Two new species of Tridentella (Crustacea: Isopoda: Tridentellidae) from Namibia

14 Pages·2001·1 MB·English

by  Brandt, Angelika

Beaufortia
BULLETIN ZOOLOGICAL MUSEUM
UNIVERSITY OFAMSTERDAM
Vol. 51, no. 11 December 14, 2001
Two new species of Tridentella (Crustacea: Isopoda:
Tridentellidae) from Namibia
AngelikaBrandt,* &Gary C.B. Poore
J
&
Zoological InstituteandZoological Museum,Martin-Luther-King-Platz 3,D-20146Hamburg, Germany
Museum Victoria, GPOBox666E,Melbourne, Victoria3001,Australia
Abstract
Tridentella namibia n. sp. and T. benguelan.sp. (Crustacea: Isopoda:Tridentellidae)aredescribed fromthe shelf and slopeoff
thecoastofNamibia,south-westernAfrica.Akeyisprovided toallthe 16 species in the genus anddistributionalinforma-
tion tabulated.
Keywords: Crustacea, Isopoda,Tridentellidae, Tridentella, taxonomy,key, newspecies, Namibia
INTRODUCTION ed together with a tabulated summary of their
knowndistributions (Table 1).
Among a collection of isopods from Namibia The drawings were prepared using a camera
donated to Museum Victoria, Melbourne, by lucida. The specimens are deposited in the col-
Enrique Macpherson (Instituto del Ciencias de lectionof Museum Victoria, Melbourne(NMV).
Mar, Barcelona, Spain), were several specimens
of the isopod genus TridentellaRichardson, 1905. SYSTEMATICS
This genushadbeenconsideredamemberof the
family Corallanidae(e.g., Bruce etal., 1982) until TRIDENTELLIDAEBruce, 1984
Bruce (1984) established the monogeneric family
Tridentellidae.The family is characterisedby the Tridentellidae Bruce, 1984: 448; 1988: 71-73;
presence of a maxillipedal endite and other Delaney and Brusca, 1985: 728; Kensley and
mouthpart characters which differ substantially Schotte, 1989: 235; Wetzer etal., 1997: 36.
from those described for the corallanid genera
(Delaney & Brusca, 1985). The genus comprises REMARKS. - The family, and its only genus, are
14 species to which we now add a further two similar to the Corallanidaebut differ most obvi-
newspecies. Akey to differentiatethemisprovid- ously in the presence of a large maxillipedal
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Table 1.Distribution ofspecies ofTridentellidae.
Species Distribution
TridentellaacheronaeBruce, 1988 New Zealand, 424-1006 m
Tridentellabengnelan.sp. Namibia,285 m
Tridentella cornulaKussakin, 1979 North-westernPacific, 20-50m
TridentellaglutacanthaDelaney& Brusca, 1985 California, 310-360 m
TridentellajaponicaThielemann, 1910 Sagami Bight,Japan, 600m
Tridentella laevicephalax Menzies, 1962 southern Chile,24 m
Tridentella namibia n.sp. Namibia, 175-351 m
Tridentella ornamenta(Menzies & George, 1972) Peru-ChileTrench,907-935 m
Tridentella quinicornisDelaney&Brusca, 1985 California, 53 m
Tridentella recavaBowman, 1986 New York Bight, 100-300 m
Tridentellasaxicola(Hale, 1925) New South Wales, and GreatBarrierReef, eastern Australia,
137-146 m
Tridenkllasculpturata Kussakin, 1955 North-western Pacific, 70-96 m
Tridentellatangaroae(Bruce, 1988) New Zealand,90-94m
Tridentellavirginiana (Richardson, 1900) VirginiatoNova Scotia, 148m
TridentellavitaeBruce, 1984 Fiji, 360 m
Tridentella ornata(Richardson, 1911)(junior South-easternUSA,GulfofMexico, Caribbean Sea,25 168 m
synonym: T.williamsiDelaney, 1990,see
Kensley & Heard, 1997)
endite as well as astyliform maxilla 1 and scaled time.
maxilla 2. Maxilla 2 in corallanids is no more Wepresent akey to the species based onpub-
than a minute lobe. The family differs from lished illustrations andliterature.
