Taxonomic notes on some advanced Tournaisian (Mississippian) siphonodellids (Conodonta)

Traditionally, biostratigraphy of the terminal Famennian (Upper Devonian) and lower part of the Tournaisian (Mississippian) is based on phylogeny of the conodont genus Siphonodella Branson and Mehl. This study is focused on a Siphonodella species with a long taxonomical history. For the last three decades it was known as S. hassi Ji, 1985 and was used as a zonal index for the eponymic hassi Zone, used worldwide. However, this species faces several taxonomical problems. The main issue is the homonymy of S. hassi and S. cooperi hassi Thompson and Fellows, 1970. However, S. cooperi hassi is a subjective junior synonym of S. obsoleta Hass, 1959. The oldest junior synonym of S. hassi is S. wilberti Bardasheva, Bardashev, Weddige and Ziegler, 2004, and, according to a statement by the International Commission on Zoological Nomenclature, the latter represents the only available name for this species. An additional problem is the similar morphology of early ontogenetic stages of S. wilberti and S. quadruplicata Branson and Mehl, 1944, the youngest stratigraphically important siphonodellid species. In advanced ontogenetic stages, P₁ elements that possess two rostral ridges belong to S. wilberti only. The smaller P₁ elements having two or less rostral ridges comprise the S. wilberti- S. quadruplicata plexus. Maintenance of the wilberti Zone in the Tournaisian global zonation is suggested.     

The fine structure of striated muscles in teleosts

Summary The organization of skeletal and cardiac muscles of fishes described on the basis of observations carried out on several species of freshwater fishes (Tinca tinca, Misgurnus fossilis, Perca fluviatilis, Lebistes reticidatus) and marine fishes (Gobius minutus, Pleuronectes platessa, Ammodytes tobianus). Truncal, subcutaneous, extrinsic eye and cardiac muscles were used for study. Glutaraldehyde-fixed tissue was refixed in OsO₄, embedded in Epon and after polymerization, cut into ultra thin sections and examined by an electron microscope.White and red muscles were distinguished in the material examined. The latter was represented by subcutaneous muscles and small fibres of extrinsic eye muscles. Particular types of fibers differ from each other in their organization of the SR and localization of the T system tubules. In the most muscles the T system tubules are situated at the level of the Z line. In the small fibers of extrinsic eye muscles alone these tubules lie at the A-I junction.The myocardiac cells consist of a cylindrically shaped myofibril. In the middle of the cylinder is the nucleus, the remaining space being filled with numerous mitochondria. A loose sarcoplasmic network is twined around the myofibril.     

AMP-deaminase in elasmobranch fish: a comparative histochemical and enzymatic study

AMP-deaminase activity was measured in white muscle from a wide range of fish, including one cyclostome, 13 chondrosteans, and one teleost to elucidate the pattern of the AMP-deaminase activity in white muscle of fish. Compared to a mammalian (rat) muscle extract, low enzyme activities are found in the cyclostome and two elasmobranchs from two families (Scyliorhinidae, Hexanchidae). In contrast, higher AMP-deaminase activities, similar to mammals, are expressed in Squalidae, all families of skates, Chimaeridae and in the teleostean fish. We then compared AMP-deaminase activities in red and white muscles from two representative elasmobranch fish, the dogfish (Scyliorhinus canicula) and the thornback ray (Raja clavata). The fibre type composition and distribution of the locomotory musculature were determined in these two elasmobranchs to establish a relationship between the morphology, the type of fibres of the locomotion-implicated muscles and the AMP-deaminase activity. Experimental data are discussed with respect to the layout of fibres in the myotome. In both species, three fibre types were identified. In the two fish myotomes, most of the axial muscles are white fibres while red fibres constitute a thin sheet. Some differences were observed between the two species in the distribution of intermediate fibres: in dogfish, these are located between the red and white fibres; in thornback ray, some are dispersed within the white fibre region, while others form an intermediary layer like in dogfish. These results suggest that in the course of evolution, an amplification of the AMP-deaminase activity in muscle was coupled with increase of complexity of the muscular structure.     

