Akiko Hayashida

Three-Dimensional Reconstruction of the Xenarthrous Process of the Thoracic and Lumber Vertebrae in the Giant Anteater

Abstract. The presacral vertebra of anteaters was examined by three-dimensional CT image analysis of the xenarthrous processes peculiar to the Order Xenarthra. The anteater is equipped with two following articulations in addition to the normal zygapophysial articulation. The dorsal xenarthrous process of the former vertebra articulates to the ventral area of the base of the mammillary process in the later vertebra. The pocket-like structure in the ventral area of the mammillary process receives the dorsal and ventral xenarthrous processes of the former vertebra. The complicated articulations do not obstruct the ability of the giant anteater to flex dorsally and laterally, however aids flexibility and strengthens the caudal thoracic and lumber regions of the animal. The xenarthrous processes and articulations may function as a supporter of the body weight during the bipedal standing posture when the anteater destroys the nests of ants and termites and protects itself from the enemies.

Phylogenetic relationship between Callosciurus caniceps andC. inornatus (Rodentia, Sciuridae): Implications for zoogeographical isolation by the Mekong River

Abstract To test the riverine barrier hypothesis in small arboreal mammals, we examined phylogenetic relationship between two Callosciurus squirrel species (C. caniceps and C. inornatus) geographically isolated in the northeastern part of the Indochina Peninsula by the Mekong River. We did this by comparing complete mitochondrial DNA cytochrome b gene sequences of these two squirrels and five other Callosciurus species: C. erythraeus, C. finlaysonii, C. nigrovittatus, C. notatus, and C. prevostii. Phylogenetic trees showed that there are three major lineages: (1) a lineage containing C. caniceps, C. erythraeus, C. finlaysonii, and C. inornatus; (2) a C. notatus lineage; and (3) a lineage containing C. nigrovittatus and C. prevostii. Callosciurus caniceps was most closely related to C. inornatus. Based on transversional divergence rate at the third codon position of cytochrome b gene, they diverged about 1.2 million years ago. The drastic eastward shift of the Mekong River may have isolated ancestors of C. caniceps and C. inornatus. Then, these two species might have evolved in the different environments of each side of the Mekong River. This phylogeographic history suggests a typical case of allopatric speciation.

Phylogenetic position of Callosciurus erythraeus griseimanus from Vietnam in the genus Callosciurus

Callosciurus squirrels are widely distributed in Southeast Asia, eastern parts of South Asia, and southern parts of East Asia (Wilson and Reeder 2005). In this genus, there are 15 species; each species has many geographical forms (Corbet and Hill 1992; Wilson and Reeder 2005). Especially, at present, the Pallas’s squirrel (Callosciurus erythraeus) has 25 subspecies (atrodorsalis, bartoni, bhutanensis, bonhotei, castaneoventris, erythrogaster, flavimanus, gloveri, gordoni, griseimanus, harringtonii, hendeei, hyperythrus, intermedius, michianus, ningpoensis, pranis, rubeculus, shanicus, siamensis, sladeni, styani, thai, thaiwanensis, and zimmeensis) (Wilson and Reeder 2005). These many geographical forms clearly make sub-specific classification of C. erythraeus complicated (e.g., Lekagul and McNeely 1988). Of these subspecies, 18 (atrodorsalis, bonhotei, castaneoventris, flavimanus, gloveri, gordoni, griseimanus, hendeei, michianus, ningpoensis, pranis, rubeculus, shanicus, siamensis, styani, thai, thaiwanensis, and zimmeensis) were previously assigned to a distinct species, the bellybanded squirrel C. flavimanus (Ellerman and MorrisonScott 1951; Moore and Tate 1965). Corbet and Hill (1992), however, regarded C. flavimanus as a subspecies of C. erythraeus (i.e., C. erythraeus flavimanus) and assigned all C. flavimanus subspecies to C. erythraeus. At present, this taxonomic status is generally accepted (Wilson and Reeder 2005). Debates on subspecific classification of C. erythraeus have been based on morphological characteristics, such as skull shapes and pelage patterns, but not on any other systematic characteristics, such as molecular and cytogenetic data. To provide additional evidence for resolving the taxonomic and systematic status of C. erythraeus subspecies, we examined the phylogenetic position of C. erythraeus griseimanus among Callosciurus squirrel species by using mitochondrial (mt) cytochrome b gene sequences. Callosciurus erythraeus griseimanus is found in only the southeastern parts of the Indochina Peninsula. Judging from its restricted distribution pattern, this subspecies may be genetically distinct from other C. erythraeus subspecies and other Callosciurus species. We discuss here where we place this squirrel in the phylogeny of Callosciurus.

