Phylogenetic relationships between arietellid genera (Copepoda: Calanoida), with the establishment of three new genera

68 Pages·1994·26.3 MB·

by  S Ohtsuka

Bull. nat. Hist. Mus. Lond. (Zool.)60(2): 105-172 Issued24 November 1994
Phylogenetic relationships between arietellid
genera (Copepoda: Calanoida), with the
establishment of three new genera
OHTSUKA
S.
Fisheries Laboratory, Hiroshima University, 1294 Takehara, Hiroshima 725, Japan
G.A. BOXSHALL
DepartmentofZoology, The NaturalHistory Museum, CromwellRoad, London SW75BD, England
ROE
H.S.J.
InstituteofOceanographicSciences Deacon Laboratory, Brook Road, Wormley, Godalming, Surrey
GU85UB, England
CONTENTS
Materialsand Methods 108
Arietellidae Sars, 1902 108
HiSTORYMiSrUM
Crassarietellusgen nov 109
.
Campaneriagen. nov 119
Paraugaptiloid.esgen. nov "":::""i:cBH!."fflH.""."!" 120
ArietellusGiesbrecht, 1892 .... 126
RhapidophorusEdwards, 1891 131
ParamisophriaT. Scott, 1897 . ZOOLOGY LIBRARY 135
MetacalanusCleve, 1901 | 138
Paraugaptilus Wolfenden, 1904 143
Scutogerutus Bradford, 1969 152
SarsarietellusCampaner, 1984 155
Pilarella Alvarez, 1985 156
Discussion 158
Acknowledgements 171
References 171
Synopsis. Tengenera, includingthree newgenera, Crassarietellus, Campaneriaand Paraugaptiloides,ofthefamily
Arietellidae (Copepoda: Calanoida) are newlydefinedor redefined with special reference to the genital systemsof
the females and fusion patterns and armature elements of appendages. The present study revealed that the single
specimen reported as the male ofSarsarietellus abyssalis (Sars, 1905) represents a new genus, Crassarietellus, and
thatParaugaptilusmohriBjornberg, 1975belongstothegenusArietellus. Ancestralandderivedstatesandcharacter
transformationsofthegenital systemsand the appendagesin the familyare discussed. Acladisticanalysisforall 10
genera except for Rhapidophorus revealed that the Arietellidae consists of two lineages, the Crassarietellus-
Paramisophria-Pilarella-Metacalanus-gTOup and the Cumpaneria-Sarsarietellus-Paraugaptiloides-Scutogerulus-Par-
augaptilus-Arietellus-group. The deep-sea hyperbenthic genera Crassarietellus and Campaneria are the most
plesiomorphic in each group, and the shallow-water hyperbenthic/epipelagic/cave-living Metacalanus and the
bathypelagicv4/"zefe//!«and Paraugaptilus are relativelyapomorphic.
INTRODUCTION dophorus Edwards, 1891, Arietellus Giesbrecht, 1892, Parami-
sophriaT. Scott, 1897(= ParapseudocyclopsCampaner, 1977),
MetacalanusCleve, 1901 (= ScottulaSars, 1902), Paraugaptilus
The family Arietellidae Sars, 1902 has been regarded asone of Wolfenden, 1904, Scutogerulus Bradford, 1969, Sarsarietellus
the most primitive families in the Calanoida based on the Campaner, 1984,andPilarellaAlvarez, 1985.ThegenusPhyllo-
segmentationofappendagesandthegenitalsystems(Andronov, pusBrady, 1883wasseparatedbyBrodsky(1950)whoproposed
1974;Park, 1986;Huys& Boxshall, 1991). TheArietellidaehad placing it in a new subfamily; it was later removed from the
hitherto accommodated the following eight genera: Rhapi- Arietellidae and placed in its own family, the Phyllopodidae
)ThcNatural HistoryMuseum, 1994
106 S. OHTSUKA, G.A. BOXSHALLAND H.S.J. ROE
Table 1 Samplingdate, locality, depth andgearused forarietellidcollection.
