Opioid modulation of ingestive behaviors in the spiny mouse (Acomys cahirinus)

Feeding and drinking behavior were studied in deprived or sated spiny mice (Acomys cahirinus) at various time intervals following peripheral administration of naloxone hydrochloride and butorphanol tartrate. Naloxone attenuated both food and water intake, but not latency to respond, indicating existence of functional opioid-sensitive feeding and drinking systems in this species. Butorphanol tartrate, a mixed opioid agonist/antagonist produced a dose-related enhancement or suppression of feeding, the former naloxone reversible, but had no measureable effect on drinking.     

The structure of the spiny mouse (Acomys cahirinus) ovary during development

The study presents the structure of the ovaries of the spiny mouse (Acomys cahirinus) during the first months of life. The ovaries in neonate females exhibit a large number of primordial and primary follicles, sometimes clustered in nests. The growing follicles were also observed within the ovary at that period. The first, early antral follicles appeared in the ovary during the second week of life. In the group of 60-day old females, the structure of the ovaries was characterized by a significant increase in the connective tissue elements. Moreover, ovarian follicles at various stages of development were observed, except for the antral ones with cumulus oophorus. The first mature follicles were identified in 3-month old females. In the ovarian follicles, apoptosis occurs at all stages of follicle development, especially in the early antral follicles. In the atretic follicles, apoptotic cells were identified in the layer of granulosa cells.     

Characterization of social behavior in the spiny mouse,Acomys cahirinus

While there are many species that are commonly used for the study of mammalian social behavior, there remains a need for lab-suitable organisms that are appropriate for examining sociality specifically in non-reproductive contexts (i.e., social behavior not in the context of mating or parenting). The spiny mouse, Acomys cahirinus, is a cooperatively breeding rodent that lives in large groups and is a species that holds great potential for studying a wide range of social behaviors in reproductive and non-reproductive contexts. Here, we characterize the basic social behaviors in male and female A. cahirinus to obtain a foundation for future study. We tested adult A. cahirinus in social approach, social preference, social interaction, social recognition, and group size preference paradigms. Regardless of sex, novelty, or familiarity, we found that both males and females rapidly approach conspecifics demonstrating high social boldness. Additionally, both sexes are significantly more prosocial than aggressive when freely interacting with conspecifics. However, we observed effects of sex on social preferences, such that males exhibit a preference to affiliate with same-sex conspecifics, whereas females exhibit a preference for affiliating with opposite-sex conspecifics. We discuss how this preference may relate to the cooperative breeding system of spiny mice. Lastly, both sexes show a robust preference for affiliating with large over small groups, indicating they may be an ideal species for the study of mammalian gregariousness. These data lay a basic foundation for future studies that seek to assess complex group dynamics and the mechanisms underlying reproductive and non-reproductive social behaviors in a highly social mammal.     

Biotransformation in Egyptian spiny mouse Acomys cahirinus

The activities of several representative biotransformation enzymes were determined in male and female spiny mouse tissues. Cytochrome P450 monooxygenase activity toward benzo(a)pyrene was significantly greater in female spiny mouse intestine than in males. Activity toward benzphetamine in both sexes was high in the liver, with little activity in the kidney and intestine. Sulfotransferase activity was high in kidney and intestine of female spiny mice but undetectable in the same tissues in males. Hepatic glutathione s-transferase activity towards 1-chloro-2,4-dinitrobenzene in females was significantly higher than in males. UDP-Glucuronosyltransferase activity toward 1-naphthol in both sexes in the kidney was significantly higher than hepatic and intestinal activity. Intestinal N-acetyltransferase activity towards 2-aminofluorene and β-naphthylamine was significantly greater in females than males. No consistent relation appeared to exist between biotransformation activities in spiny mouse and those in other related rodent species.     

