Cephaloscyllium Ventriosum Research Articles

Nanolatticed Architecture Mitigates Damage in Shark Egg Cases.

Structural versatility and multifunctionality of biological materials have resulted in countless bioinspired strategies seeking to emulate the properties of nature. The nanostructured egg case of swell sharks is one of the toughest permeable membranes known and, thus, presents itself as a model system for materials where the conflicting properties, strength and porosity, are desirable. The egg case possesses an intricately ordered structure that is designed to protect delicate embryos from the external environment while enabling respiratory and metabolic exchange, achieving a tactical balance between conflicting properties. Herein, structural analyses revealed an enabling nanolattice architecture that constitutes a Bouligand-like nanoribbon hierarchical assembly. Three distinct hierarchical architectural adaptations enhance egg case survival: Bouligand-like organization for in-plane isotropic reinforcement, noncylindrical nanoribbons maximizing interfacial stress distribution, and highly ordered nanolattices enabling permeability and lattice-governed toughening mechanisms. These discoveries provide fundamental insights for the improvement of multifunctional membranes, fiber-reinforced soft composites, and mechanical metamaterials.

Reproductive biology of the swell shark Cephaloscyllium ventriosum (Carcharhiniformes: Scyliorhinidae).

The Cephaloscyllium ventriosum shark is present in the artisanal fisheries of elasmobranchs on the western coast of Baja California Sur, Mexico. The main characteristics of the sexual maturation of this species based on individuals captured from off north-west Mexico in 2013-2016 are described. The size at maturity of this species was determined for the first time (total length 82 cm for females and 76 cm for males). Most females had one egg case per one uterus, and two per one uterus was an isolated event of low incidence. From the histological analysis of females, it was possible to show sperm storage in the oviducal gland. Fully developed sperm in immature organisms were identified in the testes. The main indicator of the maturity stage of males and their mating activity is the clasper. The present study provides evidence for a reliable estimation of the sexual maturity of these organisms, demonstrating the need for the combination of macroscopic and microscopic methods.

Stop the global slaughter of sharks

The unsustainable slaughter of millions of sharks for their fins continues unabated even in EU waters, threatening the survival of several species. Meanwhile, new discoveries about the ecology of the top predators illustrate how much we still have to learn about the life we are about to destroy. Michael Gross reports.

Uncovering the molecules behind fishy fluorescence

When a fluorescent eel photobombed David Gruber’s film of fluorescent corals, the Baruch College marine biologist realized that undersea fluorescence might be more common than he thought. The more he looked, the more examples he found, including swell sharks and chain catsharks. He asked Yale University chemist Jason Crawford—a fellow lover of the mysteries of the deep—to help work out how these sharks glow. The team compared fluorescent and nonfluorescent skin from both shark species to find the source of the fluorescence: brominated tryptophan-kynurenine metabolites including 8-bromo-kynurenine yellow. These small molecules are produced through a pathway that also makes antibiotic compounds (iScience 2019, DOI:10.1016/j.isci.2019.07.019). “We didn’t actually know what kind of molecules to detect up front,” Crawford says. “But as a small-molecule-metabolism lab, we were delighted that they were small molecules.” Siouxsie Wiles of the University of Auckland says new fluorescent molecules are always fascin...

Quantifying fish behaviour and commercial catch rates in relation to a marine seismic survey

The impact of seismic surveys on the catchability of marine fish is a contentious issue, with some claims that seismic surveys may negatively affect catch rates. However little empirical evidence exists to quantify the impacts or identify the mechanisms of such impact. In this study, we used a 2-D seismic survey in the Gippsland Basin, Bass Strait, Australia in April 2015 as an opportunity to quantify fish behaviour (field-based) and commercial fisheries catch (desktop study) across the region before and after airgun operations. Three species found in abundance (gummy shark, swell shark, tiger flathead) were acoustically tagged and released within one of two acoustic arrays (experimental and control zone) and monitored before, during and after the seismic survey. In the field study, only 35% of the gummy sharks and 30% of the swell sharks were subsequently detected two days after release, suggesting movement outside the study area. Various tagged individuals returned sporadically over the monitoring period, including during the seismic survey operations. Behaviour consistent with a possible response to the seismic survey operations was observed for flathead which increased their swimming speed during the seismic survey period and changed their diel movement patterns after the survey. We also investigated the potential impacts of the seismic survey on catch rates using Commonwealth fisheries logbook data from Jan 2012–Oct 2015. Fifteen species and two gear types (Danish seine, gillnet) were modelled to examine differences in catch rates before and after the seismic survey. The catch rates in the six months following the seismic survey were significantly different than predicted in nine out of the 15 species examined, with six species (tiger flathead, goatfish, elephantfish, boarfish, broadnose shark and school shark) showing increases in catch following the seismic survey, and three species (gummy shark, red gurnard, and sawshark) showing reductions. With the exception of flathead movement, we found little evidence for consistent behavioural or catch rate changes induced by the seismic survey in the targeted species, although behavioural data were limited because many sharks left the acoustic receiver array prior to the commencement of the seismic survey.

