Ensemble modeling of the potential distribution of the whale shark in the Atlantic Ocean

The whale shark (Rhincodon typus) is an endangered marine fish species which can be adversely affected by the fishing activities of the industrial purse seine fleet targeting tropical tuna. Tuna tend to aggregate around all types of floating objects, including whale sharks. We analyzed and modeled the spatial distribution and environmental preferences of whale sharks based on the presence and absence data from fishing observations in the Atlantic Ocean. We used a thorough multialgorithm analysis, based on a new presence–absence dataset, and endeavored to follow the most recent recommendations on best practices in species distribution modeling. First, we selected a subset of relevant variables using a generalized linear model that addressed multicollinearity, statistical errors, and information criteria. We then used the selected variables to build a model ensemble including 19 different algorithms. After eliminating models with insufficient performance, we assessed the potential distribution of whale sharks using the mean of the predictions of the selected models. We also assessed the variance among the predictions of different algorithms, in order to identify areas with the highest model consensus. The results show that several coastal regions and warm shallow currents, such as the Gulf Stream and the Canary and Benguela currents, are the most suitable areas for whale sharks under current environmental conditions. Future environmental projections for the Atlantic Ocean suggest that some of the suitable regions will shift northward, but current concentration areas will continue to be suitable for whale shark, although with less productivity, which could have negative consequences for conservation of the species. We discuss the implications of these predictions for the conservation and management of this charismatic marine species.     

<Emphasis Type="Italic">Careproctus kidoi</Emphasis>, a new Arctic species of snailfish (Teleostei: Liparidae) from Baffin Bay

Careproctus kidoi sp. nov. is described from the Baffin Bay between Greenland and Canada, in the northern most part of the western North Atlantic. During a series of bottom trawl surveys conducted in 1988–2004, 22 specimens of an undescribed species of Careproctus were caught at depths between 952 and 1,487 m. It differs from Arctic and North Atlantic congeners in the combination of the characters: pectoral fin rays 21–26, dorsal fin rays 54–60, anal fin rays 50–54, vertebrae 61–64; sucking disc oval, 4.2–6.6% SL; teeth simple; pyloric coeca 3–12; head pore formula (2-6-7-1); color light to dark brown, stomach dusky to dark brown, peritoneum black. It is generally found in deeper waters than the sympatric C. reinhardti.     

Discovery of a multispecies shark aggregation and parturition area in the Ba Estuary,Fiji Islands

Population declines in shark species have been reported on local and global scales, with overfishing, habitat destruction and climate change posing severe threats. The lack of species‐specific baseline data on ecology and distribution of many sharks, however, makes conservation measures challenging. Here, we present a fisheries‐independent shark survey from the Fiji Islands, where scientific knowledge on locally occurring elasmobranchs is largely still lacking despite the location's role as a shark hotspot in the Pacific. Juvenile shark abundance in the fishing grounds of the Ba Estuary (north‐western Viti Levu) was assessed with a gillnet‐ and longline‐based survey from December 2015 to April 2016. A total of 103 juvenile sharks identified as blacktip Carcharhinus limbatus (n = 57), scalloped hammerhead Sphyrna lewini (n = 35), and great hammerhead Sphyrna mokarran (n = 11) sharks were captured, tagged, and released. The condition of umbilical scars (68% open or semihealed), mean sizes of individuals (±SD) (C. limbatus: 66.5 ± 3.8 cm, S. lewini: 51.8 ± 4.8 cm, S. mokarran 77.4 ± 2.8 cm), and the presence of these species over recent years (based on fishermen interviews), suggest that the Ba Estuary area is a critical habitat for multiple species that are classified as “Near Threatened” or “Endangered.” Specifically, the area likely acts as a parturition ground over the studied period, and potentially as a subsequent nursery area. We identified subareas of high abundance and found that temperature, salinity and depth acted as small‐scale environmental drivers of shark abundance. The data suggests a tendency for species‐specific spatial use, both horizontally (i.e., between sampling areas) and vertically (i.e., across the water column). These results enhance the understanding of shark ecology in Fiji and provide a scientific basis for the implementation of local conservation strategies that contribute to the protection of these threatened species.     

