The distribution of parasites among hosts is often characterised by a high degree of heterogeneity with a small number of hosts harbouring the majority of parasites. Such patterns of aggregation have been linked to variation in host exposure and susceptibility as well as parasite traits and environmental factors. Host exposure and susceptibility may differ with sexes, reproductive effort and group size. Furthermore, environmental factors may affect both the host and parasite directly and contribute to temporal heterogeneities in parasite loads. We investigated the contributions of host and parasite traits as well as season on parasite loads in highveld mole-rats (Cryptomys hottentotus pretoriae). This cooperative breeder exhibits a reproductive division of labour and animals live in colonies of varying sizes that procreate seasonally. Mole-rats were parasitised by lice, mites, cestodes and nematodes with mites (Androlaelaps sp.) and cestodes (Mathevotaenia sp.) being the dominant ecto- and endoparasites, respectively. Sex and reproductive status contributed little to the observed parasite prevalence and abundances possibly as a result of the shared burrow system. Clear seasonal patterns of parasite prevalence and abundance emerged with peaks in summer for mites and in winter for cestodes. Group size correlated negatively with mite abundance while it had no effect on cestode burdens and group membership affected infestation with both parasites. We propose that the mode of transmission as well as social factors constrain parasite propagation generating parasite patterns deviating from those commonly predicted.

Consensus on placental mammal phylogeny is fairly recent compared to that for vertebrates as a whole. A stable phylogenetic hypothesis enables investigation into the possibility that placental clades differ from one another in terms of their development.Here, we focus on the sequence of skeletal ossification as a possible source of developmental distinctiveness in "northern" (Laurasiatheria and Euarchontoglires) versus "southern" (Afrotheria and Xenarthra) placental clades. We contribute data on cranial and postcranial ossification events during growth in Afrotheria, including elephants, hyraxes, golden moles, tenrecs, sengis, and aardvarks. We use three different techniques to quantify sequence heterochrony: continuous method, sequence-ANOVA (analysis of variance) and event-paring/Parsimov. We show that afrotherians significantly differ from other placentals by an early ossification of the orbitosphenoid and caudal vertebrae. Our analysis also suggests that both southern placental groups show a greater degree of developmental variability; however, they rarely seem to vary in the same direction, especially regarding the shifts that differ statistically. The latter observation is inconsistent with the Atlantogenata hypothesis in which afrotherians are considered as the sister clade of xenarthrans. Interestingly, ancestral nodes for Laurasiatheria and Euarchontoglires show very similar trends and our results suggest that developmental homogeneity in some ossification sequences may be restricted to northern placental mammals (Boreoeutheria). K E Y W O R D S :Afrotheria, development, evolution, heterochrony, ossification, phylogeny, skeletogenesis.Until the close of the 20th century, many high-level nodes in the placental mammal Tree of Life were not well understood. The last 15 years have changed this state of affairs dramatically. Although most individual orders and some interordinal groups have been accurately recognized based on comparative anatomy for over a century, few zoologists would have predicted the now-stable phylogeny consisting of four major clades: Afrotheria, Xenarthra, Laurasiatheria, and Euarchontoglires (Murphy et al. 2001). Certain elements of these clades have a long history in comparative anatomy, including elephant-sea cow-hyrax as afrotherians; primate-tree shrew-dermopteran and rodent-rabbit as euarchontoglires; sloth-armadillo-anteater as xenarthrans; pangolin-carnivoran and artiodactyl-whale as laurasiatheres. Other groups are quite novel to morphologists (e.g., tenrec-golden

Ansell's mole-rat, Fukomys anselli, is a social subterranean mammal and exhibits an extreme reproductive division of labour. Reproduction in the colony appears to be restricted usually to a single female. Complete colonies captured throughout an entire calendar year were euthanased and the histology of the gonads and plasma hormone concentrations were measured in reproductive and non-reproductive members of both sexes. In males, the circulating levels of testosterone were highest in the reproductive male. The mean testes mass for male corrected for body mass was lower than that of the non-reproductive male. However, the mean testes volume of reproductive males was greater than that for the non-reproductive males and the seminiferous tubule diameter was greater in reproductive males. Reproductive females characteristically possessed corpora lutea of ovulation and pregnancy in their ovaries and this was met with much elevated progesterone concentrations in these females. In contrast, non-reproductive females showed a complete range of follicular genesis, but they did not possess corpora lutea of ovulation or pregnancy, in turn they show depressed progesterone concentrations. The current available evidence suggests that in Ansell's mole-rats, the non-reproductive males and females refrain from sexual activity by being subordinate and moreover related to the breeding pair.

Triads of male NMRI mice were housed together and dominance hierarchies allowed to form. At age 19 weeks the mice were ranked on the basis of wins in spontaneous aggressive encounters, and whole‐body volatiles were sampled by the dynamic solvent effect and quantitatively analysed by capillary gas chromatography. At age 26 weeks the mice were again ranked on the basis of wins in aggressive encounters, number of aggressive encounters initiated, and scent marking patterns, and whole‐body volatiles were sampled and analysed. Chromatographic odour profile ranks agreed perfectly with aggressive initiator ranks and poorly with encounter winner ranks. Eight components of the whole‐body odour were identified by gas chromatography‐mass spectrometry; two of these are known semiochemicals. The results demonstrate that murine semiochemicals are accessible to quantitative analysis at the level of the individual.

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