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The genus Scyliorhinus is part of the family Scyliorhinidae, the most diverse family of sharks and of the subfamily Scyliorhininae along with Cephaloscyllium and Poroderma. This study reviews the phylogenetic relationships of species of Scyliorhinus in the subfamily Scyliorhininae. Specimens of all Scyliorhinus species were examined as well as specimens of four of the 18 species of Cephaloscyllium, two species of Poroderma, representatives of almost all other catshark (scyliorhinid) genera and one proscylliid (Proscyllium habereri). A detailed morphological study, including external and internal morphology, morphometry and meristic data, was performed. From this study, a total of 84 morphological characters were compiled into a data matrix. Parsimony analysis was employed to generate hypotheses of phylogenetic relationships using the TNT 1.1. Proscyllium habereri was used to root the cladogram. The phylogenetic analysis, based on implied weighting (k = 3; 300 replications and 100 trees saved per replication), resulted in three equally most parsimonious cladograms with 233 steps, with a CI of 0.37 and an RI of 0.69. The monophyly of the subfamily Scyliorhininae is supported as well as of the genus Scyliorhinus, which is proposed to be the sister group of Cephaloscyllium. The phylogenetic relationships amongst Scyliorhinus species are presented for the first time.

Lantern sharks are small shark species that can be seen at depths between 70 and 2000 meters. Due to their luminescent characteristics, they have been called “Lantern shark”. In total eleven specimens of the velvet belly lantern shark, Etmopterus spinax (Linnaeus, 1758), were caught in the deep seas of Northern Cyprus by using a bottom trawl. Sampling was carried out using 13 trawling operations. The collected samples were placed in 4% formalin and stored at the Museum of the Systematic, Faculty of Fisheries, Mersin University, (catalogue number: MEUFC-18-11-082). As a sampling area, the depths between 274 and 641 m were selected. Other cartilaginous fish caught during sampling except E. spinax were Galeus melastomus (1 individual), Squalus acanthias (4 individuals), Scyliorhinus canicula (85 individuals). E. spinax made up 10.89% of all cartilaginous fishes which were caught. Species identification for all fishes caught is made with the help of morphological features.

Intersexual differences in morphometrics were investigated in five species of the catshark genus Scyliorhinus. ANCOVA was used to test 59 measurements, considering capture location and total length as covariates. In all examined species, pelvic-anal distances and pelvic-fin inner margin lengths were greater in males than in females, representing a clear pattern for the genus.

The catshark genus Scyliorhinus belongs to the family Scyliorhinidae, the most diverse family of sharks, and currently presents 16 valid species according to most modern accounts. The long history of taxonomic rearrangements and inaccurate descriptions of many species have contributed to misidentification of specimens and lack of information on the distributional range and diagnostic characters of its species. Species of Scyliorhinus are reviewed and redescribed here, with detailed descriptions on external morphology, neurocranium, claspers, dermal denticles, and tooth morphology provided for the first time for all species. Sixteen species are recognized as valid: Scyliorhinus boa (Goode & Bean, 1896), S. cabofriensis Soares, Gomes & de Carvalho, 2016, S. canicula (Linnaeus, 1758), S. capensis (Müller & Henle, 1838), S. cervigoni Maurin & Bonnet, 1970, S. comoroensis Compagno, 1988, S. duhamelii (Garman, 1913), S. garmani (Fowler, 1934), S. haeckelii (Miranda Ribeiro, 1907), S. hesperius Springer, 1966, S. meadi Springer, 1966, S. retifer (Garman, 1881), S. stellaris (Linnaeus, 1758), S. torazame (Tanaka, 1908), S. torrei Howell-Rivero, 1936, and S. ugoi Soares, Gomes & Gadig, 2015. The main taxonomic decisions herein taken include the resurrection of S. duhamelii (previously a junior synonym of S. canicula) and the synonimization of S. tokubee with S. torazame. Information on geographic distribution was updated for most species, especially for those with wide ranges (S. canicula, S. haeckelii, S. retifer, and S. stellaris).

In amniotes, limb muscle precursors de-epithelialize from the ventral dermomyotome and individually migrate into limb buds. In catsharks, Scyliorhinus, fin muscle precursors are also derived from the ventral dermomyotome, but shortly after de-epithelialization, they reaggregate within the pectoral fin bud and differentiate into fin muscles. Delamination of muscle precursors has been suggested to be controlled by hepatocyte growth factor (HGF) and its tyrosine kinase receptor (MET) in amniotes. Here, we explore the possibility that HGF/MET signaling regulates the delamination of appendicular muscle precursors in embryos of the catshark Scyliorhinus canicula. Our analysis reveals that Hgf is expressed in pectoral fin buds, whereas c-Met expression in fin muscle precursors is rapidly downregulated. We propose that alteration of the duration of c-Met expression in appendicular muscle precursors might underlie the evolution of individually migrating muscle precursors, which leads to the emergence of complex appendicular muscular systems in amniotes.

In amniote embryos, skeletal muscles in the trunk are derived from epithelial dermomyotomes, the ventral margin of which extends ventrally to form body wall muscles. At limb levels, ventral dermomyotomes also generate limb-muscle precursors, an Lbx1-positive cell population that originates from the dermomyotome and migrates distally into the limb bud. In elasmobranchs, however, muscles in the paired fins were believed to be formed by direct somitic extension, a developmental pattern used by the amniote body wall muscles. Here we re-examined the development of pectoral fin muscles in catsharks, Scyliorhinus, and found that chondrichthyan fin muscles are indeed formed from Lbx-positive muscle precursors. Furthermore, these precursors originate from the ventral edge of the dermomyotome, the rest of which extends towards the ventral midline to form body wall muscles. Therefore, the Lbx1-positive, de-epithelialized appendicular muscle precursors appear to have been established in the body plan before the divergence of Chondrichthyes and Osteichthyes.