Cirolanidae in possessing a narrow rather than
tri-dentate mandibularincisorandwholly distinc- KEY TO WORLD SPECIESOF TRIDENTELLA
tive mouthparts. Maxillae 1 and 2 andthe maxil-
liped are fundamentally different from those of la. Body surface (tergites) smooth oratmost withtuber-
Cirolanidae. Maxilla 1 is similar to that of the clesonheador carinaeonpleotelson 2
Aegidae and Cymothoidae, while the maxilla 2 b. Bodysurfacewith spinesortubercles ontergites.... 11
structure is unique. Aegidae have prehensile 2a. With ornamentationonhead 3
dactyli on pereopods 1-3. b. Without ornamentation onhead 7
TRIDENTELLARICHARDSON, 1905 3a. Head only with shallow elevations onposterior mar-
gin T. japonica
b. Head with prominent, well-separated tubercles 4
Tridentella Richardson, 1905: 161; Kussakin,
1979: 223; Delaney & Brusca, 1985: 729; 4a. Headwith2 shallow elevations between eyes
Bruce, 1984: 448; Bruce, 1988: 73; Kensley & T.saxicola
Schotte, 1989: 236 (type species Cirolana virgini- b. Head with more than 2 shallow elevations between
ana Richardson, 1900). eyes 5
Smicrostoma Hale, 1925: 166 (type species
5a. Headwith 3 acute,anteriorlydirected spinesinmale
Smicrostoma saxicola Hale, 1925).
T.cornuta
b. Headwith4or 5tubercles 6
REMARKS.- Fourteenspecies were knownpriorto
this study and none is known from more than a 6a. Headwith4tubercles onhead between eyes (close to
anterior and posteriormargins T. virginiana
fewrecords. Bruce(1988) discussed differences in
b. Headwith5tubercles (female without).. T. quinicornis
sculpture and pereopodal and mouthpart mor-
phology between the 13 species known at that 7a. With pair of strong triangular posterior pleotelsonic
spines T.recava
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b. Without strongposteriorpleotelsonicspines 8 (female, 16 mm); off Orange River (Cruise BENGUELA
IX, trawl sample P-41) (29°23.4'S014°41.8'E),285-285m,
8a. Pleotelson without ridgesorgrooves ... T.laevicephalax E. Macpherson, 20-VI-1986, NMV J27635 (ovigerous
b. Pleotelsonwith ridgesand/or grooves 9 female, 18mm).
9a. Pleotelson with only carinae, but no lateral serra- DESCRIPTION OF HOLOTYPE MALE. - Length 19
tions 10
mm; body 1.9 times as long as wide (Fig. 1A);
b. Pleotelson with lateral margin strongly serrated on
bothsides oflongitudinal carinae T.vitae headwith two small elongate frontomesialeleva-
tions and two smooth ones more posteriorly
1Oa. Pleotelson with 2 distinct longitudinalcarinae betweeneyes. Eyes each occupying one-third of
T.tangaroae freeheadmargin, dark-browninfixedspecimens,
b. Pleotelsonwith 5 pairs of slight and shallow trans- broaderanteromedially than posterolaterally.
versecarinae T.benguelan.sp. Pereonite 1 slightly narrower than fourth and
fifth, fusedwith head.Pereonites 2-6 about equal
lia. Tergites covered with similar small tubercles, espe-
cially posteriorly 12 inlength (measuredonlateralmargin) andwidth,
b. Tergites coveredwithmore robust tubercles or strong pereonite 7 shorter. Pereonitesincreasingly tuber-
spines posteriorly than anteriorly 13 culateposteriorly; allwith transverse row ofblunt
tuberclesalongposterior margin; eachwithtrans-
12a. Tergitescoveredwith tinynodules;maxillipedalendite
long,reachingorsurpassing tipof lastpalp article verse row submarginally, less pronounced mid-
T.acheronae dorsally especially onanterior pereonites, leading
b. Tergites highly sculptured, with many small, blunt to broad tuberculate region over lateral third of
spines; maxillipedal endite reaching almost distal tergite. Coxaewith increasingly acuteposteroven-
aspectof fourthpalparticle T.namibia n.sp. tral corner posteriorly, with oblique ridge; coxae
4-7tuberculateespecially alongposterior margin.
13a. Tergites and pleotelson strongly covered with blunt
spines; pleotelson mediodorsally with 5 distinctlon- Pleonite 1 narrowest and shortest, largely con-
gitudinalcarinae T.sculpturata cealed by pereonite 7,with single transverse row
b. Tergites of lastpereonites and plconites with blunt of tubercles; pleonites 2-5 with increasing num-
spines; pleotelson with spines andlateral incisions ..14 bers of tubercles over dorsal surface. Pleotelson
almost semicircular in dorsal view, with promi-
14a. Pleotelson almost 3 times as wide aslong; uropods
shorter than apex T. ornamenta nent tuberculate elevation anteriorly, separated
b. Pleotelson onlyslighdy wider than long 15 from posterior region by deep ridge; posterior
area withmedianrow andaboutsix pairs of lon-
15a. Male with distinct rostrum and spinose pleotelson, gitudinal rows of tubercles, less well definedlat-
uropod longer than pleotelson, each eye occupying erally; without robustsetae.
