Two new Oncaea species (Copepoda: Poecilostomatoida) from the Red Sea

Journal of Plankton Research Vol.12 no.4 pp.861-871, 1990

Two new Oncaea species (Copepoda: Poecilostomatoida) from theRed Sea

Ruth Bottger-Schnack1 and Geoffrey A.Boxshall2

Institut fur Hydrobiologie and Fischereiwissenschaft, Zeiseweg50, D-2000Hamburg50, FRG and2British Museum (Natural History), Cromwell Road,London SW7 5BD, UK1 Present address: Institut fur Meereskunde an der Universitat Kiel,Dusternbrooker Weg 20, D-2300Kiell, FRG

Abstract. Two new Oncaea species, O.umerus and O.hawii, are described from females taken in thecentral Red Sea. They are closely related to each other and to a group of Oncaea similis-\ike species,whose morphological characteristics are reviewed for comparison.

Introduction

During studies on the community structure and vertical distribution of cyclopoidcopepods in the plankton of the central and northern Red Sea (Bottger-Schnack,1988; Bottger-Schnack, 1990a,b) several unidentified Oncaea species werefound, two of which have recently been described as new species (Boxshall andBottger, 1987). The present paper describes another two new Oncaea speciesbased on females found in plankton taken with fine mesh nets in the upper450 m of the central Red Sea, above the Atlantis II Deep. Both species arecommon and had formerly been designated as Oncaea sp. F and Oncaea sp. E/Fin the published quantitative analysis of cyclopoids (Bottger-Schnack, 1988).

Methods

The oncaeids were collected in a multiple opening and closing net with a meshsize of 0.1 mm in the upper 450 m, during cruise 29 of the R/V Valdivia in thecentral Red Sea during October and November 1980. A station list and thesampling data are given in Table I. The plankton was fixed in 4% formaldehyde-seawater solution buffered with hexamethylene tetramine and transferred into apreservation fluid of 5% propylene glycol, 0.5% propylene phenoxetol, and94.5% filtered seawater (Steedman, 1976) after ~2 years. Specimens weredissected in lactic acid, and mounted on slides in polyvinyl lactophenol. Allfigures have been prepared using a camera lucida on an Olympus BH-2interference contrast microscope.

Description of species

Oncaea umerus n. sp.

Material examined. Holotype female, 13 paratype females deposited incollection of British Museum (Natural History), registration nos 1989.904

861

at University of Sussex on O

ctober 4, 2012http://plankt.oxfordjournals.org/

Dow

nloaded from

http://plankt.oxfordjournals.org/

R.Bottger-Schnack and G.A.Boxshall

Table I. Station list

Station/haul no.

78/81-4

90/88-4

130/115-2

130/116-3

169/148-1

177/154-4

Date(1980)

Oct. 19

Oct. 21

Oct. 28

Oct. 28

Nov. 4

Nov. 5

TimeD = day, N

D

D

N

N

N

N

= nightSampling depth(m)

250-300

250-300

150-200

300-350

400-450

50-100

Geographic position

21°23.6'N38°04.7'E21°23.30'N38°04.13'E21°25.53'N38°01.91'E21°25.53'N38°01.91'E21°24.48'N38°04.31'E21°25.96'N38°04.22'E

(holotype) and 1989.905-917 (paratypes). Holotype and six paratype femalesfrom station 90 (21°23.30'N, 38°04.13'E) at 250-300 m, one female from station130 (21°25.53'N, 38°01.91'E) at 150-200 m, one female from station 177(21°25.96'N, 38°04.22'E) at 50-100 m, and five females from station 78(21°23.6'N, 38°04.7'E) at 250-300 m.

Description. Adult female body length 590 p.m (570-620 n-m) not includingsetae on caudal rami, based on three specimens in lactic acid. Length to width ofprosome ~2.0:l. Ratio of prosome to urosome length 1.6:1 (Figure 1A and B).Proportional lengths (%) of urosome somites and caudal rami 12:54:5:4:12:12.Genital complex relatively heavily sclerotized, 1.4 times longer than wide,having maximum width in anterior two-thirds, with rounded lateral margins;posterior part distinctly tapering with conspicuous 'shoulder'-like edge betweenthe two parts (Figure 1C).