Elasmobranch populations are declining worldwide, calling for urgent assessment of fishery exploitation and application of effective conservation strategies. Here, we applied a novel approach, integrating long-term time-series of landings (1945–2012) and extensive surveys at the fish market of Chioggia, Italy, home of the major fishing fleet of the northern Adriatic Sea, to evaluate the status of elasmobranch populations and fisheries in the one of the most fished Mediterranean basins. The time-series highlight a dramatic decline in elasmobranch landings, particularly for skates and catsharks (Scyliorhinus spp.), whose current catch rates are 2.4 and 10.6% of the average 1940s levels, respectively. These data likely reflect similar large reductions in abundance, as indicated by the analysis of catch-per unit-effort time-series. The biomass of landed skates and catsharks showed regular fluctuations that disappeared after the collapse of the landings. Elasmobranch market composition, assessed through the sampling of 11 900 specimens from 2006 to 2013, included 14 species, but was dominated by just two: Mustelus mustelus and M. punctulatus, which represented more than 60% of the catch. The proportion of sexually immature individuals was generally very high, up to 83% of landed females and 71% of landed males, depending on the species. Although some correlations were detected between landings and local hydrography or climatic indices, the analyses of landings and surveys at the fish market identified fishery exploitation as the main driver of the striking, long-term elasmobranch decline in the northern Adriatic Sea, calling for urgent management actions to improve the conservation status of these fish.

Sharks of the genus Scyliorhinus from the southwestern Atlantic are reviewed; identification problems and taxonomic misinformation given in the literature are rectified. After extensive examination of the external and internal morphology of specimens collected mostly off southeastern and southern Brazil, Scyliorhinus besnardi Springer & Sadowsky, 1970 is placed in the synonymy of S. haeckelii (Miranda Ribeiro, 1907), which is thoroughly redescribed. Additionally, a new species, Scyliorhinus cabofriensis, sp. nov., is described from the state of Rio de Janeiro, distinguished from all southwestern Atlantic congeners by its color pattern, clasper and neurocranial morphology, and proportional measurements. A key to Scyliorhinus species occurring in the southwestern Atlantic is also provided.

Background The present study represents the first record of Scyliorhinus hesperius in Guatemala’s Caribbean Sea. Methods Five male whitesaddled catsharks, S. hesperius , were captured in 200 m deep waters of Guatemala’s Caribbean coast. Results and Conclusion All specimens were male with total lengths ranging from 420 mm to 510 mm. These fish represent the first record of mature male S. hesperius , the first record for this species in Guatemalan territorial waters, and a range extension in the Western Central Atlantic.

Biofluorescence has recently been found to be widespread in marine fishes, including sharks. Catsharks, such as the Swell Shark (Cephaloscyllium ventriosum) from the eastern Pacific and the Chain Catshark (Scyliorhinus retifer) from the western Atlantic, are known to exhibit bright green fluorescence. We examined the spectral sensitivity and visual characteristics of these reclusive sharks, while also considering the fluorescent properties of their skin. Spectral absorbance of the photoreceptor cells in these sharks revealed the presence of a single visual pigment in each species. Cephaloscyllium ventriosum exhibited a maximum absorbance of 484 ± 3 nm and an absorbance range at half maximum (λ1/2max) of 440–540 nm, whereas for S. retifer maximum absorbance was 488 ± 3 nm with the same absorbance range. Using the photoreceptor properties derived here, a “shark eye” camera was designed and developed that yielded contrast information on areas where fluorescence is anatomically distributed on the shark, as seen from other sharks’ eyes of these two species. Phylogenetic investigations indicate that biofluorescence has evolved at least three times in cartilaginous fishes. The repeated evolution of biofluorescence in elasmobranchs, coupled with a visual adaptation to detect it; and evidence that biofluorescence creates greater luminosity contrast with the surrounding background, highlights the potential importance of biofluorescence in elasmobranch behavior and biology.

espanolEl tiburon cadena, Scyliorhinus retifer, es una especie demersal ovipara del Atlantico noroccidental, el limite sur de distribucion no es preciso. En el Golfo de Mexico la mayoria de sus registros corresponden al area nororiental, con registros esporadicos. Reportamos la presencia de la especie y su morfometria con base en dos especimenes macho maduros, 518 y 527 mm de longitud total, capturados en la costa suroccidental del Golfo de Mexico. EnglishThe chain catshark, Scyliorhinus retifer, is an oviparous demersal species from the northwestern Atlantic. The southern limit of distribution of this species is not clearly established. In the Gulf of Mexico, most of its records correspond to the northeastern area and are sporadic. The presence of the species and its morphometry is reported here based on two mature male specimens, 518 and 527 mm in total length, captured on the southwestern coast of the Gulf of Mexico. portuguesO cacao-gato, Scyliorhinus retifer, e uma especie ovipara demersal do noroeste do Atlântico, o limite sul de distribuicao nao e preciso. No Golfo do Mexico, a maior parte de seus registros corresponde a regiao nordeste, com registros esporadicos. Relatamos a presenca da especie e sua morfometria com base em duas especimes de machos maduros, 518 e 527 mm de comprimento total, capturados na costa sudoeste do Golfo do Mexico.

The discovery that small changes in hydrostatic pressure were coded by angular acceleration receptors in the crab with a mechanism involving nanometer level displacements of mechanoreceptors by differential compression of cuticular and cellular tissues [1], has pointed to a set of sensory signals fundamentally involved in navigation in a much broader range of animals. Neural correlates of hydrostatic pressure cycles have been found in a variety of crustacean equilibrium systems [2]. A more recent study has also shown that angular acceleration receptors in the semicircular canal system of the shark Scyliorhinus respond to small steps and cycles of hydrostatic pressure [3]. In order to investigate rates of changes and absolute changes in hydrostatic pressure detected by these sensory systems, we used pressure chambers together with a tide machine or a voltage controlled pressure regulator to subject balancing system neurones to steps and cycles of hydrostatic pressure, using spike density as a measure of activity. In a variety of species, responses obtained fell into the range expected from the known ranges of depth and rates of change of depth.

