Near-bottom and pelagic gammaridean amphipods in the Western Indian Ocean

2004·23 MB·

by  Georgyi M Vinogradov

NEAR-BOTTOM AND PELAGIC GAMMARIDEAN AMPHIPODS
IN THE WESTERN INDIAN OCEAN
by
GEORGYI M. VINOGRADOV
A.N. SevertzovInstitute oftheProblems ofEvolution
(formerlyInstitute ofAnimalEvolutionaryMorphology andEcology) of
theRussian Academy ofScience, 33 LeninAvenue, Moscow 117071, Russia.
With 10 figs and 2 tables
[MSacceptedAugust 1997]
ABSTRACT
BetweenOctober 1988andFebruary 1989,acollectionofpelagicandbenthopelagicgammaridswas
taken during the seventeenth cruise of R/V Vityaz in the tropical (Seamount Error, Mozambique
Channel and Saya de Malha Bank) and subtropical (Walters Shoal) regions ofthe Western Indian
Ocean. A total of2 362 specimens of34 gammaridean species were found, four ofwhich {Amaryllis
maculata,Scopelocheiropsissublitoralis Ichnopus walkeriandRegalia oculata) aredescribedasnew
,
to science. Comparison ofthe near-bottom and pelagic samples permitted detection of a group of
animals mainly confined to the near-bottom water. A key to lysianassoid amphipods of the genus
Trischizostoma is given.
CONTENTS
PAGE
Introduction 40
Materials andmethods 41
Descriptionofmaterial 43
Keyto abbreviations infigures 43
Listofspecies 43
Keytothe genus Trischizostoma 46
Discussion 77
StationList: TablesA-D 80
Acknowledgements 83
References 84
Ann. S. Afr. Mus. 112 (3), 2004:39-88, 10 figs, 2 tables
39
40 ANNALSOFTHESOUTHAFRICANMUSEUM
INTRODUCTION
Amphipods form an important element ofmarine pelagic communities. They inhabit
the surfaceanddeepwatersoftheoceanatalllatitudesfromtheequatortothepolarareas.
They do notusually form dense populations, buttheir diversity and the diversity oftheir
life-forms can be high. All amphipods are ofbenthic origin, but representatives oftheir
different suborders have radiated into pelagic biotopes to differing extents. Unlike the
hyperiids, whichhavebecome completelypelagic, andthe caprellids and ingolphyellids,
which have practically no pelagic representatives, some Gammaridea have penetrated
into this biotope.
The overwhelming majority of marine gammarids are benthic epifaunal species.
However,onlyafewbenthicgammarideans(mainlyinhabitantsofsecludedbiotopes,e.g.
wood-borers, some symbionts ofbenthic animals or highly specialized phytal animals)
never leave the sea floor. The majority ofbenthic gammarideans, representing the most
diverse life-forms, enter the pelagial some way or other. All stages of expansion into
pelagic waters may be traced among them. Some may rise briefly into the near-bottom
layer, some make regular migrations into the meroplankton, others may have a long
pelagic life without losing all connection with the bottom and, ultimately there are those
withapurelypelagicwayoflife (Vinogradov 1992, 1995). Lessthan4percentofmarine
gammaridean species are inthis finalcategory: about 100 species of50 genera, almostall
ofthembelonging to families which also have benthic representatives.
Usually it is thepurelypelagic gammarideans that are capturedby samplers operating
at a considerable distance from the bottom. Other gammarideans from the near-bottom
layersaredifficulttocatchandthereforearepoorlyrepresentedincollections. Itisclearly
necessary to carry out near-bottom trawlings as well as pelagic ones in order to obtain a
completepictureofapelagicgammaridean'staxocene. However,near-bottomtrawlingis
fraught with considerable technical difficulties, and consequently the ocean's
near-bottomlayershavebeenstudiedtoaconsiderablylesserextentthanpurelypelagicor
benthic communities. This is certainlytrue ofthe IndianOcean, where thepurelypelagic
gammaridean faunahasbeeninvestigatedindetailbypastexpeditions (oftheR/VDana,
Siboga, Vityaz(old)1 andothers). Thenear-bottomfaunaisknowntoamuchlesserextent.