Species Sex Numberof Date Locality Depth (m) Gear Remarks
specimens
Crassarietellushuysi[ 9 1 18IV 1977 20°18.5'N,21°41.2'W 3974-4036 RMT8 5-20m off
20°20.8'N,21°53.0'W bottom
9 2 18IV 1977 20°19.7'N,21o51.3'W 4008-4060 RMT8 5-20moff
20°18.4'N,21°40.5'W bottom
Crassarietellussp.2 cf 1 24VI 1908 38°02'N, 10°44'W 0-4800 Richard net
Campanerialatipes3 cf 1 4X 1968 37°07'S, 177°14'E 1234-1260 Modified Menzies Some small
trawl stones
Paraugaptiloidesmagnus4 cf 1 11 X 1968 34°38'S, 174°36'E 1697 ModifiedMenzies
trawl
Arietellusaculeatus 9 1 23II 1979 15°00'-15o05'N 400 IKMWT
158°00'-158o0r\V
cf 2 23 II 1979 15°10'-31°14'S 400 IKMWT
7r56'-71°58'W
Arieiellusmohrr 9 1 24VI 1962 31°10'-31°14'S 1932-3142 Phlengercorer
71°56'-71°58"W
Arietelluspavoninush 9 1 28XI 1965 28°05'N, 14°06'W 600-720 N113H
Arietellusplumifer 9 1 28VI 1985 31°20'N,25°17'W 600-840 RMT1
31°18'N,25°27'W
?6 1 26XI 1965 28°07'N, 14°07'W 680-800 N113H
cf6 1 13XI 1965 28°04'N, 14°12'W 360-410 N113H
Arietellussetosus'1 cf 1 29XI 1965 28°05'N, 14°10'W 50-85 N113H
Arietellussimplex''' cf 1 28XI 1965 28°05'N, 14°06'W 750-900 N113H
Arietellussp.6 9 1 11 XI 1965 28°04'N, 14°11"W 460-510 N113H
Metacalanussp. 1 9 4 23V 1989 26°17.9'N, 126°54.2'E 167 Sledge-net
cf 1 23V 1989 26°17.9'N, 126°54.2'E 167 Sledge-net
Metacalanussp. 2 9 4 23V 1989 26°17.9'N, 126°54.2'E 167 Sledge-net
Paramisophriagiselae7 9 2 3IX 1970 23°19'S,41°57'W 100 Plankton net adapted
todredge
Paramisophriajaponica* 9 1 23V 1989 26°17.9'N, 126°54.2'E 167 Sledge-net
Paramisophriareductd' cf 1 25 II 1984 Jameosdel Agua 10-28 Plankton net
Paraugaptilusbuchanfi 9 1 16X1 1969 17°41'N,25°18'W 410-500 RMT1
9 1 15 XI 1965 27°48'N, 13°55'W 450-510 N113H
cf 1 24XI 1965 28°06'N, 14°08'W 775-830 N113H
Paraugaptilussimilis 9 1 21 I 1978 04°02'S, 150WW 275 IKMWT
cf 1 21 I 1978 04°02'S, 150°00'W 275 IKMWT
Pilarellalongicornis10 9 1 22VI 1970 28°36'S,47°55'W 135 Plankton net adapted
todredge
Scutogeruluspelophilus7. 9 1 10X 1968 34°56'S. 175°23'E 1383-1397 Modified Menzies Globigerina
trawl Ooze
Sarsarietellusabyssalis2 9 1 4-5 VIII 1897 38°37'N.28°14'W 1260 'Nasse'
Samplingdataafter: ' Boxshall& Roc(1980);-Sars(1925);3Bradford(1%9); Bradford(1974);5 Bjornberg(1975);6Curricctal. (1969);7Campancr(1977)
Ohtsukactal. (1991);9Ohtsukaetal. (1993a); "'Alvarez(1985).
(Campaner, 1977;Bowman&Abele, 1982). nus)andthesimplifiedsecondexopodsegmentsandreductionof
Arietellids are widely distributed from neritic to oceanic endopod of leg 5 in the male. These are highly adapted
waters and range vertically from the epipelagic zone to the hyperbenthicformsfoundinrelativelyshallowwaters(<1000m
bathypelagic hyperbenthic layer (Campaner, 1984). deep) or in epipelagic waters in neritic regions. However,
Recently, cave-living species of Metacalanus and Parami- Campaner's(1984)classificationreliedsolelyonthestructureof
sophria have been discovered (Ohtsuka et al., 1993a). How- the fifth legs although he recognized interspecific variation
ever, neither phylogenetic nor ecological studies on the betweencongenersinlegcharacters.
