Browsing by Author "Bennett, N. C."
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Item Pattern of ovulation in an ancient, solitary mole-rat lineage: Heliophobius argenteocinereus emini from Tanzania(CORNELL UNIVERSITY, 2017) Katandukila, J. V.; Ngalameno, M. K.; Mgode, G. F.; Bastos, A. D. S.; Bennett, N. C.Heliophobius is an ancient subterranean rodent lineage within the family Bathyergidae, that displays seasonal breeding over a broad geographical range. In East Africa, reproduction in these solitary mole-rats has been shown to coincide with the long rains, but it is not clear whether Heliophobius argenteocinereus emini (Noack 1894) from Tanzania is an induced or spontaneous ovulator. To address this, urinary progesterone was measured every second day over a period of 132 days in six wild-caught females subjected to three sequential experimental treatments. In the first, control (C) treatment, females were housed singly for a period of 44 days, following which non-physical contact (NPC) with a vasectomised male and then physical contact (PC) with the same vasectomised male, occurred, in each of the subsequent 44-day treatments. Non-invasive monitoring of ovarian cyclicity confirmed that mean urinary progesterone concentration was higher during PC than during either NPC or C, despite the fact that the males were vasectomised and incapable of fertilising the females. Examination of penile morphology revealed that males possess epidermal projections on the glans penis which probably bring about cervical stimulation during coitus. These findings together with the female progesterone profiles imply the species is an induced ovulator stimulated by penile intromission.Item The pattern of reproduction in the mole-rat Heliophobius from Tanzania: do not refrain during the long rains!(NRC Research Press, 2016) Ngalameno, M. K.; Bastos, A. D. S.; Mgode, G.; Bennett, N. C.The genus Heliophobius Peters, 1846 comprises at least six cryptic, topotypical species in the Heliophobius argenteocinereus Peters, 1846 species complex. The current study investigated the breeding patterns of a wild-caught population from Tanzania where the putative species Heliophobius argenteocinereus emini Noack, 1894 resides. Individuals were collected on a monthly basis for an entire calendar year. Assessment of fœtus presence, gonadal histology, reproductive-tract morphometrics in combination with gonadal steroid (plasma progesterone and œstradiol-17 in females and testosterone in males) measurements and field observations revealed that rainfall is important for the onset of breeding. The results further confirmed that breeding is limited to a single, yearly reproductive event synchronised to the long rainfall pattern. The distinct breeding peak in July is associated with an elevation in gonadal mass, increase in concentrations of reproductive hormones, and presence of Graafian follicles and corpora lutea in the ovaries of females. These reproductive parameters coincided with the end of the long rainfall period, whereas presence of young in the maternal burrow system corresponded with the start of the short rainfall of East Africa. These findings confirm Heliophobius has a single breeding opportunity each year, and this species is therefore vulnerable to any changes that may impact their climatically attuned breeding patterns.Item Rapid molecular evolution of pain insensitivity in multiple African rodents(Science sciencemag, 2019-05-31) Eigenbrod, O.; Debus, K. Y.; Reznick, J.; Bennett, N. C.; Sánchez-Carranza, O.; Omerbašić, D.; Hart, D. W.; Barker, A. J.; Zhong, W.; Lutermann, H.; Katandukila, J. V.; Mgode, G.; Park, T. J.; Lewin, G. R.Noxious substances, called algogens, cause pain and are used as defensive weapons by plants and stinging insects. We identified four previously unknown instances of algogen-insensitivity by screening eight African rodent species related to the naked mole-rat with the painful substances capsaicin, acid (hydrogen chloride, pH 3.5), and allyl isothiocyanate (AITC). Using RNA sequencing, we traced the emergence of sequence variants in transduction channels, like transient receptor potential channel TRPA1 and voltage-gated sodium channel Na v 1.7, that accompany algogen insensitivity. In addition, the AITC-insensitive highveld mole-rat exhibited overexpression of the leak channel NALCN (sodium leak channel, nonselective), ablating AITC detection by nociceptors. These molecular changes likely rendered highveld mole-rats immune to the stings of the Natal droptail ant. Our study reveals how evolution can be used as a discovery tool to find molecular mechanisms that shut down pain.Item Relic populations of Fukomys mole- rats in Tanzania: description of two new species F. livingstoni sp. nov. and F. hanangensis sp. nov.(Faulkes / PeerJ, 2017-04-27) Faulkes, C. G.; Mgode, G. F.; Archer, E. K.; Bennett, N. C.Previous studies of African mole-rats of the genera Heliophobius and Fukomys (Bathy- ergidae) in the regions of East and south central Africa have revealed a diversity of species and vicariant populations, with patterns of distribution having been influenced by the geological process of rifting and changing patterns of drainage of major river systems. This has resulted in most of the extant members of the genus Fukomys being distributed west of the main Rift Valley. However, a small number of isolated popula- tions are known to occur east of the African Rift Valley in Tanzania, where Heliophobius is the most common bathyergid rodent. We conducted morphological, craniometric and phylogenetic analysis of mitochondrial cytochrome b (cyt b) sequences of two allopatric populations of Tanzanian mole-rats (genus Fukomys) at Ujiji and around Mount Hanang, in comparison with both geographically adjacent and more distant populations of Fukomys. Our results reveal two distinct evolutionary lineages, forming clades that constitute previously unnamed species. Here, we formally describe and designate these new species F. livingstoni and F. hanangensis respectively. Molecular clock-based estimates of divergence times, together with maximum likelihood inference of biogeographic range evolution, offers strong support for the hypothesis that vicari- ance in the Western Rift Valley and the drainage patterns of major river systems has subdivided populations of mole-rats. More recent climatic changes and tectonic activity in the ‘‘Mbeya triple junction’’ and Rungwe volcanic province between Lakes Rukwa and Nyasa have played a role in further isolation of these extra-limital populations of Fukomys in Tanzania.Item Sweeping the house clean: burrow architecture and seasonal digging activity in the East African root rat from Tanzania(2014-03) Katandukila, J. V.; Chimimba, C. T.; Bennett, N. C.; Makundi, Rhodes H.; Le Comber, S. C; Faulkes, C. G.We investigated changes in burrow architecture and fractal dimension across seasons and between the sexes in the solitary East African root rat Tachyoryctes splendens over an entire calendar year. The basic burrow system comprised a main tunnel reticulating into foraging tunnels, a nest consisting of food store chamber, latrine and sleeping area, and a bolt hole. Main tunnel length was strongly affected by sex, and contrary to expectations, it was longer for females than for males (during both the dry and the wet seasons). The number and the length of foraging tunnels were affected by both sex and season, with females’ burrows having more foraging tunnels than males in both the dry and the wet seasons. Females also had burrows with higher fractal dimension than males, while fractal dimension increased with burrow length for both sexes. We suggest that unlike the solitary bathyergid mole-rats, male T. splendens do not construct larger burrows than females in the search for mates, but rather females have larger burrows with more foraging tunnels resulting from the increased need for provisioning of their young