Pattern of ovulation in the East African root rat (Tachyoryctes splendens) from Tanzania : induced or spontaneous ovulator?

The East African root rat, Tachyoryctes splendens is a solitary dwelling subterranean rodent that exhibits a marked seasonal reproduction linked to the bimodal rainfall pattern of East Africa. The current study set out to determine whether the East African root rat is an induced or spontaneous ovulator. Five wild caught adult females were monitored non-invasively for ovarian cyclicity by measuring urinary progesterone every two days over a period of 120 days. Females were subjected to three different experimental treatments namely, initially singly housed/Control (C), Non-Physical Contact with a male (NPC) and Physical Contact with a vasectomised male (PC), respectively. The concentration of urinary progesterone was higher during PC than during either NPC or C. The act of coitus appears to be necessary for ovulation to occur in the females, despite the fact that the males were vasectomised and incapable of fertilising the females. The male root rats were found to possess epidermal spines on the penis which can be used to remove copulatory plugs as well as bring about cervical stimulation during coitus. The spines result in the induction of ovulation as has been proposed for other solitary subterranean rodents. The findings from the female progesterone profiles and the assessment of penile morphology suggest that the female root rat is an induced ovulator stimulated by penile intromission during coitus.Le rat-taupe splendide (Tachyoryctes splendens (Rüppell, 1835)) est un rongeur souterrain solitaire qui présente une reproduction nettement saisonnière associée au motif de pluviosité bimodal de l’Afrique de l’Est. L’étude visait a` déterminer si l’ovulation est provoquée ou spontanée chez ce rongeur. La cyclicité ovarienne de cinq femelles capturées a` l’état sauvage a été surveillée de manière non intrusive en mesurant la progestérone urinaire tous les deux jours pendant 120 jours. Les femelles ont fait l’objet de trois traitements expérimentaux différents, a` savoir qu’elles étaient maintenues initialement seules (témoin; C), en contact non physique avec un mâle (NPC) et en contact physique (PC) avec un mâle vasectomisé, respectivement. La concentration de progestérone urinaire était plus élevée durant le traitement PC que durant les traitements NPC ou C. Le coït semble être nécessaire pour que l’ovulation ait lieu chez les femelles. Il a été constaté que des épines épidermiques sont présentes sur le pénis des rats-taupes splendides mâles, qui peuvent être utilisées pour stimuler le col utérin durant le coït. Ces épines provoquent l’ovulation, comme cela a été proposé pour d’autres rongeurs souterrains solitaires. Les profils de progestérone des femelles et l’évaluation de la morphologie du pénis donnent a` penser que l’ovulation des rats-taupes splendides femelles est provoquée par la stimulation produite par l’intromission pénienne durant le coït. [Traduit par la Rédaction]The University of Pretoria (UP PhD fellowship grant), South Africa and the South African Research Chair of Mammal Behavioural Ecology and Physiology from the DST-NRF to NCB.http://www.nrcresearchpress.com/journal/cjzhb2017Zoology and Entomolog

Circadian rhythms of locomotor activity in captive Emin's mole-rats, Heliophobius emini (Rodentia : Bathyergidae)

Many African mole-rats (Bathyergidae) exhibit distinct circadian rhythms, despite the fact that they are strictly subterranean and are very infrequently exposed to light. We investigated the circadian system of Emin’s mole-rats (Heliophobius emini) by exposing 13 individuals to different lighting regimes. The mole-rats were subjected to a standard 12h light:12h dark light cycle, followed by constant darkness (DD) cycle to evaluate entrainment and endogenous rhythms of locomotor activity. After allowing the mole-rats to re-entrain to a 12L:12D light cycle, the light cycle was inverted to examine the duration of re-entrainment following a drastic change in the light cycle. Furthermore, we investigated the effect of different ambient temperatures on the locomotor activity of the mole-rats, and they were thus subjected to a 12D:12L light cycle at 20oC, 25oC and 30oC. Lastly, mole-rats were presented with a long day (16L:8D) and a short day (8L: 16D) light cycle to look at the effect on preferred active time. The animals showed a preference for diurnal activity with nine mole-rats entraining to the light cycle, and maintaining clear endogenous rhythms throughout DD. Subjects were excessively slow to re-entrain their activity to the inverted light cycle. When subjected to different ambient temperatures, individuals showed marked increases in average activity at 20oC, with the lowest average activity occurring at 30oC. The mole-rats maintain their diurnal preference regardless of day length, condensing their activity during the short day light cycle, while extending their active period during the long day cycle. These results suggest that Emin’s mole-rats are able to perceive light and entrain their locomotor activity to light cycles, albeit weakly. In addition, ambient temperature influences the level of overall activity, indicating that these animals may use behavioral thermoregulation to maintain a constant body temperature.A South African Research Chair of Mammal Behavioural Ecology and Physiology to NCB.http://jmammal.oxfordjournals.org2018-02-08hb2017Zoology and Entomolog