Some Galeomorph Sharks Express a Mammalian Microglia-Specific Protein in Radial Ependymoglia of the Telencephalon

Ionized calcium-binding adapter molecule 1 (Iba1), also known as allograft inflammatory factor 1 (AIF-1), is a highly conserved cytoplasmic scaffold protein. Studies strongly suggest that Iba1 is associated with immune-like reactions in all Metazoa. In the mammalian brain, it is abundantly expressed in microglial cells and is used as a reliable marker for this cell type. The present study used multiple-label microscopy and Western blotting to examine Iba1 expression in the telencephalon of 2 galeomorph shark species, the swellshark (Cephaloscyllium ventriosum) and the horn shark (Heterodontus francisci), a member of an ancient extant order. In the swellshark, high Iba1 expression was found in radial ependymoglial cells, many of which also expressed glial fibrillary acidic protein. Iba1 expression was absent from most cells in the horn shark (with the possible exception of perivascular cells). The difference in Iba1 expression between the species was supported by protein analysis. These results suggest that radial ependymoglia of the elasmobranchs may be functionally related to mammalian microglia and that Iba1 expression has undergone evolutionary changes in this cartilaginous group.

Multiple births by a captive swellshark Cephaloscyllium ventriosum via facultative parthenogenesis.

Using a novel set of 12 microsatellites, a captive, adult female swellshark Cephaloscyllium ventriosum that produced five pups via parthenogenesis is described; naturally occurring parthenogenesis has been observed in every vertebrate class with the exception of mammals. As demonstrated in this study, a captive environment is ideal for long-term monitoring of animals under controlled conditions, and easily allows the detection of particular facets of their biology.

Biofluorescence in Catsharks (Scyliorhinidae): Fundamental Description and Relevance for Elasmobranch Visual Ecology.

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.

Complete mitochondrial genome and the phylogenetic position of the Blotchy swell shark Cephaloscyllium umbratile

In this study, the complete mitochondrial genome of the Blotchy swell shark Cephaloscyllium umbratile was determined. It was a circle molecular (16 698 bp), contained 37 genes with typical order to that of most other vertebrates. The nucleotide composition was 31.0% A, 24.0% C, 14.0% G, and 31.3% T. There were 26 bp short intergenic spaces located in 11 gene junctions and 28 bp overlaps located in 7 gene junctions in the whole mitogenome. Two start codons (GTG and ATG) and two stop codons (TAG and TAA/T) were used in the protein-coding genes. The phylogenetic result showed that C. umbratile was clustered with Scyliorhinus canicula and formed the Scyliorhinidae clade, which was the most basal clade within Carcharhiniformes, and Carcharhinidae is not monophyletic.

The artisanal elasmobranch fishery of the Pacific coast of Baja California Sur, Mexico, management implications

Artisanal fisheries in Mexico account for approximately 40% of the total national catch. In 2009, Baja California Sur (BCS) had the second largest catch of elasmobranchs on the Mexican Pacific coast. This paper characterizes and describes the artisanal elasmobranch fishery of Pacific coast of BCS from 2000 to 2010. Sixty artisanal camps were documented, of which 45 targeted elasmobranchs, using primarily gillnets and longlines. We identified 52 elasmobranch species. Gillnetting accounted for 73.5% of the fishing effort and most frequently captured Rhinobatos productus, Mustelus henlei and Myliobatis californica . Longline fishing accounted for 26.5% of effort, most frequently capturing Prionace glauca and Isurus oxyrinchus . The prevalence of juveniles of several species (e.g., Cephaloscyllium ventriosum, Galeorhinus galeus, Isurus oxyrinchus , and Myliobatis californica ) within landings suggests that fishing effort may be opportunistically directed at breeding or nursery areas. Despite the dominance of species with wide distributions, we observed a significant biogeographic pattern in the abundance of some species relative to Bahia Magdalena. Results of the present study will be useful to detect changes in the structure of commercially exploited elasmobranch populations, and to provide useful indications for management purposes.

