O. F. Chernova

Architectonics of the Medulla of Guard Hair and Its Importance for Identification of Taxa

In mammals, the structure of both medulla of hair and cuticular scales considerably varies and is used for identification of taxa [1–15]. Most of researchers rely on the scheme in which several types of medulla are distinguished: lack of medulla (no medulla) and discontinuous, intermediate, continuous, and fragmentary medulla [8, 9]. These types are, in turn, divided into subtypes [4]; the nomenclature of this division has not yet been developed, and authors arbitrarily use descriptive terms. This classification does not consider the pattern of distribution of inert air in the medulla, as well as the volume and texture of the walls of the so-called medullar cells per se (the remnants of cornificated walls of metabolically active medullar cells of the hair follicle). Only recently, a new structural model of the medulla was developed based on the pattern of distribution of inert air in medullar cells, the volume of cellular remnants (“cytoplasmic nuclei” [5]), and the degree of cellular vacuolization or perforation of the walls of these cells [5]. This is the scheme which I adopted as GENERAL BIOLOGY

Polymorphism of the architectonics of definitive contour feathers.

The architectonics (microstructure) of feathers is being intensely studied in order to develop methods for species diagnosis using feathers or their fragments, which is important for various aspects of biological expert assessment [1–4]. The quantitative and qualitative parameters of feather architectonics are applicable only to adult birds, because the down of chicks lacks the informative details of barb structure.

Structural differences between the shafts of mammalian vibrissae and hairs and their causes

182 The structure of mammalian hair has been described in detail [1], but the structure of the vibrissa shaft remains poorly studied. This is probably a result of the widespread assumption that the origin and structure of hair and vibrissae have much in common. Some authors believe that vibrissae are a category of hair and the structure of vibrissae is similar to that of a guard hair [2, 3]. Nevertheless, there are published data suggesting independent origins of vibrissae from the mechanoreceptors of the ancient forms [4]. Because of this, we have compared the shaft structure of vibrissae and hair in mammals of different orders to determine what specific features of vibrissae are responsible for their functioning as a tactile organ. The members of the orders Insectivora, Rodentia, and Carnivora were the objects of our study (table). The longest and thickest vibrissae, namely whiskers (vibrissae mystaciales), eyebrows (vv. superciliares), and buccinators (vv. genales) [5, 6], were taken from adult individuals (from two individuals of each spe cies; two to four vibrissae from each individual). We used our own collection and the collection of the Zoo logical Museum of Moscow State University. The medullas of the pigmented vibrissae were studied after bleaching their shafts with a hydroperoxide solution. Vibrissa microstructure was examined under microscopes Amplival (VEB Carl Zeiss, Jena, Ger many) equipped with a DCM 300 video camera, Leica DMLS equipped with a Leica DMLS digital video camera (eyepiece, 10×; lenses, 10, 40, and 63× (total preparations), and JSM 840A electronic scanning microscope. The standard methods were used [7]. We found out that the structure of vibrissa and hair shafts differed significantly, though the structure of the vibrissa shaft was similar in different species. In males and females, the structure of vibrissae was also similar. The shaft base was usually regularly cylindrical, the shaft itself was straight or slightly curved, a little thick ened in the central part (there was no pronounced “grain”); it became gradually thinner and ended with a long thin, pointed colorless top. Such a uniform con figuration of vibrissae differed from the wide polymor phism of hair, whose structure varied both in different body regions of the same individual and in members of different taxa. The shafts of hairs of different catego ries (awn, guard, and wool) and of vibrissae were three layered and consisted of the outside cuticle, cor Structural Differences between the Shafts of Mammalian Vibrissae and Hairs and Their Causes

One more example of morphological convergence: similarity between the architectonics of feather and hair.

