Sexual size dimorphism in the lizard Oplurus cuvieri cuvieri (Squamata,Opluridae) from Madagascar

Sexual size dimorphism in the medium-sized lizard Oplurus cuvieri cuvieri, which is endemic to the dry deciduous forest of Madagascar, is presented. Adults are sexually dimorphic in body size, head size, and tail length. Males have a greater snout–vent length (SVL), head depth, head width, jaw length, tail length and body mass than females. Juvenile males have greater annual SVL growth rates than juvenile females, contributing to adult sexual size dimorphism. Moreover, the rates of increase in head depth and width differ significantly between the sexes after reaching maturity so that adult males have larger heads for a given body size than adult females. I suggest three proximate mechanisms that may cause sex-related differences in adult head size of O. c. cuvieri based on natural selection; to reduce intersexual food competition, sexual selection involving mate acquisition in males, and ontogenetic change of allometry to improve reproductive output in females.     

Seasonal effects on digging activity and burrow architecture in the Cape dune mole-rat,Bathyergus suillus (Rodentia: Bathyergidae)

Most polygynous male mammals exhibit little or no parental care or involvement raising young. Instead, they invest indirectly in their own morphological and physiological attributes which enhance their chance of reproduction. Such secondary morphological sex traits may contribute to differences in the burrow architecture of fossorial mammals, such as the Cape dune mole-rat, Bathyergus suillus. Indeed, little is known about the seasonal changes in burrow architecture or differences in burrow configuration may differ between the sexes of subterranean African mole-rats (Bathyergidae). We excavated burrow systems of male and female B. suillus during the summer and the winter to investigate whether male burrow architecture reflected putative mate-seeking behaviour. We consider burrow geometry in response to mating strategies. Male burrow systems explored the environment more efficiently than females. This is presumably because of the increase in associated energetic costs of being a large male. Males produce more mounds indicating territorial behaviour even when it is energetically costly to dispose of soil onto the surface when the soil is less friable during the summer. Overall tunnel dimensions did not differ between the sexes. It appears that a change in season does not affect the geometry of the burrow system or tunnel dimensions in a climatically buffered environment.     

Evolutionary history of mountain voles of the subgenus Aschizomys (Cricetidae,Rodentia), inferred from mitochondrial and nuclear markers

In this study, we present an assessment of the evolutionary history and phylogenetic relationships of Asian mountain voles of the subgenus Aschizomys, genus Alticola, based on extensive sampling and phylogenetic analyses of data from mitochondrial and nuclear markers. Two species of this subgenus are widespread in the mountain areas of north‐eastern Asia. However, both their distribution and taxonomic borders remained questionable for more than 100 years. Our study showed discordance in the phylogenetic patterns between nuclear and mtDNA markers. We found that mtDNA in A. lemminus is paraphyletic relative to A. macrotis, but nuclear markers demonstrated reciprocal monophyly. According to species distribution modeling, ranges of A. macrotis and A. lemminus experienced a secondary contact during the Last Glacial Maximum (approximately 22 kyr BP), and thus a hybridization event seems plausible during that period. Species tree analyses recovered a sister group relationship between the two species of the Aschizomys subgenus, with an estimated divergence date of around 0.8 Ma. Our results provided good support for currently recognized subspecies within both A. macrotis and A. lemminus based on mitochondrial and nuclear datasets. A new, yet undescribed form, supposedly of a subspecific status within A. lemminus, was found in the Bureinskiy Range in the Khabarovsk area. This finding expands the current species distribution range further to the southeast.     

Skull size and shape variation in Psammomys spp. (Rodentia,Gerbillinae) from Tunisia,with emphasis on the impact of allometric variation on species recognition

In Tunisia both Psammomys obesus and P. vexillaris are found. These taxa have been the subject of taxonomic controversy for some time, due to variability in the classical morphological characters used for taxonomic recognition. In this study we investigated skull size and shape variation in the genus Psammomys by using geometric morphometrics to evaluate the extent of intra- and interspecific shape variation and explicitly tested for the impact of allometric shape variation on species discrimination. Eleven populations of the two species from 10 localities in Tunisia were studied. Statistical analyses of size and shape showed large size variation within P. obesus, but no shape differences were revealed among populations of this species. Interspecific analysis revealed that P. vexillaris had the smallest skull. Principal component analysis and Procrustes distances showed good discrimination between the two species after removal of the allometric component of shape variation. The results obtained show that allometric-related shape variation could mask discrimination between the two Psammomys species. This finding might explain the uncertainty in classification of these species in the past. The interspecific allometric-free phenotypic differences observed may be associated with adaptive processes linked to the different environmental and trophic preferences of the two species.     

