Occipital spine of Orthacanthus (Xenacanthidae,Elasmobranchii): Structure and growth

The morphology of 16 occipital spines of the xenacanthid Orthacanthus from Upper Carboniferous deposits of Robinson (Kansas, USA), Nýřan (Czech Republic) and Puertollano (Spain) is described. The nonreplaced spines reveal the growth pattern of the shark. Moreover, the relationship between growth and paleoenvironmental conditions can be used to determine paleoecological conditions. Both external and internal morphology indicate that the spine was superficially inserted in the skin. During growth, the spine moved from a deep position in the dermis, in which trabecular dentine is formed, to a more superficial location in which centrifugally growing lamellar dentine was formed. Centripetally growing lamellar dentine was deposited more slowly than the centrifugally growing dentine; it obliterated the pulp cavity. The denticles are independent dermal elements formed by a dermal papilla and secondarily attached by dentine to the spine proper. The number of denticles per annual cycle and the density of denticulation vary with the growth rate. Moreover, the ratio of length of denticulated region to total length of the spine changes throughout ontogeny. In consequence, those features cannot be used for systematic purposes without a careful analysis of the variability. Centrifugally growing lamellar dentine in spines from Robinson shows a regular alternation of layers, suggesting tidal conditions in the environment in which the sharks lived. Monthly and seasonal cycles also occur. Tidal (lunar) cyclicity is also observed in the denticles: size and distance between denticles increase and decrease gradually, forming waves that are considered seasonal and yearly cycles. The observed regularity could be related to the variation in calcium phosphate deposition following the cyclical changes in water temperature produced in the tidal zone. Monthly and seasonal cycles are the result of the interaction of the solar and tidal (lunar) cycles. The cyclical pattern of growth is used to determine the age and growth rates. Orthacanthus was a fast‐growing shark like the Recent sharks Isurus, Mustelus, and Negaprion. J. Morphol. 242:1–45, 1999. © 1999 Wiley‐Liss, Inc.     

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.     

A new species of Numbakullidae Gu?u & Heard, 2002 (Tanaidacea,Peracarida, Crustacea) from?the?Great?Barrier Reef,Australia

A new species of Numbakulla Guţu & Heard, 2002 (Tanaidacea) is described from Heron Island (southern Great Barrier Reef, Queensland) collected during the Census of Coral Reefs Ecosystem (CReefs) program. The new species is the third member of the family and can be recognized by the combination of characters as: length/width ratio of the body, which is 6:7, pereonite 4 longer than the rest, the presence of eyes, a blunt rostrum, antenna article 2 elongated, cheliped carpus with row of inner setae, pereopod 6 carpus with spines, pleopod endopod with denticles.     

Diversity of dermal denticle structure in sharks: Skin surface roughness and three‐dimensional morphology

Shark skin is covered with numerous placoid scales or dermal denticles. While previous research has used scanning electron microscopy and histology to demonstrate that denticles vary both around the body of a shark and among species, no previous study has quantified three‐dimensional (3D) denticle structure and surface roughness to provide a quantitative analysis of skin surface texture. We quantified differences in denticle shape and size on the skin of three individual smooth dogfish sharks (Mustelus canis) using micro‐CT scanning, gel‐based surface profilometry, and histology. On each smooth dogfish, we imaged between 8 and 20 distinct areas on the body and fins, and obtained further comparative skin surface data from leopard, Atlantic sharpnose, shortfin mako, spiny dogfish, gulper, angel, and white sharks. We generated 3D images of individual denticles and measured denticle volume, surface area, and crown angle from the micro‐CT scans. Surface profilometry was used to quantify metrology variables such as roughness, skew, kurtosis, and the height and spacing of surface features. These measurements confirmed that denticles on different body areas of smooth dogfish varied widely in size, shape, and spacing. Denticles near the snout are smooth, paver‐like, and large relative to denticles on the body. Body denticles on smooth dogfish generally have between one and three distinct ridges, a diamond‐like surface shape, and a dorsoventral gradient in spacing and roughness. Ridges were spaced on average 56 µm apart, and had a mean height of 6.5 µm, comparable to denticles from shortfin mako sharks, and with narrower spacing and lower heights than other species measured. We observed considerable variation in denticle structure among regions on the pectoral, dorsal, and caudal fins, including a leading‐to‐trailing edge gradient in roughness for each region. Surface roughness in smooth dogfish varied around the body from 3 to 42 microns.     

