The pineal gland of the mole-rat (Spalax ehrenbergi,Nehring)

Summary A comparative investigation of the distribution of monoaminergic neurons in non-malacostracan crustaceans was performed with the histochemical fluorescence method of Falck-Hillarp.Two fluorophores were found: the more widespread of the two emits a green fluorescence; and the more sparsely distributed emits a yellow to brown-yellow fluorescence.Specific green fluorescent areas were shown to exist in the protocerebrum. The central body and the optic ganglia of the compound eye (where present) are always fluorescent. Moreover, the centre of the nauplius eye may have a green fluorophore, as in ostracods, and a neuropile area, here called the frontal area. These neuropile centres are known from ordinary histological studies of the nervous system. In addition, there are specific monoaminergic centres, such as the so-called dorsal area of phyllopods and anostracans as well as the copepod specific areas. Specific monoaminergic areas appear in the deutocerebrum and the suboesophageal ganglion where they are particularly well developed.Presumed sensory neurons in the cavity receptor organ of Artemia salina are shown to be monoaminergic. Monoaminergic sensory neurons have not been described previously in Arthropods.Presumed motor innervation of hind-gut and trunk muscles is also found, and it is concluded that in crustaceans neurons of every type (sensory, internuncial, motor) may be monoaminergic.We have enjoyed unrestricted laboratory facilities at the Department of Histology, Faculty of Medicine, and with great pleasure express our sincere thanks to Prof. Bengt Falck. — Grants from the Swedish Natural Science Research Council (2760-007), the Swedish Medical Research Council (04X-712), the Royal Swedish Academy of Science (Hierta-Retzius), the Royal Physiographic Society of Lund, and the University of Lund supported the work.     

The structure of mast cell secretory granules in the blind mole rat (Spalax ehrenbergi)

Eosinophils, basophils, and mast cells produce and secrete active substances whose role is to attack invading parasites and protect the host. In this study we use morphometric methods to study mast cells in the blind mole rat (Spalax ehrenbergi). The subterranean and solitary way of life of this species has led to the evolutionary development of special anatomical, morphological, behavioral, and physiological adaptations. Because of its particular lifestyle, the mole rat is less exposed to parasites than other rodents. This could provide a unique model for research into the pathobiology of mast cells. The paracrystalline structure of the mast cell granule content is composed of parallel plates. Diffraction analysis of electron micrographs of thin sections of araldite-embedded tissues indicated that each crystal line plate is a periodic array of parallelograms. The crystal unit cell volume is approximately 930 nm(3), suggesting that each unit cell is composed of one heparin molecule and one to three additional adsorbed proteins. Morphometric data show that characteristics of the secretory granules of mast cells of the blind mole rat resemble those of other rodents. The mast cell unit granule volume in the present study was calculated to be 0.055 microm(3), similar to that of rat peritoneal mast cells.     

Eimeriidae of the Herbivorous Mole-Rat, Spalax ehrenbergi Nehring

SYNOPSIS. A survey of 41 herbivorous mole-rats, Spalax ehrenbergi Nehring, in Urfa, Adiyaman, and Maras provinces of Turkey revealed 7 new species of Eimeria in addition to previously described Eimeriidae. The shape, average dimensions (in μm) of their oocysts, and the numbers of hosts from which the new species were isolated were as follows: Eimeria urfensis sp. n., ellipsoidal (33 × 21), from 8 hosts; Eimeria adiyamanensis sp. n., ovoid to ellipsoidal (33 × 18), from 6 hosts; Eimeria haranica sp. n., elongate ovoid (37 × 20), from 22 rats; Eimeria marasensis sp. n., ellipsoidal (36 × 18), from 2 rats; Eimeria oytuni sp. n., pear-shaped (24 × 17), from 2 hosts; Eimeria celebii sp. n., ellipsoidal (16 × 9), from 1 rat; and Eimeria torosicum sp. n., spherical to subspherical (11 × 10), from 2 animals.     

