Early Palaeozoic dentine and patterned scales in the embryonic catshark tail

Regular scale patterning, restricted to the caudalmost tail and organized into two opposing rows on each side of the tail, is observed in few chondrichthyans. These evenly spaced scales, in dorsal and ventral rows, develop in an iterative sequence from the caudal tip, either side of the notochord. They are subsequently lost as a scattered pattern of placoid scales develops on the body and fins. An identical organized pattern is observed in tail scales of Scyliorhinus canicula (catshark), where the expression of sonic hedgehog signal is restricted to the epithelium of developing scales and remains localized to the scale pocket. Regulation of iterative scale position by sonic hedgehog is deeply conserved in vertebrate phylogeny.These scales also reveal an archaic histological structure of a dentine type found in the oldest known shark scales from the Ordovician and Silurian. This combination of regulated pattern and ancient dentine occurs only in the tail, representing the primary scalation. Scattered body scales in elasmobranchs such as S. canicula originate secondarily from differently regulated development, one with typical orthodentine around a central pulp cavity. These observations emphasize the modular nature of chondrichthyan scale development and illustrate previously undetected variation as an atavism in extant chondrichthyan dentine.     

Epidermal and dermal integumentary structures of ankylosaurian dinosaurs

Ankylosaurian dinosaurs are most notable for their abundant and morphologically diverse osteoderms, which would have given them a spiky appearance in life. Isolated osteoderms are relatively common and provide important information about the structure of the ankylosaur dermis, but fossilized impressions of the soft‐tissue epidermis of ankylosaurs are rare. Nevertheless, well‐preserved integument exists on several ankylosaur fossils that shows osteoderms were covered by a single epidermal scale, but one or many millimeter‐sized ossicles may be present under polygonal, basement epidermal scales. Evidence for the taxonomic utility of ankylosaurid epidermal scale architecture is presented for the first time. This study builds on previous osteological work that argues for a greater diversity of ankylosaurids in the Dinosaur Park Formation of Alberta than has been traditionally recognized and adds to the hypothesis that epidermal skin impressions are taxonomically relevant across diverse dinosaur clades. J. Morphol. 275:39–50, 2014. © 2013 Wiley Periodicals, Inc.     

Spatial Ecological Hierarchies: Coexistence on Heterogeneous Landscapes via Scale Niche Diversification

Spatially heterogeneous environments are generally characterized by nested landscape patterns with resource aggregations on several scales. Empirical studies indicate that such nested landscape patterns impose selection constraints on the perceptive scales of animals, but the underlying selection mechanisms are unclear. We investigated the selection dynamics of perceptive scale within a spatial resource utilization model, where the environment is characterized by its resource distribution and species differ in their perceptive scales and resource preemption capabilities. Using three model landscapes with various resource distributions, we found that the optimal perceptive scale is determined by scale-specific attributes of the landscape pattern and that the number of coexisting species increases with the number of characteristic scales. Based on the results of this model, we argue that resource aggregations on different scales act as distinct resources and that animal species of particular perceptive scales are superior in utilizing resource aggregations of comparable spatial extent. Due to the allometric relationship between body size and perceptive scale, such fitness difference might result in discontinuous body mass distributions.     

Scale morphology and flexibility in the shortfin mako Isurus oxyrinchus and the blacktip shark Carcharhinus limbatus

