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Birth asphyxia is associated with disturbed development of the neonatal brain. In this study, we determined if low-dose melatonin (0.1 mg/kg/day), administered to the mother over 7 days at the end of pregnancy, could protect against the effects of birth asphyxia in a precocial species – the spiny mouse (Acomys cahirinus). At 37 days of gestation (term is 38–39 days), pups were subjected to birth asphyxia (7.5 min uterine ischemia) and compared to Cesarean section-delivered controls. At 24 h of age, birth asphyxia had increased markers of CNS inflammation (microglia, macrophage infiltration) and apoptosis (activated caspase-3, fractin) in cortical gray matter, which were reduced to control levels by prior maternal melatonin treatment. Melatonin may be an effective prophylactic agent for use in late pregnancy to protect against hypoxic-ischemic brain injury at birth.

Birth asphyxia can result in sensory impairment, learning and memory deficits without gross brain injury and severe motor deficits. We developed a model of birth asphyxia resulting in mild neurological injury and cognitive impairment using a long-gestation species with precocial fetal development. Spiny mice (Acomys cahirinus) underwent caesarean-section delivery or 7.5 min of asphyxia at 37 days gestational age (term is 39 days). Brain histology was examined at 1 and 7 days of age, and behaviour was evaluated to 28 days of age. Asphyxiated offspring showed significant impairment in non-spatial memory and learning tasks, accompanied by central nervous system inflammation and increased apoptotic cell death but without the presence of large necrotic or cystic lesions.

The aim of the study was to obtain details of the morphology of the autonomic innervation of pancreas. Six adult Egyptian spiny mice (Acomys cahirinus, Desmarest) were studied for the presence and location of autonomic fibres and cells in the pancreas. The macromorphological investigations were performed using the thiocholine method adapted for this type of specimens. For processing tissues two histochemical techniques were used: thiocholine method on activity of AChE and the glyoxylic acid method for adrenergic structures. Cholinergic fibres and small autonomic ganglia were found among the secretory sections and along the pancreatic duct and both pancreaticoduodenal arteries, and its branches, reaching the Langerhans islets and forming around them a kind of net. From 24 to 40 AChE-positive ganglions in the whole exocrine part were observed. The highest density of cholinergic fibres was observed in the head of pancreas. Numerous adrenergic fibres that accompanied blood vessels as well as interlobular and intralobular ducts were found inside the exocrine parts of the pancreas. Neither adrenergic cells or adrenergic fibres were observed inside the pancreatic islets. Our results can be used in comparative anatomy studies of pancreas in mammals.

Summary 1 We examined whether identity of the rodent host and previous infestation of the host affect feeding and reproduction of fleas. We predicted that feeding and reproductive success of fleas would be higher when feeding on (i) a typical host than on an atypical host; and (ii) a pristine host than on a host previously exposed to parasitism. We also predicted that the negative effect of previous infestation would not be manifested in a host-specific flea feeding on its typical host. 2 To test these predictions, we measured blood meal size, egg production and latency of oviposition in host-specific Parapulex chephrenis and host-opportunistic Xenopsylla ramesis during seven daily feedings on the Egyptian spiny mouse Acomys cahirinus (typical host of the former) and Wagner's gerbil Dipodillus dasyurus (typical host of the latter). 3 Blood meal size in P. chephrenis did not depend on either host species or previous host infestation with fleas. However, when this flea fed on D. dasyurus as opposed to A. cahirinus, blood meal size increased to the end of 7-day period. Xenopsylla ramesis took larger blood meals (i) during the first feeding; (ii) from D. dasyurus than from A. cahirinus; and (iii) from pristine than from previously infested D. dasyurus, but the blood meals taken from pristine and previously infested A. cahirinus were similar. 4 Egg production of P. chephrenis was significantly higher and oviposition started earlier when it fed on A. cahirinus; this was true for X. ramesis when it fed on D. dasyurus. Surprisingly, P. chephrenis laid more eggs and started oviposition earlier when it fed on previously infested rodents. However, egg production in X. ramesis and start of oviposition were similar in pristine and previously infested hosts. 5 These results suggest that the response of a parasite to acquired immunity of a host may depend on the host species, level of parasite host specificity as well as the degree of ‘tightness’ of a particular parasite–host association.

The reproductive response of xeric and mesic populations of the genus Acomys to photoperiod acclimation was investigated. Populations of Acomys russatus and Acomys cahirinus were used as models for xeric and mesic populations, respectively. Mice ( n =10 of each species) were acclimated to short (10L:14D) and long (14L:10D) photoperiods at the following ambient temperatures: 31±1 °C ( A. russatus ) and 28±1 °C ( A. cahirinus ) for 52 days. Estrus cycles were monitored by microscopic observation of vaginal epithelial cells three times each week. Three animals from each sex and photoperiod group were sacrificed randomly at the end of acclimation. Wet mass of left testis, uterus and testicular dimensions (for calculation of testis volume) were recorded. The stage of spermatogenesis was determined from histology of seminiferous tubules. Based on the eco-climatic conditions of their natural habitats, we expected A. russatus to be non-responsive to photoperiod and A. cahirinus to be responsive only to long photoperiod. Interestingly, our results showed that only females of A. russatus were unaffected by photoperiod while their male counterparts were unable to maintain testicular activity under a short photoperiod. However, both sexes of A. cahirinus maintained gonadal activity under short and long photoperiod. Our results were compared with those of previous studies and possible ecological explanations were discussed.

Raptor–prey encounters were studied to evaluate the strategies and success rate of both predator attack and prey defense. We compared the success of barn owls in catching stationary simulated prey (food item) with that of moving prey (food item that was pulled in various directions). We also tracked real encounters between barn owls and spiny mice in a captive environment. It was found that owls had higher success in attacking stationary prey and that they seemed to attack the prey as soon as it became motionless. When attacked, only a few spiny mice remained immobile (freeze response) whereas most fled and usually avoided capture by the owls. It was also found that spiny mice displayed a preference to escape in those directions in which owls had demonstrated a lower success in catching the simulated prey. Escape initiation dichotomized to a short or long (but rarely intermediate) distance between the spiny mouse and the owl with more successful avoidance at short-distance (last-moment) escapes. The best predictor of escape success was the velocity of the spiny mouse, and the second best predictor was its flight initiation distance (FID). We present an update for Ydenberg and Dill’s model for optimal FID in close encounters, suggesting that fleeing at the last moment is advantageous. However, a last-moment attempt to escape is also more risky with a split second differing between life and death, and is therefore appropriate mainly for agile prey under close-distance attack.