family have been carried out in detail, partly because of the The present paper describes a new arietellid genus col-
paucity of pelagic arietellids in the water column, and partly lected from the deep-sea hyperbenthic community in the
because of the lack of intense sampling effort in the hyper- northeastern Atlantic, and establishes two new genera to
benthic layers where many species are found. accommodate previously known arietellids, the male ofScu-
Campaner (1984) first examined the relationships between togerulus pelophilus Bradford, 1969 and the male of
arietellidgenera. Hedividedthemintotwomorphologicallyand Paraugaptilus magnus Bradford, 1974. Revised diagnoses of
ecologicallydifferentgroups. ThefirstgroupcomprisedArietel- all known arietellid genera, except for Rhapidophorus, are
lus,ParaugaptilusandScutogerulus,whicharecharacterizedbya givenhere togetherwith supplementarydescriptions. Charac-
reducedfemaleleg5andcomplexmaleleg5,andaredistributed ter transformations ofthe genital systems and appendages of
inthebathypelagicordeep-seahyperbenthiczones. Thesecond these arietellids are considered in detail. A cladistic analysis
groupconsistedofMetacalanus,Paramisophria,Rhapidophorus is employed to help clarify phylogenetic relationships
and Sarsarietellus and was diagnosed by characters such as the between the arietellid genera.
relativelywelldevelopedleg5inthefemale(exceptforMetacala-
. 1
PHYLOGENY OF ARIETELLID COPEPODS 107
Table2 Charactersused in thecladisticanalysisforgeneraofthe family Arietellidae. Codes to2refertotransformation seriesof
multi-statecharacters;0: plesiomorphicstate;9: missingdata.
1. Gonopore andcopulatoryporesharingcommon opening yes/no O'l
2. Rightand leftcopulatorypores separate/fused 1
3. Lengthsofright and left antennulesoffemale equal/uneuqal O'l
4. Fusionoffemale antennularysegments I-III and IV separate/fused 0/1
5. Fusion between female antennularysegmentsXXIII and XXIV separate/fused O'l
6. Aesthetascpresenton female antennulary segmentIV present/absent ( 1
7. Aesthetascpresenton female antennularysegmentVI present/absent ( 1
8. Aesthetascpresenton female antennularysegment VIII present/absent 0/1
9. Aesthetascpresenton female antennularysegment X present/absent 0/1
10. Aesthetascpresenton female antennularysegmentXII present/absent 1
11 Modificationofseta intoprocesson male antennularysegment XV no/yes 0/1
12. Fusion ofmale antennularysegmentsXXI & XXII separate/fused 01
13. Setaadjacent toaesthetascon male antennularysegmentsII present/absent O'l
14. Seta adjacent toaesthetascon male antennularysegment III present/absent O'l
15. Modificationofseta intoprocesson male antennularysegment XXII no/yes O'l
16. Processon male antennularycompoundsegment XXIV-XXV no/yes €'1
17. Setaon firstendopodsegmentofantenna present/absent O'l
18. Proximal innersetaon mid-marginofsecondendopodsegmentofantenna present/absent C 1
19. Vestigialelementonsecondendopodsegmentofantenna present/absent 0/1
20. 1-segmented, rudimentary mandibularendopod with 1 or2setae present/absent 1 1
21. Outerterminal setaon fifthexopodsegment ofmandible normal/reduced ( 1
22. Processon maxillulary praecoxal arthrite present/absent ( 1
23. Innerbasal enditicsetaofmaxillule present/absent 0/1
24. Third setaofmaxillularyendopod present/absent O'l
25. Inneranglesetaofmaxillularyendopod present/absent 0/1
26. Distalsetaon firston first praecoxal endite ofmaxilla present/absent 0/1
27. Reductionofseta aon sixthendopod segmentofmaxilliped (lengthofseta
at most aslongas thesegment) no/yes 0/1
28. Reductionofsetabon sixthendopodsegmentofmaxilliped (lengthofseta
at most as twice as longassegment) no/yes ( 1
29. Proximalspineon outermarginofthirdexopodsegment ofleg 1 present/absent ("1
30. Innercoxal setaofleg4 present/absent 0/1
31. Fusion betweenendopod and basisoffemale leg5 separate/fused 0.1
32. Innermargin ofendopodoffemale leg5 with proximal (setaA) and A+B present/ t'l
distal (seta B) setae AorB absent
33. One seta (A or B)on inner marginofendopodoffemale leg5 present/absent 0/1
34. Innerangle setaon distal marginofendopodoffemale leg5 present/absent 0/1
35. Exopodsegmentoffemale leg5 partlydefined/ 0/1/2
unsegmented/absent
36. Spine (elementd)on outerdistal angleofexopodoffemale leg5 present/absent 0/1
37. Leftendopodofmale leg5 (including incomplete fusion) 2-segmented/ 0/1/2
1-segmented/absent
38. Rightendopod ofmale leg5 1-segmented/absent CI
39. Setacon thirdexopodsegmentofleft male leg5 present/absent 0/1
40. Setaee and fofleft male leg5 transformed into bifid process no/yes 0/1
41. Thirdexopodsegmentofleft male leg5 rotatedso thatvestigial outer
marginelementsnowon innersurface no/yes 0/
42. Setafon third exopodsegmentofright male leg5 welldeveloped/minute 071
43. Setacon third exopodsegment ofright male leg5 present/absent 0/1
44. Fusion between coxa and basisofright male leg5 separate/fused C/l
Table3 Charactermatrix foranalysisusingPAUP3.0.