We quantified placoid scale morphology and flexibility in the shortfin mako Isurus oxyrinchus and the blacktip shark Carcharhinus limbatus. The shortfin mako shark has shorter scales than the blacktip shark. The majority of the shortfin mako shark scales have three longitudinal riblets with narrow spacing and shallow grooves. In comparison, the blacktip shark scales have five to seven longitudinal riblets with wider spacing and deeper grooves. Manual manipulation of the scales at 16 regions on the body and fins revealed a range of scale flexibility, from regions of nonerectable scales such as on the leading edge of the fins to highly erectable scales along the flank of the shortfin mako shark body. The flank scales of the shortfin mako shark can be erected to a greater angle than the flank scales of the blacktip shark. The shortfin mako shark has a region of highly flexible scales on the lateral flank that can be erected to at least 50°. The scales of the two species are anchored in the stratum laxum of the dermis. The attachment fibers of the scales in both species appear to be almost exclusively collagen, with elastin fibers visible in the stratum laxum of both species. The most erectable scales of the shortfin mako shark have long crowns and relatively short bases that are wider than long. The combination of a long crown length to short base length facilitates pivoting of the scales. Erection of flank scales and resulting drag reduction is hypothesized to be passively driven by localized flow patterns over the skin. J. Morphol. 2012. © 2012 Wiley Periodicals, Inc.     

Horse hooves and bird feathers: Two model systems for studying the structure and development of highly adapted integumentary accessory organs--the role of the dermo-epidermal interface for the micro-architecture of complex epidermal structures

Accessory organs of the integument are locally modified parts of the potentially feather-bearing skin in birds (e.g., the rhamphotheca, claws, or scales), and of the potentially hairy skin in mammals (e.g., the rhinarium, nails, claws, or hooves). These special parts of the integument are characterised by a modified structure of their epidermal, dermal and subcutaneous layers. The developmental processes of these various integumentary structures in birds and mammals show both similarities and differences. For example, the development of the specialised epidermal structures of both feathers and the hoof capsule is influenced by the local three-dimensional configuration of the dermis. However, in feathers, in contrast to hooves, the arrangement of the corneous cells is only partially a direct result of the particular arrangement and shape of the dermal surface of the papillary body. Whereas the diameter of the feather papilla, as well as the number, length, and width of dermal ridges on the surface of the feather papilla influence the three-dimensional architecture of the feather rami, there is no apparent direct correlation between the dermo-epidermal interface and the development of the highly ordered architecture of the radii and hamuli in the feather vane. In order to elucidate this morphogenic problem and the problem of locally different processes of keratinisation and cornification, the structure and development of feathers in birds are compared to those of the hoof capsule in horses. The equine hoof is the most complex mammalian integumentary structure, which is determined directly by the dermal surface of the papillary body. Perspectives for further research on the development of modified integumentary structures, such as the role of the dermal microangioarchitecture and the selective adhesion and various differentiation pathways of epidermal cells, are discussed.     

Skin histology and its role in heat dissipation in three pinniped species

ABSTRACT: BACKGROUND: Pinnipeds have a thick blubber layer and may have difficulty maintaining their body temperature during hot weather when on land. The skin is the main thermoregulatory conduit which emits excessive body heat. Methods: Thorough evaluation of the skin histology in three pinniped species; the California sea lion-Zalophus californianus, the Pacific harbor seal-Phoca vitulina richardsi, and the Northern elephant seal-Mirounga angustirostris, was conducted to identify the presence, location and distribution of skin structures which contribute to thermoregulation. These structures included hair, adipose tissue, sweat glands, vasculature, and arteriovenous anastomoses (AVA). Thermal imaging was performed on live animals of the same species to correlate histological findings with thermal emission of the skin. Results: The presence and distribution of skin structures directly relates to emissivity of the skin in all three species. Emissivity of skin in phocids (Pacific harbor and Northern elephant seals) follows a different pattern than skin in otariids (California sea lions). The flipper skin in phocids tends to be the most emissive region during hot weather and least emissive during cold weather. On the contrary in otariids, skin of the entire body has a tendency to be emissive during both hot and cold weather. Conclusion: Heat dissipation of the skin directly relates to the presence and distribution of skin structures in all three species. Different skin thermal dissipation patterns were observed in phocid versus otariid seals. Observed thermal patterns can be used for proper understanding of optimum thermal needs of seals housed in research facilities, rescue centers and zoo exhibits.     