New data on the evolution of the Cretan spiny mouse,Acomys minous (Rodentia: Murinae), shed light on the phylogenetic relationships in the cahirinus group

The karyotype of the Cretan spiny mouse Acomys minous was examined with chromosome banding techniques in 53 individuals from 12 localities of Crete, aiming to gain a more detailed knowledge on the chromosomal constitution and variability of its natural populations. We found that it consists of three Robertsonian (Rb) populations with 2n = 38, 2n = 40 and 2n = 42, respectively, the last one being reported for the first time, and with stable fundamental number (FNa = 66, FN = 68). The G‐banding pattern proves that the Rb populations are closely linked phylogenetically by the many common Rb fusions and the lack of monobrachial homologies. In addition, they appear to freely mate at their contact areas, producing viable and fertile hybrids. No other type of chromosomal rearrangement appears to have played part in the chromosomal evolution of this species, at least in the recent past, as indicated also by the study of the telomeric sequences. Heterochromatin appears to be restricted to the pericentromeric position of all acrocentric and most biarmed autosomes, as well as of the X chromosome, whereas the Y chromosome is uniformly, yet faintly heterochromatic. Chromosome banding comparison of the karyotypes in A. minous with those of the other species in the cahirinus group (i.e. Acomys cahirinus, Acomys cilicicus, and Acomys nesiotes) proves their very close phylogenetic relationship, further reinforced by the study of the cytochrome b sequences, and that A. minous possesses the ancestral karyotype of the group. It is suggested that at least two of the karyotypes that characterize A. minous today, pre‐existed in North Africa before it colonized Crete and that the specific status of the four members in the cahirinus group may need to be revisited. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 498–509.     

Sex-differences in the Agonistic Behavior of Spiny-mice (Acomys cahirinus)

Observations of 8 groups each containing three adult spiny mice (Acomys cahirinus) revealed that instances of chasing and physical displacement were quite common, while fighting and biting were rarely observed. The relationships between the most frequent behavioral categories were presented in a correlation matrix. In a second, study, ♀♀ tested in their home cages were dominant over ♂♂ In the ♂♂ home cages, however, no differences in the frequency of ♀ vs. ♂ aggression were observed. More instances of aggression were observed in the cages of the ♀♀ than in the cages of the ♂♂.     

Ultrastructure of Kolmer's crystalloid in the pinealocytes of the common spiny mouse (Acomys cahirinus dimidiatus)

Light-and electron-microscopical observations revealed a rod-like inclusion body in the pinealocytes of the common spiny mouse (Acomys cahirinus dimidiatus). Ultrastructurally, the body is composed of a varying number of tubes whose wall consists of thin filaments aligned in helical arrangement. The inner and outer surface of the wall is covered with ribosome-like granules. Based on a morphological analysis it is concluded that the body described in the present investigation is identical with Kolmer's crystalloid of horizontal cells in the human and primate retina.This work represents a portion of a doctoral thesis (Dr. med.) submitted to the University of Bonn and was presented at the 87th meeting of the anatomische Gesellschaft in Mainz, Germany, March 1992     

The reproductive tract of the male spiny mouse (Acomys cahirinus) and coagulation studies with other species

The testes of the spiny mice showed asymmetry, the left being significantly heavier than the right (P = 0.025). Histological studies indicated that spermatozoa were first present in the testes of animals 35--45 days of age but the maturation of the accessory glands, especially the lateral prostates and coagulating glands, occurred later. The highest fructose concentration in the adult was in the lateral prostates (126.97 +/- 22.23 mg fructose/100 g, n = 5) and coagulating glands (99.38 +/- 17.65 mg fructose/100 g gland weight, n = 5). Coagulation tests of mixtures of extracts of seminal vesicles and coagulating glands from spiny mice and rats indicated that the vesiculase of the spiny mouse was active on rat substrates and vice versa. Cross-reactions of extracts of house mouse (Mus musculus), hamster (Mesocricetus auratus), gerbil (Meriones unguiculatus), and guinea-pig (Cavia porcellus) seminal vesicles (substrate) and coagulating glands (vesiculase) with those of rats and spiny mice showed that although the substrates of rat and spiny mouse were readily coagulated by vesiculase from all the other species, rat and spiny mouse vesiculase were not equally active on substrates of the other species.     