Three new species of Tricorythopsis (Ephemeroptera: Leptohyphidae) from southeastern Brazil

Three new species of Tricorythopsis Traver (Ephemeroptera: Leptohyphidae) are described and illustrated based on nymphs from southeastern Brazil. These new species can be distinguished from other species of the genus by the following characters: Tricorythopsis araponga sp. n.: (1) femora with long setae; (2) abdominal segments 5–7 with dorsal tubercles; (3) tarsal claws with 4–6 marginal denticles and 7 + 4 submarginal denticles. Tricorythopsis baptistai sp. n.: (1) tarsal claws with 4–5 large marginal denticles and one submarginal denticle on each side; (2) abdominal colour pattern; (3) abdomen without tubercles; (4) coxae without projections. Tricorythopsis pseudogibbus sp. n.: (1) abdominal segments 6–8 with small dorsal tubercles; (2) tarsal claws with four large marginal denticles, and 3 + 1 or 2 submarginal denticles; (3) coxae dorsally projected; (4) femora broad and with short setae; (5) pronotum with anterolateral projection.     

Complex selection on life-history traits and the maintenance of variation in exaggerated rostrum length in acorn weevils

Trophic interactions can trigger the development of exaggerated specialized characters and promote morphological diversification. For example, acorn weevils (genus Curculio) present strikingly long rostrums, which are used by females to perforate oviposition holes through the seed coat. Species exhibiting longer rostrums are known to exploit larger acorns, and therefore rostrum length is thought to be subject to selection to match the preferred acorn type. However, rostrum length is strongly correlated with body size, and morphological divergence could result from either selection on rostrum length for optimal food exploitation or from other pressures acting on body size. We collected infested acorns at oak forests where the large Curculio elephas and the small-bodied Curculio glandium co-occur. There were no interspecific differences in adult female body size to rostrum length allometric relationships, and rostrum length is equally correlated with body size in either species. MtDNA-based species identification showed that C. glandium larvae were present within acorns of all sizes, whereas C. elephas larvae were restricted to acorns above a minimum size, irrespective of oak species. Hence, exploitation of large acorns can hardly have triggered rostrum enlargement, as the small sized C. glandium adults (with short rostrums) could perforate and oviposit in both small and large acorns. Rather, increased rostrum length is probably a by-product of the larger body sizes of individuals emerging from bigger acorns, which allow increased larval size and enhance larval survival likelihood. Summarizing, when exaggerated feeding traits co-vary with other body features, interspecific morphological variability may result from contrasting selective pressures acting on these correlated characters.     

Two new species of <Emphasis Type="Italic">Parspina</Emphasis> Pearse, 1920 (Digenea: Cryptogonimidae) from freshwater fishes (Gymnotiformes) of the Paraná River basin in Argentina

Two new species of the cryptogonimid genus Parspina Pearse, 1920 are described from gymnotiform fishes of the Paraná River basin, P. carapo n. sp. from the banded knifefish Gymnotus carapo Linnaeus and P. virescens n. sp. from the glass knifefish Eigenmannia virescens (Valenciennes). Parspina carapo differs from P. virescens in the number of oral spines (32–39 vs 30–33) and their length (28–47 vs 16–28 μm), the distribution of tegumental spines and their anchorage, the types of sensory papillae on the body surface (three vs two types), the extent of body length posterior to the caeca (5 vs 13% of the total body length), the dimensions of the pars prostatica (52 × 34 vs 24 × 10 μm), and in the absence of a gonotyl (vs presence). Both P. carapo and P. virescens differ from P. bagre Pearse, 1920 and P. argentinensis (Szidat, 1954) in the number of oral spines (20–21 and 21–28 in the latter pair) and their length (28–32 and 35–60 μm), and in total body length. Additionally, the two new species differ from P. argentinensis in the arrangement of the vitelline follicles (one continuous band vs two groups on each side of the body) and in having a smaller pars prostatica (149 × 49 μm in the latter). Parspina carapo is the fifth intestinal helminth found in G. carapo, and P. virescens is the first found in E. virescens.     

<Emphasis Type="Italic">Duranta neblinensis</Emphasis> (Verbenaceae,Duranteae): A new species from Sierra de la Neblina,Amazonas state,Venezuela

Duranta neblinensis, from Sierra de la Neblina, Amazonas state, Venezuela is described, illustrated, and its morphological relationships with allied species are discussed. This new species is similar to D. obtusifolia, but it differs by its stout spines; pubescent petioles and leaves; apiculate calyx lobes; and fruits with an open, slender, curved rostrum . An updated key to the six Venezuelan species of Duranta is presented, and phytogeographic information about Sierra de la Neblina is provided.     