The classes of mammals (Mammalia) and Birds (Aves) are known to be separate phylogenetic branches, which are combined, together with reptiles (Reptilia), into the taxon of higher vertebrates (Amniota) according to the developmental level rather than common origin of Mammalia and Aves. One of the similarities between mammals and birds is that they are the only true homeotherms among vertebrates (subphylum Vertebrata) and chordate (phylum Chordata) as a whole. In both classes, the external covering of the body (mammal hair and bird feathers) is one of the systems ensuring the maintenance of constant body temperature. Both feathers and hair are derivatives of the external covering but considerably differ from each other in the ontogenetic pattern, the protein (keratin) composition, distribution over the body, macromorphology, accessory structures (glands, muscles, and nerves), molting pattern, color, etc. In addition, both structures are characterized by morphological polymorphism, i.e., organs of common origin (within a class) differ in structure. Feathers vary widely (contour feathers of various types, down of young and adult birds; semidown feathers, filoplumes, brush feathers, bristles, powder down feathers, etc.), as do hairs (guard hairs of various types, down hairs, prickles, semiprickles, bristly hairs, spines, quills, vibrissae, etc.). When studying the architectonics (microstructure) of hairs and feathers, we noticed for the first time that the structure of guard hairs and spines of adult mammals was strikingly similar to that of first-order barbs (hereinafter, barbs) of the vane and second-order barbs (barbules) of the downy part of definitive guard feathers. Therefore, I attempted to analyze the similarity of these structures that is a priori known to be determined by some factors other than a common origin of the classes.

Decorative forms of hamsters of the genus Phodopus (Mammalia, Cricetinae): Analysis of genetic lines distribution and features of hair changes

Using a molecular genetic marker (combined sequences of the cytochrome b gene and mtDNA control region), the maternal species of the genus Phodopus were identified, which served as the starting material for the creation of artificial populations of these domesticated species, including their colored forms, in many countries around the world. The animals were purchased at pet stores in Europe, Southeast Asia, and North America and included 9 Ph. campbelli specimen (seven haplotypes), 17 Ph. sungorus animals (six haplotypes), and 5 Ph. roborovskii (one haplotype). The mtDNA sequences obtained were compared with 63 haplotypes of Ph. campbelli, 26 of Ph. sungorus, and 26 of Ph. roborovskii, which are known in natural populations. It is shown that all colored Ph. campbelli were obtained from breeding wild animals of the Western haplogroup. Haplotypes of hamsters from different areas of Tuva are closest to haplotypes of colored animals. The colored Ph. sungorus are divided into two groups. The animals that were obtained from the specimen of the isolate in the Minusinsk Basin are kept in Moscow and St. Petersburg. The animals that originate from the ancestors of the Karasuk District of the Novosibirsk Oblast are kept in the countries of Europe and South East Asia. The colored Ph. roborovskii are the descendants of the animals from the Zaisan Basin, and their haplotypes match the haplotype of one of the animals that we caught in the wild. The colored hamsters, unlike hamsters with natural color, have a disturbed normal state of hair. This is evidenced by its dimness, shagginess, and felt character, as well as the changing the ratio between the different categories of hair and their size characteristics, the deformation of the shaft until bending at the right angle and splitting of the upper parts, the cracking of the cuticle, the changing configuration and location of the medulla, and the uneven development of the cortex. It is assumed that these destructive changes are associated with the genetic characteristics of the colored forms.

The structure of the cuticle of guard hair in fruit-eating bats (Chiroptera, Pteropodidae).