one-quarter of head; female without rostrum, pleo-
Frontal lamina (Fig. 2A) longer than wide, lat-
telson with broad triangularplates, uropods about as
longaspleotelson T.glutacantha erally excavate; clypeus broadly triangular, dor-
b. Male without distinctrostrum, plcotelsonwith broad sally vaulted, and extended.
triangular plates laterally, uropods distincdy longer Antenna I (Fig. 2B) peduncular article 1
than pleotelson, each eye occupying one-third of widest, with ventrodistal pappose seta, article 2
head;female unknown T.ornata
shortest, with two medial simple setae, article 3
longer combined lengths ofarticles 1 and2, with
Tridentellanamibian.sp. one distalpapposeand three simple setae; flagel-
Figs. 1-4 lumextending to posterior ofpereonite 1,with at
least20 articles, article 1small,ring-like, with one
MATERIAL
Holotype:NAMIBIA,offOrangeRiver(Cruise BENGUELA pappose seta, article 2 morethan 7 timesas long
XII, trawl sample P-53) (28°24.5'S014°29.0'E), 348-351 m, as first, with one simple seta, following flagellar
inside sponge, E. Macpherson, 6-XII-1988, NMV J27636 articles slightly narrowing, article 3 withtwo sim-
(male, 19mm). ple setae, following with 1 aesthetasc and three
Paratypes: NAMIBIA,offOrangeRiver (CruiseBENGUELA
simple setae.
VIII, trawl sample P-39) (29°04.4'S 015°08.4'E), 175 m,
Antenna2 (Fig. 2C) peduncular article 1 short,
betweenstones, E. Macpherson, 16-VII-1985,NMVJ27633
201
Fig. 1. Tridentella namibian.sp. A, holotypemale of 19mm lengthin dorsal view.B,paratypefemale(16 mm)in lateralview.
ring-like, with two simple short setae, article 2 article 1 broadest, with three simple apical setae,
about as long as first, with three simple distal article 2 withtwo pairs of simple setae, following
setae, article 3 as long as 1-2 together, with two articles slightly narrowing and shortening, with
pappose and several simple setae, article 4 about groupsof threeapical simple setae.
as long as 1-3 together, with threepapposesetae Mandible (Figs. 2D, E) with incisor narrow,
and small hairs, some distally branched, article 5 acute; molarprocess, acutely triangular, setulate
longest, about 1.5 times as long as fourth, with margin at about 150°to incisor, with small apical
many distal simple setae; fiagellum of 28 articles, spines and simple setae along distal margin;
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Fig. 2.Tridentellanamibian.sp., holotypemale. A, frontallamina and clypeus.B, antenna 1.C, antenna2.D, rightmandible.
E,palpofleftmandible.F, maxilla 1.G, maxilla 2. H,maxilliped.I,pereopod 1.J,pereopod2.K, penialprocesses onpere-
onite 7.
203
Fig. 3. Tridentella namibian.sp.,holotypemale. A,pereopod 3.B, pereopod 4. C, pereopod 5.D, pereopod6.E, uropod.
204
Fig. 4. Tridentella namibia n.sp., holotypemale. A,pereopod7. B,pleopod 1. C, pleopod 2. D, pleopod 3. E, pleopod 4. F,
pleopod5.
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lacinia mobilis absent; palp article 1 slightly lobes, separated by a broad boss on posterior
longer than third, without setation, article 2 margin of pereonite 7.