青藏高原入侵杂草黄帚橐吾种群内与种群间的遗传变异研究(英文)

外来入侵物种的遗传变异以及在此基础上建立的控制措施受到了广泛关注,但是,对本地产生杂草的遗传变异却研究较少。菊科中的黄帚橐吾主要依赖根状茎和种子进行繁殖,是青藏高原高山草地生态系统中的广布杂草。本研究利用RAPD随机扩增的DNA多态性研究该物种11个种群的遗传变异。结果表明,13个随机引物获得了81条可重复的扩增带,每个引物平均产生6.23条带,74.07%(61条)的带是多态的。种群中多态位点变化为19.45%～60.49%,He是0.1698±0.03,表明该物种具有中等程度的遗传多样性。种群间的RAPD表型(基因型)十分丰富,并且变异较大。进一步分析发现,总遗传变异的67.64%存在于种群间,而只有31.74%的变异分布在种群内。与起初认为该物种由于克隆繁殖导致的遗传多样性与遗传分化均较小的预期相反,发现了十分丰富的遗传变异和较高的遗传分化,这些遗传参数接近非克隆或非入侵物种的平均值。有性繁殖、长距离扩散以及可能的杂交渗入是导致该本地杂草具有不同于其他入侵杂草遗传结构的主要原因。     

First report of a parasitic mite, Leptotrombidium (Hypotrombidium) subquadratum (Lawerence) (Acari: Trombiculidae: Trombiculinae), from dogs and children in the Bloemfontein area, South Africa

Leptotrombidium subqunadratum larvae were collected for the first time in 1994 from dogs in Bloemfontein. The larvae have been collected annually, during the summer months, over a period of 6-7 years. Previously the only known hosts were scrub hare (Lepus saxatilis) (locality unknown) and short-snouted elephant shrew (Elephantulus brachyrhynchus) (Kruger National Park). These mites cause severe itching and dermatitis in humans and dogs.     

Oligodendrocyte morphology in the developing brain of the African giant rat (Cricetomys gambianus,Waterhouse): Histology,immunohistochemistry and electron microscopy

Oligodendrocyte and myelin‐related studies have been pivotal in understanding disruption of central nervous system (CNS) myelin through injury, toxicological, pathological degeneration or genetic intervention. The African giant rat (AGR) has been postulated as an indigenous wild‐type model within the African context. This work thus describes oligodendrocyte morphologies and myelin components of the developing African giant rat brain using histological, immunohistochemical and ultrastructural techniques. Five types, precursor‐progenitor oligodendrocytes, pre‐oligodendrocytes, immature oligodendrocytes, mature non‐myelinating oligodendrocytes and mature myelinating oligodendrocytes, were identified. The first four types were observed in neonates while juvenile and adult AGR had predominantly mature myelinating oligodendrocytes with evidence of myelin sheath deposition. All cell types identified showed positive CNPase‐positive immunosignalling across all age groups. This suggests CNPase as a suitable, sensitive and reliable biomarker for studying CNS neurodegenerative/demyelinating disorders in the AGR. This baseline study has given detailed insight into the morphology of oligodendrocytes and myelin in the AGR. It may be useful for anatomical studies and detection of alterations in neurocellular profile of oligodendrocytes and myelin in the AGR in real‐life or in experimental models.     

Bioacciimulation of copper in the tissues of Potamonautes warreni (Calman) (Crustacea,Decapoda, Branchiura), from industrial,mine and sewage-polluted freshwater ecosystems

The copper concentration detected in the water and sediments of the Natalspruit River, Bronkhorstspruit River and Nooitgedacht Dam exceeded certain stated limits for the protection of aquatic life. Despite considerable individual variation, the general ranking of copper concentrations in the various tissues was carapace < muscle < gonads < midgut gland < gills. Seasonal variation was detected in the bioaccumulation of copper in crabs sampled from the Natalspruit River. However, this phenomenon did not occur in crabs from the other two water bodies. A significant increase in copper concentrations was detected with a decrease in size, indicating that the size of the crabs is an important influencing factor in the bioaccumulation of copper. It was also found that more copper accumulated in the ovary than in the testis per unit weight. The bioaccumulation factors (BF) calculated for the different tissues with respect to the water were highest in the gills and midgut gland (785,00 – 1257,50 and 432,00 – 1340,00, respectively). The BF with respect to the copper concentration in the sediments was comparatively low for all the tissues (<0,10 – 2,74). It appears that P. warreni is able to regulate the copper concentrations in its various tissues and is therefore not a suitable indicator of the presence of copper in the aquatic environment.     