In 1974, during the seventeenth cruise of the Russian R/V Akademik Kurchatov to
Peruvian coasts, hauls inthe near-bottom layerwere successfully carried out forthe first
timeusing anIsaacs-Kiddmidwatertrawlwithapressurevibrationtransducer, the signal
ofwhich was transmitted through the cable rope to the frequency meter mounted on the
vessel. The transducerreading permitted continuous information on the precise depth of
thetrawl,andsimultaneousmeasurementofbottomdepthwiththeechosounderpermitted
deployment ofthe trawl in the immediate proximity ofthe bottom. In 1987 this method
was used extensively during the eighteenth cruise of R/V Professor Stockman to the
1 'Old' Vityaz, historicallythethirdRussianresearchvesselbearingthisname,operatedbetween 1949and1979.
Expeditionsofthe'new' Vityaz(sometimesincorrectlymentionedinarticlesas Vityaz-IVorVityaz-IT)beganin
1981.
..
GAMMARIDEANAMPHIPODSINTHE WESTERNINDIANOCEAN 41
Pacific submerged ridges, Nazka and Sala-y-Gomez (Rudjakov & Zaikin 1990). That
cruise, inparticular, gatheredagreatdeal ofnear-bottomgammarideanmaterial fromthis
region (Vinogradov 19906).
MATERIALS AND METHODS
Between October 1988 and February 1989, analogous works were carried out during
the seventeenth cruise of R/V Vityaz (new) in the tropical (Seamount Error Mountain
(EM), Mozambique Channel (MC) and Saya de Malha Bank (SdM)) and subtropical
(Walters Shoal (W))regions oftheWestern IndianOcean2 The specimens ofpelagic and
.
benthopelagic gammarideans collected by this expedition are the basis of the present
work.
Animals were collected with the following apparatus:
1 Samyshev-Aseev modification of the Isaacs-Kidd midwater trawl (IKSAMT) with
transducer(see above). Trawlmouthareawas 5.5 m2 thenetwas 25 m long andmade
,
mm mm m
completely out of5 mesh, a sieve frame (1.3 mesh, 5 length) was fitted at
the cod-end. Two types ofhaul were performed: near-bottom trawling at distances of
m
10-30 fromthebottom(NBT) andpelagictrawlingfarfromthebottom(PT). Inall,
28 hauls were carried out in tropical regions and 24 on the Walters Shoal, yielding
1 788 and 502 gammarideans, respectively.
2. Towed underwater apparatus 'Sound', or 'Zvuk' in the Russian language (TUA
'Sound') (Biryukovetal. 1990). Forplanktonstudiestheconstructionoftheapparatus
was modified by the addition of a sampler consisting oftwo nets with mouth area
0.12 m2andmeshsize 0.178 mm. Thenetswere openedandclosedsuccessivelyusing
the Tucker principle. Control signals for operation of the release gear are applied
autonomously at each of the locks. Constancy of distance from the bottom was
maintainedby the winch operatorusing TV images during tows nearthe bottom, and
bytheapparatus' ownecho-sounderinothercases. Hauls of30to 60 minutes duration
were made at distances of2 m and 30 m fromthe bottom (mfb) at each station. In all,
35 stations were sampled with the TUA (15 on the Walters Shoal) from which
61 gammarideans were taken (Note: apreliminary list ofthese species was published
by Vinogradov (1990a). Here it is made more precise and given in the final variant
(Table 1)).
3 BigJudayplanktonnet(BDN37/50)withmoutharea0.1m2andmeshsize0.18mm
4. Oceanicmodel ofJudayplanktonnet(ODN 80/113)withmoutharea0.5 m2 andmesh
size 0.18 mm.
OnecanfinddetaileddescriptionsoftheWaltersShoalandzoogeographicalanalysisofitspositioninCollete&
Parin(1991).
.
42 ANNALSOFTHESOUTHAFRICANMUSEUM
StandardcatchinglayersduringstationswiththeJudaynetswere 1 000-500, 500-250,
m
250-100, 100-50 and 50-0 from the surface. Ifocean depth at the pointwas less than
m
I 000 m, the lower limit ofthe deepest haul was selected at a distance of50 from the
bottom. The Juday net hauls were usually accompaniedby hauls with the TUA 'Sound'.
