A radical approach to beating hypoxia: depressed free radical release from heart fibres of the hypoxia-tolerant epaulette shark (<Emphasis Type="Italic">Hemiscyllum ocellatum</Emphasis>)

Hypoxia and warm ischemia are primary concerns in ischemic heart disease and transplant and trauma. Hypoxia impacts tissue ATP supply and can induce mitochondrial dysfunction that elevates reactive species release. The epaulette shark, Hemiscyllum ocellatum, is remarkably tolerant of severe hypoxia at temperatures up to 34°C, and therefore provides a valuable model to study warm hypoxia tolerance. Mitochondrial function was tested in saponin permeabilised ventricle fibres using high-resolution respirometry coupled with purpose-built fluorospectrometers. Ventricular mitochondrial function, stability and reactive species production of the epaulette shark was compared with that of the hypoxia-sensitive shovelnose ray, Aptychotrema rostrata. Fibres were prepared from each species acclimated to normoxic water conditions, or following a 2 h, acute hypoxic exposure at levels representing 40% of each species’ critical oxygen tension. Although mitochondrial respiratory fluxes for normoxia-acclimated animals were similar for both species, reactive species production in the epaulette shark was approximately half that of the shovelnose ray under normoxic conditions, even when normalised to tissue oxidative phosphorylation flux. The hypoxia-sensitive shovelnose ray halved oxidative phosphorylation flux and cytochrome c oxidase flux was depressed by 34% following hypoxic stress. In contrast, oxidative phosphorylation flux of the epaulette shark ventricular fibres isolated from acute hypoxia exposed the animals remained similar to those from normoxia-acclimated animals. However, uncoupling of respiration revealed depressed electron transport systems in both species following hypoxia exposure. Overall, the epaulette shark ventricular mitochondria showed greater oxidative phosphorylation stability and lower reactive species outputs with hypoxic exposure, and this may protect cardiac bioenergetic function in hypoxic tropical waters.     

The Structure of the Gular Pouch of Mature Males of the Lamprey Geotria australis

Males of the southern hemisphere lamprey Geotria australis develop a large gular pouch during sexual maturation. The wall of this pouch contains (I) an epidermis comprising typical lamprey epidermal cells, (II) a thick dermis consisting of layers of collagen fibres, with intervening oxytalan fibres, and a vascular network, and (III) a hypodermis. The hypodermis contains active fibroblasts embedded in an extracellular matrix, comprising collagen fibrils, some of which form dense bundles, together with oxytalan fibres and an amorphous material that contains glycosaminoglycans. The hypodermis also contains arteries, which are innervated and confluent with a large anastomosing system of sinuses. Since these sinuses open at intervals into the large central cavity of the pouch, it is proposed that, at maturity, they discharge blood into the central lumen of the pouch, thereby causing the pouch to become distended. The degree of such distension would be regulated by the limited elasticity of the dermal collagen fibres. The dermis is thickest in those regions where the pouch is most susceptible to abrasion. The Weibel–Palade bodies, which are abundant in the sinus endothelia, may facilitate tissue repair where neccessary. The gular pouch is thus a specialised structure, which may play a role in courtship or the spawning act.     

The fine structure of the light organ of the glowworm Lampyris noctiluca

Summary The four main parts of the glowworm light organ are the cuticle, the hypodermis, the photocyte layer and the reflector cell layer. The hypodermis is one cell thick and it contains hypodermic glands. These glandular cells have a lumen that opens to the outside of the cuticle. Projecting into the lumen are numerous microvilli. Between the hypodermis and photocytes are typical insect tunicated nerve fibres. They pass down between the photocyte and reflector layer cells. They do not appear to innervate the photocytes and they are thought to innervate adjacent muscle fibres or to be sensory. Tracheoles are commonly present between the photocytes but no tracheolar end organs are found. The photocytes contain amorphous granules, mitochondria, photocyte granules and a vesiculated reticulum. All, except the mitochondria, are absent from the reflector layer and so probably have some connection with light production. The reflector layer contains glycogen granules, clear spaces thought to be the sites of urate crystals, and membranous granules. The latter granules are sometimes found in photocytes adjacent to the reflector layer whilst amorphous granules are sometimes absent from these adjacent cells. So a cell layer with some features of the photocyte and reflector layer cells is present. These morphological findings are discussed with regard to the unknown function of the reflector layer and the control of light emission. Acknowledgments. We would like to thank Professor J. Z. Young and Dr. E. G. Gray for their advice and encouragement, Mrs. Jane, Astafiev for drawing fig. 1, Mr. S. Waterman for photographic assistance, Miss Cheryl Martin for secretarial assistance, and many colleagues for help in collecting specimens of glowworms.     

