Dipodillus Dasyurus Research Articles

Thermal niche partitioning and phenology of Nearctic and Palearctic flea (Siphonaptera) communities on rodents (Mammalia: Rodentia) from five ecoregions.

Seasonality of fleas (Siphonaptera) may be due to species competition, prompting the idea that flea species partition temperature, along with correlated variables such as moisture (thermal-niche partitioning hypothesis). I compared the fleas of five rodent-flea communities described from the literature for thermal-niche optima by fitting non-linear LRF (Lobry-Rosso-Flandrois) curves to examine whether flea species in a community show distinct, partitioned thermal niches. LRF curves estimate physiological parameters of temperature minimum, optimum, maximum, and maximum abundance, and facilitate comparison between species by summarizing seasonal data. Flea-communities were on Nearctic Southern flying squirrel (Glaucomys volans volans), Richardson's ground-squirrel (Urocitellus richardsonii), North American deer-mouse (Peromyscus maniculatus), and Palearctic Midday jird (Meriones meridianus), and Wagner's gerbil (Dipodillus dasyurus). Flea communities appeared to show seasonality consistent with thermal-niche partitioning. Several flea families and genera had characteristic thermal niches: Ceratophyllidae had broad tolerance to extreme temperature, Leptopsyllidae (one species in this study) to cold, and Pulicidae to hot. In contrast, at the local, species level, climatic speciation could be significant in flea diversification. Non-competition hypotheses (environmental filtering, neutrality) require testing, too. Thermal-niche partitioning may increase flea species richness on hosts and could occur in other insect and plant communities. Implications for biodiversity conservation and disease ecology under global warming are wide-ranging.

Description ofCandidatusBartonella fadhilae n. sp. andCandidatusBartonella sanaae n. sp. (Bartonellaceae) fromDipodillus dasyurusandSekeetamys calurus(Gerbillinae)from the Sinai Massif (Egypt)

Bartonella spp. are parasites of mammalian erythrocytes and endothelial cells, transmitted by blood-feeding arthropod ectoparasites. Different species of rodents may constitute the main hosts of Bartonella, including several zoonotic species of Bartonella. The aim of this study was to identify and compare Bartonella species and genotypes isolated from rodent hosts from the South Sinai, Egypt. Prevalence of Bartonella infection was assessed in rodents (837 Acomys dimidiatus, 73 Acomys russatus, 111 Dipodillus dasyurus, and 65 Sekeetamys calurus) trapped in 2000, 2004, 2008, and 2012 in four dry montane wadis around St. Katherine town in the Sinai Mountains. Total DNA was extracted from blood samples, and PCR amplification and sequencing of the Bartonella-specific 860-bp gene fragment of rpoB and the 810-bp gene fragment of gltA were used for molecular and phylogenetic analyses. The overall prevalence of Bartonella in rodents was 7.2%. Prevalence differed between host species, being 30.6%, 10.8%, 9.6%, and 3.6% in D. dasyurus, S. calurus, A. russatus, and A. dimidiatus, respectively. The phylogenetic analyses of six samples of Bartonella (five from D. dasyurus and one from S. calurus) based on a fragment of the rpoB gene, revealed the existence of two distinct genetic groups (with 95–96% reciprocal sequence identity), clustering with several unidentified isolates obtained earlier from the same rodent species, and distant from species that have already been described (90–92% of sequence identity to the closest match from the GenBank reference database). Thus, molecular and phylogenetic analyses led to the description of two species: Candidatus Bartonella fadhilae n. sp. and Candidatus Bartonella sanaae n. sp. The identification of their vectors and the medical significance of these species need further investigation.

Babesia behnkei sp. nov., a novel Babesia species infecting isolated populations of Wagner's gerbil, Dipodillus dasyurus, from the Sinai Mountains, Egypt.

