Morphology and frictional properties of scales of Pseudopus apodus (Anguidae,Reptilia)

In the lizard family Anguidae different levels of limb reduction exist up to a completely limbless body. The locomotion patterns of limbless anguid lizards are similar to the undulating and concertina movements of snakes. Additionally, anguid lizards frequently use a third mode of locomotion, called slide-pushing. During slide-pushing the undulating moving body slides on the ground, while the posterior part of the body is pressed against the substrate. Whereas the macroscopic and microscopic adaptations of snake scales to limbless locomotion are well described, the micromorphology of anguid lizard scales has never been examined. Therefore we studied the macro- and micromorphology of the scales of Pseudopus apodus, an anguid lizard with a snakelike body. In addition, we measured the frictional properties of Pseudopus scales. Our data show that the microstructures of the ventral scales of this anguid lizard are less developed than in snakes. We found, however, a rostro-caudal gradient in macroscopic structuring. Whereas the ventral side of the anterior body was nearly unstructured, the tail had macroscopic longitudinal ridges. Our frictional measurements on rough substrates revealed that the ridges provide a frictional anisotropy: friction was higher in the lateral than in the rostral direction. The observed frictional properties are advantageous for a tail-based slide-pushing locomotion, for which a tail with a high lateral friction is most effective in generating propulsion.     

Scanning electron microscopy of scales from different body regions of three lizard species

The Oberhautchen of scales from the dorsal, parietal, and ventral regions of Sceloporus occidentalis (Iguanidae), Gerrhonotus multicarinatus (Anguinidae), and Anniella pulchra (Anniellidae) were examined with a scanning electron microscope. At low magnification, all scales of S. occidentalis exhibit well-defined outlines of cells belonging to the Oberhautchen layer and the previously overlying clear layer. The dorsal and parietal cells of this species exhibit a minutely dentate Oberhautchen that forms tooth-like spinules 0.2 to 0.5 μ long and arranged in irregular rows. Minute pits 0.1 to 0.3 μ in diameter characterize the Oberhautchen of a ventral scale. Cell outlines are not evident on the scales of G. multicarinatus. The Oberhautchen of dorsal and parietal scales of this species is prominently laminated. Laminae are less prominent on scales of the lateral fold, and no intrinsic surface structure is evident on a ventral scale. In contrast, the fossorial anguinomorph Anniella pulchra exhibits Oberhautchen surfaces with practically no intrinsic microornamentation. However, what appear to be outlines of Oberhautchen cells are visible on the dorsal and ventral scales. These observations suggest that modifications of Oberhautchen microornamentation may have evolved to reduce friction with the substrate or other scales. The lack of pronounced microornamentation of the Oberhautchen on some body scales may indicate that a complex interdigitation between clear layer and Oberhautchen cells is not essential to the sloughing process.     

Scale microornamentation of uropeltid snakes

Microornamentation was examined on the exposed oberhautchen surface of dorsal, lateral, and ventral scales from the midbody region of 20 species of the fossorial snake family Uropeltidae and seven species of fossorial scolecophidian and anilioid outgroups. No substantial variation was observed in microornamentation from the different areas around the midbody circumference within species. All oberhautchen cells were flat and exhibited no major surface features other than occasional posterior margin denticulations, small pores/pits, and narrow, low ridges. This is largely consistent with the hypothesis that friction reduction and dirt shedding are the main selective pressures on microornamentation, given that reducing shine is not of key importance in fossorial animals. Variations among taxa were observed in the shape and size of oberhautchen cells, in the presence of pores/pits, in the presence and size of denticulations on posterior cell margins, and in the level or imbricate nature of cell borders. Six microornamentation characters were formulated, scored, and plotted onto a selected phylogeny. Character evolution and phylogenetic signal were explored, accepting the incomplete understanding of intraspecific variation and of uropeltid interrelationships. There is evidence that all but one of these characters evolved homoplastically, probably by multiple independent origin. There is no clear evidence for character state reversal, but greater phylogenetic resolution is required to test this further. Phylogenetic signal appears to exist in some instances, including possible microornamentation synapomorphies for Uropeltidae and Melanophidium. These derived character states are found elsewhere within Squamata. A microornamentation of narrow, finely, and regularly spaced ridges is associated with scale iridescence. These ridges, and possibly pores/pits, are also associated with scales that are less wettable, and that therefore might be expected to be better at shedding dirt in moist conditions. Testable hypotheses are presented that might explain minor variations in the form of ridges and pits among uropeltids.     

