Synaphobranchus Kaupi Research Articles

OPSINS IN THE DEEP

James Bowmaker is fascinated by pineal glands. These photosensitive glands,which regulate circadian rhythms in response to light levels by releasing melatonin, are usually located on top of the brain just beneath the skull. Which is an ideal position for deep-sea fish exposed to weak downwelling light in the ocean's depths. But Bowmaker and his colleague Hans-Joachim Wagner were curious whether deep-sea fish's pineal glands were even sensitive to light when so little reaches those depths. Wagner already knew that some deep-sea species' pineal glands produced melatonin, but would they have retained the photopigments and the ability to respond to fluctuating light levels? Bowmaker and Wagner set off on the RRS Discovery to gather several deep-sea species from the tropical Atlantic Ocean to discover whether species from the ocean's depths produce pineal photopigments(p. 2379).But having successfully trawled fish from depths between 800 and 1000 m,the team faced the tricky problem of preserving the delicate pineal gland tissue ready for return to land. Bowmaker remembers that the tissue needed to be collected and stored in the dark, which required delicate surgery under weak red light while the boat bobbed about. Once Wagner had successfully extracted the glands, the team gently fixed the samples, hoping the procedure wouldn't ruin any delicate membrane bound photopigments that the tissue may contain.After five weeks at sea. the team had collected samples from eight species of deep-sea fish, but would the pineal gland tissue contain photopigment? Back in London, Bowmaker gently mounted a sample in his spectrophotometer, and measured an absorbance spectrum. The results were clear; the tissue contained opsins similar to the pineal gland opsins found in surface dwelling species. Taking a close look at the pineal glands in his lab in Germany, Wagner also realised that the gland's photoreceptors contained large amounts of the specialised opsins in dome-shaped membranes, for maximum sensitivity in the dim environment. And when they compared the pineal gland's photosensitive pigment with opsins found in the fish's retina, Bowmaker and Wagner found that the pineal gland opsins were tuned to wavelengths that were a few nanometers longer than the fish's retinal opsins, but shorter than the pineal gland opsins of surface dwelling species.But what about the pineal glands of creatures that never see the light of day, such as the deep demersal eels, Synaphobranchus kaupi, which live at 2000 m? Wagner was lucky enough to catch several of the creatures and return their pineal glands to land for investigation. Amazingly, the eel had an enormous pineal gland, packed with photopigment, even though the animals never see solar photons. Bowmaker and Wagner are puzzled why the eel produces such large amounts of photopigment. Also, the opsin's spectral sensitivity is tuned to an exceptionally long wavelength, 515 nm, similar to the wavelengths detected by surface species pineal gland opsins. Bowmaker suggests that the eels could have retained pigment in their pineal glands as they spend their juvenile life stages near the ocean surface. But until the team has evidence that components of the essential signalling cascades that propagate the receptors signal are present, they have no idea whether the mesopelagic species, or Synaphobranchus, even detect light with their pineal glands.

Variation in locomotion behaviour in northern cutthroat eel ( Synaphobranchus kaupi) on the Bay of Biscay continental slope

Based on the analysis of video sequences recorded during four dives with a manned submersible in the Bay of Biscay, NE Atlantic, evidence is provided that the northern cutthroat eel Synaphobranchus kaupi shows marked variations in abundance and in the adoption of three locomotion behaviours—forward movement, station holding, and drifting—among six ecologically different habitats. Furthermore, significant variations in association with the bottom and disturbance responses to the submersible were found. Two swimming velocity measures taken from eels during forward movement were significantly correlated with both depth and temperature. The behavioural variations observed partly occurred also between adjacent habitats that were crossed during the same dive. These results and additional observations of instantaneous fluctuations in hydrological conditions suggest that these deep-sea eels are able to adjust to ecological variability at small spatial and temporal scales in a flexible and adaptive way.

Pineal organs in deep demersal fish.