BackgroundAlthough a number of new species of Babesia/Theileria have been described recently, there are still relatively few reports of species from Africa. In this study based on the evaluation of morphology and phylogenetic relationships, we describe a novel species from Wagner’s gerbil, Babesia behnkei n. sp.MethodsRodents (n = 1021) were sampled in four montane valleys (wadies) in 2000, 2004, 2008 and 2012 in the Sinai Mountains, Egypt. The overall prevalence of Babesia spp. was highest in the Wagner’s gerbil (Dipodillus dasyurus; 38.7%) in comparison to the prevalence in the spiny mice species, Acomys dimidiatus and A. russatus. Morphological investigations were conducted for the comparison of trophozoites of the novel species of Babesia with the B. microti King’s 67 reference strain. Thirty-two isolates derived from D. dasyurus over a 9 year period (2004-2012) from two wadies (29 isolates from Wadi Gebel and 3 from Wadi El-Arbaein) were investigated by microscopic, molecular and phylogenetic analysis. A near-full-length sequence of the 18S rRNA gene and the second internal transcribed spacer (ITS2) region were amplified, sequenced and used for the construction of phylogenetic trees.ResultsA novel species of Babesia was identified in two isolated populations of D. dasyurus. Phylogenetic analysis of 18S rDNA and ITS2 sequences revealed that B. behnkei n. sp. is most closely related to B. lengau from cheetahs from South Africa and to Nearctic species found only in North America (the pathogenic B. duncani and B. conradae) and that it is more distant to the cosmopolitan rodent parasite B. microti. Trophozoites of B. behnkei were smaller and less polymorphic than trophozoites of B. microti.ConclusionBabesia behnkei n. sp. is a novel species of the ‘Duncani group’ maintained in isolated populations of Dipodillus dasyurus occurring in the Sinai Mountains of Egypt.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-014-0572-9) contains supplementary material, which is available to authorized users.

Variable effects of host characteristics on species richness of flea infracommunities in rodents from three continents

We studied the effect of host gender and body mass on species richness of flea infracommunities in nine rodent host species from three biomes (temperate zone of central Europe, desert of the Middle East and the tropics of East Africa). Using season- and species-specific generalized linear mixed models and controlling for year-to-year variation, spatial clustering of rodent sampling and over-dispersion of the data, we found inconsistent associations between host characteristics and flea species richness. We found strong support for male-biased flea parasitism, especially during the reproductive period (higher species richness in male hosts than in females) in all considered European rodents (Apodemus agrarius, Myodes glareolus and Microtus arvalis) and in one rodent species from the Middle East (Dipodillus dasyurus). In contrast, two of three African rodent species (Lophuromys kilonzoi and Praomys delectorum) demonstrated a trend of female-biased flea species richness. Positive associations between body mass and the number of flea species were detected mainly in males (five of nine species: A. agrarius, M. glareolus, M. arvalis, D. dasyurus and Mastomys natalensis) and not in females (except for M. natalensis). The results of this study support earlier reports that gender-biased, in general, and male-biased, in particular, infestation by ectoparasites is not a universal rule. This suggests that mechanisms of parasite acquisition by an individual host are species-specific and have evolved independently in different rodent host-flea systems.

The comparative gastrointestinal morphology of five species of muroid rodents found in Saudi Arabia

Meriones rex (King jird), Meriones libycus (Libyan jird), Acomys dimidiatus (Eastern spiny mouse), Acomys cahirinus (Egyptian spiny mouse), and Dipodillus dasyurus (Wagner's dipodil) are five species of small rodents of the superfamily Muroidea with distributions in Eastern Africa, Egypt, and the desert regions of the Arabian Peninsula. Water is scarce in these regions and may result in relatively low-digestible food. The aim of the present study is to describe and compare the gastrointestinal tract morphology and morphometry of these five species in order to elucidate whether morphology is influenced by phylogeny or dietary preference. Each segment of the gastrointestinal tract of each species was macroscopically examined and the length and basal surface area of each segment was measured. Standard histologic procedures were performed to determine a surface enlargement factor to determine the mucosal luminal surface area. A unilocular-hemiglandular stomach was observed in all the species examined. The caeca of all the species were long and arranged into a loose spiral toward the caecal tip with the ileocaecal and caeco-colic openings positioned close together. Two rows of oblique folds could be observed in the proximal colon of all species except in D. dasyurus which had longitudinal folds. Morphometric analysis showed the largest stomach in A. cahirinus and the largest caecum and colon in M. libycus. All the species can be grouped in the family Muridae in two subfamilies and similarities were observed including the hemiglandular stomach and relatively large caecum. It could be concluded that phylogeny plays an important role in determining gastrointestinal morphology while diet plays a subordinate role in the desert rodents in the present study.

