International Ridge-Crest Research: Biological Studies. Vol. 10(1): 15-1

Almeida, A. J.

Biscoito, M.

Segonzac, M.

English

Universidade de Lisboa: Repositório.UL

15Vol. 10(1), 2001b New zoarcid fish species from deep-sea hydrothermal vents of the Atlanticand Pacific OceansM. Biscoito1, M. Segonzac2 and A. J. Almeida31 IMAR - Museu Municipal do Funchal (História Natural), R. da Mouraria, 31, 9004-546 Funchal, Portugal2 IFREMER, Centre de Brest, BP 70, 29280 Plouzané, France3 IMAR – Laboratório Marítimo da Guia, Estrada do Guincho, 2750-642 CASCAIS, Portugal International Ridge-Crest Research: Biological StudiesIntroductionThe fish family Zoarcidae has 45genera, two of which have been re-corded from active hydrothermalvent fields, Pachycara Zugmayer,1911 and Thermarces Rosenblatt &Cohen, 1986.The genus Pachycara contains17 species occurring in the Pacific,Atlantic, Antarctic and IndianOceans (Møller and Anderson,2000).  Three of them, P. gymniniumAnderson and Peden, 1988, P. rimaeAnderson, 1989 and P. thermophil-um Geistdoerfer, 1994, have beencollected in active deep-sea hydro-thermal vents, the last two beingendemic to this type of environment(Tunnicliffe et al., 1998).To date, only one species ofPachycara (P. thermophilum) hasbeen recorded from the Mid-Atlan-tic Ridge hydrothermal vents. Thisspecies was originally describedfrom Snake Pit (23°22´N, 3,480 m)and subsequently found at Logatch-ev (14°45´N, 3,000 m), TAG (26°N,3,700 m) and Broken Spur (29°N,3,020 m) (Parin, 1995; Anderson andBluhm, 1996; Geistdoerfer, 1997).In contrast with Pachycara,Thermarces has only 3 nominal spe-cies, all of them restricted to chem-osynthetically-driven environ-ments: Thermarces cerberus Rosen-blatt & Cohen, 1986, from 21°N,13°N, 11°N and 9°N, in the EastPacific Rise and also in the Galapa-gos Ridge, T. andersoni Rosenblatt& Cohen, 1986 from 13°N EPR [con-sidered a doubtful species (Ander-son, 1994)], and T. pelophilumGeistdoerfer, 1999 from the Barba-dos accretionary complex.Collection of specimensMid-Atlantic Ridge  - (Pachycaran. sp.).In 1997 the newly discoveredRainbow vent field, in the Mid-At-lantic Ridge (36°13.8´N, 2270 – 2320m) was first visited by biologists,during Nautile’s diving cruiseMARVEL (Aug – Sept 1997, PIs: D.Desbruyères and A-M. Alayse). Inone of the dives (PL 1197, 23/8/1997)a zoarcid fish was seen dwellingamong mussels (Fig. 1). At that timeit was impossible to collect a speci-men. One year later, during AMOREScruise PICO (Jun – Jul 1998, PI: D.Desbruyères) and the Franco-Por-tuguese AMAR (Luis Mendes-Vic-tor, FCT contract PRAXIS/2/2.1/MAR/1748/95), cruise SALDANHA(July 1998, PI: F. Barriga), Rainbowvent field was revisited and exploredwith Nautile. This time 6 specimenswere collected with the submersi-ble’s slurp-gun, and preserved foridentification.Figure 1. Pachycara sp. n. amongst mussels at Rainbow vent field. Photographtaken from video recorded by the Nautile during MARVEL cruise (AtlanticOcean).InterRidge News16It is undoubtedly very closelyrelated to P. thermophilum Geistdo-erfer, 1994, which also occurs in thesame type of environment, 1,100 kmsouth of Rainbow vent field. Thefirst major difference found in ourspecimens is the presence of twobranches of the lateral line (medium-lateral only in P. thermophilum).Other differences include theinterorbitary width, which is con-sistently higher in our specimensthan in P. thermophilum and thenumber of caudal vertebrae and dor-sal and anal fin rays, whose countsare also higher in our specimens. Infact the vertebral formula do notcoincide with any of the other 17described species of Pachycara,with the exception of P. bulbiceps,Garman,1899, which can easily beseparated from our new species bythe absence of pelvic fins.Colour, uniformly light brownwith whitish scale pockets, givesthe specimens a mottled appearance.Outer margins of dorsal, anal andpectoral fins are dark. Eyes bluishand abdomen dark bluish brown. Onvideo