Ontogenetic causes and mechanisms for formation of differences in number of fish scales

Fish squamation is developed in late ontogeny. Therefore, the conditions of development significantly affect its characteristics (number of scales). This study is aimed at considering the influence of external and internal factors on variation of the number of scales in fish. Acceleration of development results in decrease of the number of scales, while it increases with retardation. Experiments on regulation of thyroid status of fish showed that the certain mechanism of alteration of the number of scales is related with heterochrony, such as a shift of the timing of squamation. Accelerated development is caused by early scale development at smaller body length, while retarded development is characterized with later scale development and at greater body length. Data considering heterochrony as the possible reason for differences in the number of scales in related fish species are represented. Moreover, alterations of the distance between scales (morphogenetic count) can serve as another alteration mechanism of the number of scales in fish (especially phyletically distant species).     

Scale diversity in bigeye tuna (Thunnus obesus): Fat‐filled trabecular scales made of cellular bone

Tunas of the genus Thunnus possess many morphological and physiological adaptations for their high‐performance epipelagic ecology. Although Thunnus anatomy has been studied, there are no quantitative studies on the structure of their scales. We investigated the scales of bigeye tuna (Thunnus obesus) from ten regions of the body using micro computed tomography (µCT)‐scanning and histology to quantitatively and qualitatively compare regional scale morphology. We found a diversity of scale sizes and shapes across the body of bigeye tuna and discriminant function analysis on variables derived from µCT‐data showed that scales across the body differ quantitatively in shape and size. We also report the discovery of a novel scale type in corselet, tail, and cheek regions. These modified scales are ossified shells supported by internal trabeculae, filled with fat, and possessing an internal blood supply. Histological analysis showed that the outer lamellar layers of these thickened scales are composed of cellular bone, unexpected for a perciform fish in which bone is typically acellular. In the fairing region of the anterior body, these fat‐filled scales are stacked in layers up to five scales deep, forming a thickened bony casing. Cheek scales also possess a fat‐filled internal trabecular structure, while most posterior body scales are more plate‐like and similar to typical teleost scales. While the function of these novel fat‐filled scales is unknown, we explore several possible hypotheses for their function.     

The Differentiation of Placoid, Ctenoid and Cycloid Scales by Means of Alizarin Red S

This technic has been used successfully by the author for staining, in situ, the placoid scales of selachians and the smaller forms of cycloid and ctenoid scales of teleosts. Sections of skin are dissected from the ventrum of the specimen, cleaned of fascia and muscle tissue and fixed in a 10% formalin solution. The section is macerated in several changes of a 3% KOH solution until translucent. Staining is accomplished in a fresh 2% KOH solution to which is added a saturated alcoholic solution of alizarin red S. The section remains in the stain for 24 hours. If necessary, the tissue may be quickly destained in acid alcohol (1% H₂SO₄ in 95% alcohol). The skin is dehydrated in cellosolve or the alcohol series and cleared in methyl salicylate. Placoid and teleost scales prepared in this manner are stained a brilliant red. The various parts of the denticle are well differentiated.     

At what spatial scale(s) do mammals respond to urbanization?

Spatial scale is fundamental in understanding species–landscape relationships because species’ responses to landscape characteristics typically vary across scales. Nonetheless, such scales are often unidentified or unreliably predicted by theory. Many landscapes worldwide are urbanizing, yet the spatial scaling of species’ responses to urbanization is poorly understood. We investigated the spatial scaling of urbanization effects on a community of 15 mammal species using ~60 000 wildlife detections collected from a constellation of 207 camera traps across an extensive urban park system. We embedded a bivariate Gaussian kernel in hierarchical multi-species models to determine two scales of effect (a scale of maximal effect and a broader scale of cumulative landscape effect) for two biological responses (occupancy and site visit frequency) across two seasons (winter and summer) for each species. We then assessed whether scales of effect varied according to theoretical predictions associated with biological responses and species traits (body size and mobility). Scales of effect ranged from < 50 m to > 9000 m and varied among species, but not as predicted by theory. Species’ occupancy generally showed a weak response to urbanization and the scale of this effect was both highly uncertain and consistent across species. We did not detect any relationship between scales of effect and species’ body size or mobility, nor was there any evident pattern of scaling across biological response or seasons. These results imply that 1) urbanization effects on mammals manifest across a very broad spectrum of spatial scales, and 2) current theories that a priori predict the scale at which urbanization affects mammals may be of limited use within a given system. Overall, this study suggests that developing general theory regarding the scaling of species–landscape relationships requires additional empirical work conducted across multiple species, systems and timescales.     

