Elephantulus myurus), while not increasing reproductive success in the absence of birds, are suitable alternative pollinators. The presence of diurnal bird and nocturnal small mammal visitors provides a diversity of pollinators in this resilient pollination syndrome.

Endoparasites of the Eastern Rock Sengi (Elephantulus myurus) from South Africa.

The endoparasite fauna of the eastern rock sengi ( Elephantulus myurus Thomas and Schwann) was studied for the first time for any sengi species from September 2007 until August 2008 in the Limpopo Province of South Africa. From the 121 sengis examined, we recovered 11 endoparasite taxa, including 9 nematodes, 1 cestode family (Hymenolepididae), and 1 pentastomid species (Armillifer armillatus (Wyman, 1834)). The overall endoparasite prevalence was high, at 100%, and largely attributable to the nematode Maupasina weissi Seurat, 1913 , with only a single individual being parasite free. Despite the high diversity, species richness was low (1.58 ± 0.06) and only M. weissi and spiruroid larvae occurred at a prevalence exceeding 8%. The abundance of M. weissi varied significantly between seasons and was lowest in summer and autumn. In contrast, the abundance of spiruroid larvae remained relatively constant across seasons in males, but was significantly higher in spring and summer compared to winter in females. These patterns may be generated by an accumulation of M. weissi with age as well as sex-specific seasonal shifts in diet. An updated list on the hosts and geographic range of parasites of sengis is provided.

Solar Radiation during Rewarming from Torpor in Elephant Shrews: Supplementation or Substitution of Endogenous Heat Production?

Many small mammals bask in the sun during rewarming from heterothermy, but the implications of this behaviour for their energy balance remain little understood. Specifically, it remains unclear whether solar radiation supplements endogenous metabolic thermogenesis (i.e., rewarming occurs through the additive effects of internally-produced and external heat), or whether solar radiation reduces the energy required to rewarm by substituting (i.e, replacing) metabolic heat production. To address this question, we examined patterns of torpor and rewarming rates in eastern rock elephant shrews (Elephantulus myurus) housed in outdoor cages with access to either natural levels of solar radiation or levels that were experimentally reduced by means of shade cloth. We also tested whether acclimation to solar radiation availability was manifested via phenotypic flexibility in basal metabolic rate (BMR), non-shivering thermogenesis (NST) capacity and/or summit metabolism (Msum). Rewarming rates varied significantly among treatments, with elephant shrews experiencing natural solar radiation levels rewarming faster than conspecifics experiencing solar radiation levels equivalent to approximately 20% or 40% of natural levels. BMR differed significantly between individuals experiencing natural levels of solar radiation and conspecifics experiencing approximately 20% of natural levels, but no between-treatment difference was evident for NST capacity or Msum. The positive relationship between solar radiation availability and rewarming rate, together with the absence of acclimation in maximum non-shivering and total heat production capacities, suggests that under the conditions of this study solar radiation supplemented rather than substituted metabolic thermogenesis as a source of heat during rewarming from heterothermy.

Ectoparasite diversity in the eastern rock sengis (Elephantulus myurus): the effect of seasonality and host sex

Globally small mammals are important hosts of ectoparasite vectors of pathogens of medical, veterinary and economic importance. Insectivores are currently understudied as hosts of pathogen vectors. However, data are needed on the diversity of such vectors before we can investigate the underlying factors affecting ectoparasite distribution. Abiotic (e.g. temperature and rainfall) and biotic (e.g. host sex) factors have been identified as the main determinants of host–parasite interactions. The present study describes the ectoparasite community of insectivorous eastern rock sengis (Elephantulus myurus) in a nature reserve in the Gauteng province, South Africa, and how it varies with season and host sex. A total of 81 sengis were examined for the presence of ticks, mites, fleas and lice between April 2010 and April 2011. The ectoparasite assemblage comprised 11 groups of tick species, a single mite family, one louse and two flea species, with ticks and mites being the most numerous ectoparasites recovered. The prevalence and/or abundance of two commonly collected ticks (Ixodes spp. and Rhipicephalus warburtoni/arnoldi) and chigger varied with season. In addition, female-biased tick burdens were apparent for one ectoparasite species possibly due to reproductive investment. The mechanisms causing the observed patterns should be addressed in future studies.