Biological characterization of the skin of shortfin mako shark Isurus oxyrinchus and preliminary study of the hydrodynamic behaviour through computational fluid dynamics

This study characterized the morphology, density and orientation of the dermal denticles along the body of a shortfin mako shark Isurus oxyrinchus and identified the hydrodynamic parameters of its body through a computational fluid‐dynamics model. The study showed a great variability in the morphology, size, shape, orientation and density of dermal denticles along the body of I. oxyrinchus. There was a significant higher density in dorsal and ventral areas of the body and their highest angular deviations were found in the lower part of the mouth and in the areas between the pre‐caudal pit and the second dorsal and pelvic fins. A detailed three‐dimensional geometry from a scanned body of a shark was carried out to evaluate the hydrodynamic properties such as drag coefficient, lift coefficient and superficial (skin) friction coefficient of the skin together with flow velocity field, according to different roughness coefficients simulating the effect of the dermal denticles. This preliminary approach contributed to detailed information of the denticle interactions. As the height of the denticles was increased, flow velocity and the effect of lift decreased whereas drag increased. The highest peaks of skin friction coefficient were observed around the pectoral fins.     

东方沙蟒显微皮纹结构与功能

对隶属蟒科的东方沙蟒唇鳞的光学显微结构和扫描电镜下的超微结构的观察发现了类似小窝的结构,可能是原始的鳞片感受器官;对鳞片感受器的大小做了测量;同时观察了头部其他鳞片和身体中部背鳞和腹鳞的显微皮纹结构。所有鳞片的角皮层细胞平坦,没有大的表面特征结构,除了后缘齿状结构、微孔和窄而短的边界。考虑到穴居种类减少反光不是主要的选择因子,而主要选择是减少摩擦和清除污物,显微皮纹特征很好地符合这一假说。不同部位鳞片的差异主要表现在角皮层细胞的形状和的大小,微孔的有无,细胞后缘齿状结构的有无和大小以及细胞边界重叠的程度。首次描述了鹅卵石样多孔细胞这一微饰类型。     

History and function of scale microornamentation in lacertid lizards

Differences in surface structure (ober-hautchen) of body scales of lacertid lizards involve cell size, shape and surface profile, presence or absence of fine pitting, form of cell margins, and the occurrence of longitudinal ridges and pustular projections. Phylogenetic information indicates that the primitive pattern involved narrow strap-shaped cells, with low posteriorly overlapping edges and relatively smooth surfaces. Deviations from this condition produce a more sculptured surface and have developed many times, although subsequent overt reversals are uncommon. Like variations in scale shape, different patterns of dorsal body microornamentation appear to confer different and conflicting performance advantages. The primitive pattern may reduce friction during locomotion and also enhances dirt shedding, especially in ground-dwelling forms from moist habitats. However, this smooth microornamentation generates shine that may compromise cryptic coloration, especially when scales are large. Many derived features show correlation with such large scales and appear to suppress shine. They occur most frequently in forms from dry habitats or forms that climb in vegetation away from the ground, situations where dirt adhesion is less of a problem. Microornamentation differences involving other parts of the body and other squamate groups tend to corroborate this functional interpretation. Microornamentation features can develop on lineages in different orders and appear to act additively in reducing shine. In some cases different combinations may be optimal solutions in particular environments, but lineage effects, such as limited reversibility and different developmental proclivities, may also be important in their genesis. The fine pits often found on cell surfaces are unconnected with shine reduction, as they are smaller than the wavelengths of most visible light.     