Bulk sampling of phosphate-rich horizons within the British Coniacian to Campanian (Upper Cretaceous) yielded very large samples of shark and ray teeth. All of these samples yielded teeth of diverse members of the Carcharhiniformes, which commonly dominate the fauna. The following species are recorded and described: Pseudoscyliorhinus reussi (Herman, 1977) comb. nov., Crassescyliorhinus germanicus (Herman, 1982) gen. nov., Scyliorhinus elongatus (Davis, 1887), Scyliorhinus brumarivulensis sp. nov., ? Palaeoscyllium sp., Prohaploblepharus riegrafi (Muller, 1989) gen. nov., ? Cretascyliorhinus sp., Scyliorhinidae inc. sedis 1, Scyliorhinidae inc. sedis 2, Pteroscyllium hermani sp. nov., Protoscyliorhinus sp., Leptocharias cretaceus sp. nov., Palaeogaleus havreensis Herman, 1977, Paratriakis subserratus sp. nov., Paratriakis tenuis sp. nov., Paratriakis sp. indet. and ? Loxodon sp. Taxa belonging to the families ?Proscylliidae, Leptochariidae, and Carcharhinidae are described from the Cretaceous for the first time. The evolutionary and palaeoecological implications of these newly recognised faunas are discussed.

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.

The dogfish egg case is a composite structure that combines mechanical tensile strength, toughness and elasticity with high permeability to small molecules and ions. Presumably, it provides both a protective and a filtering role for the egg/embryo contained within it. In this work, we performed structural studies of the Galeus melastomus egg case at two different stages of the hardening process, utilizing ATR FT-IR and FT-Raman spectroscopy. Based on these data we deduce that: (a) The G. melastomus egg case, in close analogy to that of the related species Scyliorhinus cunicula, is a complex, composite structure which consists mainly of an analogue of collagen IV. This network forming protein appears to have common secondary structural characteristics in the entire egg case. (b) The outermost layer of the non-sclerotized egg case is especially rich in tyrosine, while the innermost layer is rich in polysaccharides, presumably glycosaminoglycans, and lipids. These differences are diminished upon hardening. (c) Disulfide bonds do not appear to play a significant role in cross-linking. However, cross-links involving tyrosine residues appear to sclerotize the egg case. It is proposed that the intensity of the Raman band at ca. 1615 cm(-1), which is due to ring stretching vibrations of Tyr, might be a useful indicator of the sclerotization status of a certain proteinaceous tissue, when tyrosines are involved in sclerotization mechanisms.

Understanding the evolutionary emergence and subsequent diversification of the vertebrate skeleton requires a comprehensive view of the diverse skeletal cell types found in distinct developmental contexts, tissues, and species. To date, our knowledge of the molecular nature of the shark calcified extracellular matrix, and its relationships with osteichthyan skeletal tissues, remain scarce. Here, based on specific combinations of expression patterns of the Col1a1, Col1a2, and Col2a1 fibrillar collagen genes, we compare the molecular footprint of endoskeletal elements from the chondrichthyan Scyliorhinus canicula and the tetrapod Xenopus tropicalis. We find that, depending on the anatomical location, Scyliorhinus skeletal calcification is associated to cell types expressing different subsets of fibrillar collagen genes, such as high levels of Col1a1 and Col1a2 in the neural arches, high levels of Col2a1 in the tesserae, or associated to a drastic Col2a1 downregulation in the centrum. We detect low Col2a1 levels in Xenopus osteoblasts, thereby revealing that the osteoblastic expression of this gene was significantly reduced in the tetrapod lineage. Finally, we uncover a striking parallel, from a molecular and histological perspective, between the vertebral cartilage calcification of both species and discuss the evolutionary origin of endochondral ossification.

Tag-recapture data of lesser spotted dogfish (Scyliorhinus canicula, L., 1758) were analysed to estimate the von Bertalanffy growth parameters of this species in the Cantabrian Sea. Seven models were applied including those incorporating variability in growth among individuals and model error. Similar results were obtained among them. The Gulland and Holt (1959) method produced the most convincing estimates of von Bertalanffy growth parameters for sexes combined ( L∞ or the asymptotic length closer to observed data), although all the models underestimated L∞ . Estimates of the asymptotic length and the growth coefficient for both sexes combined were 69.3 cm and 0.21 per year, respectively. According to the different models, growth rate was slightly higher in males than females.

Monociliated surface cells were found for the first time in an elasmobranch and were common on embryos of Scyliorhinus canicula. They occurred mainly near the anterior end, until Ballard stage 30, but disappeared soon thereafter. The functions of surface ciliated cells suggested in other embryos (e.g. surface currents in lungfishes and amphibians, and determination of left right patterns in amniotes) seem unlikely in elasmobranchs.

The distribution and morphology of GFAP-immunoreactive cells was investigated in two elasmobranch species, Scyliorhinus canicula and Torpedo marmorata, in an attempt to distinguish between Horstmann's (1954) hypothesis that the presence of cells resembling mammalian astrocytes is a function of the thickness of the ventricular walls, and Cajal's (1911) hypothesis that astrocytes are a phylogenetic novelty found only in birds and mammals. Two types of GFAP-reactive elements were observed, but the distribution of these differed markedly between the two species. In Scyliorhinus, radial glial cells were predominant and astrocytes relatively rare. In Torpedo, on the other hand, a species in which the ventricles are atrophied and the ventricular walls extremely thick, the overwhelming majority of GFAP-labelled structures strongly resembled astrocytes; occasionally, GFAP-positive cells were observed in the ependyma of the spinal cord. These findings, together with previous results obtained by others in hagfish, provide strong evidence in favour of Horstmann's hypothesis.

Small, intermediate and large-sized embryos of the dogfish Scyliorhinus canicula utilize different ventilatory methods; small and intermediate embryos rely on body movement alone to stir either the jelly or sea water in the capsule, large embryos use conventional pharyngeal pumping to pump water through the case. The effects of environmental changes in O2 tension (0.5–100% air saturation) and temperature (6–18°C) upon ventilatory mechanisms in the developing embryo in situ were studied using non-invasive ultrasonography. All three embryo classes increased ventilation rate with rising temperature: for small embryos, y=2.02x+3.295 (P

Photoperiod has no effect on the growth of embryonic dogfish. Conversely, developmental rates are highly susceptible to temperature variation. Embryos maintained at 16°C grew faster and ecloded earlier than those maintained at 10°C. Increased temperature had no effect on size at eclosion.

A survey of skeletal muscles throughout craniates shows basic kinds of myosin filament arrangement, simple-lattice and superlattice, within the A-band of each sarcomere. Distribution of simple- and superlattice arrangements across a phylogeny of craniates suggests that the superlattice arrangement is primitive and that Amia and teleosts are derived in showing simple-lattice arrangements. Two taxa examined (Scyliorhinus and Acipenser) show both lattice types within the same organism implying that there is not a simple evolutionary transformation of one to the other fiber arrangement. We discuss the possible functional significance of the different lattice types. We believe that the crossbridges may have greater competition for actin binding sites in simple-lattice muscles compared to the superlattice types. © 1996 Wiley-Liss, Inc.