Babesia behnkei sp. nov., a novel Babesia species infecting isolated populations of Wagner¿s gerbil, Dipodillus dasyurus, from the Sinai Mountains, Egypt

Although a number of new species of Babesia/Theileria have been described recently, there are still relatively few reports of species from Africa. In this study based on the evaluation of morphology and phylogenetic relationships, we describe a novel species from Wagner’s gerbil, Babesia behnkei n. sp. Rodents (n = 1021) were sampled in four montane valleys (wadies) in 2000, 2004, 2008 and 2012 in the Sinai Mountains, Egypt. The overall prevalence of Babesia spp. was highest in the Wagner’s gerbil (Dipodillus dasyurus; 38.7%) in comparison to the prevalence in the spiny mice species, Acomys dimidiatus and A. russatus. Morphological investigations were conducted for the comparison of trophozoites of the novel species of Babesia with the B. microti King’s 67 reference strain. Thirty-two isolates derived from D. dasyurus over a 9 year period (2004-2012) from two wadies (29 isolates from Wadi Gebel and 3 from Wadi El-Arbaein) were investigated by microscopic, molecular and phylogenetic analysis. A near-full-length sequence of the 18S rRNA gene and the second internal transcribed spacer (ITS2) region were amplified, sequenced and used for the construction of phylogenetic trees. A novel species of Babesia was identified in two isolated populations of D. dasyurus. Phylogenetic analysis of 18S rDNA and ITS2 sequences revealed that B. behnkei n. sp. is most closely related to B. lengau from cheetahs from South Africa and to Nearctic species found only in North America (the pathogenic B. duncani and B. conradae) and that it is more distant to the cosmopolitan rodent parasite B. microti. Trophozoites of B. behnkei were smaller and less polymorphic than trophozoites of B. microti. Babesia behnkei n. sp. is a novel species of the ‘Duncani group’ maintained in isolated populations of Dipodillus dasyurus occurring in the Sinai Mountains of Egypt.

Desert Gerbils Affect Bacterial Composition of Soil

Rodents affect soil microbial communities by burrow architecture, diet composition, and foraging behavior. We examined the effect of desert rodents on nitrogen-fixing bacteria (NFB) communities by identifying bacteria colony-forming units (CFU) and measuring nitrogen fixation rates (ARA), denitrification (DA), and CO2 emission in soil from burrows of three gerbil species differing in diets. Psammomys obesus is folivorous, Meriones crassus is omnivorous, consuming green vegetation and seeds, and Dipodillus dasyurus is predominantly granivorous. We also identified NFB in the digestive tract of each rodent species and in Atriplex halimus and Anabasis articulata, dominant plants at the study site. ARA rates of soil from burrows of the rodent species were similar, and substantially lower than control soil, but rates of DA and CO2 emission differed significantly among burrows. Highest rates of DA and CO2 emission were measured in D. dasyurus burrows and lowest in P. obesus. CFU differed among bacteria isolates, which reflected dietary selection. Strains of cellulolytic representatives of the family Myxococcaceae and the genus Cytophaga dominated burrows of P. obesus, while enteric Bacteroides dominated burrows of D. dasyurus. Burrows of M. crassus contained both cellulolytic and enteric bacteria. Using discriminant function analysis, differences were revealed among burrow soils of all rodent species and control soil, and the two axes accounted for 91% of the variance in bacterial occurrences. Differences in digestive tract bacterial occurrences were found among these rodent species. Bacterial colonies in P. obesus and M. crassus burrows were related to bacteria of A. articulata, the main plant consumed by both species. In contrast, bacteria colonies in the burrow soil of D. dasyurus were related to bacteria in its digestive tract. We concluded that gerbils play an important role as ecosystem engineers within their burrow environment and affect the microbial complex of the nitrogen-fixing organisms in soils.

Use it or lose it: reproductive implications of ecological specialization in a haematophagous ectoparasite

Using experimentally induced disruptive selection, we tested two hypotheses regarding the evolution of specialization in parasites. The 'trade-off' hypothesis suggests that adaptation to a specific host may come at the expense of a reduced performance when exploiting another host. The alternative 'relaxed selection' hypothesis suggests that the ability to exploit a given host would deteriorate when becoming obsolete. Three replicate populations of a flea Xenopsylla ramesis were maintained on each of two rodent hosts, Meriones crassus and Dipodillus dasyurus, for nine generations. Fleas maintained on a specific host species for a few generations substantially decreased their reproductive performance when transferred to an alternative host species, whereas they generally did not increase their performance on their maintenance host. The results support the 'relaxed selection' hypothesis of the evolution of ecological specialization in haematophagous ectoparasites, while suggesting that trade-offs are unlikely drivers of specialization. Further work is needed to study the extent by which the observed specializations are based on epigenetic or genetic modifications.

