Sizing and scarring of whale shark (Rhincodon typus Smith, 1828) in the Cenderawasih Bay National Park

This study aims to determine the total length and scar condition of the body of whale sharks (Rhincodon typus) in Cendrawasih Bay National Park (TNTC), Papua-Indonesia. Photo-identification was used to identify individuals of the whale shark R. typus based on spot patterns behind the last gill slit of each individual. Photo-identification was also used to determine the scar of the whale shark. The total length of whale sharks were estimated based on the length of a snorkeller (assumed to be 1.6 m) swimming alongside the whale shark. We identified 21 individuals of R. typus. Of these 21 individuals, 14 were new sightings and seven were re-sightings that have been recorded in the previous photo collection database. R. typus ranged in size from 2 to 5 m total length (average 3.78 m, ±0,86, N= 21). Based on their size, all individuals of whale shark were categorized as juvenile. 52% of R. typus identified had scars and 38 % were not and 10% were unknown. The majority of whale sharks had amputation (12 individuals) and abrasion (7 individuals) scars. Scars occurred most often on the caudal fin and dorsal fin, five and four individuals respectively. This information is useful for understanding potential threats and designing better management programmes for R. typus conservation in TNTC.

Osteodiscus abyssicola, a new snailfish (Cottoidei: Liparidae) collected off the Pacific coast of northern Japan

The snailfish Osteodiscus abyssicola sp. nov. is described from a single specimen collected off the Pacific coast of Hokkaido, northern Japan, at a depth of 4,671–4,744 m. It is distinguished from all currently recognized congeners by the following combination of characters: vertebrae 49; dorsal-fin rays 44; anal-fin rays 39; principal caudal-fin rays 8; pyloric caeca 5; mouth horizontal; teeth on both jaws simple and sharp, without cusps; upper and lower jaw symphyses without diastema; cephalic pore sizes moderate, similar to or slightly larger than nostril; gill slit extending ventrally to 2nd pectoral-fin ray base; pectoral fin notched; mandibular symphysis to center of anus 101.6% head length (HL); posterior edge of pelvic disk to center of anus 15.5% HL; epural 1, reduced; epipleural ribs absent. An emended diagnosis and key to the species of Osteodiscus are provided.

A New Species of Snailfishes (Liparidae) of the Genus Careproctus from the Northern Slope of the Aleutin Basin (Bering Sea)

Abstract— A new species of snailfishes Careproctus schmidti sp. nov. from the northwestern part of the Bering Sea is described. The specimen was caught in the mesobenthal of the Aleutian Basin at a depth of 852–862 m (holotype ZIN no. 56 620—female TL 194 mm). It is distinguished from the majority of congeners of the North Pacific Ocean by a set of features: a large number of vertebrae (63) and rays in the fins (D 56, A 50, P 34, C 10), the presence of two pairs of pleural ribs, a relatively elongated (21% SL) pectoral fin with a notch and short lower lobe (12% SL), two suprabranchial pores, simple teeth, naked skin, and black peritoneum. In terms of meristic features, the new species is similar to three North Pacific species, but it differs from C. colletti in a short lower lobe of the pectoral fin, a flattened disc of triangular outlines, and a longer gill slit. It differs from C. roseofuscus by a lower body, a pectoral fin ventrally located and anus which opens immediately behind the disc. It differs from C. ambustus in purple-lilac color, fewer in number simple teeth with sharp apexes, in vertical and higher disposition of gill slit, shorter lower lobe of the pectoral fin, disc shape and position of the anus. The presence of an ovipositor may indicate existence of complicated reproductive behavior (such as carcinophilia or other types of reproductive commensalism). The northwestern slope of the Aleutian Basin, where a specimen of C. schmidti was caught, is located in the zone of influence of the Bering Slope Current and seasonal upwelling associated with the rise of deep waters. The composition of the ichthyocene in the area of ​​capture is given, including up to 20 species, dominated by Macrouridae.

Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph

The taxonomy of the gadiform fish family Macrouridae (sensu stricto) in the northwestern Pacific off Japan and adjacent waters is critically reviewed on the basis of 7846 specimens. A total of 76 species belonging to 18 genera is recognized, including four new species of the genera Coelorinchus (2 species), Kuronezumia (1), and Nezumia (1). Coelorinchus lanceolatus sp. nov. superficially resembles Coe. anatirostris Jordan & Gilbert in Jordan & Starks, 1904, but differs most notably from that species in having a distinctly longer snout (107% of the postrostral length vs. 60–88%). Coelorinchus nox sp. nov. is closely similar to Coe. smithi Gilbert & Hubbs, 1920, but readily differs from the latter in that the occipital scales are covered with short, erect, needle-like spinules in widely divergent, comb-like rows (vs. moderately reclined, keel-like to knife-like spinules in saw-toothed rows). Kuronezumia endoi sp. nov. is a distinctive species among the genus, and is clearly diagnosed from other congeners in having the highest number of pelvic-fin rays (15 vs. ≤14). Nezumia rara sp. nov. closely resembles N. tomiyamai (Okamura, 1963), but they can be distinguished from each other by the combination of a number of morphometric characters, including the orbit-preopercle distance, interorbital width, pelvic-fin length, and length of gill slit. New and reconfirmed synonymies include: Coe. abbreviatus Chu & Lo in Chu, Chan & Chen, 1963 and Coe. intermedius Chu & Lo in Chu, Chan & Chen, 1963 with Coe. multispinulosus Katayama, 1942; Coe. productus Gilbert & Hubbs, 1916 with Coe. anatirostris; Coe. asteroides Okamura, 1963 with Coe. hige Matsubara, 1943; Coe. sparsilepis Okamura & Yatou, 1984 with Coe. parallelus (Günther, 1877); Coryphaenoides filamentosus Okamura, 1970 with Cor. cinereus (Gilbert, 1896); Cor. liocephalus (Günther, 1887) with Cor. leptolepis Günther, 1877; Cor. spinulosus (Gilbert & Burke, 1912) with Cor. acrolepis (Bean, 1884); and Ventrifossa fusca Okamura, 1982 with V. misakia (Jordan & Gilbert in Jordan & Starks, 1904). Lectotypes are designated for Coe. parallelus, Cor. asper Günther, 1877, Cor. liocephalus, and Cor. nasutus Günther, 1877. Previous records of N. burragei (Gilbert, 1905) and N. propinqua (Gilbert & Cramer, 1897) from Japan represent misidentifications, and these species are eliminated from the list of Japanese grenadiers. Coryphaenoides armatus (Hector, 1875) and Cor. leptolepis are recorded for the first time from the hadal zone. All species are illustrated, with full descriptions for 14 species. Dichotomous keys to genera and species are also provided. The distribution of each species in the study area is revised based on the specimens examined here, with re-identification of voucher specimens of most previous geographical records.