As previously reported [Ishii, K., Iwasaki, M., Inoue, S., Kenny, P. T. M., Komura, H.Inoue, Y. (1989) J. Biol. Chem. 264, 1623-1630; Inoue, S., Iwasaki, M., Ishii, K., Kitajima, K.Inoue, Y. (1989) J. Biol. Chem. 264, 18520-185261, the unfertilized eggs of two different species of fresh-water fish, Plecoglossus altivelis and Tribodolon hakonensis, contain relatively large amounts of free sialooligosaccharides. These oligosaccharides were found to derive from glycophosphoproteins, owing to the activity of a peptide - N4-(N-acetyl-beta-D-glucosaminyl)asparagine amidase [Iwasaki, M., Seko, A., Kitajima, K., Inoue, Y.Inoue, S. (1992) J. Biol. Chem. 267, 24287-24296; Seko, A., Kitajima, K., Inoue, Y.Inoue, S. (1991) J. Biol. Chem. 266, 22110-22114]. Here we describe a new type of free oligosaccharides, isolated from unfertilized eggs of Scyliorhinus caniculus. From the structural analysis, based upon 1H-NMR spectroscopy, the following glycan units are proposed.[Formula: see text]

1. In oviparous elasmobranchs the oviducts vary in structure and physiology according to how they carry the sperm upwards and the eggs down. The sperm are accompanied by a large volume of fluid secreted by the siphon. In some species this contains much 5-hydroxytryptamine (5HT), produced by a gland. The muscles of the oviducts are very sensitive to 5HT in Raja , which has such a gland, but not in Scyliorhinus , which has none. 2. The female Scyliorhinus draws the egg case down the duct by attaching tendrils to a rock or weeds and swimming round and round (Dodd 1983); the muscles of the lower oviduct and vagina are weak. 3. In Raja the egg case is buried in the sand or mud and there are powerful muscles in the lower oviduct and vagina. 4. In-vitro isolated strips of longitudinal or circular muscles of the lower oviduct of Raja give slow rhythmical contractions. 5-HT 10 -8 m increased the amplitude and frequency of contraction. The same response was induced by 8-OH-DPAT 5 x 10 -6 m (a 5-HT 1A receptor agonist) but not by 5 x 10 -6 m 2-methyl-5-HT (a 5-HT 3 agonist) or by 5 x 10 -6 m x-methyl-5-HT (a 5-HT 2 agonist). The response to 5-HT was partly blocked by methysergide 10 -6 m (a 5-HT 2 antagonist) but not by ketanserin 10 -5 m (a 5-HT 2 antagonist) or granisetron (BRL 43694) 10 -5 m (a5-HT 3 and 5-H T 4 antagonist). The receptor involved may therefore be of the 5-HT 1 or perhaps 5-HT 2 type. 5. Spontaneous contractions of the oviduct in Raja were inhibited by adrenalin 10 -6 m, and less strongly by noradrenaline 10 -6 m . 6. Substance P 10 -8 m produced increased amplitude and frequency of contraction. 7. Acetylcholine produced contraction only above a dose of 10 -6 m. 8. Strips of lower oviduct or vagina of Scyliorhinus canicula showed long periods of slight rhythmic activity punctuated by large rapid contractions at intervals of 10—40 min. 9. Similar large contractions occurred after addition of 5-HT at 10 -6 m but only in half the experiments and at high concentration, and with long delay. 10. Adrenalin produced large rapid contractions but only at a dose of 10 -7 M and above, and often after a long delay. 11. Substance P and acetylcholine also produced contraction, but the latter only at 10 -6 m . 12. Strips of the oviduct or vagina of either Raja or Scyliorhinus responded to a sudden stretch by a large contraction. 13. These findings are discussed in the light of the differences in sperm transport and egg laying in the two species.

Specific dynamic action (SDA) and the return of appetite (RA) were measured in juvenile (weight range 10·9–16·3 g) and adult (weight range 588·8–802·2 g) Scyliorhinus canicula by means of respirometry and re-feeding trials respectively. Juvenile S. canicula consumed relatively more food than the adults at all times indicating faster rates of food processing in juvenile dogfish. At no time during the SDA effect was there any evidence that elevated levels of oxygen consumption completely prevented further food consumption in either adult or juvenile dogfish. The coefficient (DurationSDA/DurationRA) was similar for both adult (0·52) and juvenile (0·49) S. canicula suggesting that SDA metabolism was closely associated with the processes involved in appetite return.

By observing numerous living eggs from the lesser spotted dogfish Scyliorhinus canicula (L.) caught near Roscoff (France) and reared at recorded temperatures as they developed from first cleavage to hatching, the first reasonably complete developmental table was worked out for this classical material in vertebrate embryology. The successive stages, described and numbered from 1 to 34, correct and replace the incomplete stages A–Q proposed by Balfour (J.Anat. Physiol., 10:555–576,1876) and other even less complete series later published, and is unique in the inclusion of a timetable at 16°C. The stages can be identified, usually through the cleared eggshell wall, with naked eye or low magnification. This table of normal stages of Scyliorhinus can be adapted with slight modification to other chondrichthyan fishes. © 1993 Wiley-Liss, Inc.

Scanning electron microscopy of corroded resin casts of the renal vasculature of Scyliorhinus caniculus has revealed a novel vascular pathway arising from the afferent arteriole and bypassing the glomerulus. This glomerulus bypass shunt occurred in 36% of the glomerular casts examined. The shunt ran to join a peritubular network of capillaries and thereby offers the potential to vary the degree of glomerular perfusion and control the proportion of active glomeruli. In 29% of glomeruli two efferent arterioles drained the capillary knot. Glomeruli were located close to the dorsal margin of the posterior mass of the kidney, and towards the lateral edge of the anterior lobes of the kidney of female dogfish. In male dogfish, glomeruli were evenly distributed through the posterior mass of kidney, while in female dogfish 89% of glomeruli occurred in the posterior mass and 11% of glomeruli were located within the small anterior lobes.