The Sphyraena obtusata group (Perciformes: Sphyraenidae) with a description of a new species from southern Japan

Sphyraena iburiensis sp. nov. is described, and taxonomic reviews are provided for S. obtusata and S. pinguis. These species, characterized by having 2 gill rakers, are defined as the S. obtusata group. Sphyraena iburiensis, known only from the Pacific coast of southern Japan, is characterized by 8.5–9.5 scales above the lateral line, a single row of scales in the groove along the lower margin of the suborbital region from the posterior tip of the maxilla to below the eye (=suborbital groove) not covered with skin, 2 distinct longitudinal stripes on the lateral surface of the body when fresh (upper stripe usually lost in preserved specimens), the lower stripe reaching the caudal-fin base just below the lateral line. Sphyraena obtusata, distributed in the Indo-West Pacific, is characterized by 5–7.5 scales above the lateral line, a single row of scales in the suborbital groove covered with skin, 2 somewhat indistinct longitudinal stripes on the lateral surface of the body when fresh (upper stripe usually lost in preserved specimens), the lower stripe joining the lateral line midway between the end of the second dorsal-fin base and caudal peduncle and extending to the middle of the caudal-fin base. Sphyraena pinguis, distributed in the Indo-West Pacific, is characterized by 7.5–9.5 scales above the lateral line, a single row of scales in the suborbital groove not covered with skin, and a single longitudinal stripe on the lateral surface of the body joining the lateral line slightly before or just below the end of the second dorsal-fin base and extending to the middle of the caudal-fin base. Seven (S. aureoflammea, S. brachygnathos, S. flavicauda, S. grandisquamis, S. langsar, S. lineata, and S. strenua) and 2 (S. chrysotaenia and S. schlegelii) nominal species are regarded as junior synonyms of S. obtusata and S. pinguis, respectively. In addition, lectotypes are designated for S. flavicauda, S. langsar, S. lineata, and S. obtusata. A key to the three species of the S. obtusata group is provided.     

Imaging scale surface topography of an endemic cyprinid fish,Garra sharq from the Arabian Peninsula: An integrated optical light and scanning electron microscopy approach

The optical light microscopy and scanning electron microscopy techniques have proven to play a key and noteworthy role in the advancement of morphological studies in general, and in investigating fish scale morphology in particular. These techniques have illustrated several hidden architectural structures in scales that contribute effectively to fish identification and classification. The scale morphological and topological characters such as type, size, shape, lateral surface, focus position, circuli appearance, radii type, lepidonts, and posterior and anterior margin shapes were obtained using macro- and microscopic analysis in six body regions for three size classes of Garra sharq, a cyprinid endemic fish of the Arabian Peninsula. The general scale type in the studied G. sharq species was a basal elasmoid cycloid and a sectioned type. As a protective structure, the scales display several specific characteristics including firm attachment to the fish body, overlapping, and thin structure with a high surface area and high strength. These characteristics improve scale resistance to penetration, increase protection against mechanical injury and microbial infection, enhance scale flexibility, reduce fish weight (reduce friction drag), and increase scale transparency. The scales demonstrate plasticity in focus shape, size, and position in the six fish body parts and fish size groups. The examined scales displayed narrow or wide grooves (radii) in three types including primary, secondary, and tertiary present in all four scale fields (anterior, posterior, and laterals), thus a tetra-sectioned type that is almost specific to the genus Garra. This characteristic also increases scale flexibility. The rostral margin of scales was characterized by the presence of waved and striate types. The lepidont shape and size varied being blunt, flat, pointed, tiny, sharp, short, and long. Some of these scale characters and their morphologies could be used as an alternative tool for identification, classification, and phylogenetic interpretation among the different freshwater fish species and genera.     