longest, with setae along distal halflateral mar- Pleopods 1-4 (Figs. 4B-E) withpeduncle having
gin, article 3 weakly falcate, with lateral row of long mesial coupling hooks and simple lateral
ca. 36setae. seta, 2-4 with mesial setae. Pleopod 1 exopod
Maxilla 1 (Fig. 2F) inner lobe with two apical broader than endopod, withprominent seta near
setae; outerlobeslender, styliform,with five acute proximolateral angle, both rami with fringe of
spines andfewsmall scales distally. Maxilla2(Fig. long plumose setae along distalmargins. Pleopod
2G) slender, with distal rows of small, saw-like 2 exopod broaderthanendopod, oval, withmany
rasping scales. Maxilliped (Fig. 2H) without epi- long plumose setae along lateral and distal mar-
pod; long, lamellarenditeextending to palp arti- gins; endopod with plumose setae along distal
cle 4, distally with simple setae;palp articles 1-3 margin; with appendix masculina (broken off at
eachwithmesial seta, article 4with seven lateral mid length of endopod). Pleopod 3 exopod
setae and five mesial setae, article 5 with seven broader than endopod, oval, with partial trans-
mesialand distal setae. verse suture,withmany longplumose setae along
Pereopod 1 (Fig. 21) shorter and more robust lateralanddistal margins; endopod with fringe of
than others; pereopods 2-7 increasing in length, plumose setae along distal margin. Pleopod 4
basis becoming wider posteriorly. Pereopod 1 exopod broader than endopod, oval, with partial
basis broad, with five papposesetae along anteri- transverse suture, with many long plumose setae
or margin; ischium with few distal setae; merus along lateral and distal margins; endopod with
with fourblundy-hooked robust setae on posteri- transverse suture,with plumose setae along distal
or margin; carpus triangular with one acute margin. Pleopod 5 (Fig. 4F) exopod broader than
robust seta and four simple setae;propodus with endopod, oval, with complete transverse suture,
two small acute robustsetae on palm, one distal- with long plumose setae along lateral and distal
ly opposing dactylus; dactylus strongly curved, margins; endopod without transverse suture,
with conical unguis. without plumose setae.
Pereopod 2 (Fig. 2J) ischium and merus with Uropod (Fig. 3E) not reaching apex ofpleotel-
one and six blundy hooked robust setae along son; peduncle extended mesially, with five dis-
posterior margin, interspersed with simple short tomesial pappose setae; endopod 2.0 times as
robustsetae; carpuscylindrical, withshort robust long as greatest width, distally expanded, trun-
setae;propodus with eight robustsetae, irregular- cate, distally and distolaterally with small, blunt
lyplaced; dactylus curved. teeth, short simple setae situated in notches
Pereopod 3 (Fig. 3A) ischium-propodus with betweenteeth, mesially withrow of longpappose
irregular arrangement of stout and more conical setae; exopod 0.77 length of endopod, elongate-
robust setae along posterior margin and mesial oval, 3.2 times as longas wide, distally anddisto-
face; dactylus curved. laterally withpappose setae, laterally andmesial-
Pereopods 4-7 (Figs. 3B-D and 4A) with basis ly with simple ones, distally setae also situated in
broad (2.0 times as long as wide in pereopod 6, notches between blunt spines; without robust
slightly narrower in others), ischium-propodus setae.
with irregular arrangement of more conical
robustsetae alongposterior margin, concentrated FEMALE. - Ovigerous female(18 mm; lateral view
indense clusters on posterodistal angles of ischi- in Fig. 1B) differs from the malein having exten-
um, merus and carpus, especially of posterior sive fields of blunt tubercles laterally on anterior
limbs; anterodistalmargins of ischium andmerus pereonites.
promoted, with transverse row of long robust
setae,andof carpus withtransverse row ofpecti- ETYMOLOGY. - For Namibiaoff whose coast the
nate setae; propodus narrower than carpus,espe- species was taken (noun inapposition).
cially posteriorly; dactylus half as long as propo-
dus, gently curved. REMARKS. - Tridentellanamibia n.sp.belongs to the
Penial processes (Fig. 2K) flattened tapering group of sculptured species. It is similar to T.
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acheronae from New Zealand in possession of article 3 as long as 2, with two several simple
numerous short even tubercles over most of the setae, article 4 longer, with three pappose setae
body. It differs in lacking the two longitudinal and smallsetae, article 5 longest, about 1.5 times
carinae seen on the pleotelson of T. acheronae. as long as fourth, with many distal setae; flagel-
The maxillipedal endite of T. namibia n.sp. is lum >eight articles (broken), article 1 broadest,
shorter and moresetose than in T. acheronae. The article 2 with simple setae, following articles
only otherspecies from the region, T. benguela n. slightly narrowing and shortening, with groupsof
sp. describedbelow, lacks significant sculpture. three apical simple setae.
Mandible (Figs. 6D, E) with incisor narrow,
Tridentellabenguela n.sp. acute; molarprocess, acutely triangular, setulate
Figs. 5-7 margin almost inlinewithincisor, with smallapi-
cal spines and simple setae along distal margin;
MATERIAL lacinia mobilis absent; article 1 of palp slightly
Holotype: NAMIBIA,offOrange River(Cruise BENGUELA longer than third, without setation, article 2
IX) (29°23.4'S 014°41.8'E), 285 m, with a holothurian longest, with setae along distal half lateral mar-
between stones, trawl sample P-41, E. Macpherson, 6-II- gin, article 3 weakly falcate, with lateral row of
1986, NMVJ27634 (1 juvenile, 7 mm).