Mechanical properties of pufferfish (Lagocephalus gloveri) skin and its collagen arrangement

Skin is a biological material the mechanical properties of which are dependent on the constituents from which it is assembled. Skin, the outer covering of animals is made up of collagen fibers arranged in more or less ordered arrays. Pufferfish skin provides a rigid framework to support the body contents and a flexible covering to allow whatever changes are necessary for the remarkable inflation mechanism. Here, we describe the structure and tensile properties of the dorsal and ventral skin of the pufferfish, Lagocephalus gloveri Abe and Tabeta, 1983. The ultimate tensile strength of ventral skin was found to be around two times higher than that of the dorsal skin. It was observed that the dorsal skin could resist more deformation than the ventral skin. The collagen fibers were arranged in different ordered arrays for ventral and dorsal skin and the concentration of fibers was found to be more in ventral than dorsal skin. This provides more stiffness to ventral skin. Scanning electron microscopy studies of the ventral skin showed a unidirectional arrangement of the collagen fibers, which provides more stretching capacity. Dorsal skin, on the other hand, has an orthogonal arrangement of fibers. The present study thus showed that the mechanical behavior of the skin of L. gloveri is strongly influenced by the concentration and arrangement of collagen fibers.     

Convergent evolution of the lateral line system in Apogonidae (Teleostei: Percomorpha) determined from innervation

The lateral line system and its innervation were examined in two species of the family Apogonidae (Cercamia eremia [Apogoninae] and Pseudamia gelatinosa [Pseudamiinae]). Both species were characterized by numerous superficial neuromasts (SNs; total 2,717 in C. eremia; 9,650 in P. gelatinosa), including rows on the dorsal and ventral halves of the trunk, associated with one (in C. eremia) and three (in P. gelatinosa) reduced trunk canals. The pattern of SN innervation clearly demonstrated that the overall pattern of SN distribution had evolved convergently in the two species. In C. eremia, SN rows over the entire trunk were innervated by elongated branches of the dorsal longitudinal collector nerve (DLCN) anteriorly and lateral ramus posteriorly. In P. gelatinosa, the innervation pattern of the DLCN was mirrored on the ventral half of the trunk (ventral longitudinal collector nerve: VLCN). Elongated branches of the DLCN and VLCN innervated SN rows on the dorsal and ventral halves of the trunk, respectively. The reduced trunk canal(s) apparently had no direct relationship with the increase of SNs, because these branches originated deep to the lateral line scales, none innervating canal neuromast (CN) homologues on the surface of the scales. In P. gelatinosa, a CN (or an SN row: CN homologue) occurred on every other one of their small lateral line scales, while congeners (P. hayashii and P. zonata) had an SN row (CN homologue) on every one of their large lateral line scales.     

The innervation and adaptive significance of extensively distributed neuromasts in <Emphasis Type="Italic">Glossogobius olivaceus</Emphasis> (Perciformes: Gobiidae)

Components of the lateral line system and their innervation were examined in Glossogobius olivaceus (Gobiidae), with almost all of the trunk scales bearing a row of superficial neuromasts, the latter comprising some 2,900 of the total (ca. 4,800) neuromasts on the body. The relationship between orientation and innervation of the superficial neuromasts on the head showed the buccal and mandibular rami to be clearly separated. On the trunk, the lateral ramus detached a number of branches, typically comprising dorsal, lateral and ventral ramules, to innervate neuromasts. Extensively distributed neuromasts were considered as an adaptation to a nocturnal habit, compensating for reduced vision.     

Histology and lectin-binding patterns in the skin of the terrestrial horned frog Ceratophrys ornata