Reproduction in the East African root rat (Tachyoryctes splendens ; Rodentia : Spalacidae) from Tanzania : the importance of rainfall

The East African root rat, Tachyoryctes splendens (Rüppell, 1835) is a solitary subterranean rodent mole. The present study investigated breeding patterns in both sexes of T. splendens from data collected at monthly intervals over an entire calendar year. The study focused on the analyses from post mortem examination of males and females to assess the presence of foetuses, gonadal histology, reproductive tract morphometrics, measurement of gonadal steroids (plasma progesterone and oestradiol-17β in females and testosterone in males) and field observations (i.e., the presence of infants, juveniles, sub-adults and lactating females). The objective of this study was to assess if the reproductive biology of the root rat reflected the bimodal pattern of rainfall that is characteristic of East Africa. Rainfall has been suggested to trigger breeding in many subterranean rodents and as a consequence, this study aimed to assess the relationship between rainfall and reproductive characteristics of T. splendens. Peaks in mean gonadal mass, increases in concentration of reproductive hormones and the presence of Graafian follicles and corpora lutea in the ovaries of females, and testes mass, seminiferous tubule diameter and testosterone titre mirrored the annual peaks of precipitation at the study area. Together with field observations of the temporal occurrence of pregnancies, infants, juveniles and sub-adults, the data show that T. spendens cues its breeding with the patterns of rainfall, such that offspring are born in the latter half of each rainy season, from April to July and November to December.University of Dar es Salaam [UDSM–World Bank Fund (C1B1) ], Tanzania.South African Department of Science and Technology (DST)/National Research Foundation (NRF) SARChI Chair for Mammal Behavioural Ecology and Physiology, University of Pretoria.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1469-7998hb201

Sweeping the house clean : burrow architecture and seasonal digging activity in the East African root rat from Tanzania

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.University of Dar es Salaam (UDSM) World Bank Fund (C1B1 of the University of Dar as Salaam, Tanzania. NCB acknowledges funding from the South African DST/NRF SARChI Chair for Mammal Behavioural Ecology and Physiology,University of Pretoria.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1469-79982015-08-31hb201

Rapid molecular evolution of pain insensitivity in multiple African rodents

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 Nav1.7, 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.Grants from the European Research Council (advanced grant 294678 to G.R.L.) and the Deutsche Forschungsgemeinschaft SFB 958 (to G.R.L.), by a South African Research Chair for Mammalian Behavioural Ecology and Physiology to N.C.B., and by a National Science Foundation grant to T.J.P.http://www.sciencemag.orghj2019Mammal Research InstituteZoology and Entomolog

The pattern of ovulation in the East African Root-Rat, Tachyoryctes splendens from Tanzania: induced or spontaneous ovulator?

The East African root rat, Tachyoryctes splendens (Ruppell 1835) is a solitary subterranean rodent that exhibits a marked seasonal reproduction linked to the bimodal rainfall pattern of East Africa. The current study set out to determine whether the East African root rat is an induced or spontaneous ovulator. Five wild caught adult females were monitored non-invasively for ovarian cyclicity by measuring urinary progesterone every two days over a period of 120 days. Females were subjected to three different experimental treatments namely, initially singly housed/Control (C), Non-Physical Contact with a male (NPC) and Physical Contact with a vasectomised male (PC), respectively. The concentration of urinary progesterone was higher during PC than during either NPC or C. The act of coitus appears to be necessary for ovulation to occur in the females. The male root rats were found to possess epidermal spines on the penis which can be used to bring about cervical stimulation during coitus. The spines result in the induction of ovulation as has been proposed for other solitary subterranean rodents. The findings from the female progesterone profiles and the assessment of penile morphology suggest that the female root rat is an induced ovulator stimulated by penile intromission during coitus.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Serological Analyses of Human Brucellosis in Ngara and Kibondo Districts, Tanzania

