The functional anatomy of the neck and forelimbs of the Cape golden mole, Chrysochloris asiatica (Lipotyphla: Chrysochloridae)

The anatomy of the neck and forelimb of Chrysochloris asiatica is described and illustrated. The sequence of events during digging and modifications for fossorial action are described. Modifications include the appearance of a third bone in the forearm; the shortening and fusion of bones in the manus; enlarged processes on the scapula, humerus and ulna for greater muscle attachment; enlarged neck muscles and a dip in the spine in the cervical region to accommodate these and the enlarged shoulder muscles; an enlarged occiput for insertion of the powerful neck muscles; a greatly enlarged triceps and movement of the shoulder girdle to a position anterior to that normal in mammals. The possibility of the third forearm bone being the ossified tendon of a flexor muscle is discussed, without any conclusion being reached as to its true origin

The long-lived queen : reproduction and longevity in female eusocial Damaraland mole-rats (Fukomys damarensis)

The inverse relationship between reproduction and lifespan is one of the main concepts of life history theory. This association has been observed in most taxa, although exceptions have been found in which a breeding female outlives her non-reproductive cohorts. This relationship is well known in social insects, and it has recently come to light that reproductive females of certain social mole-rat species also exhibit extended lifespans relative to non-breeders. We analysed mark–recapture data over 13 years in 12 colonies of Damaraland mole-rats (Fukomys damarensis) to assess if colony queens lived longer than non-reproductive adult females. Queens were recaptured up to 8.5 years after initial capture (X = 6.2 years); significantly longer than non-reproductive females (X = 1.3 years), suggesting that a colony queen lives longer than her non-reproductive subordinates. This difference may be attributed to both physiological and social factors which may relax reproductive costs in queens.C.M.S. acknowledges funding from the University of Pretoria, J.U.M.J. acknowledges funding from the University of Cape Town and N.C.B. acknowledges funding from the University of Pretoria and the National Research Foundation.http://africanzoology.journals.ac.za/am2013ab201

A case of natural queen succession in a captive colony of naked mole-rats, Heterocephalus glaber

Naked mole-rats occur in large colonies where usually a single queen monopolizes reproduction. Queen succession occurs from within usually as a result of aggressive encounters with subordinate females that queue for reproductive succession following colony instability, which inevitably results in death of either the queen or the challenging conspecific. We monitored a queen succession following the death of the breeding male in a colony of the naked mole-rat, Heterocephalus glaber, prior to, during as well as after replacement of the original breeding female. The response of the pituitary luteotrophs was investigated in the non-reproductive females during this period of instability by the administration of endogenous gonadotrophin releasing hormone (GnRH) and evaluating the subsequent luteinising hormone (LH) response in the blood. Larger and older non-breeding females engaged in aggressive encounters that culminated in death. The new breeding successor which arose from within the colony was a large female who continued to procreate. The six non-breeding females that were killed during reproductive takeover were larger and older females which exhibited elevated basal circulating LH concentrations as well as increased pituitary sensitivity as measured by the amount of releasable LH to an exogenous GnRH challenge. By contrast, non-breeding females that survived the succession were smaller and younger animals with reduced basal and GnRH challenged LH concentrations. Likewise, five non-breeding males which were heavier and older than those non-breeding males which survived were killed. These animals did not, however, show elevated basal or exogenous GnRH challenged LH concentrations when compared to the surviving males. The non-breeding animals of both sexes which survived the reproductive takeover event represented individuals which posed a minimal threat to the new successor and hence promoted the continuation of the marked reproductive skew that is prevalent in this highly inbred colonial subterranean hystricomorph.The authors thank R.P. Millar, Department of Chemical Pathology, University of Cape Town, for donating the mammalian GnRH. We also thank the National Institute of Biological Standards and Control, Hertfordshire, England, for the LH pituitary preparation (2nd International Standard 1988, code 80/552). The work was supported by research grants from the then Foundation for Research Development (to N.C.B. and J.U.M.J.), the University of Pretoria (to N.C.B.) and the University of Cape Town (to J.U.M.J). This study was approved by the Animal Ethics Committee of the University of Cape Townhttp://africanzoology.journals.ac.za/am2013ab201