Food capture kinematics in the deep-water chain catshark Scyliorhinus retifer

The chain catshark (Scyliorhinus retifer) is a member of one of the most well studied groups of elasmobranchs (Order: Carcharhiniformes), yet its feeding strategy is unknown due to the inaccessible deep water environment in which it lives (greater than 200 m). To investigate the feeding biology of captive S. retifer, high-speed videography was used to document the kinematic events during capture of two differently sized fish pieces, ‘large’ (scaled to the mouth width), and ‘small’ (scaled to one-half the mouth width). Despite a significant delay in the timing of select kinematic variables for large food captures, a multivariate analysis of the feeding behaviour indicated that overall, food capture kinematics and strike behaviour in S. retifer were not statistically different between large and small items (MANOVA, Wilks' Lambda P =0.598, df=4,24). Food capture in S. retifer was suction-dominant, with items being drawn into the mouth about twice the distance that the predator moved. While suction-dominant food capture appears to be an advantage to benthic predators, it contrasts sharply with the phylogenetic position of S. retifer among several ram-feeding carcharinoid sharks including Cephaloscyllium ventriosum, a member of the same family (Scyliorhinidae). Thus, feeding mode in carcharinoid sharks seems to reflect their ecology and does not appear to have been phylogenetically constrained.

Skeletogenesis in the swell sharkCephaloscyllium ventriosum

Extant chondrichthyans possess a predominantly cartilaginous skeleton, even though primitive chondrichthyans produced bone. To gain insights into this peculiar skeletal evolution, and in particular to evaluate the extent to which chondrichthyan skeletogenesis retains features of an osteogenic programme, we performed a histological, histochemical and immunohistochemical analysis of the entire embryonic skeleton during development of the swell shark Cephaloscyllium ventriosum. Specifically, we compared staining properties among various mineralizing tissues, including neural arches of the vertebrae, dermal tissues supporting oral denticles and Meckel's cartilage of the lower jaw. Patterns of mineralization were predicted by spatially restricted alkaline phosphatase activity earlier in development. Regarding evidence for an osteogenic programme in extant sharks, a mineralized tissue in the perichondrium of C. ventriosum neural arches, and to a lesser extent a tissue supporting the oral denticle, displayed numerous properties of bone. Although we uncovered many differences between tissues in Meckel's cartilage and neural arches of C. ventriosum, both elements impart distinct tissue characteristics to the perichondral region. Considering the evolution of osteogenic processes, shark skeletogenesis may illuminate the transition from perichondrium to periosteum, which is a major bone-forming tissue during the process of endochondral ossification.

Comparison of Fasting and Postfeeding Metabolic Rates in a Sedentary Shark, Cephaloscyllium ventriosum

We measured the standard and postfeeding metabolic rates of a sedentary shark, the swellshark, Cephaloscyllium ventriosum (Scyliorhinidae). The average standard metabolic rate (SMR) of juvenile swellsharks (0.14–0.23 kg) was 44.3 ± 6.4 mg O2 kg−1 h−1. Metabolic rate increased and reached a maximum approximately 9 h postfeeding. The maximum postfeeding metabolic rate averaged 2.3 times SMR, and the entire duration of the response was approximately 12 h. The overall pattern and magnitude of the postfeeding response is similar to those previously reported for the small-spotted catshark (Scyliorhinus canicula; Scyliorhinidae) and for many teleosts. The return to a prefeeding metabolic rate appears to be much more rapid in the swellshark than in the small-spotted catshark.Section editor: R. E. Gatten Jr

Mechanics of ventilation in swellsharks, Cephaloscyllium ventriosum (Scyliorhinidae).