Anal segment approximately same length as caudal rami, length to width ratio0.75:1. Caudal rami 1.9 times longer than wide; armed with lateral seta situatedat mid-point of lateral margin, dorsal seta shorter than innermost distal seta andfour distal margin plumose setae of varying lengths, innermost more than twotimes longer than caudal ramus.

First antenna six-segmented, relative lengths (%) of segments measured alongposterior non-setiferous margin 7:22:45:11:6:9. Armature elements 1-3, II-8, III-4, IV-2 + 1 aesthetasc, V-2 + 1 aesthetasc, VI-6 + 1 aesthetasc (Figure 2A).

Second antenna three-segmented (Figure ID), long first segment with patchof setules on outer margin and bearing single plumose seta at inner distal angle,second segment subtriangular with patch of setules on outer margin and withminute denticles along inner margin. Third segment shorter than second,bearing proximal group of four and distal group of six setae on inner margin.

Labrum bilobed, with serrated margin either side of medial incision, posteriorsurface of labrum ornamented with four median structures apparently thicken-ings of integument (Figure IE).

862



Dow

nloaded from


Two new Oncaea species

Fig. 1. Oncaea umerus a. sp., female. (A) Dorsal; (B) lateral; (C) urosome, dorsal; (D) secondantenna; (E) labrum, ventral; (F) mandible; (G) first maxilla; (H) second maxilla. Scale bars in \im.

Mandible unsegmented, bearing five distal elements, three setae and twoblades, one toothed (Figure IF).

First maxilla with seven setae (Figure 1G). Second maxilla two-segmented:

863



Dow

nloaded from



Fig. 2. Oncaea umerus a. sp., female. (A) First antenna; (B) maxilliped; (C) leg 1; (D) leg 2; (E) leg3; (F) leg 4. All scale bars 50 (im.

first segment unarmed, second segment with two attenuated spiniform processesbearing a row of strong setules unilaterally and two slender setae (Figure 1H).

Maxilliped four-segmented; robust second segment armed with two innermarginal setae subequal in length, slender proximal seta minutely barbed, stoutdistal seta bearing two rows of strong denticles (Figure 2B). Fringe of long

864



Dow

nloaded from



Table n. Oncaea umerus n. sp.Arabic numerals represent setae

LeglLeg 2Leg 3Leg 4

Coxa

0-00-00-00-0

Armature

Basis

l-I1-01-01-0

of swimming legs. Roman

Endopod

0-1; 0-1; 0,1,50-1; 0-2; 1,11,30-1; 0-2; 1,11,20-1; 0-2; 1,11,1

numerals indicate spines,

Exopod

1-0; I - l ; m,1,41-0; I - l ; 111,1,51-0; I - l ; 11,1,51-0; I - l ; 11,1,5

pinnules present between proximal seta and distal end of second segment. Smallthird segment unarmed. Terminal claw, being fourth segment, stout, armed withbasal seta and row of fine spinules along whole length of concave margin.

Swimming legs 1-4 biramous (Figure 2C-F), with three-segmented rami,armature as shown in Table II. Exopods in all four legs with small hyalinelamella on outer edge of segments, most obvious on proximalmost segment.Terminal spines of exopods just shorter or equal to third exopod segment.Lateral margins of all endopod segments armed with row of fine pinnules. Thirdsegment of endopod in legs 2-4 each with terminal conical projection betweenserrated apical spines. Terminal spine of leg 2 endopod equal in length to thetwo external spines.

Leg 5 (Figure 1C) comprising a curved seta on body surface and a smallunornamented free segment which is slightly longer than wide; bearing stoutcurved seta and slender seta, similar in length.

Leg 6 (Figure 1C) represented by operculum closing off each genitalaperture; armed with single short spine and minute spinule.

Etymology. The specific name umerus (L.), meaning shoulder, refers to theshape of the lateral margins of the genital segment.

Remarks. Oncaea umerus is the species previously referred to as Oncaea sp. F byBottger-Schnack (1988). It is frequently found in the central and northern RedSea (Bottger-Schnack, (1990a,b). It also occurs in the southern Red Sea andGulf of Aden (unpublished data).

Oncaea hawii n. sp.

Material examined. Holotype female, 16 paratype females deposited incollection of British Museum (Natural History), registration nos 1989.918(holotype), 1989.919-934 (paratypes). Holotype and eight paratype femalesfrom station 90 (21°23.30'N, 38°04.13'E) at 250-300 m, one female from station130 (21°25.53'N, 38°01.91'E) at 150-200 m, one female from station 130 at300-350 m, three females from station 169 (21°24.48'N, 38°04.34'E) at400-450 m, and four females from station 78 (21°23.6'N, 38°04.7'E) at250-300 m.