The Brachial Plexus Adapted to the Semi-Elongated Neck in the Okapi

Abstract. The brachial plexus of the okapi showed the evolutionarily intermediate status between the underived ruminants and the giraffe with elongated neck. Whereas the C6 was the thinnest among the roots of the brachial plexus, the C7, C8 and T1 were much thicker in the okapi. From the data we concluded that the okapi was equipped with the intermediate characteristics of the disappearing C6. Although the nerve of the C6 should be elongated in accordance with the long neck in the Giraffidae, the extraordinary elongation of the C6 may have no advantages in the function of the innervations. In the okapi, therefore, we suggest that the function of the C6 has been mainly replaced with that of C7.

Multivariate analyses of the skull size and shape in the five geographical populations of the lesser false vampire

ABSTRACT The geographical variations of the skull in the lesser false vampire (Megaderma spasma) were osteometrically compared between the traditionally-accepted subspecies from Philippines, Borneo, Java, North and South Thailand-Peninsular Malaysia. In female the population from Philippines was larger than any other population in skull size, whereas in male, the size tendency was not clearly found. The population of North Thailand was smaller than the four other populations at least in mean value of measurements in both sexes. The canonical discriminant analysis essentially separated the populations in the scattergrams of discriminant scores. However, the plots of Java, North Thailand and South Thailand-Peninsular Malaysia populations were intermingled in male, and Borneo population could not be obviously separated from the Java and South Thailand-Peninsular Malaysia populations in female.

Absence of the Guttural Pouch in a Newborn Indian Rhinoceros Demonstrated by Three-Dimensional Image Observations

Abstract CT scanning and its related three-dimensional image techniques were applied for a carcass head of a newborn Indian rhinoceros (Rhinoceros unicornis) to clarify if the guttural pouch is well-developed or not in the early growth stages of this species. Observations from the sections of the CT three-dimensional reconstructed image reveal that the guttural pouch is not present around the stylohyoid bone in a new born Indian rhinoceros. Since the absence of the guttural pouch has been confirmed also in adult rhinoceros, we can point out that the guttural pouch does not disappear during the growth stages, but is originally absent in the newborn. Although the well-developed guttural pouch in the horse and ass has attracted anatomists, we can conclude that the guttural pouch is not commonly observed in the perissodactyls, but in a few species of Equus, and that the guttural pouch is adapted only to restricted roles in the smaller taxa within perissodactyls.

Phylogenetics of Petaurista in Light of Specimens Collected from Northern Vietnam

