Foliomolgus cucullus, a new genus and species of Clausidiidae (Crustacea: Copepoda: Poecilostomatoida) associated with a polychaete in Korea

7 Pages·2001·2.8 MB·

by  I-H Kim

PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
114(3):660-666. 2001.
Foliomolgus cucullus, a new genus and species of Clausidiidae
(Crustacea: Copepoda: Poecilostomatoida) associated with a
polychaete in Korea
Il-Hoi Kim
Department of Biology, Kangnung National University, Kangnung 210-702, Republic of Korea,
e-mail: [email protected]
—
Abstract. Foliomolgus cucullus, new genus and species, is described as an
associate of the polychaete Marphysa sanguinea (Montagu) inhabiting the in-
tertidal sands in Jeju Island in Korea Strait. The new genus possesses primitive
features such as the complete segmentation and setation of rami on legs 1-4,
7-segmented antennule, 4-segmented antenna, and 5-segmented female uro-
some. It possesses also characteristic features such as a spatulate distal segment
of the maxilla, foliaceous ventral elements and rudimentary dorsal claw on the
mandible, atrophied distal segment of the antenna, and no maxilliped in the
female.
The copepods of the family Clausidiidae lactic acid. Dissections were done using the
have been considered to be the most ances- reversed slide method (Humes & Gooding,
tral group of the order Poecilostomatoida. 1964). Drawing was done with the aid of a
They are found on/in various tubicolous in- camera lucida. In the description ofspecies,
vertebrates, including crustaceans, bivalves, the body lengths were measured from the
and polychaetes. anterior tip ofthe cephalothorax to the pos-
The host of the new genus, Marphysa terior margin of the caudal rami, excluding
sanguinea (Montagu), is a cosmopolitan the caudal setae. In the formula for the ar-
species of Polychaeta occurring in warm mature oflegs 1-4 the Roman numerals in-
seas (Imajima & Hartman, 1964). Kim dicate spines and the Arabic numerals rep-
(2000) reported Clausia lobata as anew spe- resent setae.
cies of copepod associated with M. sangui-
nea from the Yellow Sea. During a recent Family Clausidiidae Embleton, 1901
field survey in Jeju Island, the largest island Foliomolgus, new genus
in Korea, a number of the same polychaete Diagnosis.—Clausidiidae. Body cyclo-
species were collected from the intertidal piform, relatively large, 9-segmented in fe-
sands, and searched for copepod associates. male and 10-segmented in male. Prosome
At this island C. lobata was not found on composed of cephalothorax and 3 meta-
the same polychaete, but, instead, anew spe- somites. Fifth pedigerous somite of female
cies of Copepod belonging to a new genus with dorsal hood. Antennule 7-segmented;
ofthe family Clausidiidae was collected. Al- setation as for the species. Antenna 4-seg-
though only one female and two males were mented; third segment with 1 claw and 3
found, they were large enough to facilitate a setae; terminal segment atrophied, armed
thorough study, leaving type specimens with 4 spiniform setae and 3 simple setae.
available for future study. Labrum reduced, incompletely covering
Before microscopic observation and dis- oral appendages. Mandible with atrophied
section, copepod specimens were cleared in terminal process and 3 foliaceous subter-
VOLUME 114, NUMBER 3 661
minal elements. Paragnath encircling mites with pointed posterior corners. Epi-
mouth, with 2 lobate processes on inner meron of fourth pedigerous somite with
margin. Maxillule distally bilobed, with 3 rounded corners. Urosome (Fig. IC) slender
and 5 setae on respective lobes. Maxilla 2- and five-segmented. Fifth pedigerous so-
segmented, simplified, and armed with 1 mite 405 [xm wide, characteristically with
seta on basal segment and 2 setae on digi- dorsal hood (487 ixm wide) covering most
tiform distal segment. Maxilliped absent in of dorsal surface of fifth pedigerous somite
female. Male maxilliped of well-developed and anterior part of genital double-somite
and composed of4 segments, including ter- (Fig. IB). Genital double-somite 335 X 295
minal claw. Legs 1-4 with 3-segmented |xm, widest in anterior third, then tapering
rami; setation as for the species. Leg 5 with posteriorly. Genital area located laterally,
1 seta on basal segment and 4 setae on dis- invisible from dorsal and ventral views.