Water salinity effects on embryogenesis of the lesser sandeel,Ammodytes tobianus (Linnaeus, 1758)

Effects of water salinity (3.0–9.0 PSU) on the duration and outcome of embryogenesis in the lesser sandeel (Ammodytes tobianus (L.) as well as on survival, size, and malformation rate of the newly hatched larvae were followed, based on observations involving equipment consisting of a microscope and still and digital cameras. The images obtained and measurements of egg and larval dimensions were analyzed using the NIS elements Br. computer software package. The lowest salinity tested (3.0 PSU), similar to that in the inshore Baltic Sea waters native for the species studied, produced a lower fertilization rate and resulted in extended embryogenesis, reduced embryo survival, changes in the hatch size, and increased larval malformation rate. The high-end salinity (7.5–9.0 PSU), higher than that prevailing in the species’s spawning grounds in the Baltic Sea, resulted — similarly to the low-end salinity — in disturbed development and growth of the embryos.     

Distribution and diversity of the Syllidae (Annelida: Polychaeta) from the Mexican Gulf of Mexico and Caribbean

The objective of this study was to contribute to the knowledge of the syllids distributed in the eastern coasts of Mexico (Gulf of Mexico and Caribbean) taking into consideration their composition, distribution and diversity. Sampling was done at 77 stations including 49 in soft bottoms (terrigenous and carbonate sediments), and 28 in hard bottoms (coralline substrates) sampled in nine reef zones included in three reef systems (Veracruz, Campeche and Cozumel). In all 2084 individuals were collected (13.5% in soft sediments and 86.4% in coralline areas). Forty-five species were identified: 31 in soft bottoms and 38 in corals, with 21 species common to both types of environments. In soft bottoms, the highest species richness and diversity were found in the Carbonate Zone, while syllids were uncommon in the Terrigenous Zone. In hard bottoms, the highest density, species richness and diversity values were found in the Veracruz Reef System, followed by the Campeche Bank and Cozumel Island Reef Systems. The dominant species in soft bottoms were Haplosyllis spongicola, Exogone lourei, Typosyllis cornuta and T. papillosus, whereas T. alosae, T. corallicola, T. cornuta and H. spongicola dominated in hard bottoms. The importance and success of the syllids in both soft bottoms and reef environments, particularly in those of the Gulf of Mexico is emphasized.     

Comparative morphology,morphometry and distribution pattern of the trigeminal nerve branches supplying the bill tip in the ostrich (Struthio camelus) and emu (Dromaius novaehollandiae)

The subdivisions of the trigeminal nerve (N. ophthalmicus R. medialis and N. intramandibularis) innervating the upper and lower bill tip, respectively, were well developed in both the ostrich and emu and displayed extensive branching. Transmission electron microscopy revealed that both nerves displayed features typical of a mixed, peripheral nerve. Nerve fibre size in the ostrich and emu was larger than that reported in domestic poultry. There were a significantly higher number of myelinated nerve fibres in the N. ophthalmicus R. medialis in the emu by comparison with the same nerve in the ostrich, or by comparison with the N. intramandibularis of either species. As myelinated nerve fibres supply Herbst corpuscles, and these structures have been demonstrated in this region in these two species, this may indicate that the upper bill of the emu is more sensitive to vibrational stimuli than the upper bill of the ostrich or the lower bill of both species. The large size of the nerve fibres, the high nerve fibre count and the particular distribution of the nerves in the bill tip support the existence of a well‐developed sensory area in this region of the ostrich and emu.     

Are the dynamics of gastric evacuation of natural prey in a piscivorous flatfish different from what is going on in a gadoid?

Despite the fact that the stomach of turbot Psetta maxima is a curved tube that forms a half circle, it was demonstrated that gastric evacuation in this predatory flatfish fed natural prey closely followed the surface‐dependent cylinder model developed from studies on gadoids with a straight stomach. Evacuation experiments were performed on two size groups of P. maxima fed sandeel Ammodytes tobianus as well as on P. maxima fed brown shrimp Crangon crangon at three different temperatures. This enabled the provision of a gastric evacuation model for studies on P. maxima, which takes into account the effects of the explanatory variables predator size, temperature, prey energy density and resistance of prey to the digestive processes in the stomach. Basically, the cylinder model predicts that a square‐root function accurately describes gastric evacuation, which is inconsistent with the conclusion of a previous study on P. maxima that evacuation of A. tobianus is essentially linear with time. Use of the cylinder model to the values of the explanatory variables presented in the latter study, however, gave accurate predictions of the actually acquired evacuation data, which points to the generic value of the model.     