10000000000 100100 10000100000101100001000990
MCPreaatrsaascmaairilseaotnpeuhlsrluisa 110111010 1101110 1111 111000001100000101010101000011111 11 1110101021 11100000 10
110 111 111111100110110111 110111001100110111
Arietellus 100111111111110111 1111111110 11112 10 111111
Paraugaptilus 0000010000 10 10 1110 2
Scutogerulus 9 9 9 9 9 1 1 1 1 1 9 9 9 9 9 9 9 9
10 10 10 10
Sarsarietellus 1 9 9 9 9 9 9 9 9 9 9 9 9 9
10 10 10 10
PCialmarpealnlaeria 9 9 91 9 9 9 9 9 9 9 9109 10 1 1 1100001991 9919919999 91 9 9 9109 9 911909
10
Paraugaptiloides 9 9 9 9 9 9 9 1 1 1 1 9 1 1 1 1
108 S. OHTSUKA, G.A. BOXSHALLAND H.S.J. ROE
MATERIALS AND METHODS armature; 16- to22-segmented; segments I to III, rarely up to
VI fused; segments X to XII more or less fused; segments
XXIII and XXIV separate or fused; segments XXV and
The present study is based on collections deposited in The XXVI completely or incompletely fused; segments II, XXII-
Natural History Museum, London, the New Zealand XXIV, XXVI and XXVII lacking aesthetasc; segment IV,
Oceanographic Institute, the United States National VI, VIII-X, XII and XIII with or without aesthetasc; seg-
Museum, Smithsonian Institution, the Zoological Museum, ment XIII with 1 or 2 setae; compound segment XXVI-
University of Oslo, the University of Sao Paulo, and XXVIII with 8 or 9 elements; posterior margin of proximal
HiroshimaUniversity. Samplingdataand localityaresumma- segments fringed with row of setules or not. Antenna: basal
rized in Table 1. Specimens, except for those previously seta present; both rami separate from basis; endopod
mounted, were dissected and mounted in Gum-chloral and 2-segmented, first segment with 0-1 inner seta at midlength,
observed with a differential interference contrast microscope secondsegment elongate, with 1-3innersetae mediallyand 5
(Olympus BH-2). The genital double-somites of females of or6 setae terminally; exopod indistinctly 6- to 10-segmented,
several specieswereobservedwith ascanningelectron micro- ancestral segments I—III and IXunarmed. Mandible: gnatho-
scope (Hitachi S-800). The morphological terminology is base well chitinized, with 3 or 4 sharp teeth; endopod
basedon Huys& Boxshall (1991). Typespecimensofthe new rudimentary, 1-segmented with 1 or 2 setae terminally or
generaare depositedinThe Natural History Museum andthe completely absent; first exopod segment with normal or
New Zealand Oceanographic Institute. reduced seta, fifth segment carrying 2 setae, one of which
Phylogenetic relationships between genera were analyzed sometimes vestigial. Maxillule: praecoxal arthrite with 0-6
using PAUP version 3.0 prepared by D. Swofford, Illinois elements; coxal endite with 1 seta or unarmed; coxal epi-
Natural History Survey. The character matrix (Tables 2,3) podite carrying5-9setae;innerbasalsetarepresentingendite
summarizes the character distributions among the 10 genera vestigial or absent; endopod bulbous, 1-segmented, with 0-3
available for study. A multistate scoring system was setae or completely incorporated to basis; exopod lobate,
employedandmissingcharacterswere scored9. A hypotheti- bearing 3 long setae. Maxilla well developed; first praecoxal
cal composite ancestor was included in the analysis which endite with 1 or 2 setae and 1 vestigial element, second
scored for all characters. The options employed in the praecoxal endite having 1 or 2 setae; first and second coxal
analysis were Branch and Bound, which guaranteed to find enditeseachwith2setae; basalspine stout, spinulose orbare;
all the most parsimonious trees, and the MINF optimisation, endopod 4-segmented, with chitinized long setae, setal for-
