Porcupine Seabight Research Articles

Seismic evidence of current-controlled sedimentation in the Belgica mound province, upper Porcupine slope, southwest of Ireland

The Porcupine Seabight is an embayment that takes a particular position in the NE Atlantic slope. Sonographs, a few current measurements and hydrodynamic modelling suggest the presence of a strong northward-flowing bottom current, locally enhanced by internal tides, affecting the eastern slope of the Seabight. At this location a province of coral banks is described, expressed as mounds lined up in along-slope-trending ridges. In this paper, very high-resolution single-channel seismic profiles are used to evaluate to what extent the bottom currents influenced the deposition of the sediments surrounding the mounds throughout the Late Cenozoic. Three seismostratigraphic units (P1, P2 and P3) can be identified in the Belgica mound area, separated by two margin-wide discontinuities (RD2 and RD1). Within Unit P1 (probably Early to Middle Miocene) upslope-migrating sediment waves are observed, suggesting strong bottom currents were already active in the Miocene. After an early Middle Miocene erosion event, represented by reflector RD2, an acoustically transparent layer (Unit P2) of as yet unknown lithology was deposited in the studied area. A second margin-wide erosional event, marked by the Late Pliocene RD1 reflector, removed a large part of Unit P2 and has cut deeply into Unit P1. Subsequently, the Belgica mounds were constructed spectacularly fast on topographic irregularities on the RD1 paleobathymetry. The onlap within the Quaternary Unit P3, which surrounds these mounds, suggests that the mounds were already present before the deposition of P3 and were big enough to affect the intensity of the currents around them. Furthermore, the channels and the mounds are, together with the complex oceanographic regime, the key morphological elements responsible for the shaping of a contourite system in the Belgica mound area during the Quaternary. One drift body is formed by an inferred south–north-directed current, with a drift levee and associated channel located on its western side. Between this channel and the mounds, large-scale sediment waves suggest an intensified bottom current running along the foot of the steep flanks of the mounds. The Belgica mounds are embedded in another drift body. Here, an interaction of bottom and turbidity currents is suggested, creating short turbidite channels at the southern and northern flanks of the mounds. Locally, small confined drifts can be observed where Unit P3 is deposited in a narrow passage made by the paleobathymetry of RD1 and the mounds.

The summer distribution of net plankton dinoflagellates and their relation to water movements in the NE Atlantic Ocean, west of Ireland

A grid of 28 stations on the continental shelf and slope region west of Ireland, which included the Porcupine Bank and the Porcupine Sea Bight, was sampled for net phytoplankton in the summer (June and July) of 1995. Armoured dinoflagellates were recorded on both a relative abundance and presence/absence basis. Results showed good agreement with the physical circulation of the region, based on an analysis of seasonal current meter data from the upper 500 m of the water column. The distributions of some dinoflagellate species, known to have either a mainly oceanic or warm temperate distribution, indicated the existence of two separate slope currents in the region, one along the Irish Shelf with a source in the Bay of Biscay, and the other along the western slope of the Porcupine Bank fed by the North Atlantic Current waters. The data presented here support the idea that, in summer at least, the slope current west of Ireland is not entirely coherent in the upper layers of the water column.

Depth-related distribution and abundance of seastars (Echinodermata: Asteroidea) in the Porcupine Seabight and Porcupine Abyssal Plain, N.E. Atlantic

The depth-related distribution of seastar (Echinodermata: Asteroidea) species between 150 and 4950 m in the Porcupine Seabight and Porcupine Abyssal Plain is described. 47 species of asteroid were identified from ∼14,000 individuals collected. The bathymetric range of each species is recorded. What are considered quantitative data, from an acoustically monitored epibenthic sledge and supplementary data from otter trawls, are used to display the relative abundance of individuals within their bathymetric range. Asteroid species are found to have very narrow centres of distribution in which they are abundant, despite much wider total adult depth ranges. Centres of distribution may be skewed. This might result from competition for resources or be related to the occurrence of favourable habitats at particular depths. The bathymetric distributions of the juveniles of some species extend outside the adult depth ranges. There is a distinct pattern of zonation with two major regions of faunal change and six distinct zones. An upper slope zone ranges from 150 to ∼700 m depth, an upper bathyal zone between 700 and 1100 m, a mid-bathyal zone from 1100 to1700 m and a lower bathyal zone between 1700 and 2500 m. Below 2500 m the lower continental slope and continental rise have a characteristic asteroid fauna. The abyssal zone starts at about 2800 m. Regions of major faunal change are identified at the boundaries of both upper and mid-bathyal zones and at the transition of bathyal to abyssal fauna. Diversity is greatest at ∼1800 m, decreasing with depth to ∼2600 m before increasing again to high levels at ∼4700 m.