The claw closer muscle of two estuarine crab species,Cyrtograpsus angulatus and Neohelice granulata (Grapsoidea,Varunidae): histochemical fibre type composition

Longo, M.V. and Díaz, A.O. (2011). The claw closer muscle of two estuarine crab species, Cyrtograpsus angulatus and Neohelice granulata (Grapsoidea, Varunidae): histochemical fibre type composition. —Acta Zoologica (Stockholm) 00 : 1–7. This study permitted the characterization of four types of muscle fibres in the claw closer muscles of Cyrtograpsus angulatus and Neohelice granulata. Succinic dehydrogenase (SDH) for mitochondria, periodic acid Schiff (PAS) for glycogen, Sudan Black B for lipids and myosin‐adenosine triphosphatase (m‐ATPase) preincubated at alkaline and acid pHs were used for that purpose. The mean fibre diameters, the relative areas and frequencies of each muscle fibre type were calculated. Types I and IV would be considered ‘extreme’ groups with type I fibres large, weak and acid/alkaline‐labile m‐ATPase, weak SDH, PAS and Sudan, and type IV fibres small, very strong and acid/alkaline‐resistant m‐ATPase, strong SDH and PAS, and moderate Sudan. Types II and III would belong to a predominant ‘intermediate’ group. Type IV fibres were scarce in C. angulatus but represented 25% of the total fibre population in N. granulata. In C. angulatus, the relative area occupied by type I fibres was bigger than its relative proportion, whereas in N. granulata, types I and II had similar patterns. Concluding, variations in fibre type composition in the claw closer muscles of C. angulatus and N. granulata would be linked to different habitats and feeding behaviours.     

Fibre type regionalization of forelimb muscles in two mammalian species, Galea musteloides (Rodentia, Caviidae) and Tupaia belangeri (Scandentia, Tupaiidae), with comments on postnatal myogenesis

To investigate structural differences between propulsory and antigravity muscles, the spatial distribution of slow (type I) and fast (type II) muscle fibres in forelimb muscles of two species of small mammals was studied, Galea musteloides and Tupaia belangeri. Serial sections through complete forelimbs were prepared. Following histochemical fibre typing, the forelimbs were reconstructed three-dimensionally using product design software. Most forelimb muscles of both species showed a homogenous distribution of type I fibres. In the supraspinatus and triceps brachii (capita longum et laterale) muscles, however, a segregation of fibre types into ”fast” superficial areas and ”slow” deep regions was observed. Slow regions contained at least 60% type I fibres and were positioned along intramuscular extensions of the tendons of insertion. The functional implications of fibre type regionalization are discussed. An analysis of intramuscular fibre type distribution during postnatal myogenesis revealed no significant differences in muscle fibre differentiation between altricial and precocial juveniles. Differences in locomotor ability probably arise from heterochronic development of connective tissue components (endo- and perimysium). Accepted: 10 June 1999     

Geographic distribution and environmental control of vertebral count in Ammodytes spp. along the northern Pacific coast of Japan

To examine species composition and population structures in sand lance (Ammodytidae) along the northern Pacific coast of Japan, genetic analysis were carried out for specimens collected in 2014 from Otsuchi Bay, Iwate, Ishinomaki Bay, Miyagi, off Soma, Fukushima and Ise–Mikawa Bays, Aichi. The samples consisted of Ammodytes japonicus and Ammodytes heian, of which the latter is a recently described species. Neither species exhibited significant genetic differences among localities. Only A. japonicus was found in the most southern locality at Aichi, but it decreased northward to <90% in Miyagi and Fukushima and the two species occurred almost evenly in Iwate suggesting a latitudinal cline in their species composition along the northern Pacific coast of Japan, off Tohoku. The vertebral counts differed between A. japonicus and A. heian with modes of 65 and 63, respectively, but this characteristic did not differ significantly within a locality (Iwate). This suggests that the vertebral counts of Ammodytes spp. in Japanese waters are probably strongly determined by the environment than by a species‐specific genetic trait.     