Inthis case 'Sound' worksreceivedthenext stationnumber(forexample, st. 2648-ODN
and st. 2649-TUA), but catches were carried out in the same point. Only
II gammarideans were taken in all catches byboth models ofthe Juday nets.
Detailed information on the hauls yielding gammarideans is given in Station List
(Tables A-D, pages 80 to 83). All the gammarideans captured are considered below3
,
togetherwithdataonthe samplinggear, stationnumber,region,timeofcapture (D-day;
N - night), depth and characteristics ofthe haul (NBT-PT for IKSAMT, n mfb for TUA
'Sound').
TABLE
1
Gammaridean abundances at different distances above the seabed
(onbasis ofhauls ofTUA 'Sound' and Juday nets, number ofindividuals)
Group Species TUA'Sound' Judaynets
2mfb 30mfb (near-bottomhauls)
Pelagic Cyphocarisanonyx 5 3 -
-
C. challengeri 2 1
-
Stenopleuraatlantica 1 1
- -
*Eusirella lelegansjuv. 2
*Stenopleuroidesmacrops 18 4 -
*Halicemacronyx - 1 -
-
Bathystegocephalusglobosus 1 1
Parandaniaboecki 1 - -
Benthopelagic *Orchomenepelagica 1 - -
*Eurythenesgryllusjuv - 1 -
*Ichnopuswalkerisp. nov. 3 - -
- -
*Scopelocheiropsissublitoralissp. nov. 2
*Parargissacurticornis - 1 -
*Ampeliscabrevicornis 1 - -
*Stegocephaloidesattingens 5 - 2
*!Eusiruscrosnieri(damagedspcm.) 2 1 -
*Paramoeraaustrina 1 - -
-
*Halicoidestambiella 2 2
*Halicoidesdiscoveryi - 1 1
NB: asterisk(*) indicates amphipodswhichwerefoundonlyinthenear-bottomhauls (inallmaterial).
ForadescriptionofthecollectionofhyperiideanamphipodstakenbythesecatchesfromtheWaltersShoals^e
G.Vinogradov(1993).
GAMMARIDEANAMPHIPODSINTHE WESTERNINDIANOCEAN 43
DESCRIPTION OF MATERIAL
KEY TO ABBREVIATIONS IN FIGURES
Ai-Aii-antennae I and II; L- lower lip; Md-mandible; Mxi-Mxii-maxillae I and
II; Mxp-maxilliped; Pi-PVii-pereopods I-VII (pereopods I and II = gnathopods I and
II); Epm - epimeron III; Ui-Uiii- uropods I—III; T - telson.
LIST OF SPECIES
Lysianassoidae
Trischizostoma barnardi
Trischizostoma tanjae
Amaryllis maculata sp. nov.
Erikus dahli
Cyphocaris anonyx
Cyphocaris challengeri
Cyphocaris richardi
Cyphocarisfaurei
Cyphocaris cornuta
Paracyphocarispraedator
Scopelocheiropsis sublitoralis sp. nov.
Eurythenesgryllus
Eurythenes obesus
Ichnopuspelagicus
Ichnopus walked sp. nov.
Thoriella islandica
Orchomenellapelagica
Hyperiopsidae
Parargissa curticornis
Stegocephalidae
Parandania boecki
Bathystegocephalusglobosus
Stegocephaloides attingens
Pardaliscidae
Halice tenella
Halice macronyx
Halicoides discoveryi
Halicoides tambiella
—
44 ANNALSOFTHESOUTHAFRICANMUSEUM
Ampeliscidae
Ampelisca brevicornis
Synopiidae
Synopia variabilis
Eusiridae
Eusirus crosnieri
Eusiropsis riisei
Eusirella lelegans
Stenopleura atlantica
Stenopleuroides macrops
Regalia oculata sp. nov.
Paramoera austrina
Superfamily LYSIANASSOIDAE
(= Family Lysianassidae s.l.)