The ultrastructure of spines in sea urchins of the family Strongylocentrotidae

The ultrastructure of primary spines (microscopic relief of the surface of radial wedges on the spines and cross-sections of the spines) was studied by scanning electron microscopy in seven sea urchin species of the family Strongylocentrotidae. The spines were taken from the ambitus area of equally sizes individuals with a test diameter of 50 ± 5 mm. According to the number of wedges on their spines, the studied species can be divided into three groups: Strongylocentrotus intermedius, S. pallidus (18–25 wedges), S. droebachiensis, S. polyacanthus, Allocentrotus fragilis (24–32), and Mesocentrotus franciscantus, S. nudus (45–70). The species visibly differ in the microrelief of the wedges, which can be longitudinally streaked, with protuberances, with cross-dentate or non-dentate wedges, or with cross-series of denticles; in some species, the relief is absent. In S. intermedius, spines with smooth surface of the wedges, longitudinally streaked, with sparse protuberances, and with numerous cross-series of denticles only distally, only proximally, or over the entire length of the spine have been found. Wedge surface is convex or flattened in cross-sections; wedge shape in cross-section is rectangular (S. droebachiensis, S. intermedius, S. polyacanthus), triangular (S. pallidus), trapezoid (S. fragilis), or ansiform (M. franciscanus, M. nudus). Species of the genus Mesocentrotus are readily distinguished from the other species by the stereome of their spines: wider than the height of the wedges and more homogeneous, without regular concentric circles. Data on the ultrastructure of primary spines confirm the generic status of Mesocentrotus Tatarenko et Poltaraus, 1993 and do not support the recognition of Allocentrotus Mortensen, 1942 as a distinct genus.     

Effect of Temperature on Fecundity,Life Span and Morphology of Long‐ and Short‐Spined Clones of Brachionus caudatus f. apsteini (Rotifera)

We investigated the effect of temperature (20, 25 and 30 °C) on fecundity, life span and morphology of the rotifer Brachionus caudatus f. apsteini. For each temperature, short posterior‐spined and long posterior‐spined clones of B. caudatus f. apsteini were individually cultured for up to six generations. The rotifers were fed Chlorella sp. at a density of 1 × 10⁶ cells ml^–1. Morphometric data (body size and spine length) were collected. Total number of offspring producing by a single female per life cycle at high temperature was higher than at low temperature. The duration of juvenile period, reproductive period, post‐reproductive period and life span of both clones of B. caudatus f. apsteini decreased with increasing temperature. All offspring of short posterior‐spined clone produce posterior spines at 20 and 25 °C, with an average length of 19.8 ± 6.6 and 11.9 ± 2.6 μm, respectively. In contrast, they cannot develop posterior spines at 30 °C, at which the average length of the posterior spine remnant was 6.4 ± 1.3 μm. On the other hand, all offspring of long posterior‐spined clone have long posterior spines with average lengths of 36.8 ± 6.1, 36.3 ± 5.2 and 36.6 ± 6.2 μm at 20, 25 and 30 °C, respectively. This study indicated that the production of posterior spines can be induced by low temperature and that short posterior‐spined and long posterior‐spined clones are genetically different. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The denticle surface of thresher shark tails: Three-dimensional structure and comparison to other pelagic species

Shark skin denticles (scales) are diverse in morphology both among species and across the body of single individuals, although the function of this diversity is poorly understood. The extremely elongate and highly flexible tail of thresher sharks provides an opportunity to characterize gradients in denticle surface characteristics along the length of the tail and assess correlations between denticle morphology and tail kinematics. We measured denticle morphology on the caudal fin of three mature and two embryo common thresher sharks (Alopias vulpinus), and we compared thresher tail denticles to those of eleven other shark species. Using surface profilometry, we quantified 3D-denticle patterning and texture along the tail of threshers (27 regions in adults, and 16 regions in embryos). We report that tails of thresher embryos have a membrane that covers the denticles and reduces surface roughness. In mature thresher tails, surfaces have an average roughness of 5.6 μm which is smoother than some other pelagic shark species, but similar in roughness to blacktip, porbeagle, and bonnethead shark tails. There is no gradient down the tail in roughness for the middle or trailing edge regions and hence no correlation with kinematic amplitude or inferred magnitude of flow separation along the tail during locomotion. Along the length of the tail there is a leading-to-trailing-edge gradient with larger leading edge denticles that lack ridges (average roughness = 9.6 μm), and smaller trailing edge denticles with 5 ridges (average roughness = 5.7 μm). Thresher shark tails have many missing denticles visible as gaps in the surface, and we present evidence that these denticles are being replaced by new denticles that emerge from the skin below.     