应用脂肪酸组成研究热带东太平洋同域中上层鲨鱼营养生态位分化

物种对食物资源利用方式的差异,即营养生态位分化是物种共存的先决条件之一,对种间营养生态位的比较研究有助于了解同域分布物种的共存机制。脂肪酸组成可反映生物较长时间尺度的摄食信息,对探讨物种间营养生态位分化具有重要指示作用。热带东太平洋主要栖息有8种大型中上层鲨鱼,大青鲨(Prionace glauca)、大眼长尾鲨(Alopias superciliosus)、镰状真鲨(Carcharhinus falciformis)、长鳍真鲨(Carcharhinus longimanus)、浅海长尾鲨(Alopias pelagicus)、尖吻鲭鲨(Isurus oxyrinchus)、路氏双髻鲨(Sphyrna lewini)和锤头双髻鲨(Sphyrna zygaena),通过比较其肌肉脂肪酸组成,分析种间食性差异,营养关系及营养生态位分化。结果表明,尖吻鲭鲨营养级相对较高,大青鲨相对较低。3种鼠鲨与5种真鲨存在食性差异或栖息地隔离。浅海长尾鲨与大眼长尾鲨营养生态位重叠程度较高,存在激烈的资源竞争。大青鲨与镰状真鲨生态位宽度较大,表征其对环境的可塑性较强;尖吻鲭鲨和路氏双髻鲨生态位宽度较小,表现为其食性的特化。本研究解释了脂肪酸组成分析在鲨鱼摄食研究中的潜在应用,对分析大洋性鲨鱼的营养生态位分化,资源分配方式及同域共存机制有一定的应用价值。     

Monoamine storage in relation to cardiac regulation in the port jackson shark heterodontus portusjacksoni

Summary A study has been made of catecholamine stores that may be involved in cardiac regulation in the shark Heterodontus portusjacksoni. The anatomy of the anterior chromaffin bodies associated with the sympathetic chain is described. A fluoresent histochemical study shows that the chromaffin cells contain a monoamine, probably noradrenaline. The chromaffin cells have a fine structure comparable to that of chromaffin cells in other vertebrates. The heart is devoid of histochemically-demonstrable chromaffin cells or adrenergic nerve fibres, with the exception of a very sparse adrenergic innervation of the sinus venosus. It is argued that adrenergic control of the heart in Heterodontus might occur via amines released from the anterior chromaffin masses into the blood in the posterior cardinal sinus, which is then aspirated directly into the heart.     

Morphological and anatomical factors responsible for varied susceptibility of some species of spruce to infestation by spruce spider mie (Oligonychus ununguis Jacobi)

Differences in susceptibility to infestation by spruce spider mite of 3 investigated spruce species (Picea glauca ‘Conica’, P. pungens and P. omorika) may be due to features of anatomical and morphological structure of needles. In P. omorika, showing some resistance to the spruce spider mite, we noted lamellar structure of epidermal cell walls and extensive supporting tissues (hypodermis and sclerenchyma fibres) at the whole circumference of the needle.     

Studies on the ultrastructure of the integument of the rotifer Habrotrocha rosa Donner (Aschelminthes)

Summary The integument of the rotifer Habrotrocha rosa Donner is provided with pores and formed by an extrasyncytial cuticle and a syncytial hypodermis. The hypodermis peripherally contains 3 layers of dense cytoplasm and borders the cuticle by an asymmetric cell membrane. The wall of the pores is stiffened proximally like an annulus. The pores lead into cytoplasmic invaginations which are surrounded by vesicles. Close to and also beneath the condensed cytoplasmic layers microbodies are found, which are interpreted as microperoxisomes. Subhypodermal layers of muscles are connected with the cytoplasm of the hypodermis by desmosome-like structures.I am indebted to Dr. H. Breucker, Anatomisches Institut Hamburg, and Prof. Dr. W. Becker, Zoologisches Institut Hamburg, under whose direction this work was carried out. Supported by the Deutsche Forschungsgemeinschaft (Be 464/10)     

Resource-use dynamics of co-occurring chondrichthyans from the First Coast,North Florida,USA