Coronary artery anatomy was studied in 16 shark species belonging to 9 families of the orders Hexanchiformes, Squaliformes, and Carcharhiniformes. The study included 101 specimens and used an injection-corrosion technique that obtained internal casts of the main trunks and coronary arterial branches. The results showed 2 main patterns of coronary arterial arrangement: the dorsoventral coronary trunk pattern, shared by lamnoid and advanced carcharhinoid sharks, and the lateral coronary trunk pattern, shown by hexanchoid and squaloid sharks. Scyliorhinus and Galeus had intermediate arrangements of their vessels.

A new catshark,Scyliorhinus tokubee sp. nov., is described based on specimens from the coast of Shirahama, eastern Izu Peninsula, southern Japan. The present species is distinguished from other congeners in having a particular coloration with dark saddles, blotches and numerous small light spots, a wide oral cleft, the anterior nasal flap not reaching the oral cleft, a short interspace between the dorsal fins, developed clasper hooks, and some meristic characters (number of vertebrae, jaw teeth, and spiral valve turns). This species has been bred under captivity for several years in Shimoda Floating Aquarium.

The rostral cartilages of batoid fishes were examined to elucidate their development, morphology and homology. Comparison of a variety of rostral cartilages among elasmobranchs with other groups of vertebrates shows that rostral cartilages originate embryologically from the trabecula and/or lamina orbitonasalis. Because different morphogenetic patterns of the derivatives of the two embryonic cartilages give rise to a wide variety of forms of rostral cartilages even within elasmobranchs, and because morphogenesis involves complex interactions among participating structures in the ethmo-orbital area, we put forward conceptual and empirical discussions to elucidate the homology of the rostral cartilages in batoid fishes. With six assumptions given in this study and based on recent discussions of biological and historical homology, our discussions centre on: (1) recognition of complex interactions of participating biological entities in development and evolution; (2) elucidation of a set of interacting biological and evolutionary factors to define a given morphological structure; (3) assessment of causal explanations for similarities or differences between homologous structures by determining genetic, epigenetic and evolutionary factors. Examples of conceptual approaches are given to make the approaches testable. Although a paucity of knowledge of rostral cartilage formation is the major obstacle to thorough analysis of the conceptual framework, several tentative conclusions are made on the homology of rostral cartilages that will hopefully attract more research on development and evolution in vertebrate morphology. These are: (1) the rostral cartilage in each group of vertebrates examined can be defined by both developmentally associated and adult structural attributes, yet such data do not allow us to assess homology of a variety of forms of rostral cartilages at higher taxonomic categories; (2) the entire rostral cartilage in elasmobranchs is formed by the contribution of the embryonic trabecula and lamina orbitonasalis. The status of the development and homology of the rostral cartilage in holocephalans remains uncertain; (3) there is no simple picture of evolution of rostral cartilages among three putative monophyletic assemblages of elasmobranchs, galeomorphs, squaloids (possibly plus Squatina, Chlamydoselachus and hexanchoids as the orbitostylic group) and batoid fishes. It is highly likely that rostral cartilages in each subgroup or subgroups of these assemblages may be of phylogenetic significance but that it may not serve as a basis to unite these assemblages into much higher assemblages; (4) the tripodal rostral cartilage is unique in form in the group including some carcharhinoid and lamnoid sharks. The status of the analogous tripodal cartilage in some squaloids remains uncertain. The unfused tripodal cartilage of the electric ray Narke is interpreted as developmentally equivalent to, but not homologous with, the unfused or fused ones in the sharks; (5) the rostral cartilage in the electric ray Torpedo is uniquely formed because of its embryonic origin solely from the ventro-medial part of the lamina orbitonasalis, but it is regarded as homologous with the rostral cartilages which are formed by the trabecula and other components of the lamina orbitonasalis in other batoid fishes; (6) the cornu trabecula contributes to the formation of the ventral stem of the rostral cartilage at least in elasmobranchs, especially to a particular set of rostral cartilages, i.e. the tripodal rostral cartilage in the shark Scyliorhinus and dorso-ventrally flattened rostral shaft in the narcinidid electric rays; (7) there is a unique form of a rostral shaft with rostral appendix in skates and probably guitarfishes; (8) there is no rostral cartilage in adult benthic stingrays, pelagic stingrays Dasyatis violacea and Myliobatidae, although it is present in embryonic stages; (9) there is a unique form of the rostral cartilage as a rostral projection from the dorso-lateral part of the lamina orbitonasalis in pelagic stingrays Rhinopteridae and Mobulidae, which together with part of the pectoral fins, forms a pair of cephalic fins; (10) different developmental mechanisms may be responsible for the absence or loss of rostral cartilages in different groups, i.e. absence of the cartilage derived from the medial area of the trabecula in Torpedo vs absence of the rostral cartilage in benthic stingrays; (11) the rostral cartilages in some placental mammals (cetaceans and sirenians) arise only from the medial area of the trabecula because monotreme and placental mammals do not form the trabecula cranii; (12) some actinopterygians and sacropterygians possess a rostral cartilage which originates only from the medial area of the trabecula. One scombroid group, including Sardini and Thunnini, Scomberomorus, Acanthocybium, Istiophoridae and Xiphias, possesses a unique larval beak composed of the rostral cartilage, ethmoid cartilage and premaxillar bone. The development and homology of other rostral cartilages remain to be further elucidated; (13) urodeles possess a medial rostral process whose anlage is probably developmentally equivalent to that in batoid fishes but the occurrence in urodeles is either atavistic or unique (autapomorphic); (14) the upper jaw of tadpoles is unique in possessing the suprarostral cartilage; the anlage of the cartilage is probably developmentally equivalent to the outgrowth of the cornu trabecula in batoid fishes.

It is essential to consider chondrichthyans (cartilaginous fishes) in analyzing ancestral brain organization because this radiation represents the out-group to all other living gnathostomes (jawed vertebrates). It is particularly crucial to understand the evolution of the telencephalon in chondrichthyans, as this structure develops by evagination (as in most other vertebrates), whereas in most osteichthyans (bony fishes), it develops by eversion, a markedly different process. Among chondrichthyans, the Lesser Spotted Dogfish Scyliorhinus canicula (Elasmobranchii) appears to offer the most potential as a model species for study. Developmental studies of Scyliorhinus have revealed a segmentary pattern in the developing forebrain, similar to that described in other vertebrates, as well as the occurrence of tangential cell migration within the telencephalon, especially in relation to the pallial-subpallial boundary. These observations indicate that major morphogenetic processes thought to be a hallmark of mammalian brains actually existed much earlier in vertebrate phylogeny. In addition, analysis of telencephalic development in Scyliorhinus indicates the existence of telencephalic structures that are probably related to the ganglionic eminences of mammals.