Description. Adult female body length 530 u.m (490-560 u-m), based on sevenspecimens in lactic acid. Ratio of prosome to urosome 2.0:1 (Figure 3A). Length

865



Dow

nloaded from



Fig. 3. Oncaea hawii n. sp., female. (A) Dorsal; (B) urosome, dorsal; (C) first antenna; (D) secondantenna; (E) mandible; (F) first maxilla; (G) second maxilla. Scale bars in |un.

to width of prosome 2.2:1. Proportional lengths (%) of urosome somites andcaudal rami 13:54:5:6:13:10 (Figure 3B). Genital segment less sclerotized thanO.umerus, 1.4 times longer than wide, anterior two-thirds rounded, posteriorthird tapering gradually.

Anal segment 1.2 times longer than caudal rami, length to width ratio 0.66:1.

866



Dow

nloaded from



Caudal rami 1.8 times longer than wide, armature as in Figure 3 (A and B).Innermost distal seta less than twice as long as caudal ramus. Dorsal seta aboutas long as the innermost distal seta.

First antenna six-segmented, relative lengths (%) of segments measured alongposterior nonsetiferous margin 7:22:44:11:4:11. Armature elements 1-3, II-8,III-4, IV-2 + 1 aesthetasc, V-2 + 1 aesthetasc, VI-6 + 1 aesthetasc (Figure 3C).

Second antenna three-segmented (Figure 3D), with armature similar innumber to O.umerus, but lacking setules on outer margin of first segment andinner margin of second segment smooth. Third segment with row of spinules onposterior surface, absent in O.umerus. Labrum, first maxilla (Figure 3F), secondmaxilla (Figure 3G) and mandible (Figure 3E) similar to O.umerus.

Maxilliped four-segmented (Figure 4A), similar to O.umerus, except stoutdistal seta on second segment bearing smaller denticles than in O.umerus, androw of small setules present on anterior surface of second segment.

Swimming legs 1-4 (Figure 4B-E) with same armature formula as O. umerus.Endopods of legs 2-4 with long terminal conical projections.

Leg 5 represented by long seta on body surface and small unornamented freesegment bearing two terminal unequal setae: stout curved seta and a longslender seta, extending about half-way along genital segment (Figure 3B).

Leg 6 (Figure 3B) represented by operculum closing off each genital aperture;armed with single short spine.

Etymology. The species is named in memory of Hans-Wilhelm Halbeisen, calledHa-Wi, who was a fisheries scientist at the Institut fur Meereskunde an derUniversitat Kiel. He died together with three other young scientists after aterrorist bomb exploded in Djibuti, Sudan, during a cruise of the R/V Meteor tothe Red Sea and northern Indian Ocean in March 1987.

Remarks. Oncaea hawii is the species previously referred to as Oncaea sp. E/Fby Bottger-Schnack (1988). It is regularly found in the central and northern RedSea in similar abundance to O.umerus (Bottger-Schnack, 1990a,b).

Discussion

The two new Oncaea species are closely related to each other. They differ in theform of the genital segment and in the length of the slender apical seta on leg 5.These characters enabled discrimination between the two species to be madewithout dissection whilst sorting zooplankton samples (Bottger-Schnack,1990a). Other minor differences are the ornamentation of the second antennaand maxilliped.

The possession of median teeth on the labrum is a characteristic that has onlyrecently been described for oncaeids by Humes (1988) in his description of a newspecies, Oncaea praeclara, from a hydrothermal vent field. He states that from~30 other Oncaea species where the labrum has been described onlyO.praeclara showed this character. In the two new Oncaea species from the RedSea described above, four median structures are present on the labrum but they

867



Dow

nloaded from



Fig. 4. Oncaea hawii n. sp., female. (A) Maxilliped; (B) leg 1; (C) leg 2; (D) leg 3; (E) leg 4. All scalebars SO (xm.

appear to be integumental thickenings rather than teeth. A similar arrangementhas also been found in females of O.minuta from the same area (unpublisheddata). This characteristic may be more widespread among Oncaea species thanpreviously thought.