Special issue: Animal parasitology in Africa

A consistent flow of manuscripts on parasites to African Zoology prompted the Editorial Board to consider dedicating an issue on this topic. The issue attracted 11 papers. Although South African parasitologists have received international recognition for their work on parasitic diseases of domestic animals and humans for more than 100 years following the ground-breaking work of Sir Arnold Theiler, Elsdon Dew, Willie Neitz, Anna Verster, Ivan Horak and many others at the Onderstepoort Research Facility and the Veterinary Faculty at University of Pretoria, this issue centres largely on parasites of aquatic organisms, a focus of many South African researchers. The report on ectoparasites from the eastern rock sengis represents the only paper dealing with parasites of mammals and reports on the effect of host parameters on parasite occurrence.

Complex interactions within the ectoparasite community of the eastern rock sengi (Elephantulus myurus).

Concomitant infection with more than one parasite species is the rule in nature. Since co-infecting parasites are exploiting the same host, interspecific interactions at the infracommunity level are likely. The nature of such interactions can be expected to affect the distribution of parasites within host populations. Intraspecific interactions within the infracommunity are not easily discernible from cross-sectional studies and the focus of most of these studies lies on relationships between endoparasitic micro- and macroparasites. In the current study of the ectoparasite community of wild eastern rock sengis (Elephantulus myurus) we experimentally reduced tick and flea infestations and monitored ectoparasite burdens over the course of three years. We found a number of within-taxon facilitating interactions between tick species that might be the result of decreasing immune responses with increasing tick burden. In contrast, inter-taxon relationships appeared to be dominated by antagonistic relationships likely to be linked to competition over feeding sites. Only one of the observed interspecific interactions was reciprocal. Our experimental manipulation revealed additional antagonistic relationships that cross-sectional studies would not have captured. In addition, we found substantial long-term changes in the sengi ectoparasite community as a result of our experimental manipulation suggesting carry-over effects of our treatment. This study is the first that evaluates interspecific interactions within the entire ectoparasite community exploiting a mammalian host in Africa and highlights the complexity of interspecific interactions within an ectoparasite community.

Preface to the special issue of the International Congress on Parasites of Wildlife, 15-18 September 2014, Kruger National Park, South Africa.

More than two decades ago, in 1991, the Parasitological Society of Southern Africa (PARSA) organised a conference on Parasites of Wildlife, which was held at Berg-en-dal in the Kruger National Park. With the current emphasis on One Health and conservation of biodiversity, studying various aspects of wildlife parasitology is steadily becoming more important. The PARSA committee decided, therefore, that an international meeting focusing on parasites of wildlife was long overdue. Three years after being first mooted, PARSA's second international congress on Parasites of Wildlife was held at Skukuza in the Kruger National Park from 15 to 18 September 2014. The congress attracted delegates from 19 countries, who delivered 83 papers and presented 37 posters. On the final day a half-day workshop was held, aimed primarily at post-graduate students: How to Write Great Papers: From title to references, from submission to publication. The presenters were Dale Seaton, as Elsevier publisher, and Andrew Thompson, joint Editor-in-Chief of the International Journal for Parasitology: Parasites and Wildlife. The general feeling was that such meetings should take place more frequently. We wish to acknowledge the contribution of the following colleagues, without whose support the congress would not have been possible: Scientific programme committee: Professor Ian Beveridge (Australia), Professor Thoko Hove (Zimbabwe), Professor Anja Joachim (Austria), Professor Samson Mukaratirwa (South Africa) and Dr. Michael Yabsley (USA). Local organising committee: Professor Tshepo Matjila, Dr. Sonja Matthee and Dr. Sibusiso Mtjali. The success of the congress led to the selection of a representative set of papers presented for publication in this special issue of IJP-PAW. These papers cover all the major themes that were addressed during the congress and also include review papers by the three keynote speakers. These summarised the history and development of research on wildlife parasites in southern Africa (by Junker et al.), the evolutionary ecology of parasite diversity (by Morand) and the role of wildlife in the transmission of parasitic zoonoses in peri-urban areas (by Mackenstedt et al.). The research papers included in this special issue further illustrated the diversity of current work in the field of wildlife parasitology, with specific reference to the parasites studied as well as their hosts. The selected papers range from leeches and haemoparasites in frogs (Du Preez et al.; Netherlands et al.), nematodes in eels (Dangel et al.) to competition between ectoparasites (ticks and mites) parasitising eastern rock sengis (Lutermann et al.). Further papers, also included in this special issue, focused our attention on the very important role that wildlife plays as a reservoir of parasitic zoonoses and zoonotic infections (Mackenstedt et al.; Dusher and Joachim). The congress also highlighted the importance of diagnostics and epidemiology as illustrated with the case study on Theileria (Mans et al.). One session was devoted to parasites as sentinels of the environment. Finally, our attention was also drawn to the role of parasites in foodwebs and their importance in trophic linkages (Demopoulos and Sikkel). The collection of papers in this special issue is therefore a very good representation of the current trends in research on parasites of wildlife and also highlights the need for continued research into this extremely important topic. The geographical regions covered in this special issue (South Africa, Namibia, Caribbean, Germany, Australia, to name a few) also attest to the truly international nature of the congress.