Evolution of crystallins: expression of lens-specific proteins in the blind mammals mole (Talpa europaea) and mole rat (Spalax ehrenbergi)

The mole (Talpa europaea; Insectivora) and the mole rat (Spalax ehrenbergi; Rodentia) both have degenerated eyes as a convergent adaptation to subterranean life. The rudimentary eye lenses of these blind mammals no longer function in a visual process. The crystallin genes, which display a lens-specific expression pattern, were studied in these blind mammals and in related species with normal eyes by hybridizing their genomic DNAs with probes obtained from cDNA clones for alpha A-, alpha B-, and beta Bp-crystallins from calf and gamma 3- crystallin from the rat. For all crystallin genes examined, the hybridization signals of mole and mole rat genomic DNA were comparable, respectively, with those of shrew and of rat and mouse, normal-vision representatives of the orders Insectivora and Rodentia. The expression of the crystallins at the protein level was tested by using antiserum specific for alpha-crystallin in immunofluorescence reactions on lens sections of mole and mole rat eyes and by using antisera against the beta- and gamma-crystallins on sections of the mole eye. All antisera gave positive fluorescence reactions exclusively with lens tissue of these blind mammals, indicating that the crystallins are still normally expressed despite the fact that these lenses have had no function in a visual process in these mammals for at least many million years. These findings apparently imply that some unknown selective advantage has conserved the crystallin genes and their expression after the loss of normal function of the lenses.      

The effect of melatonin administration and short exposures to cold on body temperature of the blind subterranean mole rat (Rodentia, Spalax ehrenberghi, Nehring)

Improvement of the cold resistance capacity of the mole rat (Spalax ehrenbergi, Nehring), a blind subterranean rodent, was achieved following subcutaneous melatonin administration. Melatonin-treated mole rats exhibited reduction both in initial body temperature (Tbo) and in the decrease of body temperature (delta Tb) after 6 hours of exposure to cold. The tested mole rats were acclimated to and kept during the experiment, under long (16L/8D) photoperiod schedule while the effects of melatonin administration on body temperature simulated the effects of short photoperiod conditions. These results suggest that in mole rats, melatonin biochemically mediates photoperiodic information into body temperature physiological response. As a byproduct of the original experiment, it was found that frequently repeated short (6 hours) exposure to cold (Ta = 5 +/- 1 degrees C) can in itself initiate an improvement of cold resistance capacity similar to the effect of melatonin administration. This supports the idea that mole rats may improve their cold resistance in response to either photoperiodic or climatic changes.     

Effect of photoperiod variation on testes and accessory sex organs in the male blind mole rat Spalax ehrenbergi

The blind mole rat is a seasonally breeding fossorial rodent that is perceptionally blind. This study examines the effect of photoperiod on the morphology and histology of the male mole rat reproductive system, three groups of male mole rats were maintained in the laboratory under short day (SD) conditions (9L: 15D); long day (LD) conditions (15L:9D); and constant darkness (CD), and compared to animals trapped in the field (FL). It was found that the field animals revealed higher testes and prostate gland weights, higher prostate tubuli volume (v*) and lower testes tubuli volume (v*) compared to the other three groups. Distribution of the tubuli in the testes (Vv) was low in the FL group compared to the SD and LD groups but still higher than in the CD group. Distribution of lumen in the testes (Vv) was higher in the CD group in comparison to the other three groups. Distribution of interstitial tissue in the testes (Vv) was higher in the FL group than in the other three groups. Electrolytes and elements secreted from the prostate gland did not differ among the four groups. In the FL group distribution of the tubuli (Vv) in the prostate gland was low and lumen ratio (Vv) was high compared to the other three groups. Distribution of connective tissue in the prostate gland did not differ among all four groups. Testosterone levels and total sperm count was highest in the FL group. Sperm production was noted in all groups; however spermatid and spermatozoa cell production was higher in the FL group. This study shows that photoperiod could be important in initiating timing in the breeding season but that certain other conditions which are absent in the laboratory appear to be responsible for successful breeding in the field.     

Microsatellite diversity in populations of blind subterranean mole rats (Spalax ehrenbergi superspecies) in Israel: speciation and adaptation

The genetic diversity, structure, and relationships of 12 populations of blind subterranean mole rats belonging to four species of the Spalax ehrenbergi superspecies were examined. Diversity levels and divergence of 19 nuclear microsatellite markers were analysed. Results indicate that the 12 populations fall into two major clusters representing the species pairs Spalax galili (2 n  = 52) and S. golani (2 n  = 54) vs. S. carmeli (2 n  = 58) and S. judaei (2 n  = 60). There is very little gene flow between the species pairs, except for one population (Afiq) of S. carmeli (2 n  = 58), which is located near the hybrid zone between S. golani (2 n  = 54) and S. carmeli (2 n  = 58). Higher values of the mean for alleles per locus, gene diversity, and number of unique alleles were observed for the southern species pair, S. carmeli and S. judaei, than for the northern species pair, S. galili and S. golani . Microsatellite diversity increases southward toward the Negev Desert and is positively correlated with aridity stress. Climatic factors of water availability coupled with temperature account for 76.7% of microsatellite variance. Natural selection appears to adaptively determine microsatellite evolution in Spalax regionally across Israel.  © 2004 The Linnean Society of London , Biological Journal of the Linnean Society , 2004, 83 , 229–241.     