The terrestrial horned frog, Ceratophrys ornata, lives on a wet substratum and absorbs water through the ventral epidermis; water is lost by evaporation from the dorsal skin. Thus, this species may be useful as a model for determining whether or not skin histology and lectin-binding patterns, indicative of glycoconjugates, are related to skin functions such as osmoregulation and water balance. With this in mind, a histological and lectin-histochemical study was carried out on dorsal and ventral skin of aquatic tadpoles and of a young terrestrial frog of C. ornata. Sections of skin were stained with various dyes to demonstrate general histological features and with two horseradish peroxidase (HRP)-conjugated lectins, Ulex europaeus agglutinin (UEA 1) and soybean agglutinin (SBA) which bind to specific terminal sugar residues of glycoconjugates, namely L-fucose and N-acetyl-D-galactosamine or D-galactose, respectively. In early stage tadpoles both lectin-binding patterns were similar in the bilaminar epidermis of dorsal and ventral skin (i.e., each lectin stained the apical cell layer). However, metamorphic changes resulted in a young frog with typical adult-type skin composed of a stratified squamous epidermis and three distinct types of glands containing glycoconjugates in their secretions. Strikingly different lectin-binding patterns were evident in the epidermis from dorsal and ventral regions of the body. The epidermis from the dorsal region was stained by both lectins; in contrast, that from the ventral region although stained strongly by HRP-SBA, did not react with HRP-UEA 1 indicating that few, if any, fucose residues were present in the ventral epidermis. These findings, as suggested in the discussion, indicate that different glycoconjugate patterns in dorsal and ventral skin may be associated with the regulation of water balance in the frog.     

有鳞目动物鳞片表面超微结构的适应性进化

爬行动物鳞片的微结构是对环境的一种适应。本研究运用扫描电子显微镜观察了北草蜥(Takydromus septentrionalis)、脆蛇蜥(Dopasia harti)和王锦蛇(Elaphe carinata)头部、背部和腹部鳞片的微皮纹结构及感受器特征。结果表明,3个物种的微皮纹和感受器存在种间差异。北草蜥和王锦蛇背部及腹部微皮纹均为狭长带状,脆蛇蜥为不规则多边形。北草蜥和王锦蛇颔片上有感受器,北草蜥无。脆蛇蜥腹部微皮纹上无小齿状凸起,北草蜥和王锦蛇有,与北草蜥相比王锦蛇的小齿状凸起更宽更长。王锦蛇的眼部微皮纹为向上竖起的脊,而其他部位的鳞片为具有小齿状凸起的狭长带状结构。本研究共收集整理17科99种的背鳞微皮纹数据和8科25种的感受器数据,对微皮纹特征和感受器形态进行祖先重建发现,狭长带状背鳞微皮纹主要存在于蜥蜴科(Lacertidae)、游蛇科(Colubridae)和石龙子科(Scincidae)中,而鬛蜥科(Agamidae)、蛇蜥科(Anguidae)、蟒蛇科(Boidae)以及蝰蛇科(Viperidae)的大多为多边形;较原始的感受器形态为无感觉毛的透镜状,这一结构在有...     

A new species of the grenadier genus <Emphasis Type="Italic">Coelorinchus</Emphasis> (Actinopterygii: Gadiformes: Macrouridae) from the Timor Sea,Eastern Indian Ocean

Coelorinchus okamurai sp. nov. is described from five specimens collected in the Timor Sea at a depth of 610–690 m. The new species belongs to the Coelorinchus japonicus group (redefined in this study), and differs from all other congeners in having the following combination of features: snout moderately long, sharply pointed in lateral and dorsal views, length 39–42% of head length; lateral nasal ridge completely supported by nasal bone; light organ short, length less than 1/2 orbit diameter, its anterior margin falling far short of pelvic-fin bases; premaxillary teeth in short, uniformly wide band, with posterior end of the tooth band not reaching lateral corner of mouth; no teeth greatly enlarged; body scales covered with short, reclined, narrowly blade-like spinules in widely divergent rows; buttresses of body scale spinules scarcely developed; occipital scales between parietal ridges armed with divergent rows of long, erect, needle-like spinules; nasal fossa usually naked (a few small scales rarely present anteroventrally); patches of small scales sparsely distributed on ventral surface of head; scales on underside of head armed with 1–3 rows of short, erect, needle-like to knife-like spinules; interdorsal space longer than first dorsal-fin base length; subopercle terminating as a long, slender flap; body dark overall without prominent markings; fins uniformly blackish.     

