Burrow architecture and digging activity in the Cape dune mole rat

While females are traditionally thought to invest more time and energy into parental care than males, males often invest more resources into searching and displaying for mates, obtaining mates and in male–male conflict. Solitary subterranean mammals perform these activities in a particularly challenging niche, necessitating energetically expensive burrowing to both search for mates and forage for food. This restriction presumably affects males more than females as the former are thought to dig longer tunnels that cover greater distances to search for females. We excavated burrow systems of male and female Cape dune mole rats Bathyergus suillus the, largest truly subterranean mammal, to investigate whether male burrows differ from those of females in ways that reflect mate searching by males. We consider burrow architecture (length, internal dimensions, fractal dimension of tunnel systems, number of nesting chambers and mole mounds on the surface) in relation to mating strategy. Males excavated significantly longer burrow systems with higher fractal dimensions and larger burrow areas than females. Male burrow systems were also significantly farther from one another than females were from other females' burrow systems. However, no sex differences were evident in tunnel cross-sectional area, mass of soil excavated per mound, number of mounds produced per unit burrow length or mass of soil excavated per burrow system. Hence, while males may use their habitat differently from females, they do not appear to differ in the dimensions of the tunnels they create. Thus, exploration and use of the habitat differs between the sexes, which may be a consequence of sex differences in mating behaviour and greater demands for food.     

Thermoregulation and metabolism in the Cape golden mole (Insectivora: Chrysochloris asiatica)

The Cape golden mole, Chrysochloris asiatica is an insectivore which excavates superficial foraging burrows as it searches for its food. It has a mean (±S.D.) resting metabolic rate (RMR) when newly captured of 1–17±0.17 cm³ O₂g^-1 h^-1 ( n = 14), within the thermoneutral zone (TNZ) of 30–32°C.
The body temperature (Tb) of the mole in the TNZ is low 32.9 ± 0.36 ( n = 14) and remains stable at ambient temperatures (Tas) from 28–32°C. Above 32°C (range 34–37°C), Tb increases albeit slightly to 36 ± 1.75°C ( n = 14). The conductance is high 0.27 ± 006cm³ O₂g^-1 h^-l°C^-1 ( n = 46) at the lower limit of thermoneutrality. The mean RMR at 9°C (the lowest Ta tested) was 4.82±11 cm³ O₂g^-1h^-1, which is 4.1 times that of the RMR in the TNZ.
At an ambient temperature of 9°C, three of the golden moles entered a state of torpor where the RMR was reduced from 5.9±0.56 to 10 1.0 ± 0.69cm³O₂g^-1h^-1.     

LH responses to single doses of exogenous GnRH in the Cape mole rat (Georychus capensis): the pituitary potential for opportunistic breeding

The Cape mole rat Georychus capensis is a solitary mole rat that inhabits the winter rainfall region of the Western Cape Province of South Africa. Circulating basal concentrations of luteinizing hormone (LH) were found to be significantly higher in the breeding season in both sexes. During both the breeding and non-breeding season, administration of exogenous gonadotropin-releasing hormone (GnRH) increased circulatory LH levels. The magnitude of the LH response to an overdose of exogenous GnRH both in and out of the breeding season in males and females was not significantly different. Typically, seasonally breeding species exhibit a down-regulation of the pituitary and reproductive functions out of the breeding season. It appears that there is no down-regulation of GnRH receptors at the level of the pituitary out of the breeding season, because the pituitary responds to an exogenous GnRH challenge equally both in and out of the breeding period. The Cape mole rat exhibits the potential for opportunistic breeding out of the breeding period, provided that environmental factors are favourable. This finding questions whether this mole rat is actually a seasonal breeder or whether reproduction is hindered by the ecological constraint of the lack of opportunities to burrow and find mates at certain times of the year.     