Textural analyses of sidescan sonar imagery from two mound provinces in the Porcupine Seabight

Large mound structures have been discovered in the Porcupine Seabight (Northeast Atlantic) at a depth of 500–1200 m, associated with the growth of cold-water deep-sea coral species such as Lophelia pertusa (L.) or Madrepora oculata (L.). During the Training Through Research cruise in 1997, high-resolution OREtech sidescan sonar data were acquired over two provinces of these structures. This article focuses on the presentation and quantitative interpretation of representative sections of these sidescan data from areas around the Belgica and Hovland mounds. Several image analysis tools were used, but texture analysis, based on grey level co-occurrence matrices, gave the best results. Entropy and homogeneity indices were calculated, and the resulting images made it possible to discriminate between different seabed features on a quantitative basis. Mounds, moats and background sediments could be delineated accurately, and the image textures could be linked to the actual seafloor appearance through core descriptions and deep-towed video data. A major difference was found in the acoustic returns from the two provinces studied: the Belgica province shows much rougher textures. This is due to an actual difference in seabed roughness, caused by a difference in bottom currents and sediment dynamics in the two areas. The combined effect of the northward-directed North Atlantic slope current and superimposed internal waves and tides appears to be much stronger in the Belgica province. The reported difference in current strength might well influence the growth of the deep-water coral species in both areas.

First records of advanced embryos and egg capsules of Bathyraja skates from the deep north‐eastern Atlantic

Five variously developed embryos [142–279 mm total length (LT)] from egg capsules from the Porcupine Seabight, north‐eastern Atlantic (1541 m depth) are used to establish the ontogeny and early life history of Bathyraja richardsoni. The capsules of this species and two half‐formed ones from the shell glands of a large (1620 mm LT) female Bathyraja pallida taken off Ireland (c. 1900 m depth) are described and illustrated. The varying degree of yolk sac absorption found in the B. richardsoni embryos is discussed in relation to hatching size and its seeming size independence over c. 20–50 mm within the embryos’ total length range. The conservative variation in external morphology with development from advanced embryos to adults among such deep stenobathic Bathyraja skates is commented upon, as is the bathymetric segregation of adults from levels in which egg capsules are deposited and young develop.

Aspects of the structure of the Porcupine and Porcupine Seabight basins as revealed from gravity modelling of regional seismic transects

Abstract The Porcupine Basin is characterized by a large central free air gravity anomaly high (+ 55 mGal) flanked by local lows. In contrast, the Procupine Seabight Basin has low-amplitude anomalies in its centre, flanked by edge anomalies. Two transects, one in each of these basins, have been modelled using satellite gravity data; the upper parts of the transects are constrained by interpretation of recent commercial seismic reflection data and two wells. Results from the modelling suggest that the Porcupine Basin is not in isostatic equilibrium. In contrast, the essentially zero free air anomaly over the centre of the Porcupine Seabight Basin suggests that this basin is isostatically compensated. The difference in isostatic compensation between the two basins may reflect a fundamental contrast between the strength of the crust; the crust underlying the Porcupine Basin possesses the greater strength. The Clare Lineament may represent a fundamental boundary within the ‘Avalonian Terrane’ that juxtaposes basement blocks of differing rheologies.