Cytochrome b sequences reveal Acomys minous (Rodentia, Muridae) paraphyly and answer the question about the ancestral karyotype of Acomys dimidiatus

Sequences of the cytochrome b (cyt b) mitochondrial gene show that the spiny mouse Acomys from Crete, known as the endemic species A. minous, is composed of two distinct maternal lineages ("A" and "B"). Group "A" sequences cluster with A. nesiotes (Cyprus) and group "B" sequences cluster with A. cilicicus (Turkey), which is evidence of paraphyly of A. minous in regard to these two species. From cyt b sequences, the three taxa are very closely related to A. cahirinus (Egypt): the maximum divergence found among these sequences is 1.6%, which is equivalent to the intraspecific diversity observed in other Acomys species. Paleozoology evidenced that man unintentionally introduced Acomys into Crete and Cyprus during antiquity. The divergence time between Acomys cyt b sequences found in Crete was estimated at 0.4 Myr, which means that the diversity observed did not appear after the introduction but reflects a much more ancient polymorphism. Cytochrome b phylogeny and cytogenetic data together comprise evidence that, within the species A. dimidiatus (Saudi Arabia, Israel, Egypt), it is the karyotypic form with 36 chromosomes that derives from the form with 38 chromosomes, due to a single acrocentric fusion.     

Significance of anomalous thermoregulation in the pre-diabetic spiny mouse (Acomys cahirinus): oxygen consumption and temperature regulation

In keeping with studies of other desert rodents, the potentially diabetic spiny mouse has been demonstrated to have a very low basal metabolic rate, disproportionate to its body weight. The maintenance of a lower body temperature in response to high environmental temperatures and a lack of increase in metabolic rate in response to cooling have also been demonstrated. Assessments of "mechanical efficiency" have shown that spiny mice carry a potential selective advantage under fasting conditions. The findings, some of which are similar to those noted in other desert rodents, and in other species showing either spontaneous or induced hyperglycaemia, suggest that the low metabolic rate is at least partly based on ineffective glucose utilization. This phenomenon may be the common denominator of the survival advantage which has allowed both the successful evolution of species inhabiting warm, arid climes, and the persistence of the diabetic genotype in animal and human populations.     

Discrimination between full-sibling spiny mice (Acomys cahirinus) by olfactory signatures

Discrimination between individual full siblings was tested in spiny mice (Acomys cahirinus). At weaning, intact litters were separated into two pairs so that animals only had social contact with one of their full siblings. Following 10 days of being housed in pairs, the four weanlings from a given litter were reunited in an observation terrarium. Pairings by familiar siblings were more frequent than unfamiliar-sibling pairings, indicating that interactions among close kin are mediated by the recognition of individual signatures rather than general phenotypic traits shared by all members of a kin class. Animals rendered anosmic by intranasal injections of zinc sulphate displayed no evidence of discriminating between familiar and unfamiliar siblings. Olfactory cues therefore appear to function as the signatures by which individual siblings are recognized. Since all animals were fed identical diets and otherwise maintained in similar environments, the differences in olfactory signatures between full siblings are most likely a function of genetic variability within this class of kin.     

Breeding and fertility of the Egyptian spiny mouse, Acomys cahirinus: effect of different environments.

2 years experience with Acomys in one laboratory confirmed the slow breeding rate found by other workers. On moving the animals to another laboratory there was a 2-5 fold increase in breeding rate. The most likely explanation of this change was the presence of copper in the drinking water at the 1st laboratory, due to the use of copper water pipes. The data relating to maintenance and breeding of acomys for 2 years at the 2nd laboratory were analyzed to provide a more representative picture of the species.     

Electron microscope detection of biogenic amines in the medulla of the adrenal gland of the normoglycemic spiny mouse (Acomys cahirinus)

By means of a modification of the Reinecke salt method already described, characteristical amine containing granules have been demonstrated in the parenchymal cells of the adrenal medulla in normoglycemic spiny mice. By this method two types of granules have been discerned according to their different contrasts. The advantages of the modification method are discussed.     

Developmental Parameters of Mother-Offspring Interactions in Acomys cahirinus

Developmental parameters of mother-infant interactions in Acomys cahirinus were investigated in a series of observational and experimental studies. The uniquely precocial offspring associated closely with both parents beyond the time of weaning and birth of the next litter. The survival rate of foster pups was dependent upon both the age of the pups and the physiological stare of the foster mothers. While 1 and 8-day post partum ♂♂ nursed unfamiliar neonates as frequently as their own pups, they interacted with unfamiliar 8-day-old offspring less than with their own.