Microsatellite loci within sixgill sharks, Hexanchus griseus

Novel sixgill shark (Hexanchus griseus) microsatellite loci were developed and tested on five shark species. A suite of microsatellite loci previously developed for lemon sharks (Negaprion brevirostris) was also tested. Data on 15 microsatellites are presented including primer sequences, number of alleles (a), observed (H_O) and expected heterozygosities (H_E), and F_IS values for sixgill sharks (a = 10–69, H_O = 0.24–1.00, H_E = 0.76–0.96 and F_IS = –0.21–0.60), sevengill sharks (Notorynchus cepedianus) (a = 6–40, H_O = 0.20–0.73, H_E = 0.59–0.94 and F_IS = –0.47–0.58), Pacific spiny dogfish (Squalus acanthias) (a = 3–13, H_O = 0.00–0.96, H_E = 0.24–0.93 and F_IS =–0.52–1.00), angle sharks (Squatina californica) (a = 1–4, H_O = 0.00–1.00, H_E = 0.60–1.00 and F_IS =–1.00–0.25), and leopard sharks (Triakis semifasciata) (a = 3–16, H_O = 0.20–1.00, H_E = 0.53–0.92 and F_IS = –0.57–1.00). A final suite of 14 microsatellites (13 developed from sixgill sharks and one from lemon sharks) were found to be polymorphic and conform to Hardy–Weinberg equilibrium within sixgill sharks.     

The importance of habitat and life history to extinction risk in sharks, skates, rays and chimaeras

We compared life-history traits and extinction risk of chondrichthyans (sharks, rays and chimaeras), a group of high conservation concern, from the three major marine habitats (continental shelves, open ocean and deep sea), controlling for phylogenetic correlation. Deep-water chondrichthyans had a higher age at maturity and longevity, and a lower growth completion rate than shallow-water species. The average fishing mortality needed to drive a deep-water chondrichthyan species to extinction (Fextinct) was 38-58% of that estimated for oceanic and continental shelf species, respectively. Mean values of Fextinct were 0.149, 0.250 and 0.368 for deep-water, oceanic and continental shelf species, respectively. Reproductive mode was an important determinant of extinction risk, while body size had a weak effect on extinction risk. As extinction risk was highly correlated with phylogeny, the loss of species will be accompanied by a loss of phylogenetic diversity. Conservation priority should not be restricted to large species, as is usually suggested, since many small species, like those inhabiting the deep ocean, are also highly vulnerable to extinction. Fishing mortality of deep-water chondrichthyans already exploited should be minimized, and new deep-water fisheries affecting chondrichthyans should be prevented.     

Characterization of BADS-binding proteins in epithelial plasma membranes

Summary When a fluorescent stilbene was added to epithelial plasma membrane suspension the emission spectrum showed a broad peak containing overlapping emissions resulting from different adducts. By focusing on a specific emission wavelength a common site having a dissociation constant of 5m was calculated in the rat kidney, small intestine, pancreatic islets and shark rectal gland. This binding could be displaced by loop diuretics, (e.g., furosemide with an IC₅₀ of 40 m), DIDS (k _i 1 m) and thiocyanate. These results pose certain questions such as: (i) whether the evidence for multiple peaks are due to specific interactions representing multiple binding affinities and (ii) whether the binding of stilbene and the observed displacement can be identified on a specific protein. Separating the proteins present in the purified basolateral and brush-border membranes by SDS-PAGE, transfer of these proteins onto introcellulose paper and labeling of the nitrocellulose strips by radioactive BADS (4-benzamido-4 aminostilbene-2-2 disulphonic acid) and bumetanide could identify labeled proteins. These experiments showed that whereas some proteins bound either BADS or bumetanide, one protein with a molecular weight of 100 or 130,000 D appeared to bind both. This protein was found on the basolateral membrane in the rat kidney cortex and medulla and the shark rectal gland and in the basolateral and brush-border membranes of the small intestine. Displacement of the protein-bound stilbene by loop diuretics could not be quantitated on the nitrocellulose transfer strips for this protein. Antibodies raised against the cytoplasmic fragment of band 3 reacted with the stilbene-labeled 100–130,000 D proteins indicating sufficient immuno-cross-reactivity between the separate species. These experiments involving binding of BADS and bumetanide and cross-reactivity with the human band 3 antibody suggest that these kilodalton proteins could structurally resemble human band 3.     

Properties of single- and double-barreled Cl channels of shark rectal gland in planar bilayers

Chloride channels from the apical plasma membrane fraction of rectal gland of Squalus acanthias were characterized by incorporation into planar bilayers in the presence of cAMP-PK/ATP. In a total of 80 bilayer preparations, 21 Cl-selective channels were observed as single channels and 13 as pairs. This was a significantly greater number of double Cl channels than expected from a binomial distribution. The double Cl channels were divided into two groups based on kinetic and voltage-dependent behavior. One group had properties identical to the single channels (gb1) while the other was consistent with a double-barreled channel (gb2) with coordinated activity between proto-channels. The single-channel slope conductances of gb1 and gb2 from -60 to +20 mV with a 250/70 mM KCl gradient were 41 and 75 pS, respectively. With symmetrical 250 mM KCl, the I-V relation of gb1 showed outward rectification with 47.8 +/- 6.6 pS at cis negative potentials and 68.9 +/- 6.1 pS at cis positive potentials. gb1 was open from 70 to 95% at all electrochemical potentials from -80 to +40 mV. gb2 was steeply voltage dependent between -80 and -20 mV. Both gb1 and gb2 were insensitive to Ca (from 100 nm to 1 microM), blocked by 0.1 mM DIDS and highly selective for chloride. These data suggest that double-barreled Cl channels are related to the family of small, outwardly rectifying Cl channels of epithelial membranes.     