Ultrastructure and wear patterns of the ventral epidermis of four snake species (Squamata,Serpentes)

Snakes are limbless tetrapods highly specialized for sliding locomotion. This locomotion leads to the skin being exposed to friction loads, especially on the ventral body side, which leads to wear. It is presumed that snakes therefore have specific optimizations for minimizing abrasion. Scales from snakes with habitat, locomotor and/or behavior specializations have specific gradients in material properties that may be due to different epidermal architecture. To approach this issue we examined the skin of Lampropeltis getula californiae (terrestrial), Epicrates cenchria cenchria (generalist), Morelia viridis (arboreal), and Gongylophis colubrinus (burrowing) with a focus on (i) the ultrastructure of the ventral epidermis and (ii) the qualitative abrasion pattern of the ventral scales. Scanning and transmission electron microscopy revealed variations in the structure, thickness, layering, and material composition of the epidermis between the species. Furthermore, SEM and white light interferometer images of the scale surface showed that the abrasion patterns differed, even when the snakes were reared on the same substrate. These data support the idea that (i) a specific gradient in material properties may be due to a variation in epidermis architecture (thickness/ultrastructure) and (ii) this variation may be an optimization of material properties for specific ways of life.     

Contributions to the anatomy of Sararanga (Pandanaceae)

Preliminary study shows the two species of Sararanga to differ considerably in morphology and anatomy. The presence of stellate trichomes in S. philippinensis is a major character separating the two species; such trichomes are not found elsewhere in the family. Massive strands of thickened cells (buttresses) extend across the leaf of S. sinuosu but appear absent from S. philippinensis. The leaf anatomy of the latter more closely resembles that common in Freycinetia. The photosynthetic tissue is not clearly differentiated into distinct layers. Both species of Sararanga have unspecialized stomata. The presence of raphides in different structures in the two species may be distinctive. The pollen grains are ellipsoidal, with an intricate reticulate exine. The fruits contrast in structure with those of Pandanus and Freycinetia and the seeds of Sararanga philippinensis have a characteristic elaborate testa.     

Spatial differentiation of ectoparasites on small mammals

Different ectoparasitic species occur on different areas on the small mammal host: chiggers in the ear muzzle, ticks on the ears and other parts of the head, fleas and lice on the back and most gamasid mites on the posterior part of the host body.
The distribution might be affected by (1) the mechanical interference of the host. Thus attached species such as ticks and chiggers occur in areas where direct predation is limited and small and/or very mobile species are found on other parts of the body. (2) interaction between parasitic species. In areas where species meet, there might be a segregation in time or in space. Species such as Laelaps agilis (C. L. Koch) and Haemogamasus nidi Michael are most frequently found within a restricted area on the host, but differ in their seasonal occurrence. In other combinations of species, such as in fleas, there are marked differentiations in body areas used. These differentiations may be evolutionary fixed or manifested at first when species meet. (3) Abundance, where an increasing abundance enlarge the habitat used.     

A new species of Swingleus (Monogenea: Gyrodactylidae) from the mummichog Fundulus heteroclitus, in the Delaware Bay

Swingleus ancistrus n. sp. (Monogenea: Gyrodactylidae) is described from the skin and fins of Fundulus heteroclitus from Canary Creek Marsh, Lewes, Delaware. Subsequent records from New Jersey, Maryland, Virginia, and North Carolina are reported. Swingleus ancistrus is differentiated from S. polyclithroides, the only other species of the genus, primarily by its size, haptoral morphology, host, and locality. Swingleus ancistrus is larger in almost every dimension and exhibits a distinct notch on the anterior border of the opisthaptor, and several features of the haptoral anatomy and peduncular bar are unique. The prevalence of infection in hosts collected from the type locality in August was 100%. The maximum number of S. ancistrus recovered from a single host was 134. The average intensity of infection was 24 S. ancistrus per host from the type locality.     