Morphologically, phylogenetically, and biologically, fruit-eating bats (Megachiroptera) significantly differ from other bats (Microchiroptera). Their coat has been studied in much detail under a light microscope [1–9], but data on its fine structure should be revised at the level of raster electron microscopy (REM). In fruiteating bats, the diagnostic significance of the hair structure is very little, and only a number of species have a specific pattern of the cuticle layer (hereinafter, pattern). Taxonomic analysis revealed a similarity of hair in Cynopterus, Rhinopomatidae, and Megadermatidae (all of which are closer to ancestral forms than the remaining groups) and a more ancient origin of the bell-shaped cuticle compared to the imbricate cuticle [3] which is more widely spread in Microchiroptera [10]. It is thought that either specific features of hair structure have no adaptive significance in bats [1] or many functions have been lost [11]. It is supposed that a relationship exists between the irregularity of the hair profile and the ability of fertilizing flowers in nectarand pollen-eating species [5] or preserving and giving off specific animal odors [4], which allows us to classify such hair with osmetrichia (termed according to [12]). Authors explain the irregularity (indented edges) of cuticle scales (hereinafter, scales) per se in insecteating bats by adaptation to flight, namely, increasing the turbulence of air flow [11] (by analogy with lepidopterans and birds). This study is aimed to reveal specific features of the fine structure of hair cuticle in fruiteating bats with the objective of gaining an insight into its adaptive meaning. In particular, I was intrigued by the extraordinary height (throughout the length of the hair stem) and thickness of hair scales in fruit-eating bats.

The Peculiar Architectonics of Contour Feathers of the Emu ( Dromaius novaehollandiae , Struthioniformes)

The emu ( Dromaius novaehollandiae ) now belongs to a monotypic genus, because the other two species, D. ater and D. baudinianus , which were smaller (the size of a bustard) and lived, respectively, on Kangaroo and King islands, were exterminated by humans in the early 19th century. The emu (Dromaiidae), cassowary (Casuariidae), and the extinct Dromornithidae families are either combined into the suborder Casuarii of the order Struthioniformes or regarded as a separate order Casuariformes. Here, we follow the former classification. Struthioniformes is one of two modern orders of paleognaths (Palaeognathae), a relict group that diverged from the main phylogenetic line of birds (class Aves) no later than the early Cretaceous period, although their oldest fossil remnants are dated to the early Cenozoic. Their closest known phylogenetic relationship is with the order Tinamiformes, together with which Struthioniformes form the infraclass Palaeornithes (“ancient birds”). Although the current species diversity of Struthioniformes is poor, the branched taxonomic structure of the order (ten species, six genera, five families, and four suborders) definitely indicates an ancient origin of these birds. The organization of Struthioniformes combines archaic characters that have disappeared in more advanced taxa of birds and signs of extreme specialization for terrestrial locomotion, without flight. The archaic characters are the paleognathic anatomy of the palate, which is immovably joined with other skull bones (in contrast to the neognathic type in all other living birds); a primitive structure of leg muscles; and a compound rhamphotheca consisting of several pieces instead of a single sheath. The secondary primitive characters (that are assumed to develop in Struthioniformes as flightless birds) are a heavy, apneumatic skeleton; a flat sternum (without a keel); flattened and shortened bones of the wing, especially the metacarpals; a reduced furcula; fused scapula and coracoid; the absence of apteria and the coccygeal gland; etc. The wing skeleton of the emu is considerably simplified; however, there still are remnants of the clavicles.

Polymorphism of the surface sculpture of placoid scales of sharks (Selachomorpha, Elasmobranchii)

adult individual of each species: Chiloscyllium punc� tatum (Hemiscyllidae, Orectolobiformes), Carcharhi� nus plumbeus, Carcharhinus sorrah (Carcharhinidae, Carcharhiniformes), Apristurus profundorum, Penta� chus spp. (Scyliorhinidae, Carcharhiniformes), Gale� orhinus galeo (Triakidae, Carcharhiniformes), Squalus fernandinus, Scymnodon obscurus, Scymnodon squam� ulosus (Squalidae, Squaliformes), Centroscyllium spp., Etmopterus pusillus, Etmopterus spinax (= Spinax niger) (Etmopteridae, Squaliformes), Euprotomicrus bispinatus (Dalatiidae, Squaliformes), Centroscymnus crepidater (Somniosidae), Carcharius taurus (Odontaspididae, Lamniformes), Aculeola nigra (Alopiidae, Squali� formes), Notorynchus cepedianus (=Heptanchus pecto� rosus) (Hexanchiae, Hexanchiformes).