Afromontane small mammals do not follow the hump-shaped rule: altitudinal variation in the Soutpansberg Mountains, South Africa

Abstract:Altitudinal transects of biodiversity are important to understanding macro-ecological patterns. Hump-shaped altitudinal profiles in species richness are a common pattern in terrestrial small-mammal communities studied previously mostly in New World mountain ranges. Based on capture–mark–recapture live-trapping conducted over four seasons (four nights per session) along an altitudinal transect from 1000 to 1747 m asl on the southern slopes of the Soutpansberg Mountains of northern South Africa, we recorded 12 species of small mammal, including nine rodents, two shrews and one elephant shrew (sengi). Three species of rodent and the sengi dominated the communities whilst six species were recorded with three or fewer captures. Although we found no effect of season, we found a significant linear increase in terrestrial small-mammal richness (but not Simpson's diversity, D) with altitude in the Soutpansberg Mountains located just north of the Tropic of Capricorn in South Africa. This trend could best be explained by an increase in the proportion of rocky cover and a change in vegetation from savanna to grassland. Peak densities of three common rodent species and one common insectivore varied from 10 ha−1 (Elephantulus myurus) to 54 ha−1 (Micaelamys namaquensis) and density showed no significant variation with season. However, density either declined (Aethomys ineptus) or increased (Rhabdomys dilectus and Elephantulus myurus) significantly with altitude; this variation was best explained by the proportion of rocky cover. Seasonal variation had a significant effect on body mass of two rodent species. A review of small-mammal studies from major mountain ranges in Africa and Madagascar found that the hump-shaped pattern is not common. Declines in richness with increasing altitude as well as cases of no significant altitudinal change were the most common patterns noted. Tropical African mountains (including the Soutpansberg with 27 species) have far higher small-mammal diversity than temperate African mountains.

Foraging in space and time structure an African small mammal community

We used live-trapping and foraging to test for the effect of habitat selection and diet on structuring a community of six small mammals and one bird within the Soutpansberg, South Africa. We established grids that straddled adjacent habitats: woodland, rocky hillside, and grassland. Trapping and foraging were used to estimate abundance, habitat use, and species-specific foraging costs. The species with the highest abundance and foraging activity in a habitat, activity time, or food was considered the most efficient and presumed to have a competitive advantage. All species exhibited distinct patterns of spatial and temporal habitat preference which provided the main mechanism of coexistence, followed by diet selection. The study species were organized into three assemblages (α diversity): grassland, Rhabdomys pumilio, Dendromus melanotis, and Mus minutoides.; woodland, Aethomys ineptus and Micaelamys namaquensis; and rock-dwelling, M. namaquensis and Elephantulus myurus. Francolinus natalensis foraged in open rocky areas and under wooded islands within the grassland. Species organization across the habitats suggested that feeding opportunities are available within all habitats; however, distinct habitat preferences resulted from differing foraging aptitudes and efficiencies of the competing species. At Lajuma, species distribution and coexistence are promoted through distinct habitat preferences that were shaped by competition and species-specific foraging costs. The combination of trapping and foraging provided a mechanistic approach that integrates behavior into community ecology by 'asking' the animal to reveal its perspective of the environment. Using spatial and temporal foraging decisions-as behavioral indicators-enables us to guide our understanding for across-taxa species coexistence.

Eastern rock sengis as reservoir hosts of Anaplasma bovis in South Africa

Recent work has identified the presence of Anaplasma bovis, a tick-borne pathogen of cattle, in a previously undescribed species of tick collected from eastern rock sengis, Elephantulus myurus, in Limpopo Province, South Africa. These small insectivores are endemic to Africa and are important hosts of immature ticks, however, their role as reservoirs of tick-borne pathogens has not been investigated. In order to elucidate the role of sengis in the epidemiology of A. bovis, we screened the blood of 105 sengis from Limpopo Province, South Africa, for the presence of members of the genera Anaplasma and Ehrlichia by PCR. A total of 30/105 (28.6%) of individuals were infected with A. bovis, and nucleotide sequencing revealed the presence of a novel genetic variant of this pathogen. This represents the first evidence that sengis may be natural reservoir hosts of A. bovis.