This paper reports concentrations of mercury in muscle tissue of lesser-spotted dogfish (Scyliorhinus caniculus L.) from various locations within Liverpool Bay and the north-east Irish Sea. Concentrations of mercury in fish muscle showed distinct spatial variation, with values from the northern sectors of the Irish Sea significantly lower than those for the southern area, particularly sites in Liverpool Bay and around the mouth of the Mersey Estuary. The data support the hypothesis that there are several major populations of lesser-spotted dogfish within the study area, each of which remains quite distinct during seasonal movements. Consequently, exposure to environmental mercury is reflected in muscle concentrations of mercury. Regressions of mercury concentration against fish length showed significant relationships for the majority of sites, with the slope relating to distance from known sources of mercury contamination. Mean mercury concentrations were higher than in corresponding populations of flatfish from the same areas.

This paper reports concentrations of mercury in muscle tissue of three marine species of fish; plaice (Pleuronectes platessa L.), dab (Limanda limanda L.) and lesser-spotted dogfish (Scyliorhinus caniculus L.), at various locations within Liverpool Bay and the North East Irish Sea. Mean concentrations of mercury in fish muscle within any one sampling area followed the order: lesser spotted dogfish⪢dab>plaice. Concentrations in lesser spotted dogfish were 5–10× higher than in flatfish from the same site. Regressions of mercury concentration against fish length showed significant relationships for the majority of species-site combinations, with the slope of the regression relating to distance from the Mersey Estuary.

Light and electron microscopy of the excretory kidney of adolescent dogfish, Scyliorhinus caniculus (L.), revealed immature and mature nephrons as well as four developmental stages of nephrons. At stage I the nephron was characterized by a condensed mass of mesenchymal cells in the center of several concentric layers of connective tissue. At stage II of the nephron, the S-shaped body was an elongate cyst with a high prismatic epithelium that was connected by a developing collecting tubule with the collecting duct system. At stage III, the developing nephrons already possess the essential features of the mature nephron but lack complete differentiation. Developing renal corpuscles had one afferent arteriole and two efferent vessels. Developing tubules ran four times between the lateral bundle zone and the mesial tissue zone before they joined the collecting duct system. A continuous sheath of flat cells, encompassing the collecting duct system, extended around the developing lateral bundle. A rudimentary central vessel ran from the developing lateral bundle to the venous sinusoid capillaries between the mesial convolutions. Developmental stage IV was similar to the mature nephron, however, renal corpuscles and tubular segments were smaller than those of mature nephrons. Conclusive evidence for morphological homology of elasmobranch nephron segments and collecting tubule-collecting duct system with those of other vertebrates is provided. The origin and nature of the central vessel and the bundle sheath is clarified. These specific structures of marine elasmobranch kidney supposedly are of great functional relevance for the renal countercurrent system that in turn is essential for ion- and osmoregulation.

A new species of catshark (Carcharhiniformes, Scyliorhinidae), Scyliorhinus ugoi sp. nov., is described from off Northeastern and Southeastern Brazil. The new species is closest to the Scyliorhinus haeckelii/besnardi group and S. hesperius but differs in background coloration, head width, sexual maturity, and in cranial and body proportions.

The glycoprotein hormone alpha subunit and two beta subunits were cloned from the ventral lobe of the pituitary gland of an elasmobranch fish, Scyliorhinus canicula. The mature alpha subunit was 96 amino acids long and showed 64-76 amino acid residues in common with alpha subunit sequences of representatives of sarcopterygians (tetrapods and dipnoi) and actinopterigyans (chondrostei and teleostei). The Scyliorhinus beta 1 subunit was 115 amino acid long and had characteristics specific to FSH beta subunits and, in particular, the two potential N-linked glycosylation sites in conserved positions. The beta 2 sequence was 112 amino acids long. The Scyliorhinus beta 2 subunit had only one potential N-linked glycosylation site at the same position as that in LH. None of the two beta subunits from Scyliorhinus displayed the two amino acid insertions shared by TSH beta subunit sequences between the fifth and the sixth cysteines as compared to actinopterygian and sarcopterygian gonadotropins. These data indicate that Scyliorhinus beta 1 and beta 2 subunits are orthologous to FSH and LH beta subunits, respectively. It is concluded that the two FSH and LH lineages were already individualized at the emergence of chondrichthyans.

A new genus and species of diphyllidean, Ahamulina catarina n. gen. n. sp., is described from the polkadot catshark, Scyliorhi-nus besnardi, from Santa Catarina, Brazil. The new genus exhibits apical organ armature that is unique among diphyllideans inthe arrangement and shape of the apical hooks as well as in the lack of lateral hooklets. The taxon also exhibits a bipartite cirrussac. This is the seventh diphyllidean reported from a shark, and the third reported from a catshark suggesting that the dearth of cestode data for these particular sharks belies the true extent of diphyllidean diversity they host.

In contrast to most vertebrate species that possess one oxytocin-like hormone and one vasopressin-like hormone, a few groups, such as marsupials or cartilaginous fishes, are endowed with two peptides of either or both types, suggesting possible gene duplications. We have now isolated two oxytocin-like hormones from the pituitary of the spotted dogfish Scyliorhinus caniculus (suborder Galeoidei). Microsequencing as well as chromatographic and pharmacological comparisons with synthetic peptides show that these peptides are [Asn4,Val8]oxytocin (asvatocin) and [Phe3,Asn4,Val8]-oxytocin (phasvatocin). Asvatocin and phasvatocin display oxytocic activity on rat uterus, about 80 and 5 milliunits per nmol, respectively, and virtually no pressor activity on anesthetized rats. They occur in roughly equal molar amounts in the gland; vasotocin is also present in a proportional amount that is lower by about a factor of 20. In addition to the duality, conservative amino acid substitutions are observed in the two oxytocic peptides in positions 4 (Gln-4-->Asn) and 8 (Leu-8-->Val), when compared with oxytocin. Furthermore, replacement of the isoleucine residue found in position 3 of all other oxytocin-like hormones by phenylalanine in phasvatocin is exceptional; it determines a dramatic decrease of the oxytocic activity. Preservation of the C-terminal-amidated nonapeptide pattern in the 12 vertebrate neurohypophysial hormones known to date suggests that both precursors and processing enzymes have coevolved tightly. On the other hand, whereas the great evolutionary stability of the mature hormones (generally observed in vertebrates) suggests a strict messenger-receptor coevolution, the exceptional diversity found in cartilaginous fishes (six oxytocin-like peptides identified out of eight known) might be due to a looseness of selective constraints, perhaps in relationship with their specific urea osmoregulation.