which assigns character states so that the f-value is mini- mula 1,3,2,2. Maxilliped elongate; syncoxawith 1 medial and
mized. All characters were set as irreversible using the 2 terminal setae; basiswith patches ofsetules or spinules and
Camin-Sokal option. 2 setae medially; endopod 6-segmented, first segment almost
The abbreviationsused in the text andfigures 1 to37are as fullyincorporatedintobasis, setalformula 1,4,4,3 (rarely2),3
follows: cd: copulatory duct; cp: copulatory pore; g: gonop- (rarely 2),4, sixth segment with 2 outermost terminal setae
ore; o: oviduct; rd: receptacle duct; s: spermatophore rem- (setae 'a' and 'b\ see Fig. 5C) reduced ornot.
nant; sr: seminal receptacle. Legs 1^1 with distinctly 3-segmented rami or, very rarely,
with endopod segments ofleg 1 incompletely fused. Seta and
spine formula oflegs 1-4 as shown in Table 4.
Leg5 variable but not natatory, almost symmetrical; coxae
SYSTEMATICS
and intercoxal sclerite separate or fused; basis and endopod
separate or fused; endopod with 0-4 setae; exopod 1- to
3-segmented or completely fused with basis, carrying 0-5
Family Arietellidae Sars, 1902 elements.
Male. Body similar to that of female, but urosome
Diagnosis(emend.) Female. Bodyofvariablesize (fromca. 5-segmented. Leftantennulegeniculate, 16-to20-segmented;
0.8 to 7 mm), relatively robust, rarely compressed.Cephalo- segments I to IV fused; segments XI to XV more or less
some and first pedigerous somite separate or weakly fused; fused; segments XXI and XXII fused or rarely separate;
fourth and fifth pedigerous somites completely fused. Cepha- segments XXIII and XXIV separate; segments XXV and
losome round or pointed at apex; rostrum produced ven- XXVI completely or incompletely fused; segments II and III
trally, with pair of filaments. Posterior corner of prosome with 1 or2setae; segmentsX, XII-XIVandXXwithanterior
sharply or weakly produced, with or without dorsolateral process; segments XIX and XXI with 2 processes; segment
and/or ventrolateral process. Urosome comparatively short, XIII with 0-1 seta; segments XV, XXII and XXIV with or
4-segmented; genital double-somite with single or paired without process; proximal segments often with row ofsetules
gonoporesandcopulatorypores; gonopore(s) locatedventro- along posterior margins. Mouthparts and legs 1^1 similar to
laterallyorventrally, with orwithoutopercularplate; copula-
tory pore sharing common opening with gonopore or Table4 Spine andsetaformulaoflegs 1-4.
separate from gonopore, located ventro-medially or
-posteriorly, rarely ventrally on right side; seminal recep-
Coxa Basis Exopodsegment Endopodsegment
tacles usually paired, rarely left receptacle entirely lacking.
Egg-sac present or absent. Caudal rami well defined, sym-
metrical or slightly asymmetrical, relatively short, with vesti- Legl 0-1 1-1 I—1;I—1;II/1,1/1,4 0-l;0-2;l,2,2
gial seta I, well developed or reduced setae II—III, well Leg2 0-1 0-0 I-1;I-1;III,I,5 0-l;0-2;2,2,4/3
developed setae IV-VI and small seta VII. Leg3 0-1 0-0 I-1;I-1;III,I,5 0-l;0-2;2,2,4/3
Leg4 0-0/1 1-0 I-1;I-1;III,I,5 0-l;0-2;2,2,3/2
Antennules symmetrical or asymmetrical, longer on left
side than on right, sometimes differing in fusion pattern and
PHYLOGENY OF ARIETELLID COPEPODS 109
those of female or slightly different in armature elements of segment. Leg 5 having distinctly 1-segmented, rudimentary
antennary second endopod segment and mandibular first endopod with 2 setae and indistinctly 3-segmented exopod
exopod segment. with 3 outer lateral and 2 terminal spines.