Cyclic AMP-dependent stimulation of Na,K-ATPase in shark rectal gland

Summary Scatchard analysis of³H ouabain bound to isolated rectal gland cells as a function of increasing ouabain concentrations produced a concave curvilinear plot that was resolved into two specific sites with either a high (I) or low (II) affinity for ouabain. Cyclic cAMP/theophylline (±furosemide, 10^–4 m) increased the amount of³H ouabain bound to the high-affinity site I. Vanadate, a phosphate congener which promotes formation of the ouabain-binding state of the enzyme, mimicked the effects of cAMP/theophylline at low concentrations of ouabain, suggesting that cAMP/theophylline increases binding to site I by enhancing the rate of turnover of resident enzyme. Enhanced⁸⁶Rb uptake seen following cAMP/theophylline administration was primarily associated with increased flux through the high-affinity ouabain site, and this stimulation was not obliterated by the co-administration of furosemide. A model was presented which suggested the presence of two noninteracting pools of enzyme or isozymes which exhibit either a high or low affinity for ouabain. Cyclic AMP both stimulated turnover via site I, and modified the kinetics of binding of³H ouabain to site II. The (ave)K _d of³H ouabain for site II was increased from 3.6 m (controls) to 0.5 m (cAMP/theophylline) and the Hill coefficient was modified from 0.45 (controls) to 1.12 (caMP/theophylline), suggesting a transition from a negative- to a noncooperative binding state. While furosemide reversed the effects of cAMP/theophylline on site II kinetics, it did not obliterate cAMP/theophylline effects on site I. This suggests that cAMP may alter the intrinsic turnover rate of this particular pool of Na,K-ATPase in shark rectal gland.     

Diversity of isopods (Crustacea): new data from the Arctic and Atlantic Oceans

New data on the diversity pattern of isopods (Crustacea) from the northern most part of the North Atlantic and the Arctic Oceans is presented. The pattern of diversity with depth is similar at depths <1000m, but differs considerably below about 1000m. In the Arctic the diversity of isopods (expressed both as numbers of species per sled and expected number of species) increased with increased depth to a maximum at depths of about 320 to 1100m, but then declined towards deeper waters. There was a significant increase in numbers per sled and in the expected number of species with increased depth in the northernmost part of the North Atlantic Ocean. Additionally, changes occurred in the relative composition of the shallow and deep water fauna, with asellote isopods being relatively larger part of the isopod fauna in the Arctic than in the northern most part of the North Atlantic. This indicates major faunistic changes occurring at the Greenland-Iceland-Faeroe Ridge, possibly caused by rapid changes in the temperature. Furthermore, that the low diversity of the Arctic deep-sea is a regional phenomenon, and not a part of a large scale latitudinal pattern in the North Atlantic.     

Rare and new cumaceans (Crustacea,Peracarida) from?the southern margin of the Cap Ferret Canyon (Bay of Biscay)

A new cumacean genus and species, Ithyleucon sorbeigen. et sp. n., was described from material collected in the southern margin of the Cap Ferret Canyon (Bay of Biscay, NE Atlantic). Although the new genus resembles Pseudoleucon Zimmer, 1903, in terms of the general aspect of the carapace and the pseudo-rostrum position, it shows important differences in the uropod structure and in the size of the antenna 1 accessory flagellum. In addition, some comments regarding the morphology of certain rare species (Mesolamprops denticulatus Ledoyer, 1983, Hemilamprops normani Bonnier, 1896 and Schizocuma spino-culatum (Jones, 1984)) are also provided.     

Redescription of the deep-sea octopod Benthoctopus normani (Massy 1907) and a description of a new species from the Northeast Atlantic

A long-synonymized species Benthoctopus normani (Massy 1907) (Cephalopoda: Octopodidae) is redescribed from material collected over 30 years by the National Oceanography Centre, Southampton and the National Museums of Scotland. It can be distinguished from other octopodid specimens found in deep waters of the Northeast Atlantic by its biserial suckers, lack of ink sac, and simple ligula, which lacks transverse ridges. Examination of the collections led to the identification of a new species of Benthoctopus from the Northeast Atlantic, which is described herein.     

Echinorhinus brucus (Bonnaterre, 1788) in the Caribbean Sea: A recurrent visitor,or are the artisanal fisheries exploiting deeper waters?

Documentation of Echinorhinus brucus, (Bonnaterre, 1788) in the western Atlantic primarily relies on chance observations. Georeferenced records in this area remain notably scarce. This study contributes the second Venezuelan and seventh Caribbean Sea specimens, increasing the western Atlantic count to 15 individuals. All specimens gathered here were sexually mature, with a slight dominance of females. Our bramble shark record appears to be driven more by the interplay of its biology and environmental factors than being a deliberate deep-sea fishery activity, which likely occurs in the Southern Caribbean area.