Wide distribution of short interspersed elements among eukaryotic genomes.
Most short interspersed elements (SINEs) in eukaryotic genomes originate from tRNA and have internal promoters for RNA polymerase III. The promoter contains two boxes (A and B) spaced by approximately 33 bp. We used oligonucleotide primers specific to these boxes to detect SINEs in the genomic DNA by polymerase chain reaction (PCR). Appropriate DNA fragments were revealed by PCR in 30 out of 35 eukaryotic species suggesting the wide distribution of SINEs. The PCR products were used for hybridization screening of genomic libraries which resulted in identification of four novel SINE families. The application of this approach is illustrated by discovery of a SINE family in the genome of the bat Myotis daubentoni. Members of this SINE family termed VES have an additional B-like box, a putative polyadenylation signal and RNA polymerase III terminator. (+info)
The development of a biological novelty: a different way to make appendages as revealed in the snout of the star-nosed mole Condylura cristata.
The nose of the star-nosed mole Condylura cristata is a complex biological novelty consisting of 22 epidermal appendages. How did this new set of facial appendages arise? Recent studies find remarkable conservation of the genes expressed during appendage formation across phyla, suggesting that the basic mechanisms for appendage development are ancient. In the nose of these moles, however, we find a unique pattern of appendage morphogenesis, showing that evolution is capable of constructing appendages in different ways. During development, the nasal appendages of the mole begin as a series of waves in the epidermis. A second deep layer of epidermis then grows under these superficial epidermal waves to produce 22 separate, elongated epidermal cylinders embedded in the side of the mole's face. The caudal end of each cylinder later erupts from the face and rotates forward to project rostrally, remaining attached only at the tip of the snout. As a result of this unique 'unfolding' formation, the rostral end of each adult appendage is derived from caudal embryonic facial tissue, while the caudal end of each appendage is derived from rostral facial tissue. This developmental process has essentially no outgrowth phase and results in the reversal of the original embryonic orientation of each appendage. This differs from the development of other known appendages, which originate either as outgrowths of the body wall or from subdivisions of outgrowths (e.g. tetrapod digits). Adults of a different mole species (Scapanus townsendii) exhibit a star-like pattern that resembles an embryonic stage of the star-nosed mole, suggesting that the development of the star recapitulates stages of its evolution. (+info)
Skull morphology and mitochondrial DNA sequence analysis in the lesser Japanese mole (Mogera imaizumii) from the Imperial Palace (Tokyo, Japan).
Since about 1630, the Imperial Palace has been biologically isolated from other habitats by the development and urbanization of Tokyo. We morphologically examined the skulls of the lesser Japanese mole (Mogera imaizumii) from the Imperial Palace and compared them with those from Kanto District, while the sequences of the cytochrome b and 12S rRNA genes were also analyzed to clarify the genetic status of this isolated population. The skulls from the Imperial Palace were much larger than those from Kanto District in the length items. We suggest that the Imperial Palace skulls morphologically may compose a cluster as a large body-sized type in Kanto District within the dots of Mogera imaizumii in charts of principal component analysis. The mitochondrial DNA sequences of the Imperial Palace population were highly homologous to those of other Tokyo population at the level of 98.5% in cytochrome b and 98.7% in 12S rRNA genes. (+info)
Postprandial heat increment does not substitute for active thermogenesis in cold-challenged star-nosed moles (Condylura cristata).
The postprandial increase in metabolic rate associated with consuming, assimilating and excreting a meal is often termed the heat increment of feeding (HIF). The metabolic heat production of star-nosed moles, Condylura cristata, held at thermoneutrality was monitored for 4 h following a single 10 min session of feeding on a ration consisting of 0 g (controls), 3.5 g or 10 g of earthworms. Coefficients for metabolizable energy digestibility and digesta passage rate of earthworms fed to C. cristata were also determined. We then tested whether feeding-induced thermogenesis substitutes partially or completely for thermoregulatory heat production in these animals exposed to sub-thermoneutral air temperatures (9-24 degrees C). A single feeding on earthworms had both short- and long-term effects on the metabolic rate and respiratory exchange ratio of C. cristata. The observed short-term (0-65 min) rise in metabolic rate, assumed to be associated primarily with the physical costs of nutrient digestion, absorption and excretion, was similar to the calculated mean retention time (66.7+/-7.8 min; mean +/- s.e. m., N=5) of this species. This component of the HIF represented 2.9 % of the food energy ingested by moles fed a single 3.5 g (13.21 kJ) meal of earthworms and 1.4 % of the food energy ingested by moles fed a single 7.5 g (28.09 kJ) meal of earthworms. At all test temperatures, resting metabolic rate typically remained above fasting levels for 1-4 h following ingestion of the high-protein earthworm diet. This protracted rise in metabolic rate, presumably associated with the biochemical costs of amino acid oxidation/gluconeogenesis and ureagenesis, averaged 12.8 % of the metabolizable energy and 8.7 % of the gross energy intake. Despite the potential thermoregulatory benefit, we found no evidence that biochemical HIF substitutes for facultative thermogenesis in star-nosed moles exposed to low air temperatures. (+info)
Reproductive features of the eastern mole (Scalopus aquaticus) and star-nose mole (Condylura cristata).