Haemogregarines and other blood infections from deep demersal fish of the Porcupine Seabight, north-east Atlantic

Giemsa-stained blood smears were examined from 70 deep demersal fish of 27 species in 20 genera, trawled from depths of 747–4143 m in the region of the Porcupine Seabight, north-east Atlantic. Infections were found in four species of teleosts in three families: 1/3 Alepocephalus rostratus and 1/3 Narcetes stomias (Alepocephalidae); 2/3 Antimora rostrata (Moridae); and 1/1 Cataetyx laticeps (Bythitidae). Blood films from C. laticeps and Antimora rostrata were well preserved but those from the other two species were less satisfactory. The blood parasites included two types of haemogregarines, Haemohormidium-like and viral erythrocytic necrosis (VEN)-like infections. Haemogregarina (sensu lato) johnstoni sp. nov. was described from C. laticeps captured at 1541 m. This haemogregarine was unusual in apparently having dimorphic gamonts, some with prominent caps. A second, but monomorphic, haemogregarine found in Alepocephalus rostratus captured from 985 m, was named as Desseria sp. since only extracellular stages were observed. Haemohormidium-like organisms were found in Antimora rostrata taken from 2441 m, and were similar to those described previously from this deep-sea fish. A VEN-like infection from one N. stomias captured from 2567 m was reported. No marked effects on host cells were evident in any of these blood infections.

Sexually Dimorphic Expression of Glutamate Decarboxylase mRNA in the Hypothalamus of the Deep Sea Armed Grenadier, Coryphaenoides (Nematonurus) armatus

Glutamate decarboxylase (GAD), is a key enzyme in the central nervous system (CNS) that synthesizes the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) from glutamate. Our previous phylogenetic studies on the evolution of this enzyme indicates that there are at least two distinct forms: GAD65 and GAD67. They are the products of separate genes and probably derive from a common ancestral GAD gene following gene duplication prior to the emergence of the teleosts more than 200 Myr ago. Furthermore, a third GAD-like molecule, GAD3, discovered in the armed grenadier, Coryphaenoides (Nematonurus) armatus, is equally divergent from both GAD65 and GAD67. Specimens of C. (N.) armatus were collected by trawl at a depth of 4,000 m in the Porcupine Seabight (Northeastern Atlantic), and brains dissected and frozen for RNA extraction. All three GAD forms are found in the cerebellum, telencephalon and hypothalamus. Semiquantitative PCR analysis showed that males and females have similar levels of expression of GAD67 and GAD3 in the tissues studied. Independent of the sex examined, the levels of expression of GAD65 and GAD67 in the cerebellum were approximately half that in the telencephalon. GAD3 levels were approximately 30% higher in the cerebellum than in either the telencephalon or hypothalamus. In contrast to GAD67 and GAD3, hypothalamic expression of GAD65 mRNA is 1.8 times higher (p < 0.05) in males than in females. These data indicate that the expression of GAD65, a key enzyme for the synthesis of GABA is sexually dimorphic in females and males of C. (N.) armatus.

The hydrography of the mid-latitude Northeast Atlantic Ocean: II: The intermediate water masses

The intermediate water masses in the eastern Atlantic Ocean between 31°N and 53°N were studied by analysis of the distributions of potential temperature, salinity, dissolved nutrients and oxygen. Sub-surface salinity minima are encountered everywhere in the area. At the northern and southern boundary they are connected with the presence of Sub-Arctic Intermediate Water and Antarctic Intermediate Water, respectively, but towards the European ocean margin the sub-surface salinity minima shift to shallower density levels. The sub-surface salinity minima observed west of the Iberian Peninsula represent a water mass formed by winter convection in the Porcupine Sea Bight and the northern Bay of Biscay. These minima gain salt by diapycnal mixing with the underlying Mediterranean Sea Outflow water and with the overlying permanent thermocline. The core of Antarctic Intermediate Water appears to contribute to the formation of Mediterranean Sea Outflow Water since it becomes entrained into the overflow near Gibraltar. This entrainment gives rise to an enhanced concentration of the nutrients in the Mediterranean water in the North Atlantic. The deep salinity minimum, due to the presence of Labrador Sea Water, is restricted mainly to the Porcupine Abyssal Plain. In the Bay of Biscay this water type is strongly modified by enhanced diapycnal mixing near the continental slope. At all intermediate levels the continental slope in the Bay of Biscay seems to be a focal point for water mass modification by diapycnal mixing. Below the core of the Mediterranean Sea Outflow Water the Labrador Sea Water is also strongly modified. Its salinity is strongly enhanced by diapycnal mixing with the overlying core of Mediterranean Sea Outflow Water. An analysis of the oxygen and nutrient data indicates that the large spatial concentration differences at the level of the Labrador Sea Water are caused mainly by ageing of the water. The youngest water is observed at 52°N, and, especially in the Bay of Biscay and off south-west Portugal, the water at levels of about 1700 dbar are strongly enriched in nutrients and depleted in oxygen.