O2 binding and CO2 sensitivity in hemoglobins of subterranean African mole rats

Inhabiting deep and sealed subterranean burrows, mole rats exhibit a remarkable suite of specializations, including eusociality (living in colonies with single breeding queens), extraordinary longevity, cancer immunity and poikilothermy, and extreme tolerance of hypoxia and hypercapnia.With little information available on adjustments in hemoglobin (Hb) function that may mitigate the impact of exogenous and endogenous constraints on the uptake and internal transport of O2, we measured hematological characteristics, as well as Hb-O2 binding affinities and their sensitivities to pH (Bohr effect), CO2, temperature and 2,3 diphosphoglycerate (DPG, the major allosteric modulator of Hb-O2 affinity in the red cells) in four social and two solitary species of African mole rats (family Bathyergidae) originating from different biomes and soil types across Central and Southern Africa. We find no consistent patterns in hematocrit (Hct) and blood and red cell DPG and Hb concentrations or in intrinsic Hb-O2 affinity and its sensitivity to pH and DPG that correlate with burrowing, sociality and soil-type. However, the results reveal low specific (pHindependent) effects of CO2 on Hb-O2 affinity compared to humans that predictably safeguard pulmonary loading under hypoxic and hypercapnic burrow conditions. The O2-binding characteristics are discussed in relation to available information on the primary structure of Hbs from adult and developmental stages of mammals subjected to hypoxia and hypercapnia and the molecular mechanisms underlying functional variation in rodent Hbs.The Danish Council for Independent Research, Natural Sciences (grant 4181-00094) and the Faculty of Science and Technology, Aarhus University.http://jeb.biologists.org2018-11-30am2017Zoology and Entomolog

Fossorial adaptations in African mole-rats (Bathyergidae) and the unique appendicular phenotype of naked mole-rats

DATA AVAILABILITY: All the data generated and analysed in this study are included in this published article and its supplementary information files.CODE AVAILABILITY: The code for all analyses is available at: https://github.com/gabrielsaffa/african_mole_rats.Life underground has constrained the evolution of subterranean mammals to maximize digging performance. However, the mechanisms modulating morphological change and development of fossorial adaptations in such taxa are still poorly known. We assessed the morpho-functional diversity and early postnatal development of fossorial adaptations (bone superstructures) in the appendicular system of the African mole-rats (Bathyergidae), a highly specialized subterranean rodent family. Although bathyergids can use claws or incisors for digging, all genera presented highly specialized bone superstructures associated with scratch-digging behavior. Surprisingly, Heterocephalus glaber differed substantially from other bathyergids, and from fossorial mammals by possessing a less specialized humerus, tibia and fibula. Our data suggest strong functional and developmental constraints driving the selection of limb specializations in most bathyergids, but more relaxed pressures acting on the limbs of H. glaber. A combination of historical, developmental and ecological factors in Heterocephalus are hypothesized to have played important roles in shaping its appendicular phenotype.Financial support for the research trip to Kenya of J.U.M.J. was provided by The National Geographic Society, whereas funding support for the maintenance of the original NMR colonies was provided by the University of Cape Town and the South African National Research Foundation (NRF). DST-NRF is acknowledged for the financial support to establish the MIXRAD micro-focus X-ray tomography facility at Necsa.https://www.nature.com/commsbioam2023Mammal Research InstituteZoology and Entomolog

Activity patterns activity patterns in the mole-rats Tachyoryctes Splendens and Heliophobius argenteocinereus

Activity in two unrelated genera of molerats, <i>Tachyoryctes and Heiiophobius</i>, was studied in the field by recording the movements of animals tagged with radioactive wire. <i>Tachyoryctes</i> shows a single marked activity peak and only leaves its nest between 10.00 and 19.00 hour. <i>Heliophobills</i> shows a more dispersed and prolonged activity pattern although peak activity occurs over approximately the same period as in <i>Tachyoryctes. Heilophoblus</i> spends over 50 % of the day out of its nest, <i>Tachyoryctes</i>, under 25%. These differences can be attributed to a different function of the nest in the two genera (Tachyoryctes has a multipurpose nest; Heiiophoblus uses its nest solely for rest), and also to the fact that <i>Tachyoryctes</i> has light-sensitive eyes whereas <i>Heiiophoblus</i> appears unable to appreciate light; Tachyoryctes periodically comes to the surface to forage and this exposure to light may trigger the 24-hour activity cycle

The long-lived queen: Reproduction and longevity in female eusocial Damaraland mole-rats (Fukomys damarensis)