Recent studies on shark assemblages on the northeast Florida and southeast Georgia coast (hereafter referred to collectively as the “First Coast”) have demonstrated differences in species and age-class composition of catch from previously characterized estuaries and newly surveyed area beaches, demonstrating that these regions may provide a critical habitat to different segments (i.e., life stages) of local shark populations. In this study, carbon and nitrogen stable isotopes (δ¹³C and δ¹⁵N) from muscle tissue and blood plasma were used to examine trophic dynamics (and temporal variability thereof) of the three dominant co-occurring species found along First Coast beaches (the Atlantic Sharpnose shark Rhizoprionodon terraenovae, Blacknose shark Carcharhinus acronotus and Blacktip shark Carcharhinus limbatus) to determine if they exhibit overlap in resource use along with spatial and temporal habitat use. Although considered spatially segregated from the beach species, a dominant, age-class species found in First Coast estuaries (juvenile Sandbar sharks Carcharhinus plumbeus) was also included in this analysis for comparison. Temporal variability of resource-use characteristics was detected at the species level. Resource-use overlap among species varied by tissue type and was generally higher for blood plasma, suggesting greater resource sharing over more recent time periods. Over longer time periods Atlantic Sharpnose and Blacktip sharks exhibited resource-use expansion, whereas Blacknose sharks exhibited a narrowing in resource use, suggesting a more specialized foraging strategy compared to the other species. The resource-use breadth of Sandbar sharks also expanded between blood plasma and muscle tissue. Significant size relationships were detected in Blacktip and Sandbar sharks, indicating ontogenetic resource shifts for both species. A diversity of highly productive resource pools likely support shark populations along the First Coast such that resource-use differentiation is not required to facilitate species co-occurrence. This work may shed light on understanding patterns of species co-occurrence as well as aid in future conservation efforts.     

Diet of the milk shark,Rhizoprionodon acutus (Rüppel, 1837) (Chondrichthyes: Carcharhinidae), from the Senegalese coast

The diet of the milk shark, Rhizoprionodon acutus, from the Senegalese coast (12°30′N–14°45′N) was investigated in 3600 specimens with total lengths ranging from 44 to 113 cm for females and from 45 to 110 cm for males. Conducted from May 2010 to April 2011, the study revealed that of the 3600 stomachs examined, 577 contained food (16.03%). Cumulative prey diversity curves reached a stable level at 175 stomachs and thus the sample size was large enough to describe the overall milk shark diet. Relevant differences in the diet were found between sexes, maturity stages, sampling seasons and locations. The milk shark diet was composed of teleosts, crustaceans, mollucs, nematodes, annelids, and unidentified invertebrates. R. acutus seemed to have a preference for teleosts (98.75% in terms of IRI). The trophic level of milk shark calculated in this study was 4.2.     

Metazoan parasite communities and diet of the velvet belly lantern shark Etmopterus spinax (Squaliformes: Etmopteridae): a comparison of two deep‐sea ecosystems

By combining an examination of stomach contents yielding a snapshot of the most recent trophic niche and the structure of parasite communities reflecting a long‐term feeding niche, this study aimed at gaining more comprehensive information on the role of the small‐sized deep‐water velvet belly lantern shark Etmopterus spinax in the local food webs of the Galicia Bank and the canyon and valley system of the Avilés Canyon, which have been both proposed for inclusion in the Natura 2000 network of protected areas. As far as is known, this study provides the first comparative parasite infracommunity data for a deep‐sea shark species. Component parasite communities in E. spinax were relatively rich, whereas the infracommunities were rather depauperate, with similar low diversity at both localities. The significant differences in the composition and structure of both parasite communities and prey assemblages indicate differential effects of the two deep‐sea ecosystems on both long‐term and most recent trophic niches of E. spinax. These results underline the importance of the use of multivariate analyses for the assessment of geographical variation in shark populations based on parasites and diet data.     