Aggression patterns in three chromosome forms of the mole rat, Spalax ehrenbergi.

Three chromosome forms of the mole rat, Spalax ehrenbergi, 2n = 52, 2n = 58 and 2n = 60 were studied in an especially designed apparatus which simulated a natural territorial situation by permitting the animal free movement into and out of its home cage. Observed were variables representing agonistic, conflict and territorial behaviour. The data were analysed by means of a Smallest Space Analysis, SSA-II, which gave a graphic portrayal of the interrelations of behaviour categories where differences between means of single traits had been of no significance. 2n = 52 animals were found to be 'losers' in encounters. 'Lose', 'win' and 'draw' could be characterized by specific behaviour patterns: each outcome of encounter was surrounded by a cluster of behaviour categories consisting of agonistic, conflict and territorial activities that characterized its region of the SSA space.     

Circadian genes in a blind subterranean mammal III: molecular cloning and circadian regulation of cryptochrome genes in the blind subterranean mole rat, Spalax ehrenbergi superspecies

The blind subterranean mole rat superspecies Spalax ehrenbergi is an extreme example of mammalian adaptation to life underground. Though this rodent is totally visually blind, harboring a drastically degenerated subcutaneous rudimentary eye, its daily activity rhythm is entrainable to LD cycles. This indicates that it confers light information to the clock, as has been previously shown by the authors in behavioral studies as well as by molecular analyses of its Clock/MOP3 and its three Per genes. The Cryptochrome (Cry) genes found in animals and plants act both as photoreceptors and as essential components of the negative feedback mechanism of the biological clock. To further understand the circadian system of this unique mammal, the authors cloned and characterized the open reading frame of Spalax Cry1 and Cry2. The Spalax CRY1 protein is significantly closer to the human homolog than to the mice one, in contrast to the evolutionary expectations. They have found two isoforms of Cry2 in Spalax, which differ in their 5' end of the open reading frame and defined their expression in Spalax populations. They found a large and significant excess of heterozygotes of sCry2 (sCry2L/S genotype). Both sCry1 and sCry2 mRNAs were found in the SCN, the eye, the harderian gland, as well as in a wide range of peripheral tissues. Their expression pattern under different LD conditions has also been analyzed. As was already shown for other circadian genes, despite being blind and living in darkness, the Cry genes of Spalax behave in a similar, though not identical, pattern as in sighted animals. Once again, the results indicate that the uniquely hypertrophied harderian gland of Spalax plays a key role in its circadian system.     

The primary structure of the hemoglobin of the mole rat (Spalax ehrenbergi, rodentia, chromosome species 60)

Mole rat (Spalax ehrenbergi) hemoglobin consists of only one component. The complete amino-acid sequence of the alpha- and beta-chains of the species with the diploid chromosome number of 60 is presented. Following chain separation by chromatography on carboxymethyl cellulose CM-52, the primary structures were established by automatic Edman degradation on the chains, on the tryptic peptides, and on a peptide obtained by acid hydrolysis of the Asp-Pro bond in beta-chains. The alignment of the peptides was performed by homology with human alpha- and beta-chains. The comparison showed an exchange of 23 residues in the alpha-chains and 26 in the beta-chains. One substitution in the beta-chains concerns the surrounding of the heme. We found two exchanges in each chain in the alpha 1 beta 1-subunit interface and one in the beta-chain alpha 1 beta 2-contact points. Though all binding sites for 2,3-bisphosphoglycerate are unchanged, the mole rat blood has a high oxygen affinity as a part of adaptation to subterranean life under hypoxia and hypercapnia. A comparison of the sequence with known X-ray models of hemoglobins may give an interpretation of this fact. The primary structure of the mole rat hemoglobin shows more similarities with surface rodents, than with the mole, another small mammal, adapted to hypoxia in subterranean tunnels. The adaptation to hypoxia in mole rat and mole must be due to different mechanisms.     