The inverse relationship between reproduction and lifespan is one of the main  concepts of life history theory. This association has been observed in most taxa, although exceptions have been found in which a breeding female outlives her  non-reproductive cohorts. This relationship is well known in social insects, and it has recently come to light that reproductive females of certain social mole-rat species also exhibit extended lifespans relative to non-breeders. We analysed mark–recapture data over 13 years in 12 colonies of Damaraland mole-rats  (Fukomys damarensis) to assess if colony queens lived longer than non-reproductive adult females. Queens were recaptured up to 8.5 years after initial capture (X = 6.2 years); significantly longer than  non-reproductive females (X = 1.3 years), suggesting that a colony queen lives longer than her non-reproductive subordinates. This difference may be attributed to both physiological and social factors which may relax reproductive costs in queens.Key words: Fukomys damarensis, reproductive costs, sociality, longevity, trade-offs

Data from: Growth affects dispersal success in social mole-rats, but not the duration of philopatry

In naked mole-rats (Heterocephalus glaber), some non-breeding males show faster growth and are more likely to disperse than others. These differences have been suggested to be the result of a specialized developmental strategy leading to shorter philopatry and independent breeding, as opposed to extended philopatry as non-reproductive helpers. However, it is unclear whether fast-growing males disperse sooner than slow-growing males. An alternative explanation is that variation in quality between individuals causes high-quality individuals to grow quickly and maximize dispersal success without reducing philopatry. Here we show, that in Damaraland mole-rats (Fukomys damarensis), males that subsequently disperse successfully, grow faster than other non-reproductive males. This pattern is predicted by both hypotheses and does not discriminate between them. However, contrary to the suggestion that faster growth represents a developmental specialisation for early dispersal, fast-growing and slow-growing males remained equally long in their natal groups. Our study provides no evidence for adaptive divergence in male development leading either to early dispersal, or extended philopatry. Instead of representing specialized dispersers, fast-growing males of this species may be high-quality individuals

Workforce effects and the evolution of complex sociality in wild Damaraland mole rats

Please read abstract in article.The National Research Foundation of South Africa and the Universities of Cape Town and Pretoria. A.J.Y. was supported by a Biotechnology and Biological Sciences Research Council David Phillips fellowship.http://www.press.uchicago.edu/ucp/journals/journal/an.html2016-08-30am201

Subterranean mammals : reservoirs of infection or over-looked sentinels of anthropogenic environmental soiling?

Global reports of emergent pathogens in humans have intensified efforts to identify wildlife reservoirs. Subterranean mammals, such as bathyergid mole rats, are largely overlooked, despite their high-level exposure to soil-dwelling microbes. Initial assessment of bathyergid reservoir potential was determined using a broad-range 16S rRNA PCR approach, which revealed an 83% PCR-positivity for the 234 bathyergid lung samples evaluated. The presence of the Bacillus cereus complex, a ubiquitous bacterial assemblage, containing pathogenic and zoonotic species, was confirmed through nucleotide sequencing, prior to group- and species-specific PCR sequencing. The latter allowed for enhanced placement and prevalence estimations of Bacillus in four bathyergid species sampled across a range of transformed landscapes in the Western Cape Province, South Africa. Two novel Bacillus strains (1 and 2) identified on the basis of the concatenated 16S rRNA-groEL-yeaC data set (2066 nucleotides in length), clustered with B. mycoides (ATCC 6462) and B. weihenstephanensis (WSBC 10204), within a well-supported monophyletic lineage. The levels of co-infection, evaluated with a groEL strain-specific assay, developed specifically for this purpose, were high (71%). The overall Bacillus presence of 17.95% (ranging from 0% for Georychus capensis to 45.35% for Bathyergus suillus) differed significantly between host species (χ2 = 69.643; df = 3; P < 0.05), being significantly higher in bathyergids sampled near an urban informal settlement (χ2 = 70.245; df = 3; P < 0.05). The results highlight the sentinel potential of soil-dwelling mammals for monitoring anthropogenically introduced, opportunistic pathogens and the threats they pose to vulnerable communities, particularly in the developing world.The Airports Company of South Africa (ACSA) and the National Research Foundation of South Africa for research support through individual (ADSB), chair (NCB) and facilities (No: UID78566) grants.http://link.springer.com/journal/103932018-12-01hj2018Mammal Research InstituteZoology and Entomolog