Serotonin-like immunoreactivity in the epidermal club cells of teleost fishes

Summary The present immunocytochemical study concerns the distribution of serotonin in the epidermis of three species of teleost fish. Serotonin-like immunoreactivity was found in the club cells of Heteropneustes fossilis and Carapus acus but not in those from the sea eel Conger conger. This study is the first immunocytochemical identification of serotonin in the club cells of teleost epidermis. By comparing data from the literature (Zaccone et al. 1986, 1987, 1988) regarding the occurrence of serotonin and GRP/bombesin in the exocrine sacciform gland cells of piscine skin, it is worthy mentioning here that the serotonin contained in the club cells of the species studied may have the ability to affect the pheromonal or other possible functions of these cells. The presence of serotonin in these systems has been correlated with the capacity of the exocrine glands of fish skin to secrete, ectopically, amine messengers in contrast to those produced eutopically i.e. in the neuron-paraneuron system in some vertebrates (Fujita et al. 1988).     

New observations on Cucullus Steiner from the Neoproterozoic Doushantuo Formation of Guizhou,South China

Wang, Y & Wang, X. 2011: New observations on Cucullus Steiner from the Neoproterozoic Doushantuo Formation of Guizhou, South China. Lethaia, Vol. 44, pp. 275–286. The Neoproterozoic genus Cucullus is the most abundant and largest organism in the Miaohe biota in China, but has remained poorly understood both in morphology and classification. New material recently obtained from the upper Doushantuo Formation (Ediacaran) of northeastern Guizhou, South China, indicates that Cucullus bears thin organic walls composed of complex spongin fibres forming vertical filaments, which may have given rise to transverse filaments. Filaments, non‐mineralized spongin fibres, which may have served to support body, regularly interweave with each other in a body, and form openings on body sides that may have served as incurrent canals. The top pores may have served as excurrent canals. The overall features, including the organic wall, the complex spongin fibre networks, and the possible canal system of Cucullus, suggest a primitive element of the Demospongea. This benthic organism lived in a low‐energy, calm environment near or below the storm wave‐base with influence of episodic storms. Cucullus’ base nestled into the muddy substrate and its sacciform body floated in seawater. □ Cucullus, Doushantuo Formation, Neoproterozoic, Porifera, South China.     

Embryonic development and larval behavior of the kissing loach (<Emphasis Type="Italic">Parabotia curta</Emphasis>): adaptations to an ephemeral,hypoxic environment

Many teleost fishes in lowland fresh waters spawn in ephemeral flooded areas, the bottoms of which are prone to hypoxia. Little is known about how embryos and larvae deal with these potentially hostile environments. This study examines the functional and behavioral ontogeny of one such species, the kissing loach (Parabotia curta). Kissing loach eggs are demersal and adhesive. Hatching occurs at 24.8 ± 0.1 h post-fertilization at 25°C, much earlier than most fish species. The newly hatched larvae are precocious with no functional mouth, fins or eye pigmentation. Swimbladder inflation normally occurs at about 4 days posthatch, even before which the hatched larvae moved immediately toward the water surface to hang from water moss. Experiments with larvae 20 h after hatching showed that they spent significantly less time on the bottom in hypoxic water (2 mg/l) than in normoxic water, and suggest that hypoxia is a major directive factor in eliciting surfacing behavior. For the kissing loach, we have previously reported short-term spawning after the formation of flood areas as well as wide scattering of the spawned eggs in the temporal flooded areas. These traits with the present results of hatching at an early stage and the immediate upward movement of larvae are considered to be effective strategies for using ephemeral, hypoxic flooded areas for reproduction.     