The hippocampus of the eastern rock sengi: cytoarchitecture, markers of neuronal function, principal cell numbers, and adult neurogenesis.

The brains of sengis (elephant shrews, order Macroscelidae) have long been known to contain a hippocampus that in terms of allometric progression indices is larger than that of most primates and equal in size to that of humans. In this report, we provide descriptions of hippocampal cytoarchitecture in the eastern rock sengi (Elephantulus myurus), of the distributions of hippocampal calretinin, calbindin, parvalbumin, and somatostatin, of principal neuron numbers, and of cell numbers related to proliferation and neuronal differentiation in adult hippocampal neurogenesis. Sengi hippocampal cytoarchitecture is an amalgamation of characters that are found in CA1 of, e.g., guinea pig and rabbits and in CA3 and dentate gyrus of primates. Correspondence analysis of total cell numbers and quantitative relations between principal cell populations relate this sengi to macaque monkeys and domestic pigs, and distinguish the sengi from distinct patterns of relations found in humans, dogs, and murine rodents. Calretinin and calbindin are present in some cell populations that also express these proteins in other species, e.g., interneurons at the stratum oriens/alveus border or temporal hilar mossy cells, but neurons expressing these markers are often scarce or absent in other layers. The distributions of parvalbumin and somatostatin resemble those in other species. Normalized numbers of PCNA+ proliferating cells and doublecortin-positive (DCX+) differentiating cells of neuronal lineage fall within the overall ranges of murid rodents, but differed from three murid species captured in the same habitat in that fewer DCX+ cells relative to PCNA+ were observed. The large and well-differentiated sengi hippocampus is not accompanied by correspondingly sized cortical and subcortical limbic areas that are the main hippocampal sources of afferents and targets of efferents. This points to intrinsic hippocampal information processing as the selective advantage of the large sengi hippocampus.

Seasonal reproduction in the eastern rock elephant‐shrew: influenced by rainfall and ambient temperature?

AbstractBecause environmental conditions vary seasonally in most regions, many small mammals reproduce at a specific time of the year to maximize their reproductive success. In the tropics and subtropics, the breeding season is usually determined by the extent of the dry and rainy seasons. We investigated the seasonality of reproduction in the eastern rock elephant‐shrew (Elephantulus myurus), over a 12‐month period and attempted to elucidate the factors that may influence seasonal reproduction in this endemic African mammal. E. myurus breeds seasonally during the warm and wet spring and summer months and cessation of breeding occurs during the cold and dry winter months of the southern hemisphere. Pregnant females were only collected from August through to January. Ovarian size and plasma progesterone started to increase a few months prior to the first rains, were highest in October and decreased thereafter. Follicular growth and corpora body numbers corresponded to this seasonal reproductive pattern. Testes and seminiferous tubule size and plasma testosterone concentration has already started to increase during the coldest months, 2 months prior to reproductive onset in females. We propose that seasonal reproduction evolved in E. myurus because of seasonally changing food availability brought about by severe seasonal changes in rainfall and ambient temperature. The direct effects of rainfall and ambient temperature on reproduction of E. myurus are ambiguous, and we discuss other environmental factors that may trigger reproductive onset in this species.

Variation in body temperature is related to ambient temperature but not experimental manipulation of insulation in two small endotherms with different thermoregulatory patterns

AbstractMaintaining a high and constant body temperature (T b) is thought to enhance performance in endotherms, but such a thermoregulatory pattern is energetically expensive. Thus, some variation in T b is probably universal among endotherms, and several recent attempts have been made to generalize the factors that should cause this variation. Two factors that may be closely tied to the thermoregulatory pattern expressed are the cost of thermoregulation and food availability. To test these predictions, we measured T b of eastern rock elephant shrews (Elephantulus myurus; a traditionally defined heterotherm) and Namaqua rock mice (Micaelamys namaquensis; a homeotherm) in the field and under semi‐natural conditions after experimentally reducing insulation by shaving a patch of dorsal fur. After accounting for ambient temperature (T a), there was no significant difference in the level of variation in T b between shaven and unshaven elephant shrews. In rock mice, the increase in heat loss paradoxically led to decreased variation in T b in the field, but no effect was evident in captivity. Furthermore, as predicted, both species displayed significantly less variation in T b under semi‐natural conditions when given food ad libitum and predation risk involved with obtaining that food was low. Our results show that small mammals, both homeothermic and heterothermic, are capable of altering their thermoregulatory patterns in response to ecological conditions (e.g. rapid changes in food availability). However, increasing the cost of thermoregulation, at least as it was done in this experiment, does not appear to affect the expression of T b as strongly as does T a.