Ontogenetic changes in the diet of the sandbar shark, <Emphasis Type="Italic">Carcharhinus plumbeus</Emphasis>, in lower Chesapeake Bay and Virginia (USA) coastal waters

This study describes the diet of the sandbar shark, Carcharhinus plumbeus, highlighting differences in diet within various regions of the Virginia (USA) nursery area, as well as ontogenetic changes in diet. Stomach samples were obtained in 2001 and 2002 from 232 sharks caught by gillnets or longlines. Historical data from the Virginia Institute of Marine Science (VIMS) Shark Ecology Program were also analyzed. Ontogenetic changes in diet were evident, with crustacean prey decreasing in frequency with increasing shark size, and elasmobranch prey importance increasing with increasing shark size. Whereas previous research in Chincoteague Bay, VA showed the blue crab, Callinectes sapidus, was the dominant crustacean in sandbar shark diet, the mantis shrimp, Squilla empusa, dominated the crustacean portion of the diet in this study. Differences in diet of sharks were observed among locations within the study area. Small juveniles (≤80 cm precaudal length) in the lower Chesapeake Bay ate more fishes, whereas Eastern Shore juveniles ate more crustaceans. Crustacean prey items varied among locations along the Eastern Shore, with more portunid crabs consumed in waters near Wachapreague and more mantis shrimp consumed near Sand Shoal Inlet. Our study showed that Carcharhinus plumbeus is a generalist predator and is thus unlikely to strongly impact the population of any particular prey species, and in turn is not likely to be strongly affected by fluctuations in abundance of a single prey species.     

Long‐term sperm storage in the brownbanded bamboo shark Chiloscyllium punctatum

This study investigated the birth of a brownbanded bamboo shark Chiloscyllium punctatum at the Steinhart Aquarium. Genetic analyses suggest this is the longest documented case of sperm storage for any species of shark (45 months).     

The structure of immunoglobulin variable regions in the horned shark,Heterodontus francisci

The heavy and light chains of pooled antibodies of the hybodont shark,Heterodontus francisci (horned shark), were subjected to amino acid sequence analysis. Yield determinations showed that more than 90% of the available polypeptides in the respective pools were sequenced. The heavy chains were homogeneous in the initial framework segment and showed a sequence homology of approximately 70% with the corresponding region of the more recently evolved nurse shark and a 45% homology with a human myeloma heavy chain. The light chains were less homogeneous and not identifiable as either kappa or lambda chains as known in higher species. The first half-cystine characteristics of the variable domain intrachain disulfide bridge of immunoglobulins was present in the same position (22 for heavy chains; 23 for light chains) in the horned shark as in mammalian species. The sequence analysis also suggested the presence of a hypervariable region in the horned shark light chains. The combined data imply that the antigen-binding function of immunoglobulins is mediated in much the same manner in this primitive shark as in more recently evolved species, including mammals.     

Food capture kinematics of the suction feeding horn shark, Heterodontus francisci

The goal of this study was to examine the feeding kinematics of the horn shark, Heterodontus francisci, a member of the most basal clade of galeomorph sharks, the Heterodontiformes. The accessibility of the food was manipulated to determine if the horn shark modulated capture. Three different methods of presenting food were used to mimic the different positions of prey items found in the natural diet of the horn shark. Food was presented unattached to the substrate, securely attached, or fitted snugly in a tube. Using high-speed video kinematic analysis, capture events were examined. Heterodontus francisci uses inertial suction facilitated by rapid mandible depression and labial cartilage protrusion to capture food. The horn shark conforms to a capture kinematic profile characteristic of both basal and derived inertial suction feeding sharks. Unusual post-capture behaviors include body leveraging, use of the mouth to form a seal over food, and chisel-like palatoquadrate protrusion. When presented with food of different accessibility, Heterodontus francisci used one consistent kinematic pattern for capture that was not modulated. Only post-capture behaviors varied according to food accessibility.     

Assessment of multiple paternity in single litters from three species of carcharhinid sharks in Hawaii

We tested for presence or absence of multiple paternity in single litters from each of three congeneric shark species in Hawaii: the sandbar shark, Carcharhinus plumbeus, bignose shark, Carcharhinus altimus, and Galapagos shark, Carcharhinus galapagensis. Based on eight polymorphic microsatellite loci, we excluded paternity by a single sire in sandbar and bignose sharks, but could not exclude a single sire for the litter from the Galapagos shark. This study doubles the number of shark species tested for multiple paternity, and is the first demonstration of multiple paternity in sandbar and bignose sharks.     

Virtual reconstruction of the skeletal labyrinth of two lamnid sharks (Elasmobranchii,Lamniformes)

The first virtual reconstruction of the skeletal labyrinth of the porbeagle shark Lamna nasus and the shortfin mako shark Isurus oxyrinchus is presented here using high‐resolution micro‐computed tomography. The results, in comparison with previously published information, suggest relationships between skeletal labyrinth morphology and locomotion mode in chondrichthyans, but also show that further studies are required to establish such connections. Nevertheless, this study adds to the knowledge of the skeletal labyrinth morphology in two apex elasmobranch species.     