Rendiconti Delle Sedute E Brevi Comunicazioni

Abstract

Totally, 26 xerohalophytic species belonging to the associations Cakilo-Xanthietum italici and Echinophoro-Elymetum farcti were registered at the Velika pla?a beach (Montenegro); they were distributed following the spatial succession common in this type of habitat. Three transects of different terrain morphology (positioned perpendicularly to the shoreline) were surveyed to establish if there were any differences in the floristic composition and species distribution due to the configuration discrepancy. Moreover, each transect was divided into zones: The first zone from 0 to 30 m inland, the second zone from 30 m to 60 m inland, and the third zone from 60 m to the end of beach (75–115 m, depending on transect length). The floristic composition was relatively uniform in the different transects. However, the number of individuals per species differed significantly among these transects. An analysis of the qualitative composition of transects/zones showed high differences between zones within transects I and II, whereas species composition of zones within transect III was mostly similar. When analyzing the quantitative composition of species, a positive correlation between the distance from the shoreline and the number of individuals per species in transects I and II was registered for most analyzed species (Spearman correlation, p < 0.001). This indicates that terrain configuration affected the ability of present species to become established and propagate.     

A new species of Gracixalus (Amphibia: Anura: Rhacophoridae) from northern Vietnam

We describe a new species of small tree frog from northern Vietnam based on morphological differences and molecular divergence. Gracixalus waza sp. nov. is distinguishable from its congeners and other small rhacophorid species on the basis of a combination of the following characters: (1) size small (snout-vent length of males 27.1–32.9 mm, of females 37.6 mm); (2) head as wide as or wider than long; (3) vomerine teeth absent; (4) snout rounded and long (16–18 % of the snout-vent length); (5) spines on upper eyelid absent; (6) tibiotarsal projection absent; (7) dorsal skin smooth; (8) dermal fringes on forearm and tarsus absent; (9) dorsal surface of head and body greyish-green to moss-green with dark brown pattern forming an inverse Y marking; and (10) throat and chest with dark marbling. Our molecular data showed that the new species is nested in the same group with Gracixalus jinxiuensis sensu lato.     

The larvae of Diadema setosum (Leske, 1778) (Camarodonta: Diadematidae) from South China Sea

Abstract

Diadema setosum (Leske, 1778) develops from small isolecithal eggs with a diameter of 84 ± 3 μm. Embryonic development took about 6.5–7 h and finished when a blastula left the fertilization envelope and became a larva. At this stage, the first pigment cells had appeared. At 23 h a prism developed; at 44 h a pluteus with one pair of arms had appeared; at 45 h of development plutei had two pairs of arms. The pigment cells colour the pluteus of D. setosum dark red. When 20-day-old larvae were mechanically stimulated, they flared their arms which may be defensive behaviour. During further development, the post oral arms of plutei grew to 1900 μm or more. Metamorphosis took place at about 40–45 days. At this time, five primary ambulacral podia were visible within the larval body. The duration of metamorphosis from the moment of larval settlement until the juvenile sea urchins began to move along the bottom was 40–60 min. The diameter of the test of the newly metamorphosed juvenile sea urchins was about 500 μm.     

A new species of Ampelisca (Crustacea, Amphipoda) from NW Iberian Peninsula: Ampelisca troncosoi sp. nov.

A new species of Ampelisca (Crustacea, Amphipoda) is described from samples collected in shallow subtidal fine and very fine sand in the inlet of Baiona (Galicia, NW Iberian Peninsula). Ampelisca troncosoi sp. nov. is closely related to A. brachyceras and A. heterodactyla by having a rostrum between antenna 1 pair and one lateral angle at each side of the head. The new species may be distinguished by the following combination of characters: a distally rounded rostrum between the antenna 1 pair, one laterodorsal pair of corneal lenses, antenna 1 longer than antenna 2 peduncle, antenna 2 never reaching half of the body length, epimeral plates with rounded posterodistal angle, a prominent rounded urosomal carina and two rows of minute spines on the outer rami of the uropod 3.     

Sexual Dimorphisms in the Dermal Denticles of the Lesser-Spotted Catshark,Scyliorhinus canicula (Linnaeus, 1758)

The dermal layers of several elasmobranch species have been shown to be sexually dimorphic. Generally, when this occurs the females have thicker dermal layers compared to those of males. This sexual dimorphism has been suggested to occur as a response to male biting during mating. Although male biting as a copulatory behaviour in Scyliorhinus canicula has been widely speculated to occur, only relatively recently has this behaviour been observed. Male S. canicula use their mouths to bite the female’s pectoral and caudal fins as part of their pre-copulatory behaviour and to grasp females during copulation. Previous work has shown that female S. canicula have a thicker epidermis compared to that of males. The structure of the dermal denticles in females may also differ from that of males in order to protect against male biting or to provide a greater degree of friction in order to allow the male more purchase. This study reveals that the length, width and density of the dermal denticles of mature male and female S. canicula are sexually dimorphic across the integument in areas where males have been observed to bite and wrap themselves around females (pectoral fin, area posterior to the pectoral fin, caudal fin, and pelvic girdle). No significant differences in the dermal denticle dimensions were found in other body areas examined (head, dorsal skin and caudal peduncle). Sexually dimorphic dermal denticles in mature S. canicula could be a response to male biting/wrapping as part of the copulatory process.     