Hypoxic survival differs between two mole rat species (Spalax ehrenbergi) of humid and arid habitats.

1. Two chromosomal species, 2n = 52 and 2n = 60 of the mole rat superspecies (Spalax ehrenbergi), occupy humid (2n = 52) and arid (2n = 60) habitats in Israel. 2. Gas conductivity of the soil of the 2n = 52 mole rat is lower than that of the 2n = 60 mole rat, and the 2n = 52 mole rat is better adapted to hypoxia. 3. The hypothesis that the 2n = 52 mole rat can survive to a lower pO2 than the 2n = 60 mole rat was tested. 4. Terminal pO2 (Torr) of four females 2n = 52 was lower, 18.0 +/- 2.9 (SD), than the terminal pO2 of five females 2n = 60, 28.2 +/- 5.1 (SD). 5. The hypoxic survival of the 2n = 52 mole rat as compared to that of the 2n = 60 mole rat correlates with other physiological traits: breathing and heart frequencies, blood hemoglobin and tissue gas tensions.     

Adaptive variation of pelage color within and between species of the subterranean mole rat (Spalax ehrenbergi) in Israel

Summary Color notations of dorsal pelage were analyzed in 451 adult subterranean mole rats, comprising 19 populations and 4 chromosomal species (2n=52, 54, 58 and 60) of the Spalax ehrenbergi superspecies in Israel. In addition, the color notations of soil samples from the collection sites were measured. In an attempt to evaluate the degree of correlation between pelage color of mole rats and the local soil color, each color was compared both macro- and microgeographically. The macrogeographic comparisons were among populations of the 4 chromosomal species, and the microgeographic comparisons were among pairs of geographically neighboring subpopulations which occur under similar climatic conditions but differ in soil type and color. The results indicate that 1. no differences in pelage color notation exist between the sexes; 2. pelage of mole rats is generally characterized by an over-all grayish color, but its shades vary regionally and locally in accordance with varying soil color; 3. a positive correlation was found between pelage and local soil colors in the macrogeographic analysis and this correlation was verified in a microgeographic comparison; 4. specimens from populations of the northern chromosomal species (2n=52, 54) mainly inhabit terra rossa and basalt soils, respectively, with reddish brown tones, and they tend to have a more reddish shade, whereas animals from the central species (2n=58), which inhabits mainly dark soils including alluvial clays, terra rossa and brown rendzina and the souther species 2n=60, which occurs mainly in light soil types such as pale rendzina, sandy loams and loess, tend to have a more yellowish shade. The general appearance of specimens from 2n=58 was dark gray while that of 2n=60 specimens was light gray; 5. mole rats living in xeric environments (particularly 2n=60, but also 2n=54) are lighter than those which live in mesic environments (2n=52, 58). The results support the conclusion that pelage color of strictly subterranean mole rats is subject to selection pressures of overground predation of disharmonious types with their background soil color. The possibility that the pelage color variation and patterns also contributes to better thermoregulation while mole rats are above ground is discussed.     

Burrow patterns of the mole rat Spalax ehrenbergi in two soil types (terra-rossa and rendzina) in Mount Carmel, Israel

Complete burrow systems of the mole rat Spalax ehrenbergi (Rodentia; Spalacidae), from two sites on Mount Carmel in Israel, with different soil types (terra-rossa and rendzina), were excavated and described here for the first time.
A comparison was made of burrow structure patterns in the two soils and of the sexes, with special attention to the features of the feeding tunnels.
The pattern in the rendzina revealed longer burrows with a longer main tunnel and fewer branches per metre of the main tunnel, while the pattern in the terra-rossa revealed shorter burrows with a shorter main tunnel and a relatively higher number of branches. These differences can primarily be related to the different levels of food availability, which is higher in the terra-rossa. It is suggested that each of the patterns reflects the mole rat's ability to optimize foraging efficiency in accordance with its given food availability.
The average total length of the males' burrows was much greater than those of the females' burrows in the rendzina soil. It appears that food requirements determine different burrow features of the sexes rather than reproduction requirements.
Other tunnel features (e.g. structural complexity, depth and width, segment length and spatial arrangement) and the factors which may affect them, as well as burrow structure of young mole rats and evidence of the underground dispersion of young mole rats, were presented and discussed.
Many similarities were found in a comparison of S. ehrenbergi burrow features with those of other solitary subterranean rodents.     