Leg 5 variable, but not natatory, almost symmetrical to Male. Left antennule geniculate, 19-segmented; segments
strongly asymmetrical; coxae and intercoxal sclerite fused to I-IVfused, with 9 setae and4aesthetascs; segmentsXXI and
form common base or separate; right basis sometimes fused XXII fused; segments I to X fringed with setules along
with coxa; right endopod 1-segmented, bulbous or absent; posterior margin; segments IVto VIII with transverse row of
right exopod distinctly or indistinctly 3-segmented, first and setules as in female. Mouthparts and legs similar to those of
second segments each with seta on outer margin (rarely first female.
segment unarmed), second segment with tuft of setules on Leg 5 with coxae and intercoxal sclerite incompletely fused
inner distal angle of second segment, third segment with 0-3 to form common base; coxa separate from basis. Right leg
elements terminally; left endopod 1- or 2-segmented, lackingendopod; exopod, at least 2-segmented, first segment
unarmed or completely absent; left exopod distinctly or with outer spine on distal corner.Left leg: endopod incom-
indistinctly 3-segmented, first and second segmentseach with pletely2-segmented,firstsegmentexpanded, secondsegment
seta on outer margin, third segment with 1-3 elements small, semispherical; exopod distinctly 3-segmented, first
terminally. segment with spine on outer corner, second segment
expanded, bearing outer spine at midlength, third segment
Typegenus. Arietellus Giesbrecht, 1892.
small, having 2 small outer setules and chitinized, long
Remarks. The above diagnosis excludes Rhapidophorus terminal seta.
Edwards, 1891, which was inadequately described and has
TYPESPECIES. Crassarietellushuysi, gen. et sp. nov.
never been redescribed. Although the family was briefly
Other species. Crassarietellus sp. based on a male which
defined by Sars (1902), Rose (1933), Brodsky (1950) and
was erroneously assigned to Scottula abyssalis Sars, 1905 by
Campaner (1977), the present amended definition includes
Sars (1924, 1925).
new information on the genital systems of females and the
armature elements on the appendages. Remarks. Sars (1924, 1925) assigned one male collected
from offLisbon toScottulaabyssalis Sars, 1905, the female of
Genus Crassarietellus gen. nov. which was captured off the Azores. However, this male
should be included in the new genus Crassarietellus based on
Diagnosis. Female. Bodycompact, prosomeovoid indorsal the similarities of the mouthparts: the indistinctly
view; cephalosome separate from first pedigerous somite; 10-segmented antennary exopod (compare Fig. IF with Fig.
posterior corner of prosome produced posteriorly to form 7D); 5 serrate spines and a process on the praecoxal arthrite
rounded lobe. Urosome short, at most one-third as long as and 6 setae on the coxal epipodite ofthe maxillule (Figs 5A,
prosome; genital double somite wider than long, with pair of 8A); 2 non-reduced setae on the sixth endopod segment of
gonopores ventrolaterally and paired copulatory pores each the maxilliped (Figs 5C, 8E). Additionally, a transverse row
located beneath ventral projection; anal operculum not ofsetules is present, on each ofthe antennulary segments IV
developed; caudal rami symmetrical, longer than wide, with to VIII in the male (Fig. 7A), that is found only in the genus
vestigial seta I and normally developed seta II. Crassarietellus. The ornamentation of the appendages of the
Antennulesymmetrical reachingtoposteriorendofsecond male, such as the many tiny spinules along the outer margin
pedigerous somite, 22-segmented; segments I—III fused, with of the mandibular palp and the stout, outer processes on the
7setaeand2aesthetascs; segments IV, VI, XIIandXIII each exopod segments oflegs 1 to 4, also supports the proposal to
with 2 setae and 1 aesthetasc; segments XXIII and XXIV place the male in Crassarietellus. The right leg 5 of the male
separate; compound segment XXVI-XXVIII with 8 setae lacksdistal exopod segment(s), a condition which Sars (1924,
and 1 aesthetasc; posterior margin ofancestral segments I to 1925) misinterpreted as '1-segmented left' exopod.