Reconstruction of the musculature of <Emphasis Type="Italic">Magelona</Emphasis> cf. <Emphasis Type="Italic">mirabilis</Emphasis> (Magelonidae) and <Emphasis Type="Italic">Prionospio cirrifera</Emphasis> (Spionidae) (Polychaeta,Annelida) by phalloidin labeling and cLSM

Recent investigations have suggested that a lack of circular muscle fibers may be a common situation rather than a rare exception in polychaetes. As part of a comparative survey of polychaete muscle systems, the F-actin musculature subset of Magelona cf. mirabilis and Prionospio cirrifera were labeled with phalloidin and three-dimensionally analyzed and reconstructed by means of cLSM. Obvious similarities are sublongitudinal lateral, circumbuccal, palp retractor, dominating dorsal longitudinal, perpendicular lateral and ventral transverse muscles. Differences between M. cf. mirabilis and P. cirrifera are: (1) two types of prostomial muscles (transversal and longitudinal) in M. cf. mirabilis versus one type (diagonal) in P. cirrifera; (2) one type of palp muscles (longitudinal) in M. cf. mirabilis versus three types (longitudinal, diagonal, circular) in P. cirrifera; (3) five ventral longitudinal muscles (ventromedian, paramedian, ventral) in M. cf. mirabilis versus four (two paramedian, two ventral) in P. cirrifera. Ventral and lateral transverse fibers are present in the thorax, but absent in the abdomen of M. cf. mirabilis. The triangular lumen of the pharynx in M. cf. mirabilis is surrounded by radial muscle fibers; three sets of pharynx diductors attach to its dorsal side. The unique features of P. cirrifera are one pair of brain muscles and segmentally arranged dorsal transverse muscles, the latter located outside the longitudinal muscles. The transverse lateral muscles are restricted to the sides and lie beneath the longitudinal muscles, a pattern described here for the first time. A true, outer layer of circular fibers is absent in both species of Spionida that were investigated.     

The fowl tick, <Emphasis Type="Italic">Argas (Persicargas) persicus</Emphasis> (Ixodoidea: Argasidae): Description of the egg and redescription of the larva by Scanning Electron Microscopy

This scanning electron microscopy study revealed that the egg of Argas persicus was covered with chorion which appeared as a wrinkled layer containing regions of three textures. The first had elevated parts of slightly rough surface. The second had irregular smooth elevations; each carried numerous parallel horizontal foldings with vertical ridges. The last region had rough surface with irregularly shaped projections. Following the removal of the chorion, shell was observed to have one polar micropyle and numerous slit like openings. Length (L), width (W) and L/W ratio of the egg were measured. Investigation of larvae revealed extensively folded integument of idiosoma and spherical or elongated tubercles on dorsal plate. Mouth enclosed between ventral hypostome and two dorsal chelicerae. Hypostome carried four longitudinal rows of conical denticles. Each chelicera was made up of two segments; the basal one appeared as a pocket for the distal one. Haller’s organ consisted of an anterior pit containing seven sensilla and a posterior capsule with four apertures. Distribution of chemo- and mechano-sensilla on the body was examined. Measurements of whole body, idiosoma, dorsal plate, capitulum, hypostome, palp and different types of sensilla both on the body and Haller’s organ are also presented.     

Two new species ofOdilia (Nematoda: Heligmonellidae) from Australian rodents,with comments onO. bainae Beveridge & Durette-Desset, 1992

Odilia tasmaniensis n. sp.,O. praeputialis n. sp. andO. bainae Beveridge & Durette-Desset, 1992 from the small intestine of Australian murids are described and illustrated. The two new species are distinguished from the other eight species in the genus, namelyO. mackerrasae (Mawson, 1961),O. brachybursa (Mawson, 1961),O. emanuelae (Mawson, 1961),O. melomyos (Mawson, 1961),O. polyrhabdote (Mawson, 1961),O. uromyos (Mawson, 1961),O. mawsonae (Durette-Desset, 1969) andO. bainae Beveridge & Durette-Desset, 1992.O. tasmaniensis n. sp. fromRattus lutreolus is characterised by the longitudinal cuticular ridges being continuous, the presence of 18 ridges in cross-section in the middle region of the body, the joined distal ends of the spicules forming a curved bluntly rounded tip, a short genital cone with a single ventral papilla and a pair of laterally curving dorsal raylets and the posterior end of the female tapering sharply.O. praeputialis n. sp. fromZyzomys woodwardi is characterised by continuous longitudinal cuticular ridges, the presence of 22–35 ridges in cross-section in the middle of the body, the sharply pointed joined distal tips of the spicules, a complex genital cone with a flat membraneous proconus, a ventral papilla projecting from an extension of the body wall, a pair of short straight dorsal raylets and the presence of a praepuce on the posterior end of the female.O. bainae is characterised by the longitudinal cuticular ridges being continuous, the presence of 17–22 ridges in cross-section in the middle region of the body, the joined distal ends of the spicules surrounded in an oval transparent cap, a long genital cone with a single ventral papilla and a pair of laterally curving dorsal raylets, and the absence of a praepuce on the posterior end of the female.Rattus lutreolus and the pseudomyine rodentsPseudomys higginsi andMastacomys fuscus are new host records for this species.     