Ossicular differentiation of airborne and seismic stimuli in the Cape golden mole (Chrysochloris asiatica)

Comparison between the middle ear anatomy of the Cape golden mole (Chrysochloris asiatica), which exhibits a club-shaped malleus head, and the Desert golden mole (Eremitalpa granti), with a ball-shaped malleus head, suggests differences in sensitivity to airborne sound. Scanning laser Doppler vibrometric measurements of the ossicular behavior in response to both vibration and airborne sound were made in C. asiatica. Two distinct vibrational modes were observed. In response to low-frequency vibration (70–200 Hz), the malleus oscillates about the ligament of the short process of the incus, whereas in response to high-frequency airborne sound (1–6 kHz) the ossicular chain rotates about the long axis of malleus. It is proposed that the club-shaped malleus head in C. asiatica constitutes an adaptation towards bimodal hearing—sensitivity to substrate vibrations and airborne sound. Possible functional differences between these two middle ear types are discussed.     

Determinants of helminth infection in a subterranean rodent, the Cape dune mole-rat ( Bathyergus suillus )

The helminth fauna of the largest bathyergid, the Cape mole-rat ( Bathyergus suillus ) was studied throughout an entire calendar year. The species richness encountered was low, with only 3 species of nematodes ( Longistriata bathyergi , Mammalakis macrospiculum, and Trichostrongylus sp.) and 2 species of cestodes ( Taenia sp. and Rodentolepis sp.). At less than 10%, the prevalence for all helminths species was similarly low and may be a result of the solitary lifestyle and the subterranean habitat exploited by this rodent. Clear seasonal patterns were apparent for the most common nematode ( L. bathyergi ), and prevalence and abundance were highest among non-pregnant females compared to males and pregnant females. Dispersal patterns associated with the mating system of the host could explain this pattern. In contrast, the prevalence of the most common cestode ( Taenia sp.) was neither determined by season nor host sex, suggesting that foraging habits may constantly expose B. suillus to this parasite.     

Diet of samango monkeys (Cercopithecus mitis erythrarchus) in the Cape Vidal dune forest, South Africa

The samango monkey ( Cercopithecus mitis erythrarchus Peters, 1852) is the southernmost representative of the widely-distributed polytypic Cercopithecus mitis species-group. At Cape Vidal (28 S) climatic seasonality causes significant seasonal fluctutation in food abundance. There are, however, no congeneric competitors, and few arboreal frugivores (birds, bats). In spite of seasonality of food abundance at Cape Vidal, samango monkeys maintain a high quality diet, dominated by fruit (51.7%), throughout the year. To a large extent this is made possible by their broad dietary tolerances and the effect of competitive release on food choice. Seasonal insect abundance does, however, place serious constraints on the availability of readily-digestible protein and the acquisition of protein-rich foods must be seen as the critically limiting factor in the dietary behaviour of the samango monkey. Adaptation of gut morphology and symbiotic microflora permit samangos to supplement the diet with large amounts of protein-rich foliar and floral items. Where necessary, even large quantities of less palatable items, such as unripe fruits and mature leaves, may be ingested. Although insects form a small part of the diet a larger variety, than used by equatorial C. mitis populations, are included in the diet. Given that there are no congeneric competitors, nor are the monkeys particularly food stressed, I suggest that the diet of the samango monkey at Cape Vidal most closely reflects the intrinsic food choices of the C. mitis species-group.     

Off road vehicle impact in Cape Cod national seashore: Disruption and recovery of dune vegetation

An on-going investigation of the rates of vegetation breakdown and natural recovery under controlled conditions has been established at Cape Cod National Seashore, Massachusetts, U.S.A. In this study, the effects of controlled impacts on a variety of coastal habitats were measured in terms of above and below ground biomass. Dune sites, ranging from unstabilized to moderately stabilized, were driven on at varying levels of intensity and along different exposures relative to slope and prevailing wind direction. Preliminary evidence suggests that a single summer season of driving (300–700 passes) on a confined track through dense stands ofAmmophila vreviligulata, Arctostaphylos uva-ursi, andDeschampsia flexuosa, can completely destroy the above-ground portions but leave adequate underground roots and thizomes for a small amount of vegetative regrowth after cessation of impact in the late summer and fall. Large differences in wind speed at ground level have been noted in driving tracks with different alignments relative to wind direction. Deflation rates may be excessive in tracks devoid of above ground cover and aligned parallel to strong prevailing winter winds.Presented at the Seventh International Biometeorological Congress, 17–23 August 1975, College Park, Maryland, USA.     