XIII fringed with long setules; segments IV-VIII with trans-
verse row of long setules along distal end of segment. Etymology. The new generic name Crassarietellus (Latin
Antenna: first endopod segment with medial inner seta; crassus meaning thick) refers to the ovoid, compact body
second segment bearing 3 midlength and 5 terminal setae; form ofthe newgenus. The specificname isnamedin honour
exopod indistinctly 10-segmented exopod. Mandibular gna- ofMr. Rony Huys.
thobase with tuft of setules at midlength and 3 teeth on Ecological note. The type species of the new genus was
cutting edge. Mandibular palp: endopod rudimentary,
found in near-bottom samples taken at depths of 3974-4060
1-segmented, with 2 setae; seta on first exopod segment not m. The plump body and the relatively short antennules
reduced; outer seta on fifth exopod segment relatively long. indicates that the new genus is hyperbenthic.
Maxillule: praecoxal arthrite with 5 stout, serrate spines
and 1 process; coxal epipodite having 6 setae; coxal endite
bearing long seta; second basal endite with vestigial seta; Crassarietellus huysi gen. et sp. nov. (Figs 1-6)
endopod rudimentary, 1-segmented with 2 setae. Maxilla: Materialexamined. 3 99-
first syncoxal endite with 2 setae and vestigial element;
second syncoxal endite with 2 setae; basal endite carrying Types. Holotype: 9, 18IV 1977, NorthAtlantic(offwestern
stout spine with row of spinules medially. Maxilliped with Africa), 20°8.5'N, 21°1.2'W-20°20.8'N, 21°53.0'W,
second to sixth endopod segments bearing 4, 4, 3, 3 and 4 3974-4036 m in depth, dissected and mounted on slides,
setae, respectively; innermost seta on fourth and fifth endo- prosome and urosome preserved in 70% ethanol, BM(NH)
pod segments not reduced; setae a and b on sixth endopod 1993. 424. Paratype 1: $, 18 IV 1977, 20°19.7'N,
segment not reduced. 21°51.3'N-20°18.4'N, 21°40.5'W, 4008-1060 m in depth, dis-
Leg 1 bearing 2 outer lateral spines on third exopod sected and mounted on slides, prosome preserved in 70%
110 S. OHTSUKA, G.A. BOXSHALLAND H.S.J. ROE
CO
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Fig. 1. Crassarietellushuysigen. etsp. nov., female (holotype: F,G; paratype: A-E). A, Habitus, dorsalview; B, Habitus, lateralview; C,
Urosome, ventralview; D, Genital double-somite, ventral view; E, Genital double-somite, lateralview, cd: copulatoryduct;cp: copulatory
pore;g: gonopore; rd: receptacle duct;o: oviduct;s: spermatophore remnant; sr: seminal receptacle; F, Antenna,one terminalsetaon
secondendopodsegmentmissing; G, Terminalpartofsecondendopodofotherantenna. Scalesin mm.
PHYLOGENY OF ARIETELLID COPEPODS 111
Fig. 2. Crassarietellushuysigen. etsp. nov., female. SEM micrographsofgenitaldouble-somite offemale. A, Genitaldouble-somite,
ventralview, scale bar = 200 p-m (arrowsindicatingpositionsofcopulatorypores); B, Gonopore andcopulatorypore (indicatedbyarrow)
scale bar = 100 (xm; C, Rightgonopore, scale bar = 30 |xm; D, Leftgonopore,scale bar = 30 p.m.
112 S. OHTSUKA, G.A. BOXSHALLAND H.S.J. ROE
Fig. 3 Crassarietellushuysigen. etsp. nov., female. SEM micro-graphsofremnantofspermatophore attached togenital double-somite of
female. A, Spermatophore remnantpenetratingcopulatorypore, scalebar = 20 u.m; B, Spermatophore remnant, scale bar = 20 u.m.
ethanol, BM(NH) 1993. 425. Paratype 2: £, the same collec- patch of minute spinules. Integument of body and append-
tion date and locality as in paratype 1, only legs 2 and 3 ages pitted.
dissected and mounted on glass slides, urosome mounted on Antennules (Fig. 4A-C) equal in length, distinctly
stub for SEM examination, prosome preserved in 70% etha- 22-segmented, reaching to posterior end of second pediger-
nol, BM(NH) 1993. 426. ous somite; distal 2 segments incompletely fused; fusion
Body length. 3.1 mm (holotype); 3.88, 3.85 mm pIaVt-t2ern+ aanedsthaertmaastc,urVe-a2s +folaleoswtsh:etIa—scII,I—V7I-+2 2+aaeesstthheettaassccs,,
(paratypes).