A new blind loach, <Emphasis Type="Italic">Oreonectes elongatus</Emphasis> sp. nov. (Cypriniformes: Balitoridae) from Guangxi,China

A new loach, Oreonectes elongatus sp. nov. is described based on collections from Mulun Township, Huanjiang County, Guangxi in China. It is distinguished from its congeners by the combination of the following characters: most elongate body (body depth/SL 8.62–10.68%), blind, a forked caudal fin, obvious adipose dorsal crest and ventral crest; entire body naked and de-pigmented. Although the new species has a similar distribution with O. macrolepis, it can be distinguished by scales (absent in O. elongatus vs. present in O. macrolepis), shape of snout (elongate vs. round), the opposite position of the dorsal and pelvic fins origins (behind vs. front). The new species shares the same possession of dorsal and ventral crests, a forked caudal fin, eyeless, naked body and incomplete lateral line with O. translucens, but can be distinguished from the latter by caudal fin crest (more developed and translucent in O. translucens), longer anterior nostril tube and barbel, extreme of pectoral fin reaching 2/3 of the distance between origin of pectoral and pelvic fins, more vertebrae (4 + 38–39 vs. 4 + 32).     

Suttonema delta n. g., n. sp. (Nematoda: Trichostrongylina: Heligmosomoidea) from Oxymycterus rufus (Rodentia: Sigmodontinae) in Argentina

A new nippostrongyline, Suttonema delta n. g., n. sp., is described from the intestine of Oxymycterus rufus (Rodentia: Sigmodontinae) from Argentina, in a host from which trichostrongylid nematodes were hitherto unknown. The new genus is very similar to Stilestrongylus Freitas, Lent & Almeida, 1937 and Malvinema Digiani, Sutton & Durette-Desset, 2003, both parasites of Neotropical sigmodontines, in the features of the caudal bursa (with a pattern of type 1-4, asymmetrical with hypertophied right lobe) and the presence of cephalic structures resembling cuticular cordons. The larval synlophe is also identical to that of Stilestrongylus freitasi Durette-Desset, 1968. The new genus is differentiated by an adult synlophe with few ridges (9-12 at mid-body) of two different types: small, rounded ridges without cuticular support on the dorsal side, and pointed ridges of unequal size on the ventral side and in lateral fields. It is also characterised by the presence of comaretes on the left ventral and ventral fields of the synlophe.     

Morphology of the Mechanosensory Lateral Line System in Elasmobranch Fishes: Ecological and Behavioral Considerations