Betaherpesvirus Sequences in Eastern Spiny Mice and Wagner’s Dipodils

Eastern spiny mice (Acomys dimidiatus; also known as Sinai spiny mice) have been extensively studied in terms of the influence of parasite load on population size and reproductive fitness. The physical isolation of these rodent populations makes them interesting models for disease interactions in a real-life population as opposed to a laboratory. We identify betaherpesvirus sequences in eastern spiny mice and Wagner's dipodils (Dipodillus dasyurus), species that inhabit dry montane wadis (dry creek valleys) of the Sinai, highlighting the need for a comprehensive analysis of the full pathogen repertoire of these rodents in long-term studies.

Infestation experience of a rodent host and offspring viability of fleas: variation among host–parasite associations

We studied survival and development of preimagoes and the ability to withstand starvation of adults in two flea species, host-specific Parapulex chephrenis and host-opportunistic Xenopsylla ramesis, when parent fleas fed on a typical (Acomys cahirinus and Dipodillus dasyurus, respectively) or an atypical (D. dasyurus and A. cahirinus, respectively) rodent host that either had never been parasitized by fleas (pristine) or had previously been exposed to fleas. We asked whether a repeatedly infested host acquired resistance that would cause decreased viability of the next generation fleas. Survival of preimaginal P. chephrenis was similar, independent of host species or its infestation status. Preimaginal X. ramesis had a higher survival rate when their parents fed on preinfested than on pristine typical hosts, whereas no effect of infestation status of an atypical host was found. P. chephrenis developed faster if their parents fed on atypical than on typical hosts and on pristine than on preinfested hosts of either species. X. ramesis developed faster if parents fed on pristine than preinfested typical hosts, but no difference in duration of development was found for atypical hosts. Under starvation, P. chephrenis lived longer if their parents fed on preinfested than on pristine typical hosts, but their lifespan did not depend on infestation status of atypical hosts. The latter was also true for X. ramesis and both host species. We conclude that a host is constrained in its ability to cope with a parasite, whereas a parasite is able to cope with defence responses of a host.

The effect of larval density on pre-imaginal development in two species of desert fleas

We studied the effect of density of larvae on pre-imaginal development in 2 flea species (Xenopsylla conformis and Xenopsylla ramesis) parasitic on 2 desert rodent species (Dipodillus dasyurus, adult body mass 20 g and Meriones crassus, 80 g). We predicted a decrease in duration of development with an increase in density of larvae. In general, in both flea species, duration of larva-to-pupa development decreased with an increasing larval density. In addition, this stage of development was longer in male fleas and in fleas from parents fed on D. dasyurus. The effect of larval density on larval development was manifested mainly when parent fleas fed on D. dasyurus. Duration of pupation decreased with increasing larval density only in offspring of fleas fed on G. dasyurus. In both fleas, pupation was longer in males. The effect of parent host on duration of pupation was found in X. ramesis only (longer if the host was M. crassus). Resistance of newly emerged fleas to starvation depended mainly on parent host species. Young X. conformis survived longer if their parents fed on D. dasyurus, whereas young X. ramesis survived longer if their parents fed on M. crassus. It was also found that (a) an individual flea that spent more time as a larva also spent more time as a pupa and (b) longer larval development resulted in a shorter time that a newly emerged flea was able to survive when starved.

Does acquired resistance of rodent hosts affect metabolic rate of fleas?

We studied whether (a) previous infestation of a rodent host with fleas and (b) the reproductive effort of fleas affect the rate of CO(2) emission in two flea species, host-specific Parapulex chephrenis and host-opportunistic Xenopsylla ramesis when feeding on their typical and atypical rodent hosts. We measured the rate of CO(2) emission in preovipositing and ovipositing female fleas fed on either pristine or previously infested Acomys cahirinus (typical host of P. chephrenis) and Dipodillus dasyurus (typical host of X. ramesis). When P. chephrenis fed on a typical host, its mass-specific rate of CO(2) emission was not affected by previous infestation of a host, whereas when this flea fed on the atypical host, its rate of CO(2) emission was higher when a host was previously infested. This was manifested, however, mainly during the oviposition period. The rate of CO(2) emission by X. ramesis feeding on pristine hosts was significantly lower than in conspecifics feeding on previously infested hosts, independent of host species. Both flea species feeding on their typical hosts emitted CO(2) at similar mass-specific rates during preoviposition and oviposition, except for P. chephrenis feeding on D. dasyurus, which increased its rate during oviposition. There was no effect of the number of eggs produced per female on the rate of CO(2) emission during oviposition.