VII-2 + aesthetasc, VIII-2 + aesthetasc, IX-2 + aesthetasc,
Description. Female. Body (Fig. 1A,B) oval in dorsal X-2 + aesthetasc, XI-2 + aesthetasc, XII-2 + aesthetasc,
view. Cephalosome and first pedigerous somite separate; XIII-2 + aesthetasc, XIV-2 + aesthetasc, XV-2 + aes-
fourth and fifth pedigerous somites completely fused; poste- thetasc, XVI-2 + aesthetasc, XVII-2 + aesthetasc, XVIII-2
rior corner of prosome produced posteriorly into rounded + aesthetasc, XIX-2 + aesthetasc, XX-2 + aesthetasc,
lobe directed backwards, reaching half length of genital XXI-2 + aesthetasc, XXII-1, XXIII-1, XXIV-XXVIII-12
double-somite. Urosome (Fig. 1C) 4-segmented, one-third as + 2 aesthetascs. Segments I to XIII fringed with long setules
long as prosome; genital double-somite (Figs 1D,E,2A,B) along posterior margin; segments IV to VIII each furnished
wider than long; pair of medial gonopores (Fig. 2C,D) with transverse row of minute setules near posterior corner.
located ventro-laterally near mid-level of double-somite; Sutures between segments I to III weakly visible.
paired copulatory pores posterior to gonopores, each con- Antenna (Fig. 1F,G): coxa unarmed; basis with spinulose
cealed beneath ventrolateral projection; remnants of diver- seta at inner angle; endopod 2-segmented, first segmentwith
gent fertilization tubes of spermatophore (Fig. 3) still minute seta at three quarters length, covered with minute
attached to genital double-somite of both paratypes, each spinules distally, second with 3 setae of unequal lengths
connecting through posteroventral groove with copulatory mediallyand5setaedistallyandsparselycoveredbyspinules;
pore beneath projection; copulatory duct swollen in ventro- exopod indistinctly 10-segmented, second to fourth segments
lateralprojection, almosthorizontal, extendingtolarge semi- almost fused; armature as follows: 0,0,0,1,1,1,1,1,0,3; ninth
nal receptacle; 1 medial and 2 pairs of lateral shallow segment sparsely ornamented with minute spinules.
chitinized pits anteriorly; anal somite small, anal operculum Mandible (Fig. 4D): gnathobase heavilychitinized, ventro-
not developed; caudal ramus (Fig. 1C) longer than wide, medial margin with dense fringe oflong setules; cutting edge
fringed with long setules along inner margin, with vestigial with 3 acute teeth, dorsalmost ofwhich bifid at tip; 2 patches
seta I and developed setae II to VI, seta VII originating of dagger-like spinules present dorsally; tuft of long setules
dorsally near base of seta VI; inner margin near anus with present medially on knob; basis of palp with patches of
PHYLOGENY OF ARIETELLID COPEPODS 113
Fig.4. Crassarietellushuysigen. etsp. nov., female (holotype: E,F;paratype: A-D). A, AntennularysegmentsItoXV;B, Antennulary
segmentsXVI toXXVIII;C, AntennularysegmentsXXIItoXXVIII; D, Mandible; E, Maxillularypraecoxal arthriteandcoxalendite;F,
Proximalspineonpraecoxal arthriteofmaxillule. Scalesin mm.
114 S. OHTSUKA, G.A. BOXSHALLAND H.S.J. ROE
Fig.5. Crassarietellushuysigen. etsp. nov., female (holotype: C; paratype: A,B). A, Maxillule, with arrowheadindicatingenditicsetaof
basis; B, Maxilla; C, Maxilliped. The armatureelementson the sixthendopod segmentofmaxilliped areidentifiedindividuallybythe
lettersa tod. Scalesinmm.