Comparative chromosome painting with mouse (Mus musculus, MMU) chromosome-specific DNA probes was performed for three Muridae species, the Indian soft-furred field rat (Millardia meltada), the spiny mouse (Acomys dimidiatus) and the harvest mouse (Micromys minutus). All probes except for the Y probe were successfully hybridized to the chromosomes of all species, and homologous chromosome segments between mouse and the three species were identified at the molecular level. Comparison of our data with the published data of six other genera (Mus, Rattus, Apodemus, Otomys, Rhabdomys and Cricetulus) of the Muridae suggested that the associations MMU1b/17a, 2b/13a, 5b/11a, 7/19, 10b/17b, 10c/17c, 11b/16a, 12/17d and 13b/15, and the single painted chromosomes and chromosome segments MMU3, 4, 5a, 8a, 8b, 16b, 18 and X were probably contained by the ancestral karyotype of the Muridae, and have been strongly conserved throughout murid evolution.

The desert-adapted spiny mouse has a significantly lower glomerular number, increased glomerular size, and a more densely packed renal papillae compared with the similar-sized laboratory-adapted C57BL/6 mouse. In the present study we examined the functional consequences of these structural differences in young adult male spiny and C57BL/6 mice and detailed the impact of 1 wk of a high-salt (10% wt/wt NaCl) diet. Basal food and water intake, urine and feces production, and urinary electrolyte concentrations were not different between species, although urinary urea concentrations were higher in spiny mice ( P < 0.05). On normal salt, MAP of the anesthetized spiny mouse was ∼18 mmHg lower, effective renal plasma flow (ERPF) was 40% lower ( P < 0.001), and glomerular filtration rate (GFR) tended to be lower than in the C57BL/6 mouse. On the high-salt diet, both species had similar 24-h NaCl excretions; but C57BL/6 mice required a significantly increased amount of water (lower urine NaCl concentration) than the spiny mice. Filtration fraction was greater in both species on the high-salt diet. Spiny mice had greater GFR and ERPF after the high-salt diet, whereas the C57BL/6 mouse showed little change in GFR. The ability of the spiny mouse to tolerate a significantly higher plasma osmolality after salt, measured by a decreased drinking response, and the ability to increase ERPF at a lower MAP are features that allow this species to conserve water more efficiently than can be done in the C57BL/6 mouse. These features are important, particularly since the desert mouse has a smaller kidney, with fewer nephrons.

Using stained acryl latex-injected techniques, the arterial circle of the brain in Acomys cahirinus Desmarest was studied. Results revealed an important individual variability of investigated structure. Three morphological variants were found: (1) the lack of typical arterial circle--opened in front and the back side, (2) partial opened at the back side, (3) completely closed arterial circle. This finding is opposed to many species of mammals, including rodents, and especially laboratory mouse. In our point of view, it seems to be a specific character.

The proportion of mucin phenotypes (which form the protective biofilm of the gastrointestinal tract) differs between intestinal regions. This study examines the distribution of mucin secreting cells in the gastrointestinal tracts of the Eastern spiny mouse (Acomys dimidiatus), King jird (Meriones rex) and Libyan jird (Meriones libycus), which inhabit the dry and hot deserts of Saudi Arabia. Intestinal tract samples were processed to wax and tissue sections stained with Alcian Blue-Periodic Acid Schiff (AB-PAS) and High Iron Diamine-Alcian Blue (HID-AB) in order to determine different mucin phenotypes by quantitative analysis. Mixed mucin secreting cells (combined neutral and acid) was the predominant mucin secreting cell type observed throughout the gastrointestinal tract in all species. Acid mucin secreting goblet cells were mainly located in the colon. A. dimidiatus presented with significantly more total sialo than sulfomucin secreting cells while the opposite was true for both Meriones species. The distribution of mucin secreting cells is therefore similar to previously reported results for small mammals not living under arid conditions.

Synthesis of dehydroepiandrosterone (DHEA) by the fetal adrenal gland is important for placental oestrogen production, and may also be important for modulating the effects of glucocorticoids on the developing brain. We have preciously shown that the enzymes and accessory proteins needed for DHEA synthesis-cytochrome P450 enzyme 17α-hydroxylase/17,20 lyase (P450c17), cytochrome-b5 (Cytb5), 3β-hydroxysteroid dehydrogenase (3βHSD)-are expressed in the adrenal gland from 30 days gestation, and DHEA, cortisol and aldosterone are present in fetal plasma from this time. Explant culture of fetal adrenal tissue showed that the spiny mouse adrenal gland, can synthesize and secrete DHEA from at least 0.75 of gestation, and suggest that DHEA may have an important role(s) in placental biosynthesis of oestrogens and in modulating the actions of glucocorticoids in the developing brain in this species. Post-natally, increased immuno-expression of P450c17 and Cytb5 expression in the zona reticularis of the adrenal gland and a significant increase in the synthesis and secretion of DHEA in plasma from 8 to 20 days of age in the spiny mouse, are representative of a period of high adrenal androgen production consistent with the human phenomenon of adrenarche. The studies summarised in this review also show that DHEA is produced de novo in the developing brain of the spiny mouse. These results showed that the spiny mouse brain can indeed produce DHEA from pregnenolone in a time-dependant manner, and coupled with the identification of P450c17 and Cytb5 protein in several regions of the brain, support the idea that DHEA is an endogenous neuro-active steroid in this species. Together, the studies outlined in this review indicate that the androgen DHEA is an important hormone of adrenal and Central Nervous System (CNS) origin in the fetal and postnatal spiny mouse. Disturbance of the development of these fetal tissues, and/or of the relationship between the fetal adrenal gland and placenta during pregnancy, may have significant consequences for fetal development, placental function, and maturation of the brain. It is proposed that such disturbances of normal adrenal function could account for some of the neuropathologies that arise in juvenile and adult offspring following illness and stress experienced by the mother during pregnancy.