The taste buds (TBs) of animals of different systematic groups differ considerably in structure [1], but our knowledge of these sensory organs across the vertebrate lineage is currently too limited to derive a TB phylogenetic tree. Since only a single report exists on gustatory receptors of selachians [2], the present study of the structure of TBs of the spotted dogfish, Scyliorhinus caniculus, was initiated to learn more of the interrelationships among TBs of vertebrates. Spotted dogfish were immersion-fixed in a glutaraldehyde-paraformaldehyde-picric acid solution. Pieces of skin removed from different parts of the head and oral cavity were processed conventionally for transmission electron microscopy. In the spotted dogfish, TBs were rare and occurred exclusively at the tip of epidermal papillae within the oral mucosa. In longitudinal section, the TBs were pear-shaped, were approximately 50 μm high and 30 μm wide, were located in the upper third of the squamous non-keratinized epithelium, and were surrounded by marginal cells, the normal epidermal cells. The base of each TB rested on the marginal cells and not on the underlying dermal (corium) papilla, which projected into the basal portion of the epithelium. Each TB was innervated by a nerve that ran through the corium papilla, penetrated the basal lamina of the epithelium, and ascended between the epithelial cells to the TB. Blood capillaries were present in the dermal papilla, but did not reach the TB. The sensory epithelium within the TB consisted of a total of about 25 slender light and dark cells bearing microvilli and situated parallel to the TB’s longitudinal axis. Light cells, which stained less electron dense than dark cells, had a cytoplasm rich in mitochondria, smooth endoplasmic reticulum (sER), and microtubules, and their apical ends terminated in three to five large and divided microvilli. Intermediate (tono)-filaments were rarely observed. Dark cells occurred in two forms. In form one, the cell ended apically in long, slender, and divided microvilli. This dark cell was rich in mitochondria, sER, and dark-staining secretory vesicles of about 200 nm diameter, and contained numerous intermedate filaments. Form two of the dark cell showed long, thin, and undivided microvilli. These form two dark cells contained numerous mitochondria, numerous profiles of the sER, and solitary intermediate filaments. Also, small filament bundles occurred in the basal portions of the cell. Some of the basal marginal cells, which were also rich in organelles, appeared to be basal stem cells, and were different from those of teleosts [1,3,4]. In the spotted dogfish, basal cells comparable to the ones in teleosts did not form the base of the TB, but lay directly on top of the corium papilla. The TB was innervated by unmyelinated nerve fibers, and presynaptic 130-nm dense core and 40-nm clear vesicles occurred mainly at the bases of both the light and dark (form 1) cells. Efferent synapses were not observed. Thus, the TBs of the spotted dogfish differed in the following ways from those of other vertebrates: (1) the TBs were not located directly on top of the corium papillae; (2) the TBs contained at least three types of elongated cells which reached the epithelial surface; and (3) the TBs did not contain basal cells analogous to those of teleosts and amphibians [1,3,4].

The Chain Dogfish, Scyliorhinus retifer, is known from southwestern Georges Bank in the United States but until now there have been no verifiable records of this shark in Canadian waters. We report on two specimens Georges Bank, Big LaHave Bank, Nova Scotia, that represent the first and second records for the Canadian Atlantic.

The distribution of vasotocin-like peptides in the central nervous system of the cartilaginous fish Scyliorhinus canicula was determined by indirect immunofluorescence and peroxidase anti-peroxidase techniques, using a specific antiserum raised in rabbits against synthetic vasotocin. Immunoreactive perikarya were mainly detected in the anterior hypothalamus, within the midcaudal part of the preoptic nucleus. The most rostral positive cell bodies were located in the dorso-lateral parts of the preoptic area, whereas at a more caudal level, they took a ventro-medial position within the deepest layers of the nucleus. Throughout the preoptic region these cells varied in shape according to their location. Occasionally, scattered vasotocin-like immunopositive cells were also identified in the nucleus periventricularis hypothalami. Vasotocin immunoreactivity was detected in numerous varicose nerve fibers of the preopticohypophysial tract. These fibers were seen to course through the medio-basal hypothalamus and caudally, after having passed the hypophysial stem, they reached the neurointermediate lobe of the pituitary. Numerous immunoreactive fibers were also observed within the rostro-medial region of the median eminence. At this level the fibers were in close proximity to the capillary loops. In the preoptic region, some stained cells exibited short processes that appeared to contact non-reactive perikarya. By comparing the distribution of vasotocin- and corticotropin-releasing factor immunoreactivity on adjacent then serial sections, it was revealed that these peptides, in S. canicula, do not coexist in the same perikarya. The present results, are compared with those obtained in other vertebrate groups, and their possible functional implications are discussed.

1. 1. Testes of the dogfish, Scyliorhinus caniculus , were incubated with [ 3 H]pregnenolone and [ 3 H]testosterone at a range of temperatures from 1 to 36°C. 2. 2. Yields of testosterone from pregnenolone were maximal between 11 and 16°C, corresponding to the breeding temperature of the species. 3. 3. Yields of glucuronides and sulphates increased from 1 to 26°C. 4. 4. Yields of an unidentified polar metabolite increased with temperature and it is suggested that this may play a regulatory role in elasmobranch reproduction.

