Underlying bases of recognition signatures in spiny mice, Acomys cahirinus

Model systems for regeneration: the spiny mouse, Acomys cahirinus

The spiny mouse, Acomys spp., is a recently described model organism for regeneration studies. For a mammal, it displays surprising powers of regeneration because it does not fibrose (i.e. scar) in response to tissue injury as most other mammals, including humans, do. In this Primer article, we review these regenerative abilities, highlighting the phylogenetic position of the spiny mouse relative to other rodents. We also briefly describe the Acomys tissues that have been used for regeneration studies and the common features of their regeneration compared with the typical mammalian response. Finally, we discuss the contribution that Acomys has made in understanding the general principles of regeneration and elaborate hypotheses as to why this mammal is successful at regenerating.

Social recognition in wild fish populations

The ability of animals to gather information about their social and physical environment is essential for their ecological function. Odour cues are an important component of this information gathering across taxa. Recent laboratory studies have revealed the importance of flexible chemical cues in facilitating social recognition of fishes. These cues are known to be mediated by recent habitat experience and fishes are attracted to individuals that smell like themselves. However, to be relevant to wild populations, where animals may move and forage freely, these cues would have to be temporally flexible and allow spatial resolution. Here, we present data from a study of social recognition in wild populations of three-spined sticklebacks (Gasterosteus aculeatus). Focal fish preferentially associated with conspecifics from the same habitat as themselves. These preferences were changed and updated following translocation of the focal fish to a different site. Further investigation revealed that association preferences changed after 3 h of exposure to different habitat cues. In addition to temporal flexibility, the cues also allowed a high degree of spatial resolution: fish taken from sites 200 m apart produced cues that were sufficiently different to enable the focal fish to discriminate and associate with fish captured near their own home site. The adaptive benefits of this social recognition mechanism remain unclear, though they may allow fish to orient within their social environment and gain current local information.

Effect of dietary cues on kin discrimination of juvenile Atlantic salmon (Salmo salar) and brook trout (Salvelinus fontinalis)

Several salmonid species can discriminate kin from non-kin using recognition cues. These are known to involve both genetic and environmental components. This study examined the effect of diet, an environmental cue, on kin discrimination in juvenile Atlantic salmon ( Salmo salar L., 1758) and brook trout ( Salvelinus fontinalis (Mitchill, 1814)). Juveniles were reared in kin and non-kin groups. Three different diets were fed to three kin groups and three non-kin groups. Juveniles were then tested for their ability to discriminate kin. We found that juveniles discriminated individuals between kin and non-kin when they shared a common diet with kin, but did not do so when kin were fed a different diet. Moreover, we predicted that diet and genotype together would provide stronger cues than sharing either dietary cues or genetic cues. When the juveniles were given a choice between kin fed the same diet and kin fed a different diet, they did not show a consistent preference for the former. However, in the absence of kinship, juveniles preferred cues from a common diet, i.e., they preferred cue water conditioned by non-kin sharing a common diet than cue water from non-kin fed a different diet. Our results show that dietary cues affect kin discrimination in juvenile Atlantic salmon and brook trout and provide the first empirical evidence for the influence of diet on kin discrimination in salmonids. The functional explanation of these results is that the preferences in kin discrimination are likely context dependent.

Kin recognition in golden hamsters: evidence for kinship odours

Differential treatment of kin and non-kin has been well documented, but much remains unclear about how kin are recognized. If kin are recognized by a phenotype-matching mechanism, there must be a correlation between genetic relatedness and the similarity of cues used for recognition. A habituation technique was used with golden hamsters, Mesocricetus auratus, to investigate the relative similarity of the odour quality of flank gland secretions from siblings and unrelated individuals. Hamsters discriminated between the odours of their own, same-sex siblings but also treated these odours as similar compared to odours of non-siblings (experiment 1). They did not discriminate between the flank gland odours of unfamiliar siblings from another family (experiment 2). They also did not discriminate between the flank gland odours of unfamiliar, paternal half-siblings from another family (experiment 3). These results indicate that subjects perceived odours from genetically similar individuals as similar and provide evidence for kinship odour cues. The discrimination between the flank gland odours of subjects' own siblings, however, indicates that hamsters learn the subtle differences between the odours of their close kin, probably through experience with siblings in the nest. When only volatile components from flank gland secretions were available to subjects (experiment 4), they again discriminated between the odours of their own siblings, suggesting that the volatile components from the flank gland secretion were sufficient for recognition of individual litter-mates. Copyright 1998 The Association for the Study of Animal Behaviour.

Sibling recognition in the beaver: a field test for phenotype matching

The hypothesis of kin recognition by phenotype matching predicts that relatives can be identified without previous contact, and/or that cues used for recognition can be learned indirectly from a third but related individual. This hypothesis was tested in the field using 22 beaver, Castor canadensisfamilies. Individually identifiable beavers were provided with a two-way choice between two experimental scent mounds, one of which was scented with the anal gland secretion (AGS) from an unfamiliar sibling of the test subjects, the other with AGS from an unfamiliar non-relative. Beavers showed less strong territorial responses to AGS from their siblings than to that from non-relatives. The mates of the test subjects, which were not related to, or familiar with, either of the AGS donors, also responded less strongly to the AGS from their mates' siblings than to that from other unfamiliar non-relatives. This discrimination was not shown when castoreum samples were tested instead of AGS. Therefore, it was concluded that (1) information about kinship in the beaver is coded in the AGS but not in the castoreum, (2) the mechanism of phenotype matching is used in beaver sibling recognition, and (3) the cue used in phenotype matching can be learned and used for recognition of related individuals by an unrelated individual.1997The Association for the Study of Animal Behaviour

Prenatal neurogenesis in the telencephalon of the precocial mouse Acomys cahirinus

[3H]thymidine autoradiography was employed to examine the times of formation of the major neuronal classes in the forebrain of the precocial mouse Acomys cahirinus. Dams received 3 thymidine injections over a 24 h period on either embryonic Day 14, 18, 20, 22, 29 or 36. Age-related changes in the distribution and number of heavily labeled cells were noted. Acomys exhibited later onset and more protracted periods of cell generation than the phylogenetically related, altricial laboratory rat or mouse, indicating considerable differences in patterns of early growth between the species. Understanding the factors responsible for these differences could lend important insights into evolutionary mechanisms involved in the process of speciation.