Nematode abundance at the oxygen minimum zone in the Arabian Sea

This paper supports the hypothesis that low oxygen does not influence deep-sea nematode abundance by investigating an oxygen minimum zone (OMZ) on the Oman slope in the Arabian Sea. Correlation with a number of environmental variables indicated that food quality (measured as the hydrogen index) rather than oxygen was the major predictor of nematode abundance. Nematode abundance was also positively correlated with abundance of total macrofauna, annelids, spionid polychaetes and macrofaunal tube builders. Comparison with published data showed Arabian Sea nematode abundance to be similar to that of the Porcupine Seabight and Bay of Biscay regions of the northeast Atlantic, which also receive significant quantities of phytodetritus but have no OMZ.

Diversity patterns in macrobenthos across a continental slope in the NE Atlantic

Different estimates were used to assess the diversity of the total macrofauna and its major taxonomic groups separately from a broad bathymetric range at a site in the NE Atlantic. In the Goban Spur region, a transect was sampled from the shelf to the abyssal plain over a depth range from ∼200 to ∼4500 m and in the Porcupine Sea Bight two stations were sampled (at 3670 m and 4115 m). Species diversity (the number of species per number of individuals) increased with increasing water depth, both when expressed as Hurlbert's E(S n ) and as Shannon's H′ log e . The expected number of species in a 100-individual sample E(S 100) of total macrofauna increased from 30 on the shelf to 68 on the abyssal plain. Evenness (the proportional abundance of species), estimated with Shannon's J′, also increased with water depth from 0.66 to 0.91, whereas dominance (Simpson's D) decreased from 0.09 to 0.01. Species richness (the number of species per unit of area), however, showed a parabolic pattern with a peak at the upper slope. The largest number of species was found at the slope station at 1425 m (232 species within 0.66 m 2). It is argued that species richness is not a synonym of species diversity, but that species richness depends both on species density (which decreases with increasing water depth) and on species diversity. Across the whole bathymetric range (∼200 to ∼4500 m) a total of 696 species within 8327 specimens in a total sampled area of 4.12 m 2 were counted, yielding mean values of ∼12 individuals per species and ∼169 species per m 2. Different communities were found to exist on the shelf, slope and abyss. It is suggested that this could have been caused by different selection processes. Differences in life-history strategies and organic-matter supply could (at least partly) explain the different community structures and diversity patterns found along the depth gradient.

In situ comparison of activity in two deep-sea scavenging fishes occupying different depth zones

The activity of two scavenging deep-sea fishes occupying the same niche in overlapping depth zones were compared by in situ measurements of swimming speeds, tail-beat frequencies and by arrival time at baits. At 4800 m on the Porcupine Abyssal Plain, the grenadier Coryphaenoides (Nematonurus) armatus was the dominant scavenger, arriving at baits after 30 min, and swimming at relatively slow speeds of 0.17 body lengths (BL) sec-1. At 2500 m in the relatively food rich Porcupine Seabight both C. (N.) armatus and the blue-hake, Antimora rostrata, were attracted to bait, but A. rostrata was always the first to arrive and most of the bait was consumed before the C. (N.) armatus arrived. A. rostrata swam at mean speeds of 0.39 BL sec-1, similar to related shallow water species at equivalent temperatures. Observations on tail-beat frequency from video sequences confirmed the greater activity of A. rostrata. The data indicate that, given sufficient food supply, high pressure and low temperature do not limit activity levels of demersal deep-sea fishes. Low activity of C. (N.) armatus is an adaptation to poor food supply in the abyss, where these fishes dominate, but prevents it competing with the more active A. rostrata in shallower depths.