On the winter enhancement of adaptive humoral immunity: hypothesis testing in desert hamsters (Phodopus roborovskii: Cricetidae,Rodentia) kept under long‐day and short‐day photoperiod

We tested the winter immunity enhancement hypothesis (WIEH) on male desert hamsters (Phodopus roborovskii) kept under long‐day (LD) and short‐day (SD) photoperiods. We assumed that under SD in a laboratory, the adaptive humoral immune responsiveness to the antigenic challenge would be enhanced due to the lack of winter physical stressors and food shortages and/or because of the action of an endogenous winter bolstering mechanism, while under LD the immune responsiveness would be suppressed by the activity of the reproductive system. The results support the WIEH in part. We did not find a difference in antibody production in response to sheep erythrocytes between SD and LD hamsters, but SD males had the lower number of granulocytes and the higher number of lymphocytes in white blood cell counts. Reproductive activity was lower in SD males. These males demonstrated an increase in their mass‐specific resting metabolic rate, their mass‐specific maximal metabolic rate and their level of cortisol. The result of a generalized linear model analysis indicates the negative effect on secondary immunoresponsiveness to sheep erythrocytes of mid‐ventral gland size, the organ characterizing individual reproductive quality, and designates a tradeoff between antibody production and reproductive effort. The mass‐independent maximal metabolic rate also negatively affected antibody production, indicating a tradeoff between maximal aerobic performance and the adaptive immune function. The higher stress in SD males seems to be the most likely reason for the lack of the effect of daylight duration on antibody production.     

Henneguya corruscans n. sp. (Myxozoa,Myxosporea, Myxobolidae), a parasite of Pseudoplatystoma corruscans (Osteichthyes,Pimelodidae) from the Paraná River,Brazil: A morphological and morphometric study

This paper describes the parasite Henneguya corruscans n. sp. which infects the gills of Pseudoplatystoma corruscans Spix and Agassiz, 1829 found in the Paraná River, Brazil. The parasites belong to the interlamellar-epithelial type as defined by Molnár (2002) [Molnár, K., 2002. Site preference of fish myxosporeans in the gills. Dis. Aquat. Org. 48, 197–207]. The spores examined had thin, smooth walls with symmetric valves; the total length of the spores was 27.6 (25–29) μm. The spore body was ellipsoidal in frontal view and biconvex in lateral view and they measured 14.3 (13–15) μm long by 5 μm wide and 4 μm in thickness. The polar capsules were small and elongated, equally sized, with a rounded posterior extremity and tapering anteriorly, and they corresponded more or less the half the length of the spore body; they were 6.8 (6–7) μm long by 2 μm wide, and the polar filament formed 5–6 coils obliquely to the axis of the polar capsule. The tail was 13.7 (12–15) μm long and bifurcated shortly after the end of the spore body. The importance of the infection for the farming of P. corruscans is discussed.     

Molecular identification,morphological characterization and new insights into the ecology of larval Pseudoterranova cattani in fishes from the Argentine coast with its differentiation from the Antarctic species,P. decipiens sp. E (Nematoda: Anisakidae)

Larvae of the genus Pseudoterranova constitute a risk for human health when ingested through raw or undercooked fish. They can provoke pseudoterranovosis in humans, a fish-borne zoonotic disease whose pathogenicity varies with the species involved, making their correct specific identification a necessary step in the knowledge of this zoonosis. Larvae of Pseudoterranova decipiens s.l. have been reported in several fish species from off the Argentine coasts; however, there are no studies dealing with their specific identification in this region. Here, a genetic identification and morphological characterization of larval Pseudoterranova spp. from three fish species sampled from Argentine waters and from Notothenia coriiceps from Antarctic waters was carried out. Larvae were sequenced for their genetic/molecular identification, including the mitochondrial cytochrome c oxidase subunit II (mtDNA cox2), the first (ITS-1) and the second (ITS-2) internal transcribed spacers of the nuclear ribosomal DNA, and compared with all species of the P. decipiens (sensu lato) species complex (sequences available in GenBank). Further, adults of Pseudoterranova spp. from the definitive host, the southern sea lion, Otaria flavescens, from Argentine and Chilean coasts were sequenced at the same genes. The sequences obtained at the ITS-1 and ITS-2 genes from all the larvae examined from fish of Argentine waters, as well as the adult worms, matched 100% the sequences for the species P. cattani. The sequences obtained at mtDNA cox2 gene for Antarctic larvae matched 99% those available in GenBank for the sibling P. decipiens sp. E. Both MP and BI phylogenetic trees strongly supported P. cattani and P. decipiens sp. E as two distinct phylogenetic lineages and depicted the species P. decipiens sp. E as sister taxon to the remaining taxa of the P. decipiens complex. Larval morphometry was similar between specimens of P. cattani from Argentina, but significantly different from those of P. decipiens sp. E, indicating that larval forms can be distinguished based on their morphology. Pseudoterranova cattani is common and abundant in a variety of fish species from Chile, whereas few host species harbour these larvae in Argentina where they show low levels of parasitism. This pattern could arise from a combination of factors, including environmental conditions, density and dietary preferences of definitive hosts and life-cycle pathways of the parasite. Finally, this study revealed that the life-cycle of P. cattani involves mainly demersal and benthic organisms, with a marked preference by large-sized benthophagous fish.