Paratype: collected with holotype,NMVJ47043 (1 juvenile, setae. Maxilla 1 (Fig. 6F) inner lobe(not dissect-
5mm). ed); outer lobe slender, styliform, with five acute
spines andfewsmall scales distally. Maxilla2(Fig.
DESCRIPTION OFHOLOTYPEJUVENILE . - (Manca 6G) slender, with distal rows of small, saw-like
II). - Length 7 mm; body twice as long as wide rasping scales. Maxilliped (Fig. 6H) without epi-
(Figs. 5A-C); head smooth. Eyes large, pinkish in pod; long, lamellar endite extending to palp arti-
fixedspecimen, broaderanteromedially thanpos- cle 4, distally with simple setae; palp articles 1-3
terolaterally, of manyocellae. Pereonite 1 longest eachwith mesial seta, article 4 with threelateral
and narrowest but only slightly narrower than setae andsix mesial setae,article 5withsix mesial
fourth and fifth, fused with head.Pereonites 2-6 and distal setae.
aboutequal in length (measured on lateral mar- Pereopod 1 (Fig. 61) shorter and stronger than
gin) and width, pereonite 7 shorter. Pereonites others; pereopods 2-7 increasing in length, with
smooth. Coxae with increasingly acute pos- basis becoming wider posteriorly. Pereopod 1
terovental corner posteriorly, with oblique ridge, basis broad, withfourpappose setae alonganteri-
otherwise smooth. Pleonite 1 narrowest and or margin; ischium with few distal setae; merus
shortest; pleonites smooth. Pleotelson almost with threebluntly hookedrobustsetae onposteri-
semicircular in dorsal view, with seven pairs of or margin; carpus triangular; propodus with two
obscure radiating ribs, most obvious closer to small robust setae on palm, one distally; dactylus
midline. hooked, with conical unguis. Pereopod 2 (Fig. 6J)
Frontal lamina (Fig. 6A) longer thanwide, lat- ischium and merus with two and eight blunt
erally excavate; clypeus broadly triangular, dor- robustsetae along posterior margin; carpuscylin-
sally vaulted, and weakly extend- drical, with short robust simple and pectinate
ed. setae; propodus with three robust setae, evenly
Antenna1 (Fig. 6B) peduncular article 1 broad- spaced; dactylus hooked, unguis fine.Pereopod 3
est, article 2shorter, withmedialsimple seta, arti- (Fig. 6K) ischium-propodus with irregular
cle 3 longer than first and second together, with arrangementof conical robustsetae along poste-
distal pappose and three simple setae; flagellum rior margin and mesial face plus pectinate setae
with eigh articles, article 1 small, ring-like, with distally on merus; dactylus curved. Pereopods 4-6
onepappose seta,article 2 longer than first, with (Figs. 6Land 7A, B) with basis moderately nar-
one simple seta, following flagellar articles slight- row (2.7 times as long as wide in pereopod 6,
lynarrowing, article 3 with simple seta, following slightly narrower in others), ischium-propodus
with aesthetascs and simple setae. with irregular arrangement of more conical
Antenna2 (Fig. 6C) peduncular article 1 short robustsetaealong posterior margin, concentrated
(not figured), article 2 withtwo simple distal setae, in denseclusters on posterodistal angles of ischi-
207
Fig. 5. Tridentellabenguela n.sp.,juvenile(mancaII) of7 mm length. A, in dorsal view. B,in lateral view. C, detail ofpleotel-
sonwithindication ofshallow grooves.
um, merus and carpus, especially of posterior pleopods 3-5,
limbs; anterodistal margins of ischium andmerus Uropod (Fig. 71) reaching apex of pleotelson;
promoted, with transverse row of long robust peduncle extended mesially, with five distomesial
setae, andof carpuswithtransverse row of pecti- pappose setae; endopod 1.8 times as long as
nate setae;propodus scarcely narrower than car- greatest width, distally expanded, curved-trun-
pus; dactylus half as long as propodus, gently cate, distally and distolaterally with small, blunt
curved. Pereopod 7 of manca (Fig. 7G), not fully teeth, short simple setae situated in notches
developed. betweenteeth, mesially withrow of long pappose
Pleopods 1-5 (Figs. 7D-H) as described for T. setae; exopod 0.81 length of endopod, elongate-
namibian.sp. except forabsence of appendix mas- oval, 2.7 timesas long as wide, distally and disto-
culina and absence of sutures on exopods of laterally with papposesetae, laterally and mesial-
208