Trischizostoma Boeck, 1861
The species belonging to this genus are semiparasitic. They have strong prehensile
pereopods andnarrowpiercingmouthparts. The genus falls into two distinctgroups. The
firstgroupincludes T serratum, T. remipesandT.paucispinosum,characterizedbytelson
cleft to middle and weakly specialized mouthparts. They are symbionts of benthic
animals, e.g. sponges (K. Barnard 1925). Representatives ofthe secondgroupriseup into
the water column where they occupy an atypical ecological niche for gammaridean
amphipods. Theyareectoparasitesoffishes,mainlyofsharks(Stephensen 1935;Vader—&
Romppainen 1985). These species have telson small entire (only one T. crosnieri
weakly cleft) and highly specialized mouthparts, e.g. maxillae are elongated stylets,
mandibles are narrow and have well-developed incisors, maxillipeds are considerably
reduced, and they have digitate grooved innerplates.
It is a long time since the existing key to Trischizostoma was published in English4
(J.L. Barnard 1961) andthegenusnowincludesmorethantwicethenumberofspeciesas
it did then (see Ledoyer 1978; G. Vinogradov 19906, 1991; Lowry & Stoddart 1993,
1994).Anewkeythatincludesallthe Trischizostomaspeciesknownto 1996isprovided.
4 Russiankeyto the genus Trischizostoma was publishedbyVinogradov (1991) anddoesnotincluderecently
describedT crosnieriand T. richeri(seeLowry&Stoddart 1993, 1994).
GAMMARJDEANAMPHIPODSINTHE WESTERNINDIANOCEAN 45
Trischizostoma barnardi G. Vinogradov, 1990
Trischizostoma barnardiG. Vinogradov, 1990/?: 37.
Material
m—
IKSAMT: st. 2598 (MC), D, PT 400 1 specimen, 7 mm.
Distribution
Formerly recorded from the Pacific Ocean (submerged Nazka Ridge).
Trischizostoma tanjae G. Vinogradov, 1991
Trischizostoma tanjae G. Vinogradov, 1991: 26.
Material
m—
IKSAMT: st. 2575 (EM), D,NBT 380^100 5 cf, 5-7.5 mm; st. 2576 (EM), D, PT
50-0 m—1 ?, 6 mm; st. 2823 (EM), D, NBT 390^100 m—139 specimens, 5-7 mm;
st. 2826 (EM), N, NBT 390-370 m—3 ?, 7.5-8 mm, 1 o\ 7.5 mm, 7juv., 5-7 mm.
Description
The description of T. tanjae published elsewhere was based on this collection, all
specimens ofwhichmustbe regarded as type material. The holotype (? reif. 5 mm, from
st. 2575) and most ofthe paratypes are stored in the Zoological Museum ofthe Moscow
State University, Moscow (ZMMU), holotype No Mb-032 and paratypes No Mb-1013
(104specimens)andMb-1033. However,25paratypesfromst. 2823 havebeendeposited
in the SouthAfricanMuseum (catalogue numbers SAM-A40854 to SAM-A40878).
Distribution
Found only nearthe submerged ErrorMountain (Indian Ocean).
Remarks
Sharks, ashas alreadybeennoted, arethetypicalhostsoffish-associatedsemiparasitic
Trischizostoma. On the Error Mountain, near-bottom catches of commercial fish and
shrimp trawls included numerous sharks Halaelurus hispindus (Scyliorhinidae). Sharks
madeup 12percentofthetotalnumberofcaughtfishes(Scherbatchev 1989).Halaelurus
hispindus may be a host ofT tanjae. During the Vityaz cruise, many H. hispindus were
caughtnearthe SocotraIsland, butunfortunatelyno IKSAMTtrawlingwas done thereto
catch amphipods. In otherregions, neitherH. hispindus nor T tanjae were found.