Background Pregnancy induces adaptations in maternal metabolism to meet the increased need for nutrients by the placenta and fetus. Creatine is an important intracellular metabolite obtained from the diet and also synthesised endogenously. Experimental evidence suggests that the fetus relies on a maternal supply of creatine for much of gestation. However, the impact of pregnancy on maternal creatine homeostasis is unclear. We hypothesise that alteration of maternal creatine homeostasis occurs during pregnancy to ensure adequate levels of this essential substrate are available for maternal tissues, the placenta and fetus. This study aimed to describe maternal creatine homeostasis from mid to late gestation in the precocial spiny mouse. Methods Plasma creatine concentration and urinary excretion were measured from mid to late gestation in pregnant (n = 8) and age-matched virgin female spiny mice (n = 6). At term, body composition and organ weights were assessed and tissue total creatine content determined. mRNA expression of the creatine synthesising enzymes arginine:glycine amidinotransferase (AGAT) and guanidinoacetate methyltransferase (GAMT), and the creatine transporter (CrT1) were assessed by RT-qPCR. Protein expression of AGAT and GAMT was also assessed by western blot analysis. Results Plasma creatine and renal creatine excretion decreased significantly from mid to late gestation (P < 0.001, P < 0.05, respectively). Pregnancy resulted in increased lean tissue (P < 0.01), kidney (P < 0.01), liver (P < 0.01) and heart (P < 0.05) mass at term. CrT1 expression was increased in the heart (P < 0.05) and skeletal muscle (P < 0.05) at term compared to non-pregnant tissues, and creatine content of the heart (P < 0.05) and kidney (P < 0.001) were also increased at this time. CrT1 mRNA expression was down-regulated in the liver (

This study was designed to determine the expression pattern of estrogen receptor (ER) subtypes in the Acomys cahirinus ovarian cells during its postnatal development. Immunohistochemical studies revealed the presence of ERalpha and ERbeta in germinal epithelium cells and interstitial tissue. Both these ER subtypes were also seen in granulosa cells and oocytes of growing follicles, however, the level of ERbeta expression was higher in comparison with ERalpha. In contrast to ERbeta, ERalpha protein was also present in theca cells. The expression of ERs increased with animals' age, but it decreased during follicular maturation. Moreover, the immunolocalization of ER subtypes in luteal cells showed that not ERbeta, but ERalpha expression is up-regulated throughout corpus luteum development. These immunohistochemical studies demonstrate, for the first time, that ERalpha is also expressed in the mouse granulosa cells and it may be a mediator of estrogen action in granulosa cells proliferation and differentiation.

Key words: Muscardinus avellanarius, tail loss, demographic parametersCaudal autotomy – the ability to shed the tail– is a common and well-recognised antipre-dator defence mechanism in reptiles andamphibians. A review of the occurrence ofthis phenomenon in rodents is presented byShargal et al. (1999). These authors state thattail autotomy occurs in at least 35 species andhas evolved separately in eight rodentfamilies, with no clear pattern in systematics,geography, or habitat use. Two major typesof tail loss are recognised in rodents: simul-taneous loss of an entire part of the tail, whenthe tail breaks across vertebrae, and sheddingof a portion of the tail skin alone withsubsequent loss of the denuded part of thetail (Mohr 1941). These two types are calledtrue autotomy and false autotomy, respec-tively (Dubost and Gasc 1987; McKee andAdler 2002).In general, earlier studies of tail loss were notaccompanied by field research, and onlyanatomical/histological aspects of this phe-nomenon were studied (e.g., Go¨gl 1930;Mohr 1941). Several later studies dealt alsowith some ecological aspects of tail loss inrodents: Florida mouse (Peromyscus florida-nus)(Layne 1972), black rat (Rattus rattus)(Michener 1976), common spiny mouse(Acomys cahirinus) and golden spiny mouse(A. russatus)(Shargal et al. 1999) as well asCentral and South American spiny rats(Proechimys)(Dubost and Gasc 1987;McKee and Adler 2002).False tail autotomy in dormice (Gliridae) is awell-known phenomenon, which is men-tioned in some generalised publications onthese rodents (e.g., Vietinghoff-Riesch 1960;Storch 1978; Airapetyants 1983; Morris 1997;Rossolimo et al. 2001). However, onlyanatomical/histological aspects of tail autot-omy have been studied in dormice (Go¨gl1930; Mohr 1941), any ecological aspects ofthis phenomenon were not reflected. The aimof the present study was to analyse thefrequency of occurrence of tail autotomy inseparate demographic groups, annual survi-val rates of tail-less individuals and someother ecological aspects of tail autotomy inthe common dormouse (Muscardinus avella-narius) populations.Studies of two isolated common dormousepopulations were carried out in Lithuania intwo locations: at study site A (south-westernLithuania, Sˇakiai district; 55103

Eimeria cahirinensis Couch et al. 1997 was found in faecal samples of Acomys dimidiatus from three different localities in the Near East. Twenty-two of 104 (21%) A. dimidiatus trapped on both the south- and north-facing slopes of "Evolution Canyon", Lower Nahal Oren, Mt. Carmel, Israel in August 2001 and 2002 were infected with E. cahirinensis. Oocysts were also obtained from a single individual of A. dimidiatus trapped in Wadi Ramm, Jordan in the summer of 1999. Laboratory-reared spiny mice (Acomys spp.) were inoculated to determine the prepatent and patent period, sporulation time, site of infection, immunogenicity, pathogenicity, pathology and morphology of endogenous stages of E. cahirinensis. Both asexual and sexual stages were localised in the apical part of duodenal and jejunal villi. An experimental inoculation of representatives of several rodent genera revealed the host range of E. cahirinensis to be limited to the genus Acomys.