A simple two-pump model has served to describe the mechanics of ventilation in cartilaginous and bony fishes since the pioneering work of G. M. Hughes. A hallmark of this model is that water flow over the gills is continuous. Studies of feeding kinematics in the swellshark Cephaloscyllium ventriosum, however, suggested that a flow reversal occurred during prey capture and transport. Given that feeding is often considered to be simply an exaggeration of the kinematic events performed during respiration, I investigated whether flow reversals are potentially present during respiration. Pressure and impedance data were coupled with kinematic data from high-speed video footage and dye studies and used to infer patterns of water flow through the heads of respiring swellsharks. Swellsharks were implanted with pressure transducers to determine the pattern and magnitude of pressures generated within the buccal and parabranchial (gill) cavities during respiration. Pressure traces revealed extended periods of pressure reversal during the respiratory cycle. Further, impedance data suggested that pressures within the buccal and parabranchial cavities were not generated by the cyclic opening and closing of the jaws and gills in the manner previously suggested by Hughes. Thus, the classic model needs to be re-evaluated to determine its general applicability. Two alternative models for pressure patterns and their mechanism of generation during respiration are provided. The first depicts a double-reversal scenario common in the swellshark whereby pressures are reversed following both of the pump stages (the suction pump and the pressure pump) rather than after the pressure-pump stage only. The second model describes a scenario in which the suction pump is insufficient for generating a positive pressure differential across the gills; thus, a pressure reversal persists throughout this phase of respiration. Kinematic analysis based on high-speed video footage and dye studies, however, suggested that during respiration, as opposed to feeding, distinct flow reversals do not result from the pressure reversals. Thus, water is probably pooling around the gill filaments during the long periods of pressure reversal.

Feeding kinematics of hatchling swellsharks, Cephaloscyllium ventriosum (Scyliorhinidae): the importance of predator size

Capture, manipulation, and transport of prey were quantified from high-speed video of hatchling swellsharks, Cephaloscyllium ventriosum. Kinematic variables were contrasted with those of 1 yr-old swellsharks. Hatchling prey-captures were ram-dominated, while 1 yr-old prey-capture events had a detectable suction component. Timing differences between kinematic patterns of the age groups were not detected. Significant differences in displacement maxima of kinematic variables between the two age groups during feeding were detected, but were consistent with the expectations of isometry; they doubled in accordance with a doubling in shark length. A scaling analysis confirmed that swellsharks grow isometrically. A simple model of the head during prey capture confirmed that buccal expansion scaled isometrically between age groups. Thus, this study suggests that hatchlings generally perform the suite of movements necessary for suction generation within the buccal cavity during feeding. A suction component to the strike, however, was generally not detected by the “ram:suction index”. It appears that although it is probably generated within the buccal cavity, suction has little effect on the prey item and makes a minimal contribution to prey capture. Suction may be ineffective due to the highly active nature of the hatchlings. During a strike, a hatchling's forward locomotion may be sufficient to overwhelm any suction produced by the expanding buccal cavity; thus, the swimming shark effectively “scoops” the prey up in its open mouth (i.e. ram feeding) before the prey can be entrained in the flow of water entering the mouth (i.e. suction feeding). It is also likely that the hatchling sharks are sufficiently small to render any suction generated ineffective. Even though the sharks scale isometrically, the sheer size of the 1 yr-old sharks allows a greater amount of force to be generated, that will ultimately draw the prey to the open mouth. Thus, there are absolute consequences of size for feeding behaviors.

Feeding kinematics of juvenile swellsharks, Cephaloscyllium ventriosum

To investigate how feeding behaviors change with prey size, high-speed video recording was used to examine the kinematics of prey capture and transport in 1-year-old swellsharks Cephaloscyllium ventriosum (Scyliorhinidae: Carchariniformes) feeding on two differently sized prey items. Prey capture in these sharks generally consisted of an initially ram-dominated capture bite, one or more manipulation bites, a holding phase during which the food was held in the teeth of the shark, and then suction-dominated prey transport. During initial capture and transport, most of the water taken in is forced back out of the mouth anteriorly rather than continuing posteriorly out through the gill openings. Dye experiments in which dye-perfused prey items were ingested by the sharks confirm this observation; distinct jets of colored water were video-taped as they were ejected from the mouth. Very late in prey transport, a bolus of water is ejected through the gill slits; however, by this time, the majority of water appears already to have exited the buccal cavity through the mouth. Such patterns were observed for sharks feeding on both small and large prey items. Although a basic pattern of prey capture and transport was regularly repeated among strikes, kinematic patterns during prey capture and transport were variable both within and among individuals, indicating that prey acquisition is not tightly controlled. However, the amount of variability was similar among prey sizes. In addition, there were no detectable changes in behavior due to prey item size. Ram-suction index values confirmed that similar capture modes were being utilized for both prey sizes.