46 ANNALSOFTHESOUTHAFRICANMUSEUM
KEY TO THE GENUS TRISCHIZOSTOMA
1A. Telson partly cleft 2
IB. Telson entire 5
2A. Pereopod I dactyl innermargin serrate T. serratum
2B. Pereopod I dactyl innermargin smooth 3
3A. Palm ofpereopod I very spinose 4
3B. Palm ofpereopod I scarcely spinose T.pincispinosum
4A. 6th article ofpereopod I 1.5 times as wide as long. 7th article ofpereopodVII
slender (normal dactyl) T. crosnieri
4B. 6th article ofpereopod I 2-3 times as wide as long. 7th article of
pereopodVII oval T. remipes
5A. Maxillipedal palp much longerthan outerplates ofmaxillipeds 6
5B. Maxillipedal palp not longerthan outerplates ofmaxillipeds 12
6A. Pereopod I 6th article oval, width exceeding lengthby at least 1.5 times 7
6B. Pereopod I 6th article ofanother shape. Widthnever exceeding lengthbymore
than 1.5 times. Iflength:width ratio approximates to 1.5, the posteriormargin
of6th article forms a distinct angle withpalmarmargin so that article is nearly
triangular 10
7A. Pereopod I 6th article spiniferous palmarmarginwithouttriangularprocesses 8
7B. Pereopod I 6th article spiniferous palmarmarginwithtriangularprocesses
T. denticulatum5
8A. Pereopod II 5th article as long as or slightly longerthan 3rd article and twice
as long as oval 6th article. Pereopod III 2nd article twice as long as 5th article.
PereopodVI 2nd article as long as 4th and 5th articles combined 9
8B. Pereopod II 5th article shorterthan 3rd article and not more than 1.5 times as
long as pyriform 6th article. Pereopod III 2nd article not longerthan 5th article.
Pereopod VI 2nd article shorterthan 4th and 5th articles combined
T. macrochela6
Ledoyer(1978)didnotfindeyesinT. denticulatumbutsuggestedthattheymayhavedisappearedasaresultof
preservationofthespecimen. Sothischaracterisnotincludedinthiskey.
The description of T. macrochela erroneously reported that the palp of maxilla I is completely absent
(Vinogradov 19906). Repeated investigation of the holotype shows that a very delicate 1-articulated
rudimentarypalpofmaxillaI(withoutanysetae)ispresentin T. macrochela.
GAMMARIDEANAMPHIPODSINTHE WESTERNINDIANOCEAN 47
9A. Rostrum length greater than halfhead. Pereopod VI 2nd article length hardly
exceeds its width T. longirostra
9B. Rostrum length does not exceed halfofhead. Pereopod VI 2nd article length
clearly exceeds its width T. richeri
10A. Coxa II maximum height equal to that ofthe corresponding pereonite.
Rostrum horizontal, its top reaching beyond peduncle ofantenna I 11
10B. Coxa II maximum height equal to halfheight ofcorresponding pereonite.
Rostrum rounded, its top not reaching beyond peduncle ofantenna I ... T. nicaeense
11A. Coxae II to VII decreasing in height progressively. Pereopod I 6th article
approximately triangular, with pronounced angle between palmar and
posteriormargins T. rashii
11B. Coxae II to IV equally high. Coxa V halfas high as coxa IV. Other coxae
decreasing in heightprogressively. Pereopod I 6th article irregularly rounded
T. circulare
12A. Maxillipedal palp halfas long as outerplates ofmaxillipeds. Pereopod I
6th article spiniferous palmarmargin is even. Pereopods V to VII 2nd
articles posteriormargins rounded lobate T. nascaensis
12B. Maxillipedal palp is slightly shorterthan outerplates ofmaxillipeds.
Pereopod I 6th article spiniferous palmarmargin forming declivitous
serrations orpronounced outgrowth. At leastpereopod VII 2nd article
posteriormargin is concave or skewed distally 13
13A. Pereopod II 6th article length exceeds width. Maxillipedal palp with all
3 articles approximately equal in length 14
13B. Pereopod II 6th article width exceeds length. Maxillipedal palp 2nd article
twice as long as first orthird T. tanjae
14A. Pereopod I 6th article spiniferous palmarmarginwith declivitous serrations.
PereopodV 2nd article posterodistalmargin skewed. Uropod III rami halfas
long as peduncle T. barnardi
14B. Pereopod I 6th article spiniferous palmarmarginwith a ridge oflarge
outgrowths. PereopodV 2nd article posterodistal margin forming around
lobe. Uropod III rami slightly longerthanpeduncle T. cristochelata
ANNALSOFTHESOUTHAFRICANMUSEUM