牙鲆、大黄鱼和小黄鱼不同部位鳞片类型的比较

真骨鱼类的骨鳞有圆鳞和栉鳞两种类型,观察了大黄鱼(Larimichthys crocea)和小黄鱼(Pseudosciaena polyactis)成体的鳞片类型,发现同一个体同时存在圆鳞和栉鳞,有典型的圆鳞和栉鳞结构,也有两者的过渡型形态。而对100日龄和成体牙鲆(Paralichthys olivaceus)不同部位鳞片类型的观察发现,100日龄牙鲆眼侧存在圆鳞向栉鳞过渡的Ⅲ型鳞片、Ⅳ型初始栉鳞和Ⅴ型典型栉鳞,而成体牙鲆有眼侧仅覆盖Ⅴ型典型栉鳞,推测栉鳞和圆鳞可能存在发育上的联系。通过统计大黄鱼和小黄鱼不同部位的圆鳞和栉鳞数量,发现二者体表栉鳞数量均为从头部到尾部依次减少,而背部与腹部之间没有明显差异。     

Far field scattering pattern of differently structured butterfly scales

The angular and spectral reflectance of single scales of five different butterfly species was measured and related to the scale anatomy. The scales of the pierids Pieris rapae and Delias nigrina scatter white light randomly, in close agreement with Lambert’s cosine law, which can be well understood from the randomly organized beads on the scale crossribs. The reflectance of the iridescent blue scales of Morpho aega is determined by multilayer structures in the scale ridges, causing diffraction in approximately a plane. The purple scales in the dorsal wing tips of the male Colotis regina act similarly as the Morpho scale in the blue, due to multilayers in the ridges, but the scattering in the red occurs as in the Pieris scale, because the scales contain beads with pigment that does not absorb in the red wavelength range. The green–yellow scales of Urania fulgens backscatter light in a narrow spatial angle, because of a multilayer structure in the scale body.     

Molecular phylogenetics and diagnosis of Anisakis, Pseudoterranova, and Contracaecum from northern Pacific marine mammals

Individual specimens of Anisakis, Pseudoterranova, and Contracaecum collected from marine mammals inhabiting northern Pacific waters were used for comparative diagnostic and molecular phylogenetic analyses. Forty-eight new sequences were obtained for this study of 14 Anisakis taxa, 8 Pseudoterranova taxa, 4 Contracaecum taxa, and 4 outgroup species. Partial 28S (LSU) and complete internal transcribed spacer (ITS-1, 5.8S, ITS-2) ribosomal DNA was amplified by the polymerase chain reaction and sequenced. Sequences of ITS indicated that Pseudoterranova specimens from Zalophus californianus (California sea lion), Mirounga angustirostris (northern elephant seal), Phoca vitulina (harbor seal), Enhydra lutris (sea otter), and Eumetopias jubatus (Steller's sea lion) exactly matched P. decipiens s. str., extending the host and geographic range of this species. Anisakis from northern Pacific marine mammals were most closely related to members of the A. simplex species complex. Comparison of Anisakis ITS sequences diagnosed the presence of A. simplex C in 2 M. angustirostris hosts, which is a new host record. Anisakis specimens from Phocoena phocoena (harbor porpoise), Lissodelphis borealis (Pacific rightwhale porpoise), and E. jubatus included 3 ITS sequences that did not match any known species. Contracaecum adults obtained from Z. californianus were most closely related to C. ogmorhini s.l. and C. rudolphii, but ITS sequences of these Contracaecum specimens did not match C. ogmorhini s. str. or C. margolisi. These novel Anisakis and Contracaecum ITS sequences may represent previously uncharacterized species. Phylogenetic analysis of LSU sequences revealed strong support for the monophyly of Anisakinae, Contracaecum plus Phocascaris, Pseudoterranova, and Anisakis. Phylogenetic trees inferred from ITS sequences yielded robustly supported relationships for Pseudoterranova and Anisakis species that are primarily consistent with previously published phenograms based on multilocus electrophoretic data.