The two new species are similar to O.dentipes (Giesbrecht, 1891), O.minuta(Giesbrecht, 1892), O.similis (Sars, 1918), and O.rufa (Boxshall and Bottger,

868



Dow

nloaded from


Tab

le I

II. C

ompa

riso

n be

twee

n th

e fe

mal

es o

f O

ncae

a si

mil

is s

peci

es g

roup

s

Len

gth

of g

.c. t

o le

ngth

of r

est

of u

roso

me

Len

gth:

wid

thof

g.c.

Form

of

g.c.

Len

gth

of s

lend

er a

pica

l set

aon

leg

5

Len

gth

of d

.s.M

engt

hof

c.r.

Len

gth

of d

.s.M

engt

h of

inne

rmos

t api

cal s

eta

on c

.r.

No.

of s

lend

er s

etae

on

Mx2

Lab

rum

with

med

ian

teet

h

Tot

al le

ngth

(^m

)

"Ow

n un

publ

ishe

d da

ta.

0.si

mil

is

O.m

inut

aSa

rs

Gie

sbre

cht

2.6-

2.8:

1 2.

0-2.

3:1

2.2:

1 1.

7:1

O.d

enti

pes

Gie

sbre

cht

1.8:

1

1.5:

1

mor

e or

less

gra

dual

ly ta

peri

ng f

rom

grea

test

wid

th p

oste

rior

ly

<V

i as

long

as

g.c.

<2:

1 2:

1

<1:

1 1:

1

2 1

no

yes°

620-

900

450-

580

? ? ? ? 510-

520"

440-

490°

O.r

ufa

Box

shal

l an

d B

ottg

er

1.9:

1

1.3:

1

ante

rior

% si

nuou

s

as lo

ng a

s g.c

.

<2:

1

>l:

l 1

no 600-

620

O.u

mer

us n

. sp.

2.5:

1

1.4:

1

ante

rior

% ro

unde

dta

peri

ng p

oste

rior

lyw

ith d

istin

ct 's

houl

ders

'

<Y

i as

long

as

g.c.

>2:1

<l:

l 2

yes 570-

620

O.h

awii

n. s

p.

2.4:

1

1.4:

1

as in

O.u

mer

us b

utw

ithou

t 'sh

ould

ers'

Vi-

Vi a

s lo

ng a

s g.c

.

<2:

1

1:1

2

yes

490-

560

I 1b G

iesb

rech

t (1

892)

.cR

ed S

ea s

peci

men

s (B

ottg

er-S

chna

ck e

t al.,

198

9).

Abb

revi

atio

ns a

re:

g.c.

= g

enita

l co

mpl

ex,

c.r.

= c

auda

l ra

mus

, d.s

. =

dor

sal

seta

on

caud

al r

amus

, M

x2 =

sec

ond

max

illa.

00

at University of Sussex on October 4, 2012http://plankt.oxfordjournals.org/Downloaded from



1987), in size, in the armature formula of the swimming legs, in the proportionallengths of urosome somites and caudal rami, and in the possession of conicalprojections on the tips of the endopods of legs 2-4 (Giesbrecht, 1892; Sars,1918; Boxshall and Bottger, 1987). Together these six species form a well-defined group of species within the genus Oncaea which is called the O.similis-group hereafter. A comparison of morphological characters within the O.similis-group is presented in Table III. For O.similis data have been taken from the typedescription by Sars (1918) and from Heron (1977). Specimens of O.similisdescribed by Olson (1949) and by Ferrari (1975) differ from the other twoauthors in the shape and the measurements of the genital complex. Ferraridescribes the genital complex as follows: 'The genital complex does notgradually taper posteriorly from its widest to narrowest width; rather theanterior area is more rounded and the posterior portion distinctly cylindrical asin Olson (1949)'. This is very similar to the newly described O.umerus from theRed Sea, and their specimens may possibly represent the same species.However, the length to width ratio of the genital complex of their specimens(1.6:1) is intermediate between that of O.similis (2.2:1) and O.umerus (1.4:1)(Table III). Furthermore, Olson's specimens differ from those found in the RedSea and from O.similis in the length of the terminal spine on the endopod of leg2, which is shorter than the two external spines in his specimens, while beingequal in length in the other species compared.