Vascular aging in the longest-living rodent, the naked mole rat

The naked mole rat (NMR; Heterocephalus glaber) is the longest-living rodent known [maximum lifespan potential (MLSP): >28 yr] and is a unique model of successful aging showing attenuated declines in most physiological function. This study addresses age-related changes in endothelial function and production of reactive oxygen species in NMR arteries and vessels of shorter-living Fischer 344 rats (MLSP: approximately 3 yr). Rats exhibit a significant age-dependent decline in acetylcholine-induced responses in carotid arteries over a 2-yr age range. In contrast, over a 10-yr age range nitric oxide (NO)-mediated relaxation responses to acetylcholine and to the NO donor S-nitrosopencillamine (SNAP) were unaltered in NMRs. Cellular superoxide anion (O(2)(*-)) and H(2)O(2) production significantly increased with age in rat arteries, whereas they did not change substantially with age in NMR vessels. Indicators of apoptotic cell death (DNA fragmentation rate, caspase 3/7 activity) were significantly enhanced ( approximately 250-300%) in arteries of 2-yr-old rats. In contrast, vessels from 12-yr-old NMRs exhibited only a approximately 50% increase in apoptotic cell death. In the hearts of NMRs (2 to 26 yr old), expression of endothelial NO synthase, antioxidant enzymes (Cu,Zn-SOD, Mn-SOD, catalase, and glutathione peroxidase), the NAD(P)H oxidase subunit gp91(phox), and mitochondrial proteins (COX-IV, ATP synthase, and porin, an indicator of mitochondrial mass) did not change significantly with age. Thus long-living NMRs can maintain a youthful vascular function and cellular oxidant-antioxidant phenotype relatively longer and are better protected against aging-induced oxidative stress than shorter-living rats.     

Development of vegetation in dune slack wetlands of Cape Cod National Seashore (Massachusetts,USA)

Interdunal seasonal wetlands, known as dune slack wetlands, were mapped and their vegetation surveyed across a large region of dunes within the Cape Cod National Seashore. Wetland sizes and ages were estimated from digitized, georeferenced aerial photographs available from 1938, 1947, 1960, 1986, 1994, and 2001, and from LIDAR elevation data. A total of 346 sites were found, covering an area of ∼45.4 ha., in which 97 species of vascular plants were identified. Vegetation structure and composition exhibited a distinct sequence of development with age, following a pattern of succession from herbaceous, graminoid-dominated communities to shrub- and tree-dominated communities. Floristic variables were not related to proximity to the coast and although wetland size appeared to have some bearing on species richness, the correlation was statistically weak. Soil organic matter determined for a subset of 60 wetlands was positively correlated with age and woody cover but showed no relationship with water depth. The results suggest that vegetation development is primarily driven by the internal mechanisms of succession. Notwithstanding, any changes in the environment that alter the process of succession will collectively influence these wetlands. In addition, stabilization of the dunes resulting in a reduction in the formation of new wetlands, may translate into permanent loss of early and mid-successional dune slack communities. Maintenance of these communities will depend on succession being periodically reset by disturbance or active management.     

The molecular basis of defective lens development in the Iberian mole

Background  

Fossorial mammals face natural selection pressures that differ from those acting on surface dwelling animals, and these may lead to reduced visual system development. We have studied eye development in a species of true mole, the Iberian mole Talpa occidentalis, and present the molecular basis of abnormal lens development. This is the first embryological developmental study of the eyes of any fossorial mammal at the molecular level.     