We studied a system in which 2 desert rodent species coexist through temporal partitioning. Previous research suggests that the common spiny mouse (Acomys cahirinus) competitively forces the golden spiny mouse (A. russatus) into diurnal activity, but the mechanism driving this separation is not entirely understood. To test whether aggression is the driving force in this exclusion, we analyzed interactions between pairs of these 2 species. In contrast with our working hypothesis, the golden spiny mouse was more aggressive as reflected in its significantly more frequent chasing and biting behaviors. These results suggest that aggressive interference does not explain the temporal partitioning between these species. Other factors such as foraging efficiency, antipredator avoidance, water conservation, or productivity may account for the shift of golden spiny mice into diurnal activity.

Animals inhabiting environments with low productivity and food availability commonly have reduced energy demands and increased digestive efficiencies. The dry matter intake (DMI), apparent digestible dry matter (ADDM), digestible efficiency (DE) and digestible energy intake (DEI) of two populations of common spiny mouse Acomys cahirinus were compared during both winter and summer under conditions of simulated water stress. Mice were captured from the north- and south-facing slopes (NFS and SFS) of the same canyon that represent mesic and xeric habitats, respectively. Measured variables were also compared between F1 mice that had been born to either NFS or SFS mice, and raised in the laboratory. SFS mice were able to assimilate energy more efficiently than NFS mice during the summer. By comparison, NFS mice were able to assimilate more energy during the winter. During winter, NFS mice assimilated more energy at low levels of water stress, whereas SFS mice assimilated more energy at higher levels. Differences were also apparent in F1 mice. It is therefore suggested that local climatic conditions can impose physiological adaptations that are retained in succeeding generations, creating unique meta-populations.

In order to identify a reservoir host of Leishmania tropica, we have trapped mammals in a cutaneous leishmaniasis focus in the Galilee region of Northern Israel. During May 2003, racoon traps (in total 275 in 11 nights) and Sherman traps (in total 170 in 8 nights) were put in boulders surrounding four endemic villages. In total, 34 hyraxes (Procavia capensis), 32 spiny mice (Acomys cahirinus) andone house mouse (Mus domesticus) were caught. Biopsies were taken from anaesthesized animals, which were released after recovery. Parasites were isolated from the nose of one hyrax. The strain was typed as L. tropica and was identical with previous isolates from patients and sand flies originating from the focus. Biopsies from other hyraxes and mice (ear biopsy) were culture and PCR negative, while PCR from the infected hyrax was positive. Previously, L. tropica DNA was detected in two hyraxes trapped in the focus but parasites were not isolated. Thus, we have confirmed the potential of hyraxes to serve as reservoir hosts. After inoculation of the hyrax strain into the ear of spiny mice, 2/4 animals were culture-positive, and 5/5 were PCR positive. Moreover, parasite DNA was detected not only in the inoculation site, but also in the nose and hind foot of one Acomys. L. tropica is thus able to disseminate in its host. Differences in biology between the two most abundant mammals in the focus are probably the reason why the hyrax, and not the spiny mouse, is a suitable reservoir of L. tropica.

We studied temporal partitioning between two spiny mouse species that coexist in hot rocky deserts in the Middle East: nocturnal common spiny mice (Acomys cahirinus) and diurnally active golden spiny mice (A. russatus). Although A. russatus is diurnally active, it retains the physical activity and body temperature rhythms of nocturnal mammals. We studied the two species in four 1000-m 2 enclosures at Ein Gedi, Israel: two experimental enclosures with A. russatus kept alone, and two controls with individuals of both species kept together. We monitored activity with Sherman traps and by studying foraging microhabitat use and efficiency using giving-up densities (GUDs) in food trays. The trays contained broken sunflower seeds mixed in local soil and placed in three micro- habitats: under boulders, between boulders, and in the open. Trapping revealed that, in the absence of A. cahirinus, the usually diurnal A. russatus was active both day and night. However, during the day A. russatus still foraged in significantly more patches and to significantly lower GUDs than during the night. Both species, but in particular A. russatus, preferred to forage in the boulder habitat. Spiny mice foraged in the same number of trays in the under- and between-boulder microhabitats, but to lower GUDs in the under-boulder microhabitat, both during the day (A. russatus) and during the night (both species). The nocturnal A. cahirinus exploited more patches with greater efficiency than did A. russatus either during the day or during the night. This result suggests that foraging trade-offs that give each species a competitive advantage along some portion of the resource axis cannot be a mechanism of nocturnal coexistence between the two species. Perhaps this is why A. russatus resorts to diurnal activity in this hot rocky desert and why the otherwise rare mechanism of temporal partitioning occurs for these species.

We determined water budget in the reproducing female common spiny mouse (Acomys cahirinus) offered ad libitum millet seeds and water. We hypothesized that the proportional increase in water input in lactating mice compared with nonreproducing mice would be greater than the proportional increase in energy intake, given that more water would be required for higher heat production and for milk production. Females gave birth to 1 or 2 offspring; results of water budget and energy intake did not differ among litter sizes and were combined. Lactating females increased water input and energy intake by 59.1% and 35.2%, respectively, compared with nonreproducing females, confirming our hypothesis. Milk production (1.04 ml/day) accounted for 29% of the difference in water output between lactating and nonreproducing spiny mice.

When attacking a spiny mouse in an experimental arena, a barn owl launched a few attacks from distant perches, made repetitive short-distance swoops in each attack and remained in the vicinity of the prey while chasing it. The spiny mouse fled in response, and typically oriented to face the owl whenever it stopped. When attacking a vole, the barn owl performed a greater number of attacks from distant perches, and left the vicinity of the prey after a few short-distance chases or capture attempts. Voles responded to these attacks in unspecific combinations of freezing and fleeing, and did not turn to face the owl when they stopped. Four conclusions are drawn from these encounters. First, two strategies characterized these predator-prey interactions; in one, both predator and prey continuously maintained awareness of each other's location; whereas in the other they continuously attempted to avoid the attention of the other. Second, responses of spiny mice and voles were a manifestation of protean behavior, with spiny mice fleeing in an alternating pattern and voles alternating between running and freezing. Third, locomotor response to owl attack comprised behavior that is an augmentation of normal behavior, with voles clinging to the walls and spiny mice running with frequent and irregular changes in direction. Fourth, the different defensive responses accord with the motor capacities and habitat of each rodent species. All in all, these results demonstrate the dynamic and multidimensional nature of predator-prey interactions.