Diet,trophic interactions and possible ecological role of commercial sharks and batoids in northern Peruvian waters

The Peruvian sea represents one of the most productive ocean ecosystems and possesses one of the largest elasmobranch fisheries in the Pacific Ocean. Ecosystem-based management of these fisheries will require information on the trophic ecology of elasmobranchs. This study aimed to understand the diet, trophic interactions and the role of nine commercial elasmobranch species in northern Peru through the analysis of stomach contents. A total of 865 non-empty stomachs were analysed. Off northern Peru, elasmobranchs function as upper-trophic-level species consuming 78 prey items, predominantly teleosts and cephalopods. Two distinctive trophic assemblages were identified: (a) sharks (smooth hammerhead shark Sphyrna zygaena, thresher shark Alopias spp. and blue shark Prionace glauca) that feed mainly on cephalopods in the pelagic ecosystem; and (b) sharks and batoids (Chilean eagle ray Myliobatis chilensis, humpback smooth-hound Mustelus whitneyi, spotted houndshark Triakis maculata, Pacific guitarfish Pseudobatos planiceps, copper shark Carcharhinus brachyurus and school shark Galeorhinus galeus) that feed mainly on teleosts and invertebrates in the benthonic and pelagic coastal ecosystem. This study reveals for the first time the diet of T. maculata and the importance of elasmobranchs as predators of abundant and commercial species (i.e., jumbo squid Dosidicus gigas and Peruvian anchovy Engraulis ringens). The results of this study can assist in the design of an ecosystem-based management for the northern Peruvian sea and the conservation of these highly exploited, threatened or poorly understood group of predators in one of the most productive marine ecosystems.     

Epifluorescent and histochemical aspects of shoot anatomy of Typha latifolia L., Typha angustifolia L. and Typha glauca Godr

Using epifluorescent and histochemical techniques, we examined anatomical differences in the shoot organs of Typha latifolia, T. angustifolia and T. glauca. The leaf lamina of T. latifolia and T. glauca had enlarged epidermal cells and a thickened cuticle above the subepidermal vascular bundles; that of T. angustifolia lacked these characteristics. Leaf sheaths were similar among the species and all lacked the epidermal thickenings found in the lamina. The fertile stems had typical scattered vascular bundles with a band of fibres that was most prominent in T. glauca. The sterile stems were only 1 cm in length and contained a multiseriate hypodermis and a uniseriate endodermis over part of their length. The rhizomes were similar except for a pronounced band of fibres surrounding the central core in T. angustifolia. The rhizome was also characterized by an outer cortical region with a large multiseriate hypodermis/exodermis and a uniseriate endodermis with Casparian bands, suberin lamellae and secondarily thickened walls.     

In the Water with White Sharks (Carcharodon carcharias): Participants’ Beliefs toward Cage-diving in Australia

White shark (Carcharodon carcharias) cage-diving tourism is a controversial activity that provokes emotional and often opposing points of view. With increasing demand for shark tourism since the 1990s, the un- derlying determinants driving this growth in participation remain unclear. This paper adopts a qualitative approach to investigate beliefs underlying tourists’ choice to observe white sharks while cage-diving at the Neptune Islands, South Australia. Elicitation surveys gathered responses from a sample (n = 86) of cage-diving participants. Content analysis of the responses revealed the decision to cage-dive with white sharks is driven by factors including education and the perceived naturalness of the experience. The findings of this study indicate an opportunity for cage-dive operators to pro- vide in situ education and interpretation with potential for increased tourist satisfaction and shark conservation outcomes.     

Structure and Variation in the Sarcotubular System of the Extraocular Muscle Fibres in the Shark Scyliorhinus canicula L.

The microscopic anatomy of the extraocular eye muscles of the shark Scyliorhinus canicula is described. In contrast to swimming muscles, the fibres are not differentiated into distinct fibre type groups. The sarcoplasmic reticulum has narrow terminal cisternae in the Z band region, longitudinal tubules and a fenestrated cisterna in the H band region. Triads or dyads are mostly located at the Z discs. A number of variations from this general pattern is described, with main emphasis on triad location, orientation and structure. Since triads in vertebrates usually are located either at the Z disc or at the A-I junction, and with a fixed structure, these variations in shark muscles are of phylogenetic interest, as they may provide basis for an explanation of development to the two different triad locations.