Evidence for a negative fitness−density relationship between parent density and offspring quality for two Xenopsylla spp. parasitic on desert mammals

We tested the hypothesis of negative fitness-density relationships and predicted that an increase in the density of parent fleas would result in lower survival rates and longer development time of pre-imagoes as well as shorter time to death from starvation of newly emerged imagoes. These predictions were experimentally tested on Xenopsylla conformis Wagner and Xenopsylla ramesis Rothschild feeding on two rodent species, Meriones crassus Sundevall or Dipodillus dasyurus Wagner. Survival of larvae and pupae, but not eggs, was negatively affected by parent density. An increase in parent density led to a decrease in the number of imagoes of the next generation. Eggs of both species developed faster when the parents were at low densities on either host. The same was true for larval X. ramesis, but not larval X. conformis. The negative effects of parent density on the duration of pupal development were evident in X. conformis, parents of which fed on both hosts, and X. ramesis from parents fed on M. crassus, whereas X. ramesis from parents fed on D. dasyurus developed faster at low densities. A negative effect of density on the development of offspring from egg to imago in X. conformis was manifested mainly when parent fleas fed on D. dasyurus, whereas the negative effect of density on offspring development in X. ramesis was manifested mainly when parent fleas fed on M. crassus. Although there was no general effect of parent density on the resistance of imago offspring to starvation, male X. ramesis from parents fed at the highest density survived starvation for significantly shorter times compared with those from parents fed at lower densities. Manifestation of the negative effect of parent density on offspring quality appears to vary with flea species and may be affected by host species.

Effects of parasite specificity and previous infestation of hosts on the feeding and reproductive success of rodent‐infesting fleas

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.

Wheel-Running Activity Patterns of Five Species of Desert Rodents

In contrast to the extensive laboratory data on activity patterns in rodent species inhabiting temperate zones, much less is known about the activity patterns of desert rodents. In order to address this issue, we measured wheel-running activity patterns in males and females of five species of wild-trapped desert rodents (Dipodillus dasyurus, Gerbillus andersoni, Gerbillus pyramidum, Meriones shawi, and Acomys cahirinus) in long ‘summer-like’ and short, ‘winter-like’ day lengths. The specific goals of the present study were to characterize activity patterns in several desert rodent species in the laboratory and to determine if activity patterns are expressed in a seasonal or sexually dimorphic manner. Specifically, wheel-running was measured for 11 weeks in long days followed by 11 weeks in short days to test for photoperiodic entrainment as well as responsiveness to changes in the light-dark cycle. All animals exhibited rhythmic patterns of wheel-running with consistent onsets and offsets that had well-defined relations with the light-dark cycle. All individuals of G. andersoni showed nocturnal activity patterns. Most individuals of G. pyramidum had nocturnal activity patterns, but some individuals showed a short bout of activity at the beginning of the light period. Most individuals of D. dasyurus and M. shawi showed bimodal (i.e., nocturnal and diurnal) activity patterns, although some showed markedly nocturnal activity patterns. There was no sexual dimorphism in wheel running activity rhythms in any of the species examined. As expected, decreases in day length resulted in an overall increase in the duration of activity in all species. Collectively, these data provide an initial characterization of activity patterns within desert rodents in a controlled laboratory setting.

Photoperiodic responses of four wild-trapped desert rodent species.

The purpose of this study was to examine the effect of the photoperiod on reproductive status and body and lipid masses in four Egyptian desert rodent species (Dipodillus dasyurus, Acomys cahirinus, Gerbillus andersoni, and Gerbillus pyramidum). Adult males and females were housed in long days for 11 wk. At that time, one-half of the animals were killed and the remaining animals were moved to short days (SDs) for 11 wk. Some individuals of Gerbillus andersoni and Gerbillus pyramidum had access to running wheels. Testes index and spermatogenesis, but not testis mass, were decreased in all species in SDs. In contrast, SDs did not affect female reproductive status in all species. Exercise stimulated spermatogenesis but did not affect female reproductive status. SDs increased body and lipid masses in male Acomys cahirinus, but not in other species. Collectively, these desert rodent species were responsive to day length changes, but these changes alone did not induce robust alterations in reproductive status and body and lipid masses.