Synaptonemal complex analysis of mole rats (Spalax ehrenbergi): unusual polymorphisms of chromosome 1

Two unusual structural polymorphisms in the largest chromosomal pair of the Israeli mole rat, Spalax ehrenbergi, were analyzed from surface-spread and silver-stained preparations of synaptonemal complexes. A C-band negative polymorphism for the length of the 1p arm was visible as axial length differences during late zygonema and early pachynema. This region underwent synaptic adjustment resulting in a fully paired, mid-pachytene synaptonemal complex with equalized axial lengths. The somatically variable and nonargentophilic secondary constriction in the 1q arm was evident as a distinct silver-stained thickening along the synaptonemal complex. Presence of this structure on the synaptonemal complex varied both among individuals and among cells within individuals. The intraindividual variation of this region is hypothesized to represent differential biochemical activity with its cellular visualization being regulated in a manner similar to that of nucleolus organizer regions.     

Speciation and adaptive radiation of subterranean mole rats, Spalax ehrenbergi superspecies, in Jordan

The major initial mechanism of speciation in subterranean blind mole rats, Spalacidae, is chromosomal, primarily through Robertsonian rearrangements. Here we highlight another scenario of chromosomal rearrangement leading to ecological speciation and adaptive radiation apparently initiated by pericentric inversions and genie divergence to different ecologies in mole rats in Jordan. We analysed karyotype, allozyme, size and ecological diversity across the range of mole rats in Jordan from mesic Irbid in the north to xeric Wadi Musa (Petra region) in the south, a transect of 250 km. We examined mole rats for chromosome ( N =71), size ( N =76), and allozyme ( N =67) diversities, encoded by 32 loci, in 12 populations of the Spalax ehrenbetgi superspecies in Jordan. By a combination of chromosome morphology, genetic distance, body size and ecogeography, we identified four new putative biological species. All species (except two animals in Madaba) share 2 n = 60 but vary in chromosome morphology, caused by pericentric inversions and/or centromeric shifts. The 'north Moav' species is karyotypically polymorphic for 2 n (2 n = 60; including locally also two animals with 2 n = 62). The distribution of the four species is associated with ecogeographical different domains and climatic diversity. Genetic diversity indices were low, but like chromosome arms (NFa) were positively correlated with aridity stress. Discriminant analysis correctly classified 91% of the individuals into the four species utilizing combinatorially chromosome, allozyme and size diversities. It is hypothesized that mole rat evolution underground is intimately associated with climatic diversity stress above ground.     

Old views and new insights: taxonomic revision of the Bukovina blind mole rat,Spalax graecus (Rodentia: Spalacinae)

As a result of their rather uniform external appearance and gross cranial morphology, the systematics of blind mole rats has been hotly debated over the last century; however, the separation of the large‐bodied and small‐bodied blind mole rats at the genus level (Spalax and Nannospalax, respectively), suggested earlier on morphological grounds, is strongly supported by recent molecular biological evidence. The species of Spalax have so far been distinguished from each other by cranial traits only, especially the outline of sutures of the cranium, and the shape and relative size of the nasal and parietal bones. Based on mitochondrial DNA sequences (with the widest taxonomic and geographic coverage so far) and detailed anatomical comparisons of museum specimens, we herewith provide a revision of the taxonomic and phylogenetic status of the westernmost representative of the genus, Spalax graecus s.l. We clarify that antiquus and istricus – presently regarded as synonyms of graecus – are well‐defined species, and they together form a separate clade within Spalax. The robustness of our conclusions is supported by the combined evidence of morphology, multilocus phylogeny, species distribution, and taxon history (species congruence with past tectonic and climate events). © 2013 The Linnean Society of London     

Immunohistochemical localization of melatonin in the rat Harderian gland.

Using fluorescence and double antibody techniques, melatonin was localized immunohistologically in the secretory cells of the Harderian gland of mature male rats. The presence and quantity of melatonin in the acinar cells seem to correlate with the amount of porphyrins inside the lumen. The specificity was proven by disappearance of yellow fluorescence after saturation of antibody with melatonin or after use of nonspecific antibody only.