A peptide fraction has been purified from intestinal extracts of the dogfish Scyliorhinus canicula which is a powerful stimulant of rectal gland secretory activity. This peptide is distinct from elasmobranch vasoactive intestinal polypeptide (VIP). The elasmobranch VIP fraction is not active in the rectal gland assay and mammalian VIP is only an effective agonist in Squalus and not in Scyliorhinus or Raja. Preliminary characterisation of the elasmobranch VIP indicate that it has strong N-terminal similarities with mammalian VIP but has limited C-terminal comparability. It is suggested that the rectal gland stimulating peptide, rectin, rather than VIP is responsible for the control of fluid and electrolyte secretion of elasmobranchs.

As representatives of the vertebrate class of chondrichthyes the plagostomian species Squalus acanthias, Scyliorhinus canicula and Raja clavata as well as the holocephalan species Chimaera monstrosa were investigated for the presence of cardiac hormones of the atrial natriuretic polypeptide/cardiodilatin- (ANP/CDD-) family. ANP/CDD-immunoreactive cells were detected in the atria and the ventricles of all species studied. While these cells failed to react with antisera raised against the N-terminus of CDD-126 (= gamma-ANP) they reacted with all antisera directed against sequences of the C-terminus of CDD-126 (CDD 99-126) which is identical to alpha-ANP. The ANP/CDD-immunoreactive cells were found in high numbers in all regions of the atria and in moderate density also in the ventricles. In correspondence, in the electron microscope, myoendocrine cells which were characterized by dense-cored secretory granules were identified in the atrial and ventricular myocardium. With the use of the protein A-gold technique, ANP/CDD-immunoreactivity was determined within the secretory granules. Furthermore, in the bioassay, prepurified extracts of the atria and the ventricles of Scyliorhinus and Chimaera exerted dose-dependent relaxations of the pre-contracted mammalian (rabbit) aorta. In both cases the atrial extracts proved to be more potent than the ventricular extracts. The present findings indicate that myoendocrine cells occur in the atria and ventricles of chondrichthyes and that these cells contain homologous cardiac hormones of the ANP/CDD-family in their secretory granules. The results are compared with those obtained earlier for the other vertebrate classes and their phylogenetic and functional significance is discussed.

Resume 1. 1. On decrit un essai de localiser trois glycosyl transferases dans les hepatocytes de la roussette ( Scyliorhinus caniculus ), en utilisant le fractionnement cellulaire et la determination par marquage des enzymes. 2. 2. Nous n'avons trouve aucune galactosyltransferase, meme en presence d'un detergent comme le Triton X-100. 3. 3. La N-acetyle glucoseaminyl transferase est entierement localisee dans la fraction microsomique. La methode de Dallner montre que cette enzyme est egalement contenue dans les microsomes lisses et ceux irreguliers. 4. 4. Une activite mannosyl transferase a ete trouvee dans les trois fractions isolees: 18,000 g et 105,000 g sediments et 105,000 g surnageant. 1. 1. An attempt to localize three glucosyl transferases in dogfish ( Scyliorhinus caniculus ) hepatocytes is described, using cellular fractionation and marker enzyme determination. 2. 2. We did not find any galactosyltransferases, even in the presence of a detergent such as Triton X-100. 3. 3. N-Acetyl glucosaminyl transferase is entirely localized in the microsomal fraction. Dallner's method shows that this enzyme is equally contained in rough and smooth microsomes. 4. 4. A mannosyl transferase activity was found in the three fractions isolated: 18,000 g and 105,000 g sediments and 105,000 g supernatant.

The peptidergic nature of most of the fibres of the neurosecretory system of Scyliorhinus caniculus has been demonstrated with the oxidation method of Naumann and Sterba (1976). Some of the fibres of this peptidergic system terminate on capillaries in the hypothalamic floor, some on neurointermediate cells. The evolutionary aspects of these observations are discussed.

A simple radioimmunoassay method for the simultaneous determination of 1α-hydroxycorticosterone, 1-dehydrocorticosterone, corticosterone, and cortisol in small samples of elasmobranch plasma has been developed. Chromatographic separation of these steroids, followed by acid dehydration of 1α-hydroxycorticosterone and chromatography and subsequent radioimmunoassay of the resultant 1-dehydro derivative using an antibody raised for corticosterone, gave a highly specific and sensitive method for the determination of 1α-hydroxycorticosterone. 1α-Hydroxycorticosterone concentrations in the ray Raja clavata ranged from less than 0.08 to 13.9 μg/100 ml of plasma, and in the dogfish Scyliorhinus caniculus from 0.1 to 0.54 μg/100 ml of plasma. This compound was not detected in the rainbow trout Salmo gairdneri . Corticosterone and 1-dehydrocorticosterone were either undetectable or were present in extremely low concentrations in both species of elasmobranch. Cortisol, the major corticosteroid in the rainbow trout (8 μg/100 ml), was not detectable in either of the elasmobranch species.

We have used a combination of gel filtration, ion exchange chromatography and reversed-phase HPLC to isolate and characterize a VIP-related peptide from the gut of the elasmobranch Scyliorhinus canicula. The N-terminal decapeptide of the Scyliorhinus material was identical with that of porcine VIP. However, Scyliorhinus VIP did not cross react with antisera specific for the C-terminus of porcine VIP. Like porcine VIP, Scyliorhinus VIP was a potent stimulant of exocrine pancreatic secretion in the turkey, but the response to Scyliorhinus VIP had a shorter duration. VIP from a second elasmobranch, Squalus acanthius was partially purified, and had biological and immunochemical properties similar to those of Scyliorhinus VIP. The results indicate that elasmobranch VIP is identical to porcine VIP at its N-terminus, but differs at the C-terminus. These structural differences may influence the rate of metabolism of the peptide.

Activities of phosphomonoesterases were measured at acid and at alkaline reaction (pH 4–5 or 9–65) in homogenates of elasmobranch tissues especially lymphomyeloid structures. The animals were dogfish(Scyliorhinus caniculd)and two species of ray(Raja brachyura, R. naevus).Acid phosphatase activity was high in the epigonal tissue, Leydig's organ, the spleen and the thymus. High activity was also found in the pancreas and the kidney, whereas skeletal and cardiac muscle showed low values. The activity of alkaline phosphatase was very high in the kidney and relatively low in other tissues. Ultrasonification of homogenates from the dogfish resulted in increase of acid phosphatase activity but had little effect on alkaline phosphatase activity. The high activity of acid phosphatase in lymphomyeloid tissue may be due to the presence of large numbers of various types of leucocytes.