Early skeletal development in Talpa europaea, the common European mole

An ontogenetic series of 22 cleared and double-stained prenatal specimens was used to study the sequence of ossification of selected postcranial skeletal elements of Talpa europaea. Results were compared with nine other therian mammals, with Alligator, Chelydra, and Lacerta as outgroups. Using the event-pairing method, shifts in the onset of ossification in T. europaea, Sus, and Homo were identified. In T. europaea, the ossification of the cervical vertebrae starts before the metatarsals. In Homo and Sus, the tarsals ossify before the pubic bone. These shifts in the sequence of ossification are unique among the mammals examined, whereas many other changes, characterising monophyletic groups and/or evolving convergently, were also identified. Particular attention was given to some peculiar calcified elements of the hand in T. europaea, which were identified as accessory ;sesamoid bones', and do not display a chondrified precursor. They start to calcify before all others of the hand and later fuse. They appear in all fingers and function as reinforcement for the distal phalanges, most likely as an adaptation for burrowing. The development of the sesamoid bones was examined using histological sections and macerated adults.     

Above and belowground community development in a marine sand dune ecosystem

Transects across undisturbed marine sand dunes sequentially traversed the following plant communities: littoral, foredunes, intradune complex of ridges and hollows, deflation plain, myrtle forest, and mature conifer forest. Organic carbon levels were low in the littoral zone and increased across the dune ecosystem landward to the forest communities. The highest percentage of nutrients was isolated from the heavy fraction of soil residues. Soil microfloral populations responded to vegetation, physical dune characteristics, and seasonal moisture patterns. Populations of bacteria and actinomycetes were higher in winter than during summer sampling periods in all communities. Populations of microscopic fungi were higher in winter in all the communities except the hollows. The distribution of vesicular-arbuscular mycorrhizal fungi responded to vegetation and sand dune succession but did not display seasonality. Species of Gigaspora and Acaulospora were the most commonly isolated VAM fungi.Sand aggregation increased along the dune transect and was correlated to plant community succession: the most highly aggregated soil was found in the two forest communities. With scanning electron microscopy, sand grains and organic residues were observed entangled by strands of filamentous mciroorganisms. Many of the filaments were of the dimensions of VAM fungi, which may be important for the release of nutrients associated with the cementing agents of sand aggregates and for the survival of early pioneer plants of sand dunes.     

Seismic communication in demon African mole rat Tachyoryctes daemon from Tanzania

We describe the production of substrate-borne vibrations in a subterranean mole rat of the genus Tachyoryctes for the first time. These signals with a supposed communication function were recorded using two approaches. Firstly, we recorded the production of spontaneous substrate-borne vibrations of individual test animals in artificial tunnels simulating a mole rat burrow system. Secondly, we recorded substrate-borne vibrations in individuals with interconnected home systems divided by a barrier. We found that Tachyoryctes produces these seismic signals by striking its head against the ceiling of the tunnel. Two types of seismic signals differing in physical parameters were identified. A slow signal (inter-pulse distance 0.12 s, inter-bout distance 3.89 s, number of pulses within each bout 9.53) was produced in both experiments, whereas a fast signal (inter-pulse distance 0.05 s, inter-bout distance 18.44 s, number of pulses within each bout 22.54) was produced mainly in close proximity to another individual. Our results indicate that fast signals are probably individually specific, because the success rate of classification according to discriminant function analysis was 70.4 % for the three tested individuals.     

印度地鼠的性成熟和窝仔数

为有效地进行有害脊椎动物的控制 ,研究了栖息于巴基斯坦Punjab中部的 348只印度地鼠的繁殖模式。在所捕捉到的 10 7雄鼠和 2 4 1只雌鼠中 ,分别有 75只和 179只是性成熟的个体。性比偏雌。使用被捕个体标本的体重和体长作为指标 ,发现最小的性成熟的雄性个体体重为 70 - 89g ,体长 13 1- 14 0cm ;一窝仔里面的平均胚胎数为 2 74± 0 15 (范围 ,1- 5 ) ,而平均胎斑数为 4 2 9± 0 19(1- 11) .体重似乎对窝仔数有显著影响 ,而体长和估计的年龄对窝仔数没影响。当老鼠繁殖不活跃和不繁殖时 ,控制害兽最有效     

Eye development: random precision in color vision

In insect and vertebrate eyes, different types of color-detecting photoreceptors are randomly distributed throughout the retina. A recent study has provided important new insights into the developmental mechanisms that generate the retinal mosaic required for color vision.