Squalus bassi sp. nov., a new long‐snouted spurdog (Chondrichthyes: Squaliformes: Squalidae) from the Agulhas Bank

The long‐snouted African spurdog Squalus bassi sp. nov. is described based on material collected from the outer shelf and upper continental slope off South Africa and Mozambique. Squalus bassi shares with S. mitsukurii, S. montalbani, S. chloroculus, S. grahami, S. griffini, S. edmundsi, S. quasimodo and S. lobularis a large snout with prenarial length greater than distance between nostrils and upper labial furrows, dermal denticles tricuspidate and rhomboid and elevated number of vertebrae. Squalus bassi can be distinguished from all its congeners by a combination of body and fin colouration, external morphometrics, vertebral counts and shape of dermal denticles. Similar long‐snouted congeners from the Indo‐Pacific region, including S. montalbani, S. edmundsi and S. lalannei are compared in detail with the new species. This new species has been misidentified as the Japanese S. mitsukurii and the Mediterranean S. blainvillei due to the lack of comparative morphological analyses. The validity of the nominal species S. mitsukurii in the south‐eastern Atlantic Ocean and western Indian Ocean is also clarified herein, indicating it has a more restricted geographical distribution in the North Pacific Ocean.     

Trigonognathus kabeyai,a new genus and species of the squalid sharks from Japan

Two specimens of the peculiar squalid shark,Trigonognathus kabeyai gen. et sp. nov., were collected from the coastal waters of Wakayama and Tokushima, Japan, by bottom trawl at depths of 330 and 360 meters. Shape of teeth similar in both jaws; slender, unicuspid, canine-like, without any cusplets or serrations, with weak thin fold on both lingual and labial sides in anterior teeth on both jaws; tooth at symphysis of each jaw longest. Interspace between teeth very wide. Both jaws triangular in shape. Most of dermal denticles on body and head roughly rhombic, swollen very much near central part, with about 10–40 facets on the dorsal surface of its crown. Preoral snout length very short. Many small organs considered to be photophores present mainly on ventral surfaces of head and body.     

Karyotype analysis of the southernmost South American species of Stemodia (Scrophulariaceae)

Abstract

The aim of the present study was to examine the somatic chromosomes of seven species of Stemodia (Scrophulariaceae). The karyotypes of Stemodia ericifolia (2n = 22 = 20m + 2 sm), S. hassleriana (2n = 22 = 20m + 2sm), S. hyptoides (2n = 22 = 20m + 2sm), S. hyptoides (2n = 44 = 40m + 4sm), S. lobelioides (2n = 44 = 40m + 4sm) and S. stricta (2n = 22 = 20m + 2sm) were analyzed for the first time. All the species studied showed a predominance of metacentric chromosomes and a lower proportion of submetacentric pairs. The chromosomes in all the species were found to be small with a mean chromosome length of 1.42 μm, varying from 0.77 μm in S. hyptoides (2n = 66) to 2.10 μm in S. lanceolata. The differences in the asymmetry of the karyotypes were small, for which it is possible to assume that the great diversification of the genus has been accompanied by very small changes in the structure of the chromosomes.     

Density functional studies on copper-catalysed asymmetric aziridination of diazoacetate with imines

Density functional theory has been used to study copper(I)-catalysed aziridination of diazoacetate with imines. All the intermediates and the transition states were optimised completely at B3LYP/6-31G(d) level. Calculation results confirm that copper(I)-catalysed aziridination of diazoacetate with imines is exothermic, and the total released Gibbs free energy is about ? 170 kJ/mol. Copper(I)-catalysed aziridination has two reaction modes: I and II, and thus the reaction mode I is dominant. The formation of the copper(I)–carbene–imine complex M3 (i.e. the attack of imines on copper–carbon(carbene) of copper–carbene intermediate M2) is the rate-determining step and the chirality-limiting step for copper-catalysed asymmetric aziridination. The reaction channel CA2 → M1a → TS1a → M2 → TS2a2 → M3a2 → TS3a2 → M4a2 → P1 is the most favourable one. The dominant products predicted theoretically are of (R)-chirality.