For one species of Oncaea similis-group, O.rufa, the presence of a dorsalprojection on the third prosome segment, variable in size and conspicuousness,has recently been discovered during a re-examination of female specimens fromthe Red Sea. This might indicate a relationship between the O.conifera-group ofspecies, including O.conif era (Giesbrecht, 1891), O.borealis (Sars, 1918),O.clevei (Friichtl, 1923), O.antarctica (Heron, 1977), and O.inflexa (Heron,1977), and the O.similis-grovip.

Acknowledgements

Thanks are due to Professor Dr D.Schnack and Dr H.Weikert for their supportand help. The valuable comments of two anonymous referees are gratefullyacknowledged. Cruise 29 of R/V Valdivia was financially supported by theSaudi-Sudanese Red Sea Joint Commission, Jeddah, and the Bundesmini-sterium fur Forschung und Technologie, FRG. This study was supported byDeutsche Forschungsgemeinschaft grant We 695/9 to H.Weikert.

References

Bottger-Schnack.R. (1988) Observations on the taxonomic composition and vertical distribution ofcyclopoid copepods in the central Red Sea. In Boxshall,G.A. and Schminke.H.K. (eds), Biologyof Copepods. Kluwer Academic Publishers, Dordrecht, pp. 311-318.

B6ttger-Schnack,R. (1990a) Community structure and vertical distribution of cyclopoid copepods inthe Red Sea. I. Central Red Sea, autumn 1980. Mar. Biol., in press.

B6ttger-Schnack,R. (1990b) Community structure and vertical distribution of cyclopoid copepods inthe Red Sea. II. Aspects of seasonal and regional differences. Mar. Biol., in press.

Bottger-Schnack.R., Schnack,D. and Weikert.H. (1989) Biological observations on small cyclopoidcopepods from the Red Sea. J. Plankton Res., 11, 1089-1101.

870



Dow

nloaded from



Boxshall.G.A. and Bottger.R. (1987) Two new species of Oncaea (Copepoda: Poecilostomatoida)from the Red Sea and a redescription of O.atlantica Shmeleva. J. Plankton Res., 9, 553-564.

Ferrari.F.D. (1975) Taxonomic notes of the genus Oncaea (Copepoda: Cyclopoida) from the Gulf ofMexico and Northern Caribbean Sea. Proc. Biol. Soc. Washington, 88, 217-232.

Friichtl,F. (1923) Cladoceren und Copepoden der Aril-Inseln (Vorlaufige Mitteilung: Artenliste undkurze Diagnosen der neuen Formen). Abh. senckenb. naturforsch. Ges., 35, 449-457.

Giesbrecht.W. (1891) Elenco dei Copepodi pelagici raccolti dal tenente di vascello GaetanoChierchia dOrante U viaggio della R.Corvetta 'Vettor Pisani' negli anni 1882-1885, e dal tenente divascello Francesco Orsini nel Mar Rosso, nel 1884. Att. Accad. naz. Lincei Re, 7, 474-481.

Giesbrecht.W. (1892) Systematik und Faunistik der pelagischen Copepoden des Golfes von Neapelund der angrenzenden Meeresabschnitte. Fauna und Flora des Golfes von Neapel, XIX, 1-831.

Heron,G.A. (1977) Twenty-six species of Oncaeidae (Copepoda: Cyclopoida) from the SouthwestPacific-Antarctic area. In Pawson.D.L. (ed.), Biology of the Antarctic Seas, VI. Antarctic Res.Ser., 26, 37-96.

Humes,A. G. (1988) Oncaea praeclara n. sp. (Copepoda: Poecilostomatoida) from deep-seahydrothermal vents in the eastern Pacific. J. Plankton Res., 10, 475-485.

Olson,J.B. (1949) The pelagic cyclopoid copepods of the coastal waters of Oregon, California andLower California. PhD thesis, University of California, Los Angeles, 208 pp.

Sars.G.O. (1918) An account of the Crustacea of Norway. VI. Copepoda Cyclopoida. Parts 13-14,173-225. Bergen Museum.

Steedman.H.F. (1976) Examination, sorting and observation fluids. In Steedman.H.F. (ed.),Zooplankton fixation and preservation. Monographs on Oceanographic Methodology 4, UnescoPress, Paris, pp. 182-183.

Received on October 13, 1989; accepted on March 22, 1990

871



Dow

nloaded from


Documents

Two new Oncaea species (Copepoda: Poecilostomatoida) from the Red Sea