Since moles are closely related to shrews, the gametes and reproductive tracts of the star-nose mole (Condylura cristata) and the eastern mole (Scalopus aquaticus) were examined to gain further insight into unusual reproductive traits of the Soricidae. Moles display many of these soricid traits, but with some important differences. The cumulus oophorus of Scalopus, ovulated about 16 h after hCG injection, was largely dispersed by hyaluronidase and, though quite dense, was nevertheless more similar to that of higher mammals than to the compact 'ball of the soricid cumulus. Within the female tract in these moles, approximately 85% of the length of the oviduct comprises a narrow ampulla with numerous differentiated crypts that, in shrews, house spermatozoa. However, in contrast to shrews, moles produce considerably larger numbers of spermatozoa, which challenges the proposal that, in shrews, oviductal sperm crypts specifically permit lower sperm production by the males. In the sperm head of these two moles, the acrosome displays the long rostrum that is typical of other Insectivora, and the perforatorium has the barbs by which soricid spermatozoa probably bind to the zona pellucida. Perhaps allied to this, immunoblots indicated that the immunoreactive acrosomal matrix of Scalopus spermatozoa is simpler than the polypeptide complex of the bovine and hamster acrosomal matrix. (+info)
Molecular phylogeny of East Asian moles inferred from the sequence variation of the mitochondrial cytochrome b gene.
Taxonomic analysis has previously revealed that the species of moles that inhabit Japan are characterized by exceptional species richness and a high level of endemism. Here, we focused on the evolutionary history of the four Japanese mole species of the genera Euroscapter and Mogera, examining mitochondrial cytochrome b (cyt b) gene sequences and comparing them with those of continental Mogera wogura (Korean and Russian populations), M. insularis from Taiwan, and Talpa europaea and T. altaica from the western and central Eurasian continent, respectively. Our data support the idea that in a radiation center somewhere on the Eurasian continent, a parental stock evolved to modern mole-like morph and radiated several times intermittently during the course of the evolution, spreading its branches to other peripheral geographic domains at each stage of the radiation. Under this hypothesis, the four lineages of Japanese mole species, E. mizura, M. tokudae, M. imaizumii, and M. wogura, could be explained to have immigrated to Japan in this order. Mogera wogura and M. imaizumii showed substantial amounts of geographic variation and somewhat complicated distributions of the cyt b gene types. These intraspecific variations are likely to be associated with the expansion processes of moles in the Japanese Islands during the Pleistocene glacial ages. (+info)
The cycle of the seminiferous epithelium in the greater Japanese shrew mole, Urotrichus talpoides.
Spermatogenesis and acrosomal formation in the greater Japanese shrew mole, Urotrichus talpoides, were studied by light microscopy. On the basis of acrosomal changes, morphology of spermatid head, nuclear shape, appearance of meiotic figures, location of spermatid and period of spermiation, the cycle of the seminiferous epithelium was classified into 12 stages, and developing spermatids could be divided into 15 steps. The mean relative frequencies of stages from I to XII were 10.9, 8.7, 9.8, 7.3, 8.5, 10.3, 12.5, 8.7, 5.8, 5.4, 5.1 and 7.1%, respectively. Similar to the case in the musk shrew, the spermatid nucleus of the greater Japanese shrew mole remained in the middle region of the seminiferous epithelium and only the acrosome extended towards the basement membrane. The elongation of the acrosome, however, was not prominent. The proacrosomal vesicle first appeared in stage II and then one large and round granule was seen in stage III. The acrosomal vesicle became flattened on the surface of the nucleus in stage IV. Spreading of the acrosomic system has been recognized from stage VII. In stage VII, spermiation occurred. In stage IX, the spermatid nucleus began to elongate. Elongation and condensation of the nucleus were clearly observed in stage X. In stage XII, pachytene spermatocytes divided into diplotene spermatocytes. In stage XII, meiotic figures and secondary spermatocytes were observed. (+info)
Body oxygen stores, aerobic dive limits and diving behaviour of the star-nosed mole (Condylura cristata) and comparisons with non-aquatic talpids.
The dive performance, oxygen storage capacity and partitioning of body oxygen reserves of one of the world's smallest mammalian divers, the star-nosed mole Condylura cristata, were investigated. On the basis of 722 voluntary dives recorded from 18 captive star-nosed moles, the mean dive duration (9.2+/-0.2 s; mean +/- S.E.M.) and maximum recorded dive time (47 s) of this insectivore were comparable with those of several substantially larger semi-aquatic endotherms. Total body O(2) stores of adult star-nosed moles (34.0 ml kg(-1)) were 16.4 % higher than for similarly sized, strictly fossorial coast moles Scapanus orarius (29.2 ml kg(-1)), with the greatest differences observed in lung and muscle O(2) storage capacity. The mean lung volume of C. cristata (8.09 ml 100 g(-1)) was 1.81 times the predicted allometric value and exceeded that of coast moles by 65.4 % (P=0.0001). The overall mean myoglobin (Mb) concentration of skeletal muscles of adult star-nosed moles (13.57+/-0.40 mg g(-1) wet tissue, N=7) was 19.5 % higher than for coast moles (11.36+/-0.34 mg g(-1) wet tissue, N=10; P=0.0008) and 54.2 % higher than for American shrew-moles Neurotrichus gibbsii (8.8 mg g(-1) wet tissue; N=2). The mean skeletal muscle Mb content of adult star-nosed moles was 91.1 % higher than for juveniles of this species (P<0.0001). On the basis of an average diving metabolic rate of 5.38+/-0.35 ml O(2) g(-1) h(-1) (N=11), the calculated aerobic dive limit (ADL) of star-nosed moles was 22.8 s for adults and 20.7 s for juveniles. Only 2.9 % of voluntary dives by adult and juvenile star-nosed moles exceeded their respective calculated ADLs, suggesting that star-nosed moles rarely exploit anaerobic metabolism while diving, a conclusion supported by the low buffering capacity of their skeletal muscles. We suggest that a high mass-specific O(2) storage capacity and relatively low metabolic cost of submergence are key contributors to the impressive dive performance of these diminutive insectivores. (+info)