The southern part of China and northern part of Indochina Peninsula is one of the hot-spots of biodiversity (e.g., Cincotta et al. 2000; Cox and Moore 2005). In this area, there are many endemic mammalian species, such as giant panda Ailuropoda melanoleuca, saola Pseudoryx nghetinhensis, Tonkin snub-nosed monkey Rhinopithecus avunculus, Inornate squirrel Callosciurus inornatus, black-eared red-backed vole Eothenomys olitor, and Yunnan hare Lepus comus (e.g., Wilson and Reeder 2005). Meijaard and Groves (2006) also found high mammalian diversity in the east side of the Mekong River including this area. Therefore, this area would be very important for the speciation and diversity of mammals in Asia. Giant flying squirrels (genus Petaurista) are widely distributed throughout South and Southeast Asia and in southern China, Taiwan, and Japan (Corbet and Hill 1992; Wilson and Reeder 2005). At present, they are split into eight species: P. alborufus, P. elegans, P. leucogenys, P. magnificus, P. nobilis, P. petaurista, P. philippensis, and P. xanthotis (Wilson and Reeder 2005). In each species, many variations and synonyms are reported (e.g., Ellerman and Morrison-Scott 1951; Corbet and Hill 1992; Wilson and Reeder 2005). In the southern China and northern Indochina Peninsula, three giant flying squirrel species (P. alborufus, P. petaurista, and P. philippensis) are commonly found (Lekagul and McNeely 1988; Corbet and Hill 1992). Based on genetic variations and morphological characteristics, in southern China, Yu et al. (2006) recognized as distinct two additional species (P. hainana from Hainan Island and P. yunanensis from Yunnan), although these species had been classified as P. philippensis by Wilson and Reeder (2005). Thus, this area may also be a biodiversity hotspot for Petaurista species. Based on molecular data, Oshida et al. (2004a) proposed that Petaurista might have some geographical evolutionary units or groups. Southern China and the northern Indochina Peninsula may be the source of one geographical evolutionary unit of Petaurista. To explore this conjecture further, we examined the phylogenetic position of two Petaurista species collected from northern Vietnam, the Indian giant flying squirrel (P. philippensis) and the spotted giant flying squirrel (P. elegans). These two forms were phylogenetically compared with those from southern China and the island of Sumatra. Here, we discuss the phylogenetic relationships of P. philippensis and P. elegans.

The morphological basis of the armor-like folded skin of the greater Indian rhinoceros as a thermoregulator

Abstract. The armor-like folded skin of the Indian rhinoceros (Rhinoceros unicornis) was examined by CT image analyses and microscopic observation. The three-dimensional reconstructed images demonstrate that the folded skin has the subcutaneous tissues including cutaneous muscles and connective tissues inserted to the deepest holes and grooves of 2–3 mm thickness in each fold. The cutaneous muscles are well-developed in subcutaneous tissues, in which many small blood vessels are found. We conclude that the folded skin acts as a thermoregulator, since the thin blood vessels and capillaries and cutaneous muscles in the subcutaneous tissues transmit the thermal energy from the core region of the body to the skin folds. We suggest that the greater Indian rhinoceros, Rhinoceros unicornis, has evolved the extraordinary thermoregulation mechanism in the folded skin adapted to high temperature in the tropical and subtropical regions.

Mitochondrial DNA Evidence Suggests Challenge to the Conspecific Status of the Hairy-Footed Flying Squirrel Belomys pearsonii from Taiwan and Vietnam

Tatsuo Oshida1,*, Liang-Kong Lin2, Shih-Wei Chang3, Can Ngoc Dang4, Son Truong Nguyen4, Nghia Xuan Nguyen4, Dang Xuan Nguyen4, Hideki Endo5, Junpei Kimura6, Motoki Sasaki7, Akiko Hayashida8 and Ai Takano9 1 Laboratory of Wildlife Biology, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080-8555, Japan 2 Laboratory of Wildlife Ecology, Department of Life Science, Tunghai University, Taichung 407, Taiwan, R.O.C. 3 Division of Zoology, Taiwan Endemic Species Research Institute, Chichi 552, Taiwan, R.O.C. 4 Institute of Ecology and Biological Resources, Vietnam Academy of Sciences and Technology, Hanoi, Vietnam 5 The University Museum, The University of Tokyo, Tokyo 113-0033, Japan 6 College of Veterinary Medicine, Seoul National University, Seoul 151-742, Korea 7 Laboratory of Veterinary Anatomy, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080-8555, Japan 8 Nasu Animal Kingdom, Nasu 329-3223, Japan 9 Laboratory of Epidemiology, Department of Veterinary Medicine, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi 753-8515, Japan