Summary Using the thiocholine method and histological techniques, the topography and morphology of cardiac ganglia in midday gerbil, Egyptian spiny mouse, chinchilla laniger and pigeon were studied. The results demonstrated that cardiac ganglia in all investigated species are embedded in epicardial fat. They formed plexo-ganglionic structures. Each of them composed of many ganglia (from seven up to 36) different in size and shape, and interconnected by fascicles of nerve fibres. Comparative analysis showed that the density of neural network and cell aggregations was different in individual species. The richest plexo-ganglionic structure was in pigeon. It was organized in three plexo-ganglia with an average of 30 ganglia. The largest one was located along the anterior interventricular sulcus. The cardiac ganglia of investigated mammals were localized mainly on the epicardium of atria; in Egyptian spiny mouse and chinchilla laniger on the ventral surface of right atrium, but in midday gerbil on the dorsal surface of left atrium. Moreover, in midday gerbil and Egyptian spiny mouse the little plexo-ganglionic structure on the ventricle were noticed. Additionally, in midday gerbil the single nerve cells might be observed between cardiac muscle of atria. It can be said that, the strongly developed cardiac plexus in pigeon is probably connected with his behaviour and functional properties of the heart. The arrangement of neurones in cardiac ganglia of all examined mammals was uniform over the whole surface of the sections, while in the pigeon, neurones were located mainly in the peripheral part of the ganglion.

Ovary development was compared in two closely related rodent species, the precocial spiny mouse (Acomys cahirinus) and the altricial rat (Rattus norvegicus). Different overall patterns of ovary maturation were found in the two species. The newborn spiny mouse exhibits considerably more advanced ovary growth than the same aged rat; however, differences gradually disappeared during the second postnatal week. Both species reached maturity at a common age, which suggests that the rate of postnatal ovary development in the spiny mouse is much slower than that of the rat.

Comparative chromosome painting was applied to the Indian spiny mouse (Mus platythrix) with mouse (M. musculus) chromosome-specific probes for understanding the process of chromosome rearrangements between the two species. The chromosome locations of the 5S and 18S-28S ribosomal RNA genes and the order of the 119 and Tcp-1 genes in the In(17)2 region of the t-complex were also compared. All the painting probes were successfully hybridized to the Indian spiny mouse chromosomes, and a total of 27 segments homologous to mouse chromosomes were identified. The comparative FISH analysis revealed that tandem fusions were major events in the chromosome evolution of the Indian spiny mouse. In addition, other types of chromosome rearrangements, i.e. reciprocal translocations and insertions, were also included.

Simply grabbing an African spiny mouse can cause it to lose up to 60% of the skin on its back. Analysis of the mouse's astounding shedding and healing capacity provides insight into the biomechanics of tissue regeneration. See Letter p.561 Many animals can regenerate tissues, organs and even whole limbs after injury. In mammals, this capability is believed to be at best extremely limited, but these authors report that the African spiny mice (Acomys) are potentially important exceptions. Live-trapped A. kempi and A. percivali from Kenya are shown to share with certain lizards the ability to shed and then rapidly regenerate areas of skin. This skin autotomy is an effective defence against predators, who may gain a mouthful of easily-torn skin but miss out on the main prize as the spiny mouse scuttles away. Quite large, deep lesions can be regenerated, complete with hair follicles and cartilage in damaged ears, and with no scarring. The authors propose that these mice produce a pro-regenerative environment similar to that seen in limb-regenerating salamanders. This study suggests that mammals may retain a higher capacity for regeneration than previously recognized, and introduces spiny mice as a novel model organism for study of this subject.

The infectivity of Cryptosporidium muris and Cryptosporidium andersoni in various species of voles was studied using experimental infections. None of the experimental voles inoculated with 1 × 10(5) oocysts of Cryptosporidium spp. shed any oocysts during 40 DPI, except Brandt's vole (Lasiopodomys brandtii), which was susceptible to C. muris infection. Experiments confirmed the resistance of voles of the genus Microtus sensu stricto to infection with mammalian gastric cryptosporidia, which provides a new study model with prospects to more fully understand the processes involved in the phenomenon of host specificity of this group of protists.

We hypothesized that energy intake of lactating females is the main factor determining growth of the young and that use of maternal energy reserves is less important when food is available in abundance. We studied reproducing female common spiny mouse (Acomys cahirinus) offered millet seeds and water ad libitum. Females gave birth to 1 or 2 young, and growth rate was similar between litters of 1 infant and 2 infants combined. In addition, energy intake of the 2 groups of females was similar. Lactating females increased energy intake by 45% (per g0.75) over that of nonreproducing females. Energy intake and change in body mass of the lactating female each explained about 50% of the variance in infant growth and, therefore, our hypothesis was not supported. Energy intake and change in body mass of the lactating female together explained approximately 76% of the variance in growth of young.

The relationship between Protea humiflora and its small mammal pollinators was investigated at the fynbos/karoo ecotone in the Riviersonderend Mountains, South Africa. Acomys subspinosus occurred in low densities at Jonaskop, with around 3.9 ± 2.0 (mean ± 1 S.D.) individuals/ha (six months of trapping). Low repeat trapping may result may result from low survivorship or emigration from the area after flowering of P. humiflora. Mean mass of A. subspinosus was lower than published values due to a high proportion of juveniles in the population, coinciding with P. humiflora flowering. Comparison with other published data suggests that A. subspinosus is an opportunistic breeder. This contrasts with its geographically nearest congener, A. spinosissimus, in which breeding is restricted to the summer months, but is similar to data for other Acomys species. Minimum home range areas (-0.23 ha, minimum overnight distance 39 ± 6 m), were relatively high and may indicate a species surviving on thinly dispersed resources.