The relationship between morphology of the mechanosensory lateral line system and behavior is essentially unknown in elasmobranch fishes. Gross anatomy and spatial distribution of different peripheral lateral line components were examined in several batoids (Raja eglanteria, Narcine brasiliensis, Gymnura micrura, and Dasyatis sabina) and a bonnethead shark, Sphyrna tiburo, and are interpreted to infer possible behavioral functions for superficial neuromasts, canals, and vesicles of Savi in these species. Narcine brasiliensis has canals on the dorsal surface with 1 pore per tubule branch, lacks a ventral canal system, and has 8–10 vesicles of Savi in bilateral rows on the dorsal rostrum and numerous vesicles ( = 65 ± 6 SD per side) on the ventral rostrum. Raja eglanteria has superficial neuromasts in bilateral rows along the dorsal body midline and tail, a pair anterior to each endolymphatic pore, and a row of 5–6 between the infraorbital canal and eye. Raja eglanteria also has dorsal canals with 1 pore per tubule branch, pored and non-pored canals on the ventral surface, and lacks a ventral subpleural loop. Gymnura micrura has a pored dorsal canal system with extensive branch patterns, a pored ventral hyomandibular canal, and non-pored canal sections around the mouth. Dasyatis sabina has more canal pores on the dorsal body surface, but more canal neuromasts and greater diameter canals on the ventral surface. Sphyrna tiburo has primarily pored canals on both the dorsal and ventral surfaces of the head, as well as the posterior lateral line canal along the lateral body surface. Based upon these morphological data, pored canals on the dorsal body and tail of elasmobranchs are best positioned to detect water movements across the body surface generated by currents, predators, conspecifics, or distortions in the animal's flow field while swimming. In addition, pored canals on the ventral surface likely also detect water movements generated by prey. Superficial neuromasts are protected from stimulation caused by forward swimming motion by their position at the base of papillar grooves, and may detect water flow produced by currents, prey, predators, or conspecifics. Ventral non-pored canals and vesicles of Savi, which are found in benthic batoids, likely function as tactile or vibration receptors that encode displacements of the skin surface caused by prey, the substrate, or conspecifics. This mechanotactile mechanism is supported by the presence of compliant canal walls, neuromasts that are enclosed in wide diameter canals, and the presence of hair cells in neuromasts that are polarized both parallel to and nearly perpendicular to the canal axis in D. sabina. The mechanotactile, schooling, and mechanosensory parallel processing hypotheses are proposed as future directions to address the relationships between morphology and physiology of the mechanosensory lateral line system and behavior in elasmobranch fishes.     

Morphological features of mucous secretory organ and mucous secretion of loach Misgurnus anguillicaudatus skin for friction drag reduction

We examined the functional morphology of loach Misgurnus anguillicaudatus skin by using synchrotron X-ray micro-computed tomography (SR-μCT) and high-contrast staining using osmium tetroxide or phosphotungstic acid (PTA), which enhances the image contrast of soft tissues. The captured high-spatial resolution images revealed that the surface ornamentations were stuck in the basement membrane of the loach scales. The ornamentations consisting of grooves (radii) and ridges (circuli) that can move freely and bend flexibly. The cross-sectional lateral microstructures of flat, concave and convex loach skins were observed from a live image of loach skin obtained through dark-field optical coherence tomography (OCT) imaging. The thickness of loach skin was changed with varying empty space between the mucous-cell layer and the scales by bending motion of loach. In addition, through direct measurement of drag reduction of loach skin, the mucous layer was found to have a strong influence on the reduction of skin friction. The present results enhance the understanding of the functional morphologies of mucous layer of loach to secrete mucus for skin friction reduction.     

THE FLAGELLAR APPARATUS AND RESERVOIR/CANAL CYTOSKELETON OF CRYPTOGLENA PIGRA (EUGLENOPHYCEAE)1

The flagellar apparatus and reservoir cytoskeleton of Cryptoglena pigra Ehrenberg are described. Three flagellar roots are associated with the two basal bodies. The four-membered dorsal root arises from the dorsal basal body and extends anteriorly following the reservoir membrane. At the base of the reservoir the dorsal root nucleates a large microtubular group termed the dorsal band. The dorsal band continues anteriorlhy between the reservoir and eyespot and is continuous with the microtubules of the canal and ultimately the pellicle. The ventral basal body is associated with two roots. The four-membered intermediate root proceeds anteriorly and extends the length of the reservoir. The seven-to eight-membered ventral root projects anteriorly along the reservoir membrane and bends away from the reservoir. At this point, the microtubules of the ventral root line a cytoplasmic pocket and are termed the MTR (reinforcing microtubules). The canal region is composed of longitudinal microtubules surrounded by two semicircles of microtubles. Ultimately, the fifteen ridges of the canal give rise to the pellicular ridges.