The Insulating Properties of the Pelage of the North-American Porcupine (Erethizon dorsatum): The Influence of Quill-Like Structures on Heat Transfer

Multifunctionality is characteristic of the hairy pelage of mammals, the key function of which is insulation. As a rule, mammalian fur can effectively insulate the body at a certain density of thin hair in it and sufficient thickness of the pelage in general [1]. The fulfillment of other functions (in particular, mechanical protection) may be related to changes in the pelage, as a result of which its structure becomes markedly different from the structure that may be regarded optimal from the standpoint of insulation. Apparently, more or less significant redistribution of roles between the insulating and defensive functions of the pelage took place in parallel more than once in the course of evolution of mammals. In particular, quill-like modifications of hair differing in the degree of modification occur in different taxa [2]. In extreme cases, the pelage turns into a strongly differentiated multilayer defensive formation consisting of a great number of various quills of a complex structure. Nevertheless, the functional aspects of these transformations have not been studied thus far. For example, it is unknown to which extent the presence of quills may affect the insulating properties of the pelage. Filling up this gap was the goal of this study, in which we performed quantitative estimation of the effect of the presence of quills on the insulating properties of the pelage using the North American porcupine ( Erethizon dorsatum L . ) as an example.

New Findings of a Specialized Spine Cuticle in Porcupines (Rodentia: Hystricomorpha) and Tenrecs (Insectivora: Tenrecidae)

Earlier, we demonstrated the presence of inverted cuticle on the protective spines of New World porcupines. In this cuticle, the scales do not point upwards (to the top of the stem) as they usually do; they have an opposite orientation towards the base of the spine and form a distinctive harpoonlike structure [1‐3]. In Old World porcupines, the cuticle of protective spines either is inverted or forms a brush that has a stopper function and consists of large scales that are normally oriented but modified and stuck out ( Atherurus ). Examples of characteristic cuticles are the stratified mosaic cuticle in the grooves of A. macrourus spines and the folded, ribbed, and concave spine cuticle in Proechimys, Lonchotrix , tropical Neacomys, Tokudaia, Maxomys, Arvicanthis, Leopoldamys, Acomys , and Niviventer [2, 3]. Continuing the studies in this field, I found new facts of the presence of a specialized cuticle in mammalian spines. Using a JSM 840 A scanning electron microscope, I studied the fine structure of spines and hair taken from napes (sometimes, from bellies and tails) of several species. The material was kindly provided by the National Museum of Natural History (Smithsonian Institution, Washington, DC, United States). New World porcupines (Erethizontidae) include the prehensile-tailed porcupine Coendou prehensilis (male, specimen no. USNM 281902) and porcupines from Amazon ( Echinoprocta rufescens , USNM 236908), Columbia, and Mexico ( Sphiggurus mexicanus , USNM 324111). I studied the long-tailed porcupine Trichys fasciculatus macrotis (a male obtained from western Malaysia, USNM 489379) as a representative of Old World porcupines (Hystricidae). The tenrec species studied (Insectivora: Tenrecidae) included the small Madagascar hedgehog Echinops telfairi (female, USNM 328615), the burrowing tenrec Geogale aurita (juv., USNM 395676), the striped tenrec Hemicentetes semispinosus (USNM 294508), the aquatic tenrec Limnogale mergulus (USNM 398583), the long-tailed tenrec Microgale cowani (female, USNM 328671), the rice tenrec Oryzorictes hova (female, USNM 578789), the hedgehog tenrec Setifer setosus (male, USNM 341635), the giant African water shrew Potamogale velox (a female obtained from Zaire, USNM 5378789), and the tailless tenrec Tenrec ecaudatus (a female obtained from Mauritius Island, USNM 341849).