Echinorhynchus brayi n. sp. (Acanthocephala: Echinorhynchidae) from Pachycara crassiceps (Roule) (Zoarcidae), a deep-sea fish.

Echinorhynchus brayi n. sp. (Palaeacanthocephala: Echinorhynchidae) is described from Pachycara crassiceps (Roule) (Zoarcidae) from the Porcupine Seabight, Northeast Atlantic. The new species closely resembles E. canyonensis Huffman & Kliever, 1977, a parasite of a Pacific zoarcid, but has longer lemnisci, larger eggs and larger testes. E. brayi n. sp. can be readily differentiated from the ten other Echinorhynchus spp. recorded from deep-sea fishes (E. abyssicola, E. gadi, E. longiproboscis, E. malacocephali, E. melanoglaeae, E. muraenolepisi, E. petrotschenkoi, E. sebastolobi, E. trachyrinci and E. truttae), because it has fewer hooks per longitudinal row.

The vertical distribution of micronektonic decapod and mysid crustaceans across the Goban Spur of the Porcupine Seabight

Abstract The vertical distribution of micronektonic Decapoda and Mysidacea (Crustacea) is examined along a cross-slope transect of stations with soundings ranging from 192 m to 1800 m in the Porcupine Seabight during spring 1994. Eight species were found only at the three deep-water open oceanic stations to the west of the slope, while the horizontal ranges of others extended from deep-water to the outer (lower) slope station. The numbers of species caught at the inner (upper) slope and shelf station were lower than offshore. The species assemblages were broadly different at the deep-water, upper slope and shelf stations with no species occurring continuously across the whole of the transect. Three deep-living species were found in higher concentrations near-bottom over the slope than at similar depths at the adjacent open ocean stations. Factors affecting distribution of species are discussed.

Aspects of the biology of Nezumia aequalis from the continental slope west of the British Isles

Nezumia aequalis is one of the most abundant fishes on the upper and middle continental slopes (500–1750 m depth zones) of the North‐east Atlantic with a peak abundance of three to four individuals 1000 m−2 swept area in the 750‐m zone. Mean and modal size increased with depth, fish from the Rockall Trough (RT) being larger than those at equivalent depths in the Porcupine Seabight (PSB). Sex ratios were close to parity in all depth zones. Females grew larger than males. Head length to total length and to total weight did not differ significantly between sexes but RT fish were heavier at any given length than PSB fish. Serial batch spawning occurred over the first three quarters of the year. Ovaries contained five size groups of eggs, the three largest groups being vitelline and contributing 27% of the absolute individual fecundity which was positively correlated with body size and ranged from 9109 to 26 847. Age determined from sagittal otoliths ranged from 1 to 10 years, the ageing method being validated by a time‐series study of the growing edge of otoliths. The von Bertalanffy growth parameter (k) was estimated at 0·175 and 0·216 from head length and otolith length, respectively.

Abstract: Aspects of the structure and evolution of the frontier deep water Porcupine Seabight Basin

Abstract: Aspects of the structure and evolution of the frontier deep water Porcupine Seabight Basin

Glacial-interglacial variation in organic carbon burial on the slope of the N.W. European Continental Margin (48°–50°N)