We studied ten species of demersal fish from depths of 1500-4800 m, i.e. regions of the abyss outside the reach of sunlight. A pineal window in the skin and/or the skull, often found in mesopelagic fish, was never observed in demersal specimens. Nine species had a well-developed pineal organ, with light- and electron-microscopic features, well known in other teleosts living in surface waters, including photoreceptor cells with inner and outer segments, synaptic ribbons, neuronal perikarya, and (radial) glial cells. One species ( Bathypterois dubius) showed signs of regression; it also had reduced eyes. We observed considerable morphological variation in location, size, microscopic structure and ultrastructural organisation, including the frequency of photoreceptor cells, size of outer segments and the number of myelinated and unmyelinated axons. No systematic trend in the sense of an increase of sensitivity with greater depths was observed. Melatonin contents varied between 4 pg and 92 pg per pineal in the grenadier Coryphaenoides ( Nematonurus) armatus and between 2 pg and 70 pg per pineal in the eel Synaphobranchus kaupi. Differences between day and night values and between autumn and spring suggest that pineal melatonin acts as neurochemical signal mediating rhythmic processes and behaviour. The role of an alternative non-solar zeitgeber in the demersal environment is discussed.

A Note on the Diet Synaphobranchus Kaupi (Pisces: Synaphobranchidae) from the Porcupine Seabight, North-East Atlantic

The diet of Synaphobranchus kaupi from the Porcupine Seabight is described. A sample of 110 eel stomachs containing food, were analysed and the general size–depth trend among eels with food in their stomachs. Larger individuals are found in deeper waters. Fish are the main prey for larger eels and crustaceans are preferred by smaller individuals.Synaphobranchus kaupi Johnson, 1862 is a slope dwelling eel, abundant in the north-east Atlantic Ocean from 230 to 2420 m deep on the continental slope (Haedrich & Merrett, 1988). It is the most abundant species on the slopes of the Porcupine Seabight, off south-west Ireland (Merrett et al, 1991; Priede et al., 1994) and was classified as a benthopelagic predator of the fourth level, predator of predators (Saldanha, 1991).The diet of S. kaupi has been described from the slope off the middle Atlantic coast of the USA (Sedberry & Musick, 1978), from the Portuguese slope and in the Bay of Biscay (Saldanha, 1991), from the west African slope (Merrett & Marshall, 1981; Merrett & Domanski, 1985) and from the Rockall Trough (Gordon & Mauchline, 1996).Our specimens were captured during a joint IOS/SAMS survey (Merret et al., 1991). From a total catch of 8792 S. kaupi, captured between 1979 and 1983 in the Porcupine Seabight, ranging from 470 to 2230 m deep, fish stomachs were removed aboard ship and 110 with food were kept in 5% formalin for further analysis.

Estimation of abundance of abyssal demersal fishes; a comparison of data from trawls and baited cameras

The abundance of the macrourid Coryphaenoides (Nematonurus) armatus was investigated using a single warp trawl and baited camera at soundings from 2500 to 5000 m in the north‐east Atlantic Ocean. There was no significant relationship between abundance (n km−2) as determined from swept area of the trawl and numbers of fish photographed at standard baits. However, timing of the first arrival (tarr s) of the first fish at bait correlated well with the trawl data through the relationship: image It is concluded that by measurement of arrival times, the baited camera provides a cost‐effective complement to trawl sampling for estimating abundance of deep‐water fish including Synaphobranchus kaupi, Anlimora rostratu and C. (N). armatus. However, some abundant species such as the roundnose grenadier Coryphaenoides rupestris were not attracted to baited long‐lines or baited cameras and therefore could be sampled only by trawl.

A comparison of the deep‐water demersal fish assemblages of the Rockall Trough and Porcupine Seabight, eastern North Atlantic: continental slope to rise

Fishery surveys of the continental slope to the west of the British Isles have shown quite marked differences between areas in both the proportion and abundance of marketable or potentially marketable species. In general, the northern slopes lying to the west of Scotland were considered to have a greater potential for exploitation than the southern slopes off Ireland. Subsequent detailed studies of a northern (Rockall Trough) and a southern slope area (Porcupine Seabight) sampled the demersal fish fauna using a Granton trawl fished on paired warps to depths of 1200 m, and a semi‐balloon trawl fished on a single warp to depths of about 3000 m. The Granton trawl catches differed significantly between the two areas, especially at the greatest depths fished. The semi‐balloon trawl catches did not differ between the areas. This slower trawl was poor at catching large, mobile species and efficient in the capture of the deep‐waler eel Synaphobranchus kaupi. This eel was numerically dominant over the mid to lower slope and probably accounts for much of the similarity between areas at these depths.