Development of ovule,embryo sac,and endosperm in Dipterostemon and Dichelostemma (Alliaceae) relative to taxonomy

Dipterostemon capitatus and all species of Dichelostemma have the following characters in common: the ovule is anatropous and bitegmic; the nucellar epidermis is penetrated by the embryo sac; the remaining chalazal part of the nucellus expands, partly due to periclinal divisions in its epidermis; the micropyle is formed by the inner integument only; parietal cells are present; the embryo sac develops according to the Polygonum type; the endosperm is nuclear; after fertilization, the cells of the inner integument enlarge greatly. One difference between the genera is that the inner integument is two cells thick in Dipterostemon, but five to seven cells thick in all Dichelostemma species. In Dipterostemon, embryogenesis is of the Asterad type, and the formation of walls in the endosperm occurs much as in wheat. The absence of variation in embryological characters among the species of Dichelostemma strongly supports the view that these species all belong in one genus, despite differences in gross morphology. Dichelostemma is very closely related to Brodiaea, since species of these two genera show identical embryology. Dipterostemon must be retained as a genus because a deviating inner integument adds to uniqueness in gross morphology. Dipterostemon, Dichelostemma, and Brodiaea, are embryologically quite different from Triteleia. Neither Dipterostemon nor Dichelostemma show any close affinity with Allium.     

Histochemical definition of muscle fibre types in the trunk musculature of a teleost fish (cod,Gadus morhua,L.)

Summary Cryostat sections incubated for myofibrillar ATPase, SDH, LDH, and -GPDH as well as p-phenylene-diamine stained semithin sections were used to define muscle fibre types in the trunk musculature of the cod (Gadus morhua, L.).Three zones (superficial, intermediate, deep) containing different muscle fibre types are present within both epaxial and hypaxial parts of each myomere subjacent to the lateral line.Atypical relations concerning myofibrillar ATPase activity probably reflects instability of myosin during storage of frozen tissue. The histochemical reaction does not distinguish between myofibrillar and mitochondrial ATPase in cod muscle.Based on ATPase and SDH activities, seven different histochemical profiles of muscle fibres can be identified in trunk musculature of this teleost fish. Attempts to homologize these fibre types with those in cyclostomes or those in higher animals proved futile. The higher number of histochemically defined muscle fibre types in cod might be explained by developmental processes and an admixture of immature fibres throughout life.     

Muscle fibre types and size distribution in sub-antarctic notothenioid fishes

The presumptive tonic muscles fibres of Cottoperca gobio, Champsocephalus esox, Harpagifer bispinis, Eleginops maclovinus, Patagontothen tessellata, P. cornucola and Paranotothenia magellanica stained weakly or were unstained for glycogen, lipid, succinic dehydrogenase (SDHase) and myosin ATPase (mATPase) activity. Slow, intermediate and fast twitch muscle fibres, distinguished on the basis of the pH stability of their mATPases, showed intense, moderate and low staining activity for SDHase, respectively. Slow fibres were the major component of the pectoral fin adductor profundis muscle. The proportion of different muscle fibre types varied from the proximal to distal end of the muscle, but showed relatively little variation between species. The myotomes contained a lateral superficial strip of red muscle composed of presumptive tonic, slow twitch and intermediate fibres, thickening to a major wedge at the horizontal septum. All species also had characteristic secondary dorsal and ventral wedges of red muscle. The relative abundance and localization of muscle fibre types in the red muscle varied between species and with body size in the protandric hermaphrodite E. maclovinus. The frequency distribution of diameters for fast twitch muscle fibres, the major component of deep white muscle, was determined in fish of a range of body sizes. The absence of fibres <20 μm diameter was used as a criterion for the cessation of muscle fibre recruitment. Fibre recruitment had stopped in P. tessellata of 13·8 cm L_T and E. maclovinus of 32·8 cm L_T, equivalent to 49 and 36·5% of their recorded maximum sizes respectively. As a result in 20‐cm P. tessellata, the maximum fibre diameter was 300 μm and 36% of fibres were in excess of 200 μm. The unusually large maximum fibre diameter, the general arrangement of the red muscle layer and the extreme pH lability of the mATPase of fast twitch fibres are all common characters of the sub‐Antarctic and Antarctic Notothenioids, including Cottoperca gobio, the suggested sister group to the Notothenidae.     