Brucellosis, a zoonotic disease transmitted by Brucella species, is transmitted to humans from infected animals through handling dairy products like milk, blood, and semen. Although some human communities in Tanzania live close to livestock, the status of human brucellosis in Ngara and Kibondo Districts in Kagera and Kigoma regions, respectively, is poorly understood. As such, the present study aimed to investigate the status of human brucellosis in north-western Tanzania, particularly Ngara and Kibondo Districts, where the risk of contracting zoonotic diseases, including brucellosis, is high due to the abundance of livestock. Among the screened sera (n = 450), the prevalence was 13.11% with an incidence rate of 6.22% in 581,378 population size intimating that the risk is alarming. Brucellosis patients admitted in dispensaries and other lower health facilities ranged from 6% to 26%, while those admitted in hospitals ranged from 4% to 14%  indicating that communities prefer primary health facilities to hospitals when they show symptoms of brucellosis. The present study has also revealed that communities engaged in slaughtering, milking, skinning and helpers during births of livestock are at high risk of acquiring Brucella spp. because the odds ratios’ of these activities range between 1.583 and 8.400. Therefore, awareness and education should be enhanced by veterinary officers and associated stakeholders. A comprehensive study of brucellosis using molecular techniques to reveal species-specific in north-western Tanzania is highly recommended. Keywords: brucellosis; prevalence; incidence; risk factors; seru

Pattern of ovulation in an ancient, solitary mole-rat lineage : Heliophobius argenteocinereus emini from Tanzania

The genus Heliophobius Peters, 1846 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 the silvery mole-rat subspecies 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 nonphysical 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. Noninvasive 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.The University of Pretoria (International UP Funds). The South African Research Chair of Mammal Behavioural Ecology and Physiology from the DST-NRF to N.C.B.http://www.nrcresearchpress.com/journal/cjzhj2017Mammal Research InstituteZoology and Entomolog

Pattern of ovulation in an ancient, solitary mole-rat lineage: Heliophobius argenteocinereus emini from Tanzania

HHeliophobius 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.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Pattern of ovulation in the East African root rat ( Tachyoryctes splendens

The East African root rat, Tachyoryctes splendens is a solitary dwelling subterranean rodent that exhibits a marked seasonal reproduction linked to the bimodal rainfall pattern of East Africa. The current study set out to determine whether the East African root rat is an induced or spontaneous ovulator. Five wild caught adult females were monitored non-invasively for ovarian cyclicity by measuring urinary progesterone every two days over a period of 120 days. Females were subjected to three different experimental treatments namely, initially singly housed/Control (C), Non-Physical Contact with a male (NPC) and Physical Contact with a vasectomised male (PC), respectively. The concentration of urinary progesterone was higher during PC than during either NPC or C. The act of coitus appears to be necessary for ovulation to occur in the females, despite the fact that the males were vasectomised and incapable of fertilising the females. The male root rats were found to possess epidermal spines on the penis which can be used to remove copulatory plugs as well as bring about cervical stimulation during coitus. The spines result in the induction of ovulation as has been proposed for other solitary subterranean rodents. The findings from the female progesterone profiles and the assessment of penile morphology suggest that the female root rat is an induced ovulator stimulated by penile intromission during coitus.Le rat-taupe splendide (Tachyoryctes splendens (Rüppell, 1835)) est un rongeur souterrain solitaire qui présente une reproduction nettement saisonnière associée au motif de pluviosité bimodal de l’Afrique de l’Est. L’étude visait a` déterminer si l’ovulation est provoquée ou spontanée chez ce rongeur. La cyclicité ovarienne de cinq femelles capturées a` l’état sauvage a été surveillée de manière non intrusive en mesurant la progestérone urinaire tous les deux jours pendant 120 jours. Les femelles ont fait l’objet de trois traitements expérimentaux différents, a` savoir qu’elles étaient maintenues initialement seules (témoin; C), en contact non physique avec un mâle (NPC) et en contact physique (PC) avec un mâle vasectomisé, respectivement. La concentration de progestérone urinaire était plus élevée durant le traitement PC que durant les traitements NPC ou C. Le coït semble être nécessaire pour que l’ovulation ait lieu chez les femelles. Il a été constaté que des épines épidermiques sont présentes sur le pénis des rats-taupes splendides mâles, qui peuvent être utilisées pour stimuler le col utérin durant le coït. Ces épines provoquent l’ovulation, comme cela a été proposé pour d’autres rongeurs souterrains solitaires. Les profils de progestérone des femelles et l’évaluation de la morphologie du pénis donnent a` penser que l’ovulation des rats-taupes splendides femelles est provoquée par la stimulation produite par l’intromission pénienne durant le coït. [Traduit par la Rédaction]The University of Pretoria (UP PhD fellowship grant), South Africa and the South African Research Chair of Mammal Behavioural Ecology and Physiology from the DST-NRF to NCB.http://www.nrcresearchpress.com/journal/cjzhb2017Zoology and Entomolog