Neutral and Nonneutral Mitochondrial Genetic Variation in Deep-Sea Clams from the Family Vesicomyidae

Nucleotide sequences at two mitochondrial genes from 57 individuals representing eight species of deep-sea clams (Vesicomyidae) were examined for variation consistent with the neutral model of molecular evolution. One gene, cytochrome oxidase subunit I (COI), deviated from the expectations of neutrality by containing an excess of intraspecific nonsynonymous polymorphism. Additionally, one species, Calyptogena kilmeri, showed a significant excess of rare polymorphism specifically at the COI locus. In contrast, a second mitochondrial gene, the large-subunit 16S ribosomal RNA gene (16S), showed little deviation from neutrality either between or within species. Together, COI and 16S show no deviation from neutral expectations by the HKA test, produce congruent phylogenetic relationships between species, and show correlated numbers of fixed differences between species and polymorphism within species. These patterns of both neutral and nonneutral evolution within the mitochondrial genome are most consistent with a model where intraspecific nonsynonymous polymorphism at COI is near neutrality. In addition to examining the forces of molecular evolution, we extend hypotheses about interspecific relationships within this family for geographical locations previously unexamined by molecular methods including habitats near the Middle Atlantic, the Aleutian Trench, and Costa Rica. Received: 10 March 1999 / Accepted: 13 September 1999     

Chondrichthyan‐like scales from the Middle Ordovician of Australia

Abstract: Microvertebrate sampling of the Stairway Sandstone (Darriwilian, Middle Ordovician, central Australia) has yielded scales that are chondrichthyan‐like in their overall construction, and Tantalepis gatehousei gen. et sp. nov. is erected here to describe these specimens. Tantalepis gatehousei gen. et sp. nov. is the stratigraphically oldest microsquamous taxon described thus far, and the ‘shark‐like’ appearance of the scales may extend the chondrichthyan lineage back into the Middle Ordovician. The presence of ‘shark‐like’ scales in the fossil record some 50 myr prior to the first articulated chondrichthyan body fossils and 44 myr before the first clearly identifiable chondrichthyan teeth suggests there is a considerable scope for the recovery of articulated specimens with which to document the early history of crown gnathostomes. Traditional hypotheses of phylogenetic relationships among early jawed vertebrates were recently challenged by the proposal of a radically different tree topology. However, the development of a new data set specifically addressing scale‐based characters is required before taxa such as Tantalepis, that are based upon disarticulated remains alone, can be firmly placed within the emerging, revised, evolutionary narrative.     

Considerations on the diet composition and feeding rate of dermersal sharks in 15 European public aquaria

To get an overview of the feeding practices applied to dermersal sharks in captivity, a questionnaire was sent to 15 European public aquaria. The most common dermersal shark species kept in the participating aquaria are Carcharhinus plumbeus (n=9), Carcharias taurus (n=7), and C. melanopterus (n=6). Body weight (BW) was calculated using captive estimated body length (BL) and actual weight data obtained from commercial fisheries. The estimated BW for C. plumbeus in all participating aquaria is higher than the calculated BW. The feeding rate (FR) for adult C. plumbeus varied widely within participating aquaria (2.3–11.5% BW_cal/week or 32–112 kcal/kg BW_cal/week). The FR for adult C. plumbeus was lower (1.2–7.9% BW_est/week or 17–99 kcal/kg BW_est/week) using the estimated BW. Adult Carcharias taurus were fed at 1.3–5.0% BW_cal/week or 70–170 kcal/kg BW_cal/week. Negaprion brevirostris was fed at 5.0% BW_est/week or 57 kcal/BW_est/week. The relationship between FR and estimated BW is expressed as FR=54.5 e^?0.033BW. In this study, the feeding frequency for C. plumbeus varied between 1–7 times a week, with an average of 3.3 times a week. Diet in all aquaria consisted of both lean and fatty fish, and sometimes squid or crustaceans. Supplementation of vitamins is common practice in 80% of the surveyed aquaria, although a wide variety of quantity and quality was observed. Ten aquaria (66%) add iodine, as potassium iodide (0.4–12.5 mg KI/kg BW/week) or calcium‐iodate (322–1,500 mg/kg food/week), to their food. Zoo Biol 22:203–226, 2003. © 2003 Wiley‐Liss, Inc.     