Inter- and intraspecies comparisons of fibre type distribution and of succinate dehydrogenase activity in type I,IIA and IIB fibres of mammalian diaphragms

Summary Fibre types in the costal region of the diaphragm muscle of several mammalian species with widely different respiratory rates were examined microphotometrically for succinate dehydrogenase (SDH) activity. Mean activities indicated no significant (p>0.05) difference between the type I and IIA fibres for any of the species examined. SDH activities in type IIB fibres were significantly lower (p<0.05) than either the type I or type IIA fibres in the cat, guinea pig, rat and rabbit whereas in the mouse no difference was found. The dog had no classical type 1B fibres. Analysis of the distribution of SDH activities by fibre type indicated a wide scattering of scores with no distinct separation between fibre types. Large differences in SDH activity were noted between species. Mean SDH activities were highest in the mouse and rat, intermediate in the rabbit and guinea pig and lowest in the cat and dog. These data suggest an association between respiratory rate and aerobic oxidative potential of the various fibre types in diaphragms of the species examined.     

The fine structure of red and white myotomal muscle fibres of the coalfish (Gadus virens)

Summary The fine structure of the red and white myotomal muscles of a marine teleost, the coalfish Gadus virens, has been examined and ultrastructural measurements and analyses carried out. The sarcomere lengths of the red and white fibres were found to be 1.60 minimum, 1.82 maximum and 1.70 minimum, 1.85 maximum, respectively. No significant difference was found between the red and white fibres in their percentage of sarcoplasmic reticulum and T system. Both were found to have regularly occurring triads at the Z disk level, to have distinctive M lines and to be multiply innervated. Ultrastructurally the two fibres can be distinguished by the thicker Z line and more abundant mitochondria of the red fibre, and by the ribbon-shaped peripheral myofibrils of the white fibres. The structure of the fibres in these two types of muscle is discussed in relation to their possible role in swimming.This work was supported by a research grant from the National Environmental Research Council.     

The macrofauna of a stony sand area in the German Bight (North Sea)

The sublittoral macrofauna of the Steingrund, a stony area east-northeast of Helgoland, was investigated from May till October 1991 using a van Veen grab and a small dredge. The diverse endo- and epifauna of the sandy bottoms, pebbles and boulders of this Saalian end moraine comprised 289 taxa, whereby the polychaetesMagelona papillicornis, Lanice conchilega andSpiophanes bombyx dominated in terms of abundance. Species rare in the German Bight, such as the spongeLeucandra fistulosa, the sea urchinEchinus esculentus, and the sea anemoneHaliplanella lineata, were also found. The two sample sets were processed separately with multivariate techniques, and differentiated on the basis of occurrence and numbers of the abundant species. The analysis of the grab samples revealed two types of theTellina-fabula-community. These associations were differentiated by the presence of species of the coarse-sand-inhabitingGoniadella-Spisula-community and were related to the distribution of the grain size of the sediment. Likewise, two epifaunal assemblages were distinguished. Sandy bottoms were characterized byOphiura albida, Liocarcinus holsatus andPagurus bernhardus, while boulders and pebbles were covered by a varied sessile and mobile epifauna dominated by the sessile bryozoanFlustra foliacea and the mobile pantopodeAechelia echinata. Numerical density, biomass and annual production estimates are in the range of values determined for the macrobenthos of the German Bight, while annual P/B ratios mounted up to 5.     

Muscle differentiation in blackspot seabream (Pagellus bogaraveo, Brunnich): histochemical and immunohistochemical study of the fibre types

The aim of this work was to gain insights into the mechanism of muscle differentiation and growth in Pagellus bogaraveo, by studying muscle fibre phenotypes identified by immunohistochemistry. At hatching, several layers of deep fast-white fibres were covered by a superficial fibre monolayer. At 5 days, slow-red fibres appeared near the lateral line nerve. At 40 days, the intermediate-pink muscle became visible, and in the slow-red and fast-white muscle layers transitions from larval myosin isoforms to the isoforms typical of adult muscle occurred. Between 70 and 100 days, small fibres with a distinct ATPase profile appeared throughout the fast-white muscle, marking the onset of “mosaic” hyperplasia. The myosin of the original superficial monolayer fibres underwent two myosin transformations, before being slowly replaced by an adult slow-red isoform. In juveniles and adults, the slow-red muscle layer could be resolved into two distinct types. The analysis of fibre phenotypes indicated that post-larval muscle growth occurred by two distinct stages of hyperplasia. This study offers a basis for further comparative and experimental studies with this economically relevant species, namely for identifying factors influencing its muscle growth dynamics and disclosing underlying mechanisms.