Rod Outer Segment Renewal in the Retinae of Deep-sea Fish

Outer segment renewal involves the synthesis of disc material in the photoreceptor inner segments, the shedding of the tips of the photoreceptor outer segments, and their phagocytosis by the retinal pigment epithelial cells. It has been suggested that in the retinae of deep-sea fish no renewal of outer segments may take place. In order to assess outer segment renewal in deep-sea fish retinae we counted (i) periciliary vesicles in rod inner segments as a parameter for disc-synthesis activity and (ii) phagosomes in retinal pigment epithelial cells as a parameter of shedding and phagocytosis in 12 species of deep-sea fish with multibank or single bank retinae. We also measured the lengths of rod outer segments in order to evaluate the balance between synthesis and phagocytotic activity. In four of these species ( Synaphobranchus kaupi, Nematonurus armatus, Coryphaenoides guentheri and Halosauropsis macrochir) we further recorded size-related changes of these parameters and their relation to the position of a given rod within the banks in the retina. The number of periciliary vesicles was highest in inner segments of the most vitread bank and in the periphery of the retina. Phagosomes were most abundant in retinal pigment epithelial cells of the central retina. Long rod outer segments were most frequently recorded in the peripheral retina indicating that in this region new synthesis may outbalance shedding. Vitread rod outer segments were only slightly longer than sclerad ones. Larger animals had shorter rod outer segments than small ones. We present evidence that rod outer segment renewal takes place in the retina of all deep-sea fish. Vitread rods may be more active in this respect than sclerad ones. Copyright © 1996 Elsevier Science Ltd.

The Distribution and Diet of the Dominant, Slope-Dwelling Eel, Synaphobranchus Kaupi, of the Rockall Trough

INTRODUCTIONThe deep-sea eel, Synaphobranchus kaupi, is widely distributed on the continental slopes of the North Atlantic (Saldanha & Bauchot, 1986; Haedrich & Merrett, 1988). It was a dominant fish species in epibenthic sledge and semi-balloon otter trawl (OTSB) hauls on the West African slope (Merrett & Marshall, 1981; Merrett & Domanski, 1985). Also in the eastern North Atlantic, it was the most abundant species on the slopes of the Porcupine Sea Bight off south-west Ireland (Merrett et al., 1991; Priede et al., 1994). In the western North Atlantic, it was the dominant species on the middle and lower slopes of the Middle Atlantic States of the USA and on the upper slopes of the Grand Banks off Newfoundland (Sedberry & Musick, 1978; Houston & Haedrich, 1986).

Scavenging deep demersal fishes of the Porcupine Seabight, north-east Atlantic: observations by baited camera, trap and trawl

Demersal fishes on the continental rise and slope were sampled by trawl, baited trap and a baited camera. Seventy-one different species were trawled, but only 18 species approached baits. At rise soundings (4100 m to 2250 m) Coryphaenoides (Nematonurus) armatus was dominant at baits and comprised 41·5% of the trawl catch. On the slope (<2250 m) Synaphobranchus kaupi was dominant at baits and comprised 32·7% of the trawl catch. At 1500–2501 m Antimora rostrata competed at baits and comprised 5–10% of trawl catches. At 1500–1650 m Centroscymnus coelolepis also consumed baits but was not captured by trawl. For C. (N.) armatus abundance was proportional to tarr2 (where tarr= arrival time), demonstrating that arrival time of the first fish at baits provides an estimate of population density. Maximum estimated abundance at 2897 m was 877 km-2, more than five times the abundance on the abyssal plain. Halosauropsis macrochir, Lepidion eques, Coryphaenoides guentheri, Gadiculus argenteus and Coryphaenoides rupestris were important in trawl samples but absent or rare at baits.

Deep Demersal Fish Assemblage Structure in the Porcupine Seabight (Eastern North Atlantic): Slope Sampling By Three Different Trawls Compared

The demersal ichthyofauna of the continental slope of the Porcupine Seabight, eastern North Atlantic, was studied from 144 samples taken by three different types of otter trawl. At least 118 species from 43 families were represented among some 54,000 specimens collected from 247 to 2172m soundings. Collectively, the catches were dominated in species richness by the Macrouridae, Alepocephalidae and Squalidae and in abundance by the Synaphobranchidae, Macrouridae and Moridae. Separately, relative abundance of species was more similar between the two larger trawls, setting their catches apart from the smaller net. Gear selectivity evidently accounted for this variation, which was examined by an index we developed and call species fidelity. This accounts for patterns of continuous faunal change with increased soundings concomitant with variance in species adult size and mobility. In pursuance of a more accurate representation of relative biomass and abun-dance than achieved hitherto, the best estimate, within the limitations imposed by the sampling gears and regime, was derived from a combination of the mean values per 200m stratum of the two large trawls with the addition of those of the eel, Synaphobranchus kaupi, from the small gear. Tentative comparisons between these results and those from elsewhere suggest that the Porcupine Seabight is generally lower in biomass and similar or lower in abundance. It was concluded that an accurate indication of ichthyofaunal structure with increased soundings can only be achieved through a detailed knowledge of the size structure of each species over its entire sounding range synthesized from a multi-trawl investigation via analyses of species fidelity.