We compared non-shivering thermogenesis between two adjacent populations of the common spiny mouse Acomys cahirinus from different habitats, in relation to increasing salinity. Individuals were captured from the north- and south-facing slopes of the same valley, that represent "Mediterranean" and "desert" habitats, respectively. We hypothesized that the two populations of mice would differ in their thermoregulatory capacities, reflecting their need to cope with the environmental stress in each habitat. We measured resting metabolic rate by recording oxygen consumption, body temperature and response to an injection of exogenous noradrenaline. Mice were maintained on diets with increasing levels of salt intake to examine their abilities to cope with increasing osmotic stress. Mice from north-facing slopes generally had a higher resting metabolic rate and a higher increase in oxygen consumption in response to noradrenaline than mice from south-facing slopes. Increasing salinity decreased resting metabolic rate values, body temperature, and oxygen consumption in response to noradrenaline in both populations, and diminished slope-dependant differences. We suggest that these differences could be a result of an ongoing adaptive process to different climatic conditions, typical of the Mediterranean region, that are a demonstrable example of evolution in action.

Advances in research relating to menstruation and associated disorders (eg, endometriosis and premenstrual syndrome) have been hindered by the lack of an appropriate animal model. Menstruation, the cyclical shedding of the decidualized endometrium in the absence of pregnancy, is believed to be limited to 78 higher-order primates (human beings and Old World monkeys), 4 species of bat, and the elephant shrew. This represents only 1.5% of the known 5502 mammalian species and0.09% of these are nonprimates. Thus, many aspects of menstruation remain poorly understood, limiting the development of effective treatments for women with menstrual disorders. Menstruation occurs as a consequence of progesterone priming of the endometrial stroma and a spontaneous decidual reaction. At the end of each infertile cycle as progesterone levels decline the uterus is unable to maintain this terminally differentiated stroma and the superficial endometrium is shed. True menstruation has never been reported in rodents.Here we describe the first observation of menstruation in a rodent, the spiny mouse (Acomys cahirinus).Virgin female spiny mice (n = 14) aged 12-16 weeks were sampled through daily vaginal lavage for 2 complete reproductive cycles. Stage-specific collection of reproductive tissue and plasma was used for histology, prolactin immunohistochemistry, and enzyme-linked immunosorbent assay of progesterone (n = 4-5/stage of the menstrual cycle). Normally distributed data are reported as the mean ± SE and significant differences calculated using a 1-way analysis of variance. Nonnormal data are displayed as the median values of replicates (with interquartile range) and significant differences calculated using Kruskal-Wallis test.Mean menstrual cycle length was 8.7 ± 0.4 days with red blood cells observed in the lavages over 3.0 ± 0.2 days. Cyclic endometrial shedding and blood in the vaginal canal concluding with each infertile cycle was confirmed in all virgin females. The endometrium was thickest during the luteal phase at 322.6 μm (254.8, 512.2), when plasma progesterone peaked at 102.1 ng/mL (70.1, 198.6) and the optical density for prolactin immunoreactivity was strongest (0.071 ± 0.01 arbitrary units).The spiny mouse undergoes spontaneous decidualization, demonstrating for the first time menstruation in a rodent. The spiny mouse provides a readily accessible nonprimate model to study the mechanisms of menstrual shedding and repair, and may therefore be useful in furthering studies of human menstrual and pregnancy-associated disorders.

The use of the spiny mouse (Acomys cahirinus) in experimental research is steadily increasing, due to the precocial nature of this species and the similarities in endocrinology to the human. The characterisation of normal behavioural traits throughout development has not been comprehensively measured in the spiny mouse. Therefore the aim of this study was to behaviourally phenotype the spiny mouse, with the use of behavioural paradigms commonly used to assess behaviour in rat and mouse models of human behavioural disorders such as autism, attention-deficit disorder, and schizophrenia. Male and female spiny mice were assessed at 1-5, 10-15, 20-25, 40-45 and 80-85 days of age using the open field test, novel object recognition test, rotarod, elevated plus maze, a social interaction test, and prepulse inhibition. Exploratory activity, motor coordination, fear, anxiety and social behaviours could be accurately measured from 1 day of age. Open field exploration and motor coordination on a modified rotarod were precociously developed by 10-15 and 20-25 days of age, respectively, when they were equivalent to the performance of conventional adult mice. Learning and memory (assessed by the novel object recognition test), and sensory gating (prepulse inhibition) could be reliably determined only after 20-25 days of age, and performance on these tests differed significantly between male and female spiny mice, particularly in adulthood. This study characterises the behavioural traits of spiny mice and provides important information about critical periods of behavioural development throughout postnatal life.

We studied the effects of early weaning on immunocompetence and parasite resistance in a precocial rodent Acomys cahirinus. We hypothesized that if parasite resistance is energetically expensive and nutritional and immunological support from mothers are necessary for the long-term health of offspring, then early weaned animals would be immunologically weaker and less able to defend themselves against parasites than later weaned animals. We weaned pups at 14, 21, or 28 d after birth and assessed their immunocompetence and resistance against fleas Parapulex chephrenis when they attained adulthood. Immunocompetence was assessed using leukocyte concentrations (LC) and a phytohaemagglutinin injection assay (PHA test). To estimate resistance against fleas, we measured performance of fleas via the number of produced eggs and duration of development and resistance to starvation of the flea offspring. We found a significant positive effect of weaning age on the PHA response but not on LC. The effect of age at weaning on flea egg production was manifested in male but not female hosts, with egg production being higher if a host was weaned at 14 than at 28 d. Weaning age of the host did not affect either duration of development or resistance to starvation of fleas produced by mothers fed on these hosts. We concluded that even in relatively precocial mammals, weaning age is an important indicator of future immunological responses and the ability of an animal to resist parasite infestations. Hosts weaned at an earlier age make easier, less-resistant targets for parasite infestations than hosts weaned later in life.