images taken by the submers-ible, the specimens appear almostwhite, with dark dorsal, anal andpectoral fins.To date, this species is onlyknown from Rainbow hydrothermalvent field, Mid-Atlantic Ridge(36°13.8’N, 2 270 – 2 320 m).Thermarces n. sp. (Fig. 4)This new species, being de-scribed elsewhere, is diagnosed bythe following characters: vertebralformula 26-27+61=87-88, 79-81 dor-sal fin rays, 15 pectoral fin rays andfour teeth in a single row on vomer.Our two specimens can easily beseparated from T. cerberus and T.pelophilum by the above mentionedcharacters. Moreover, in all speci-mens of T. cerberus examined, teethon vomer are not only more numer-ous, but always arranged in a patch,and not in a single row. Althoughcolour should not be used as a diag-nostic characteristic, it is worthwhilenoting that our two specimens wereuniformly dusky brown, when cap-Figure 2. Thermarces sp. n. at 9°50’N, EPR. Photograph taken from videorecorded by the Nautile during HOT’96 cruise (Pacific Ocean).Figure 3. Pachycara sp. n. Drawing of the holotype, 247 mm SL.Figure 4. Thermarces sp. n. Drawing of the holotype, 375 mm SL.Two specimens were collectedwith a baited fish trap during HOT 96cruise (Feb – Mar 1996, PI: F. Gaill.)(Nautile dive PL 1079, 08/03/1996) atthe East Wall site (9°50.6’N, 2530 m)among mussels (many of them dead)(Fig. 2).ResultsPachycara n. sp. (Fig. 3)This new species, being de-scribed elsewhere, is distinguishedby the following characters: 31-32+85-86=117 vertebrae, gill rakers2+14, dorsal fin with 109 rays, analfin with 90-91 rays, pelvic finspresent, with 2 rays, their length11.4-13.5% HL, lateral line with me-dium-lateral and ventral branches,the latter very inconspicuous,scales absent from cheek, nape andabdomen. International Ridge-Crest Research: Biological Studies: Biscoito et al., cont ....East Pacific Rise, 9°N (Thermarces n. sp.).17Vol. 10(1), 2001btured. After four years in preserva-tive, they have more or less kept thesame colour. On the contrary, T.cerberus when fresh, are very lightyellowish brown, sometimes mot-tled. After an equivalent time in pre-servative they become colourless.Another remarkable difference is thesize of the body. Thermarces n. sp.is noticeable more corpulent than T.cerberus. Both differences, in col-our and size, were confirmed by vid-eo observations.This new species is only knownwith certainty from 9°N, 2520 m, EastPacific Rise.Ecological informationPachycara n. sp. lives well in-side the active areas, usuallyamongst mussels and in betweensmall boulders at the base of chim-neys. Direct observations showedthat these fish are usually solitary,the minimum observed distance be-tween two specimens being 1.5 m.Consequently they seem not to bevery abundant. In general they arenot very active, unless disturbed.The temperature measured withNautile’s probe in the exact placewhere a specimen was collected atRainbow (marker PP37, 2287 m), was15°C. Sea water temperature outsidethe active site was 3.8°C.Stomach content analysis in onespecimen revealed the remains ofshrimp Rimicaris exoculata (Crus-tacea, Decapoda, Bresiliidae) to-gether with orange-brown particlesof oxides, very characteristic of Rain-bow vent field. Based on the infor-mation available, Pachycara n. sp.can probably be considered endem-ic to Rainbow.Thermarces n. sp. collected atEast Wall (EPR, 9°N) lives inside orin the periphery of mussel beds(Bathymodiolus thermophilus) cov-ering certain depressions on thebasalts, bathed by mild temperaturehydrothermal fluids (6.7°C) comingfrom diffuse vents (sea water tem-perature was 1.7°C). At this site thedensity of these fish was very low(4-5 individuals over several tens ofsquare metres).During the mission HOPE 99 (Apr– May 1999, PI: F. H. Lallier), greateffort was made to obtain more spec-imens of this new species. All ventzoarcids collected at 13° and 9°Nbelonged to the species T. cerberus,which live in great numbers amongstclumps of