Effects of the piezo-tolerance of cultured deep-sea eel cells on survival rates, cell proliferation, and cytoskeletal structures

We investigated the pressure tolerance of deep-sea eel (Simenchelys parasiticus; habitat depth, 366–2,630 m) cells, conger eel (Conger myriaster) cells, and mouse 3T3-L1 cells. Although there were no living mouse 3T3-L1 and conger eel cells after 130 MPa (0.1 MPa = 1 bar) hydrostatic pressurization for 20 min, all deep-sea eel cells remained alive after being subjected to pressures up to 150 MPa for 20 min. Pressurization at 40 MPa for 20 min induced disruption of actin and tubulin filaments with profound cell-shape changes in the mouse and conger eel cells. In the deep-sea eel cells, microtubules and some actin filaments were disrupted after being subjected to hydrostatic pressure of 100 MPa and greater for 20 min. Conger eel cells were sensitive to pressure and did not grow at 10 MPa. Mouse 3T3-L1 cells grew faster under pressure of 5 MPa than at atmospheric pressure and stopped growing at 18 MPa. Deep-sea eel cells were capable of growth in pressures up to 25 MPa and stopped growing at 30 MPa. Deep-sea eel cells required 4 h at 20 MPa to finish the M phase, which was approximately fourfold the time required under atmospheric conditions.     

Cultivated anaerobic acidophilic/acidotolerant thermophiles from terrestrial and deep-sea hydrothermal habitats

Metabolic and phylogenetic diversity of cultivated anaerobic microorganisms from acidic continental hot springs and deep-sea hydrothermal vents was studied by molecular and microbiological methods. Anaerobic organotrophic enrichment cultures growing at pH 3.5–4.0 and 60 or 85°C with organic energy sources were obtained from samples of acidic hot springs of Kamchatka Peninsula (Pauzhetka, Moutnovski Volcano, Uzon Caldera) and Kunashir Island (South Kurils) as well as from the samples of chimneys of East Pacific Rise (13°N). The analyses of clone libraries obtained from terrestrial enrichment cultures growing at 60°C revealed the presence of archaea of genus Thermoplasma and bacteria of genus Thermoanaerobacter. Bacterial isolates from these enrichments were shown to belong to genera Thermoanaerobacter and Thermoanaerobacterium, being acidotolerant with the pH optimum for growth at 5.5–6.0 and the pH minimum at 3.0. At 85°C, domination of thermoacidophilic archaea of genus Acidilobus in terrestrial enrichments was found by both molecular and microbiological methods. Five isolates belonging to this genus possessed some phenotypic features that were new for this genus, such as flagellation or the ability to grow on monosaccharides or disaccharides. Analyses of clone libraries from the deep-sea thermoacidophilic enrichment cultures showed that the representatives of the genus Thermococcus were present at both 60 and 85°C. From the 60°C deep-sea enrichment, a strain belonging to Thermoanaerobacter siderophilus was isolated. It grew optimally at pH 6.0 with the minimum pH for growth at 3.0 and with salinity optimum at 0–2.5% NaCl and the maximum at 7%, thus differing significantly from the type strain. These data show that fermentative degradation of organic matter may occur at low pH and wide temperature range in both terrestrial and deep-sea habitats and can be performed by acidophilic or acidotolerant thermophilic prokaryotes.