The genus Acomys is represented by 19 species in a vast area in the African and eastern Mediterranean regions. Acomys cilicicus, belonging to the genus Acomys, is an endemic species in Turkey. In this study, by evaluating the reproductive data in laboratory conditions and the natural habitat of A. cilicicus, the reproductive biology of the species was researched in detail for the first time. The data concerning the reproduction of 1404 samples, reproduced from 1 male and 2 females in the laboratory and 34 samples obtained from 6 localities near Silifke, were recorded. For A. cilicicus, it was determined that the pregnancy period was 38-40 days, litter size was 1-3 (n = 321, mean = 2.05), and time to maturity was 2-4 months. The newborns' eyes were closed, their auricles were bonded to the head, they had short hair, their abdomens were hairless, and their backs were dark gray. Dentition was completed within 9-10 days and therefore the newborn could easily take food. Suckling was under control of the mother and carried on for approximately 2-3 months. Furthermore, the reproductive, infanticidal, and cannibalistic behaviors of this species were monitored periodically. These data were compared with A. cahirinus, russatus, nesiotes, minous, and dimidiatus, whose reproductive biologies are known and who are close to A. cilicicus geographically. Finally, it was determined that some reproductive findings of A. cilicicus were compatible with the findings of other species, and some findings were different from those of the species above.

This guide to animal models of human placentation assesses the strengths and weaknesses of species in common use. We argue that structural differences from human placenta, though important in some contexts, are less of a drawback than differences in reproductive strategy. Many laboratory rodents have brief gestations resulting in the birth of poorly developed young. They can provide useful insights on placental development and function relevant to early human pregnancy. However, to model the events of a 9-month gestation, which imposes added requirements on the placenta, it is necessary to consider animal models with longer gestations and well-developed neonates. Placentation in different orders of mammal is surveyed and their proximity to humans described in an evolutionary context. Animal models are then compared with the human in terms of the functional anatomy, physiology, and immunology of the placenta. This information is collated both to assess common animal models such as mouse, sheep, and primates and to introduce some alternatives that we consider worthy of attention.

The development of human kidney is a complex process requiring intricate cell and tissue interactions to assure the concerted program of cell growth, differentiation, and morphogenesis. Although the molecular and cellular nature of each of these interactions remains currently unclear, significant findings regarding nephrogenesis and its completion among different animal species have been reported over the last two decades. Research so far indicates that there are differences regarding the completion of the process of nephrogenesis among different animal species. In human, sheep, and spiny mouse, nephrogenesis is completed prior to birth, while in rat, mouse, and swine, nephrogenesis continuous after birth.

The golden spiny mouse (Acomys russatus), an inhabitant of rocky deserts, exhibits adaptations to diurnal activity, but also some characteristics that appear evolutionarily constrained to a nocturnal mode of life. This species is probably driven into diurnality by its congener, the common spiny mouse (A. cahirinus). We carried out a comparative study of the retinal morphology of A. russatus and A. cahirinus, in search of possible anatomical adaptations for diurnal activity in the eyes of golden spiny mice. The observed photoreceptors of both species had rod-pattern properties that characterize nocturnal mammals. We also carried out a field study of the foraging microhabitat use of golden spiny mice and of illumination levels in those microhabitats. Throughout the year, golden spiny mice preferred to forage between and particularly under boulders, where light intensities were lower than in the open. Thus, the retinal structure of golden spiny mice has not evolved to meet with their needs as a diurnal species, but the combination of the biochemical properties of their eyes, coupled with their foraging microhabitat selection, may enable them to withstand diurnal activity with nocturnally adapted retinas.

The common spiny mice Acomys dimidiatus and golden spiny mice Acomys russatus coexist in the extreme warm and dry parts of the Rift Valley in Israel. However, they are temporally segregated in that the former is nocturnal, whereas the latter is diurnal. Daily rhythms of physiological and behavioral variables in A. russatus responded to semiochemical signals released by A. dimidiatus (in the urine and feces). Both species feed upon the same food items but at different times of the 24-hr cycle. The main aim of the present study was to test under field conditions the foraging response of A. russatus to odors of different ages released by A. dimidiatus. Various feeding and behavioral variables were compared in three groups of A. russatus. The results show that fresh semiochemical signals released by A. dimidiatus decrease the feeding efficiency and increase the rate of smelling from a distance in A. russatus. These results support the idea that temporal segregation between the two coexisting species is at least partly through semiochemicals present in the urine and feces.

We constructed the comparative cytogenetic maps of X chromosomes in three rodent species, Indian spiny mouse (Mus platythrix), Syrian hamster and Chinese hamster, using 26 mouse cDNA clones. Twenty-six, 22 and 22 out of the 26 genes, which were mapped to human, mouse and rat X chromosomes in our previous study, were newly localized to X chromosomes of Indian spiny mouse, and Syrian and Chinese hamsters, respectively. The order of the genes aligned on the long arm of human X chromosome was highly conserved in rat and the three rodent species except mouse. The present results suggest a possibility that the rat X chromosome retains the ancestral form of the rodent X chromosomes.

Rodents usually respond to the presence of owls by reducing overall activity, in particular foraging. In this study, a playback of recorded tawny owl, Strix aluco, calls was sufficient to induce a marked effect in the social (Gunther's) vole, Microtus socialis. Some of the voles exposed to owl calls reduced their activity ('freeze' pattern) unlike control voles exposed to a human voice. Other voles, however, dashed around the cage ('flee' pattern). Owl calls also increased corticosterone levels in the voles, showing that the calls induced stress. We suggest that the behavioural dichotomy to freeze or flee in voles is a result of differences in individual normal behaviour and/or in stimulus interpretation. In the common spiny mouse, Acomys cahirinus, no behavioural changes were detected after exposure to owl calls, despite increased cortisol levels which are indicative of stress. Differences in the habitats of voles and spiny mice may explain the apparent lack of behavioural response in the latter. They are rock-dwelling rodents preferentially foraging between boulders and in rock crevices, where they are relatively protected from aerial predation, whereas voles forage in relatively open spaces. Copyright 1999 The Association for the Study of Animal Behaviour.