Riftia pachyptila. On vid-eo images, all specimens observedshowed the typical whitish coloura-tion, leading us to conclude thatthey were all T. cerberus. At 9°N,none of the specimens recorded onvideo during the mission could beassigned to this new species, nei-ther at East Wall, nor at variousother sites extending 5 km furthernorth.ConclusionsThe finding of these new speciesreinforces the position of the familyZoarcidae, as the dominant fish taxonin the hydrothermal vent environment.In the description of Thermarces n.sp., the authors will deal with the affin-ities of the new species with the T.cerberus/T. andersoni complex. Infuture missions to the EPR, emphasisshould also be put in obtaining morespecimens from Thermarces n. sp.,not only to obtain material for geneticanalyses in order to establish the rela-tionship between the two species, butalso to ascertain their distribution.We also expect to be able to collectmore specimens of Pachycara n. sp.during the forthcoming ATOS cruise,scheduled for June 2001, in order toobtain material for genetic analyses.AcknowledgementsThe authors are indebted toFrançoise Gaill, Daniel Desbruyères,Fernando Barriga and François Lalli-er, Chief-Scientists of HOT 96, MAR-VEL and PICO, SALDANHA andHOPE 99 cruises respectively, for theinvitations to take part in these cruis-es and collaboration on board. Thanksare also due to the Captains and crewsof the French N/O Nadir and N/OL’Atalante, the pilots and techniciansof the deep submersible Nautile, andseveral colleagues for all their help atvarious levels during the cruises. Hele-na Encarnação of the Museu Munci-pal do Funchal (História Natural) madethe fine illustrations.This work was made possiblethrough funds obtained from the EU-MAST3 funded AMORES (AzoresMOR Ecosystem Studies, Coordina-tor D. Desbruyères, MAST III con-tract MAS3-CT95-0040.) (Contract n°MAS3 95-0040), Portuguese PRAXISXXI AMAR Project (Contract n°PRAXIS/2/2.1/MAR/1748/95, and bythe URM 7 Ifremer and Dorsales Pro-gramme. The examination of materialat the MNHN in Paris was sponsoredby the ICCTI-IFREMER Agreement inOceanology.ReferencesAnderson, M. E., Systematics andosteology of the Zoarcidae(Teleostei: Perciformes).Ichthyological Bull., 60: 1-120, 1994.Anderson, M. E. & H. Bluhm,Description of new species ofPachycara Zugmayer, 1911 fromthe abyssal south-eastern Pacificand redescription of P.thermophilum Geistdoerfer, 1994,with a new key to the species.Transactions of the Royal Societyof South Africa, 51: 219-227, 1996.Geistdoerfer, P., Pachycarathermophilum Geistdoerfer, 1994,226. In: Handbook of deep-seahydrothermal vent fauna.Desbruyères, D. & M. Segonzac(Eds.). IFREMER, Brest. 279 , 1997.Møller, P. R. & M. E. Anderson,Assignment of Lycodesmicrocephalum Jensen, 1902 toPachycara Zugmayer, 1911(Teleostei: Zoarcidae). Cybium,24(1): 61-65, 2000.Parin, N. V., Deep-Sea Fishes,Haptenchelys texis(Synaphobranchidae) andPachycara thermophilum(Zoarcidae) from Broken SpurHydrothermal Vent Field (Mid-Atlantic Ridge). Journal ofIchthyology, 35(9): 328-332, 1995.Tunnicliffe, V., A. G. McArthur & D.McHugh, A BiogeographicalPerspective of the Deep-SeaHydrothermal Vent Fauna.Advances in Marine Biology, 34:353-442, 1998. International Ridge-Crest Research: Biological Studies: Biscoito et al., cont ....

Assignment of Lycodes microcephalum Jensen,

Description of new species of Pachycara Zugmayer,

Fishes, Haptenchelys texis (Synaphobranchidae) and Pachycara thermophilum (Zoarcidae) from Broken Spur Hydrothermal Vent Field (MidAtlantic Ridge).

International Ridge-Crest Research: Biological Studies: Biscoito et al., cont ....

Pachycara thermophilum Geistdoerfer,

with a new key to the species.

New zoarcid fish species from deep-sea hydrothermal vents of the Atlantic

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New zoarcid fish species from deep-sea hydrothermal vents of the Atlantic

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