The sources and fate of organic carbon (C org) were examined at two sites on the Goban Spur and a single site within the Porcupine Sea-Bight on the N.W. European slope between 48°N and 50°N. Here we present data on the sedimentary C org concentration, its 13C/ 12C composition (δ 13C org) and C org/N of 224 total and 119 fine fraction (<63 μm) samples as a time series running from the instantaneous marker horizon Heinrich Layer 2 (25.5 ka BP) through the last glacial isotope stage 2 and interglacial isotope stage 1 to the present. The significance of the N.W. European slope as a depositional sink for C org has declined in the past twenty thousand years, with flux values decreasing two to three-fold from the late glacial (60–70 mg C cm −2 ka −1) to low late Holocene values. Significant shifts are seen in the δ 13C org signature of both the total and fine fractions between the present interglacial and last glacial. The open slope of the Goban Spur is characterised by relatively low values over the last glacial, with minimum values for the total sediment of around −24.5‰ occurring at ca. 18 ka BP, and generally increasing values during the Holocene with the most recent samples having values of ca. −19.2 to −20.2‰. In the Porcupine Sea-Bight a different relationship is evident with samples from the Last Glacial Maximum being generally higher, while values from the Holocene are lower with a minimum of −23.3‰ occurring just below the mixed layer. Similar trends are observed in the fine fraction albeit with a different dynamic range. Paired analysis of δ 13C org and C org/N are consistent with the organic matter being a climatically forced mixture from C 3-photosynthetic terrigenous and marine organic matter sources. An increased influence of terrestrial C org is suggested on the glacial Goban Spur and Holocene Porcupine Sea-Bight, and vice versa. We suggest that this may be explained by modern wind-driven flushing of terrigenous carbon across the Armorican and Celtic shelves to the N.W. and thence into Porcupine Sea-Bight. During the last glacial increased strength of westerly winds created a residual current regime driving material to the S.W., where it was transported in vigorous tidal off-shelf flushing to the upper slope, followed by slope current transfer to the Goban Spur. Much of this material was presumably delivered by the `Great Channel River' to the outer shelf, thus leading to enhanced flux of terrestrial C org on the Goban Spur. The influence of a freshwater plume from meltwater discharge of the European ice sheet in this region is supported by foramininiferal δ 18O data from which a palaeo-salinity reconstruction shows a greatest negative anomaly of −2.55 (that is S-35) at the time of maximum terrestrial C org content in the sedimentary material. In addition to showing that surface waters over Goban Spur were relatively fresh throughout the glacial, our results also reveal variability in surface salinity on shorter timescales.

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 &amp; 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 &amp; Musick, 1978), from the Portuguese slope and in the Bay of Biscay (Saldanha, 1991), from the west African slope (Merrett &amp; Marshall, 1981; Merrett &amp; Domanski, 1985) and from the Rockall Trough (Gordon &amp; 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.

A tentative chronology of the Moho undulations in the Celtic sea region

A Bouguer anomaly map of the Celtic sea and the Western Approaches of the English Channel has been computed from the free air anomaly which is affected by the variations in sea bed topography. Low pass filters of progressively increasing wavelengths are used to remove the effect of the surfacial features and the broad regional trend associated with the thinning of the continental margin. Application of a low pass filter with a cut off wavelength of 150 km results in a relatively smooth map by suppressing major trends associated with shallow structures; this processing also evidences a few new trends. Another map with a cut off wavelength of 300 km approximates the major gradient associated with changes in the Moho depth over continental margin. These two maps are used to prepare a residual map which exibits three major structural trends, viz., (a) a NE SW trend coinciding with the Mesozoic and Cenozoic Celtic basin is related to the compensation of the near surface mass deficits; (b) a NS trend associated with upwarping of the mantle may represent a subdued echo of the Porcupine Seabight openning; and (c) an EW trend in line with the South Armorican shear zone is distinct from the shelf break of the Western Approaches. A map of the Moho depth over the continental shelf, prepared from the residual anomaly, is explained in terms of basement tectonics. The proposed analysis has been constrained through known seismic refraction and reflection results.

Prodistomum priedei n. sp. (Digenea: Lepocreadiidae) from the deepwater cardinalfish Epigonus telescopus (Perciformes: Epigonidae) in the northern Atlantic Ocean

Prodistomum priedei n. sp. is described from Epigonus telescopus from the Porcupine Seabight. It differs from its closest relatives, P. waltairensis, P. hynnodi and P. alaskensis (Ward & Fillingham, 1934) n. comb. [originally Opechona], in its relatively smaller ventral sucker and smaller eggs. Other differentiating features are tabulated. Attention is drawn to the host-parasite relationship associating a lepocreadiine lepocreadiid with a perciform host, a relationship which is common in warm shallow waters but unusual in cold deep-sea conditions. This may indicate that host and parasite have colonised the deep sea simultaneously and co-evolved in that environment.