Myxozoa of Deep-Sea Fishes in the Northwestern Atlantic

The gall bladder of 5 species of deep-water fishes (Coryphaenoides armatus, Coryphaenoides rupestris, Macrourus berglax, Antimora rostrata, and Synaphobranchus kaupi) from the New York Bight and Carson Canyon areas in the northwest Atlantic were examined for myxozoan parasites. Myxidium coryphaenoidium was found in 4 fish species, whereas Auerbachia pulchra and Ceratomyxa sp. were each observed in 1 fish species. Prevalence of myxozoan infections was greater in fishes taken off the New York Bight than from the Carson Canyon.

Little evidence for faunal zonation or communities in deep sea demersal fish faunas

Demersal fish data from 9 deep-sea surveys in the North Atlantic were examined to assess (1) the coherence and continuity of zones around the ocean basin, and (2) the persistence of structured communities over more than just a local scale. The 63 cruises took 96,779 specimens and 325 species in 692 benthic trawl hauls between 204 and 5345m depth. Measures of similarity and overlap applied to this faunal data did not produce patterns other than those reflecting the occurrence of two widespread and abundant species - Synaphobranchus kaupi at slope depths and Nematonurus armatus on the rise. Communities defined within a survey area by commonly-used analytical procedures cannot be identified from place to place over broader areas, and the concept along with its implication should be abandoned.

Pseudolernaeopodina synaphobranchi n. gen., n. sp. (Copepoda: Lernaeopodidae) from the Eye of Synaphobranchus kaupi Johnston, 1862, in the Northwest Atlantic Ocean

A new genus of parasitic copepod from the family Lemaeopodidae, Pseudolernaeopodina synaphobranchi, is described from a single specimen found on the eye of the demersal eel, Synaphobranchus kaupi. The specimen exhibits a mixture of morphological features found in 3 other lernaeopodid genera; Clavellistes, Lernaeopodina, and Pseudocharopinus. Distinguishing morphological characters of the new genus include a nonprehensile second antenna armed at the apex of the endopod with 1 degenerate hook and 1 attenuated process, an absence of posterior processes, and a seta at the base of the lateral exopod of the first maxilla. Pseudolernaeopodina synaphobranchi is tentatively aligned with the Charopinus group of the Lernaeopodidae, but is considered an aberrant genus, probably having evolved separately from other groups of genera in the family. During a research cruise of the R/V Oceanus off the coast of New Jersey in March 1987, a single specimen of a lernaeopodid copepod was found attached to the cornea of Synaphobranchus kaupi, a demersal eel. When examined, the copepod exhibited features that could not be accommodated in any presently known genus of the Lernaeopodidae. The specimen, Pseudolernaeopodina synaphobranchi n. gen., n. sp. is herein described and figured, and its phylogeny

Rarely Seen Fishes Captured in Hudson Submarine Canyon

The alepocephalid Rouleina mollis (Koehler 1896), the ophidiid Xyelacyba myersi Cohen 1961, and the two macrourids Nezumia longebarbatus (Roule and Angel 1933) and Sphagemacrurus grenadae (Parr 1946) were trawled in Hudson Submarine Canyon (ca. 39°18′N 72°00′W) between 1500 and 1960 m on the bottom. These records constitute considerable extensions of the known ranges. The eretmophorid Halargyreus johnsoni Günther 1862, previously recorded from Hudson Canyon but unknown elsewhere in the area, was also taken. The trawl haul which captured these noteworthy species took, in addition, 290 specimens in 18 species of deep benthic fishes. Abundant species included Antimora rostrata, Synaphobranchus kaupi, Alepocephalus agassizi, Nezumia bairdii, Dicrolene intronigra, and Aldrovandia phalacra. These species also predominated in a catch made in a similar haul at the same place 4 yr previously, suggesting that the species composition of such deep-living canyon assemblages is quite stable.