Adult and fetal hemoglobins in the oviparous swell shark, Cephaloscyllium ventriosum

Cephaloscyllium ventriosum is an oviparous, bottom-dwelling shark inhabiting shallow waters from central California to Chile. Hemoglobin oxygen affinities for adult, juvenile (5 and 8 months old), and pre- and posthatch (fetal up to 10 days posthatching) individuals were determined using thin-layer spectrophotometry of hemoglobin solutions stripped of organic phosphates. Adult hemogiobin had a P 50 of 4.72± 0.30 mm Hg ( N = 4, mean ± SE), juvenìle hemoglobin had a P 50 of 3.77 ± 0.65 mmHg ( N = 3), and pre- and posthatch hemoglobin had a P 50 of 2.51 ± 0.19 mmHg ( N = 6)—significantly ( P < 0.05) higher than adult hemoglobin oxygen affinity. Adult blood was slightly alkaline (7.60–8.04; N = 4), had low venous P O 2 values (0.5–14.5 mmHg; N = 4), and hematocrit and hemoglobin concentration increased with age. SDS-polyacrylamide gel electrophoresis revealed slight structural differences between the hemoglobin of adult and prehatch individuals. A hemoglobin with a higher intrinsic oxygen affinity may enable fetuses of C. ventriosum to more efficiently extract oxygen from the relatively stagnant environment within the egg case.

Tonic immobility in 12 elasmobranchs: Use as an aid in captive husbandry

AbstractTonic immobility (TI), also known as animal hypnosis, has been observed in a wide variety of taxa and reported in all vertebrate classes with the exception of Agnatha. To date, TI has been reported in six species of elasmobranchs. Preliminary results are presented here for five species of galeomorph sharks, one species of squalomorph shark, and six species of batoids. Tonic immobility was induced in the leopard shark. Triakis semifasciata; the whitetip reef shark, Triaenodon obesus; the blacktip reef shark, Carcharhinus melanopterus; the Caribbean reef shark, Carcharhinus perezi; the swellshark, Cephaloscyllium ventriosum; the California round ray, Urolophus halleri; the shovelnose guitarfish, Rhinobatos productus; the clearnose skate. Raja eglanteria; the cownose ray, Rhinoptera bonasus; and the southern stingray, Dasyatis americana. The broadnose sevengill shark, Notorynchus cepedianus and the yellow stingray, Urolophus jamaicensis failed to exhibit the tonic immobility response, but only one individual of each species was tested. The average induction time ranged from 16.7 sec in the shovelnose guitarfish to 45.7 sec in the clearnose skate. Average duration times ranged from 34.3 sec in the clearnose skate to 274.0 sec in the Caribbean reef shark. Depending upon the species involved, TI has been used as an aid in a few husbandry and medical procedures in captive elasmobranches at the National Aquarium in Baltimore. These procedures have included gross examination, measuring lengths, tube feeding, and drawing blood via caudal venipuncture. Using tonic immobility during these procedures is beneficial as once induced, the subject's struggling is minimal and usually requires little restraint. © 1994 Wiley‐Liss, Inc.

The effectiveness of sodium lauryl sulphate as a shark repellent in a laboratory test situation

Swim‐through chemical repellency tests, using sodium lauryl sulphate (SLS), cupric acetate, and rotenone, were conducted in a specially‐designed roundabout tank on horn sharks, Heterodontus francisci, swell sharks, Cephaloscylliun ventriosum, and leopard sharks, Triakis semifasciata. Effective concentration thresholds (EC50s) were calculated for two levels of response: (1) minimum noticeable and (2) strong. The SLS EC50s were: horn shark 43.6 and 174.5 ppm; swell shark 95.1 and 160.0 ppm; and leopard shark inconclusive and 113.1 ppm. No response was discernible from cupric acetate. Rotenone evoked a weak response with an EC50 of 5.7 ppm, but no strong response.The ratio of the minimum noticeable EC50: 24‐hour lethal concentration (LC50) indicated the relative repellency (compared to toxicity) of the chemicals. The ratio for SLS was 19:1 and for rotenone 57:1. SLS did not provoke a repellency response at a low enough concentration to function effectively as a classical, surrounding‐cloud type, repellent. The range of potency of SLS, however, does allow it to be used as a directional repellent.

Bioelectric-Mediated Predation by Swell Sharks, Cephaloscyllium ventriosum

Bioelectric-Mediated Predation by Swell Sharks, Cephaloscyllium ventriosum