Predator cues (both mammalian odour or avian vocalizations) are known to elicit fear-associated responses in rodents, including analgesia. In previous studies it was reported that spiny mice fail to show fear responses when presented with the calls of an owl. In order to test the hypothesis that this species (living in semiarid and rocky areas) may react to stimuli coming from reptilian predators, 40 sexually mature spiny mice (20 males, 20 females) were individually exposed to a small cylinder containing either fresh sawdust or snake odour. Behavioural changes (5 min before and 15 min after odour exposure) as well as the subsequent performance in a hot-plate test (50 +/- 0.5 degrees C) were assessed. Results indicate that exposure to the odour of a sympatric terrestrial predator affected both behavioural and physiological responses of spiny mice. Upon exposure to snake odour both sexes showed significant changes in the patterns of inactivity, Sniffing, grooming, sniffing the stimulus object (SO), withdraw reaction and in the frequency of somersaults. However, males increased the frequency of rearing, sniffing the SO, decreasing grooming more than females. No analgesic effect of odour exposure emerged; however, males showed significantly shorter latencies and higher frequencies of hindpaw licking compared to females. (C) 1999 Elsevier Science B.V. All rights reserved.

Predator cues (both mammalian odour or avian vocalizations) are known to elicit fear-associated responses in rodents, including analgesia. In previous studies it was reported that spiny mice fail to show fear responses when presented with the calls of an owl. In order to test the hypothesis that this species (living in semiarid and rocky areas) may react to stimuli coming from reptilian predators, 40 sexually mature spiny mice (20 males, 20 females) were individually exposed to a small cylinder containing either fresh sawdust or snake odour. Behavioural changes (5 min before and 15 min after odour exposure) as well as the subsequent performance in a hot-plate test (50 +/- 0.5 degrees C) were assessed. Results indicate that exposure to the odour of a sympatric terrestrial predator affected both behavioural and physiological responses of spiny mice. Upon exposure to snake odour both sexes showed significant changes in the patterns of inactivity, Sniffing, grooming, sniffing the stimulus object (SO), withdraw reaction and in the frequency of somersaults. However, males increased the frequency of rearing, sniffing the SO, decreasing grooming more than females. No analgesic effect of odour exposure emerged; however, males showed significantly shorter latencies and higher frequencies of hindpaw licking compared to females. (C) 1999 Elsevier Science B.V. All rights reserved.

The pronounced increase in the protein/mRNA ratio of ammonia-metabolising enzymes in rat liver in the last prenatal week represents a clear example of a post-transcriptional level of control of gene expression. Both the underlying mechanism, namely an increase in translational efficiency of the mRNA and/or enhanced stability of the protein, and its importance for perinatal adaptation are unknown. We investigated this process in spiny mouse liver, because the comparison of rat and spiny mouse can discriminate adaptively from developmentally regulated processes in the perinatal period. We focused on glutamine synthetase (GS) because of the conveniently small size of its mRNA. Prenatally, GS enzyme activity slowly accumulated to approximately 1.3 U x g-1 liver at birth and postnatally more rapidly to 5.5 U x g-1 at 2 weeks. Both phases of enzyme accumulation obeyed exponential functions. Western-blot analysis showed that changes in GS activity reflected changes in GS protein content. GS mRNA content of the liver was 45 fmol x g-1 at 2 weeks before birth and slowly declined to approximately 25 fmol x g-1 at 2 weeks after birth. The GS protein/mRNA ratio increased 2.5-fold prenatally and sixfold postnatally. Analysis of prenatal and postnatal polysome profiles revealed no evidence of GS mRNA-containing ribonucleoprotein particles. Instead, GS mRNAs were (fully) occupied by 12 ribosomes, indicating regulation at the level of elongation. The kinetics of GS protein accumulation, in conjunction with GS mRNA content, are consistent with an approximately sixfold increase in its rate of synthesis at birth as the result of a corresponding stimulation of the rate of elongation.

So far the experiments in altered gravitational conditions on the prenatal development have used altricial rodent species. The aim of this study is to explore the differences in the intrauterine development of locomotor system in precocial (guinea pig, spiny mouse) and altricial (rat, mouse, and golden hamster) rodent species and to determine which of these mammalian groups represent a better study model to conduct research on the influence of altered gravitational conditions on human fetal development. Findings suggest that the influence of altered gravitational conditions on development of locomotor system significantly vary according to the maturity of mammals. By the characteristics of maturity at birth precocial rodents are more similar to a human than altricial species. Since precocial species have similar maturity of locomotor system to human, the changes caused by altered gravity among them should be similar as opposed to altricial species.

Beta-adrenergic stimulation induces melatonin synthesis and non-shivering thermogenesis (NST) in rodents. The golden spiny mouse, Acomys russatus is a nocturnal species capable of diurnal activity when coexisting with its congenitor the common spiny mouse A. cahirinus. We have investigated the impact of beta-adrenergic blockade on 6-sulphatoxymelatonin (6-SMT--a metabolite and index of melatonin production) and body temperature (Tb) daily rhythms in male A. russatus. Mice were acclimated to an ambient temperature (Ta) of 28 degrees C, under two photoperiod regimes (16L:8D; 8L:16D). The daily rhythms of Tb and urinary 6-SMT were measured for a period of 30 h at intervals of 4 h. Propranolol (4.5 mg/kg, i.p.) was administered one hour before lights went off (i.e. when beta blockade does not affect NST in this species) and both variables were measured for another 30 h. The beta blocker markedly augmented melatonin output of A. russatus under both photoperiod regimes. The elevation in melatonin secretion was accompanied with an increase in Tb of only 16L:8D-acclimated mice (i.e. shorten duration of melatonin peak). However, in 8L:16D-acclimated mice, a phase advance of about 4 h was noted in 6-SMT daily rhythm. These results indicate that the role of sympathetic innervation in regulation of melatonin synthesis in A. russatus differs from that in the rat. In addition, these data are compatible with the hyperthermic action of melatonin in this species. Therefore, it is suggested that in A. russatus, other neural pathways are involved in its pineal regulation.