Gill slits provide a window into the respiratory physiology of sharks

Metabolically important traits, such as gill surface area and metabolic rate, underpin life histories, population dynamics and extinction risk, as they govern the availability of energy for growth, survival and reproduction. Estimating both gill surface area and metabolic rate can be challenging, especially when working with large-bodied, threatened species. Ideally, these traits, and respiratory physiology in general, could be inferred from external morphology using a faster, non-lethal method. Gill slit height is quick to measure on live organisms and is anatomically connected to the gill arch. Here, we relate gill slit height and gill surface area for five Carcharhiniform sharks. We compared both total and parabranchial gill surface area to mean and individual gill slit height in physical specimens. We also compared empirical measurements of relative gill slit height (i.e. in proportion to total length) to those estimated from field guide illustrations to examine the potential of using anatomical drawings to measure gill slit height. We find strong positive relationships between gill slit height and gill surface area at two scales: (i) for total gill surface area and mean gill slit height across species and (ii) for parabranchial gill surface area and individual gill slit height within and across species. We also find that gill slit height is a consistent proportion of the fork length of physical specimens. Consequently, relative gill slit height measured from field guide illustrations proved to be surprisingly comparable to those measured from physical specimens. While the generality of our findings needs to be evaluated across a wider range of taxonomy and ecological lifestyles, they offer the opportunity that we might only need to go to the library and measure field guide illustrations to yield a non-lethal, first-order approximation of the respiratory physiology of sharks.

An early chondrichthyan and the evolutionary assembly of a shark body plan

Although relationships among the major groups of living gnathostomes are well established, the relatedness of early jawed vertebrates to modern clades is intensely debated. Here, we provide a new description of Gladbachus , a Middle Devonian (Givetian approx. 385-million-year-old) stem chondrichthyan from Germany, and one of the very few early chondrichthyans in which substantial portions of the endoskeleton are preserved. Tomographic and histological techniques reveal new details of the gill skeleton, hyoid arch and jaws, neurocranium, cartilage, scales and teeth. Despite many features resembling placoderm or osteichthyan conditions, phylogenetic analysis confirms Gladbachus as a stem chondrichthyan and corroborates hypotheses that all acanthodians are stem chondrichthyans. The unfamiliar character combination displayed by Gladbachus , alongside conditions observed in acanthodians, implies that pre-Devonian stem chondrichthyans are severely under-sampled and strongly supports indications from isolated scales that the gnathostome crown group originated at the latest by the early Silurian (approx. 440 Ma). Moreover, phylogenetic results highlight the likely convergent evolution of conventional chondrichthyan conditions among earliest members of this primary gnathostome division, while skeletal morphology points towards the likely suspension feeding habits of Gladbachus , suggesting a functional origin of the gill slit condition characteristic of the vast majority of living and fossil chondrichthyans.

The distribution and abundance of electrosensory pores in two benthic sharks: a comparison of the wobbegong shark, Orectolobus maculatus, and the angel shark, Squatina australis

Electroreception is an ancient sense found in many aquatic animals, including sharks, which may be used in the detection of prey, predators and mates. Wobbegong sharks (Orectolobidae) and angel sharks (Squatinidae) represent two distantly related families that have independently evolved a similar dorso-ventrally compressed body form to complement their benthic ambush feeding strategy. Consequently, these groups represent useful models in which to investigate the specific morphological and physiological adaptations that are driven by the adoption of a benthic lifestyle. In this study, we compared the distribution and abundance of electrosensory pores in the spotted wobbegong shark (Orectolobus maculatus) with the Australian angel shark (Squatina australis) to determine whether both species display a similar pattern of clustering of sub-dermal electroreceptors and to further understand the functional importance of electroreception in the feeding behaviour of these benthic sharks. Orectolobus maculatus has a more complex electrosensory system than S. australis, with a higher abundance of pores and an additional cluster of electroreceptors positioned in the snout (the superficial ophthalmic cluster). Interestingly, both species possess a cluster of pores (the hyoid cluster, positioned slightly posterior to the first gill slit) more commonly found in rays, but which may be present in all benthic elasmobranchs to assist in the detection of approaching predators.