tal segment. Basal segment of male leg 5 Three abdominal somites 210 X 165, 162
fused with fifth pedigerous somite. Maleleg X 142, and 115 X 115 |xm, respectively.
6 represented—by 1 seta on genital flap. Anal somite with spinules along posterov-
Etymology. The generic name Foliom- entral border. Caudal ramus slender, diver-
olgus is a combination offolium (=leaf in gent, 221 X 40 iJim (5.53:1), with parallel
Latin) and molgus (the ending of many ge- lateral margins and 6 setae. Posteroventral
neric names of copepod associates). It al- border of caudal ramus armed with several
ludes to the foliaceous subterminal ele- denticles (Fig. ID). All caudal setae naked.
ments on the mandible in both sexes. The One of terminal setae distinctly larger than
mm
gender is masculi—ne. others, 1.05 long.
Type species. Foliomolgus cucullus, Egg sac not seen.
new species Rostrum wider than long, rounded pos-
terior margin (Fig. IE). Antennule (Fig. IF)
Foliomolgus cucullus, new species 7-segmented, 731 (xm long, with armature
Figs. 1-3 formula 5, 15, 6, 3, 4+1 aesthetasc, 2+1
aesthetasc, and 7+1 aesthetasc. Antenna
—
Type specimens. One female and two (Fig. 2A) 4-segmented, elongate, with ar-
males found on the external surface of the mature formula 1, 1, 3+1 claw, and 7. First
polychaete Marphysa sanguinea (Montagu) and second segments slender, each about 3
collected from the intertidal coral sands at times as long as wide. Seta on these seg-
Sinhung-ri on the northern shore of Jeju Is- ments relatively small and naked. Third
land (approximately 33°33'N, 126°39'E), on segment armed with spinules on inner mar-
3 Jun 2000. Holotype female (USNM gin. Claw on this segment prominent, one
309082; left antennule, left antenna, and oral of three setae very small. Fourth segment
appendages dissected out and mounted on a originating from proximal part of outer
sHde) and allotype (USNM 309083; an intact margin of third segment, wider than long,
male) have been deposited in the National armed terminally with 4 spiniform setae
Museum ofNatural History, Smithsonian In- and 3 simple setae, outermost setaplumose.
stitution. Dissected paratype (one male) is re- Labrum (Fig. 2B) reduced, distinctly
tained in th—e collection of the author. shorterthan wide, covering only part oforal
Female. Body (Fig. lA) cyclopiform, appendages. Mandible (Fig. 2C) armedwith
2.67 mm long. Greatest width 1.02 mm. 1 terminal fleshy, atrophied element tipped
Prosome composed of cephalothorax and with a small claw-like process, and 3 long,
three pedigerous somites. Rostral area of very thin, foliaceous subterminal elements
cephalosome produced anteriorly. Prosomal covered with minute spinules on all surfac-
somites with well developed epimera. Epi- es. Paragnath (Fig. 2D) with 2 hairy lobes
mera of second and third pedigerous so- on medial side. Maxillule (Fig. 2E) taper-
662 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
Fig. L FoUomolguscucullus, newgenus,newspecies,female.A,habitus,dorsal;B,anteriorpartofurosome,
dorsal; C, urosome, ventral; D, caudal rami, ventral; E, rostral area, ventral; F, antennule. Scale bars: A, 0.5
mm; B, C, 0.2 mm; D-F 0.1 mm.
VOLUME 114, NUMBER 3 663
ing, proximally with several setules, and abdominal somites 154 X 187, 175 X 155,
terminally bilobed, with 5 setae (3 lateral 150 X 135, and 104 X 113 [xm, respectively.
ones larger) on anterior lobe and 3 setae on Caudal ramus 198 X 33 [xm (6.0:1), more
posterior lobe. Maxilla (Fig. 2F) 2-seg- slender than that of female.
mented. Basal segment greatly expanded Antennule with 1 additional setaon distal
proximally, roughly triangular, with 1 ter- portion of third segment. Antenna, labrum,
minal seta. Distal segment terminally trun- paragnath, and maxillule similar to those of
cated and sclerotized, and armed with 3 un- female. Mandible (Fig. 3E) with more
equal lateral setae; terminal portion ofdistal prominent claw on tip of terminal element.
segment covered with numerous, minute Maxilla (Fig. 3F) with first segment not ex-
spinules (Fig. 2G). Maxilliped absent. panded, but distal segment as in female.
Leg 1 (Fig. 2H), leg 2 (Fig. 3A), leg 3, Maxilliped (Fig. 3G) 4-segmented. First
and leg 4 (Fig. 3B) with 3-segmented rami. segment with 1 long distal seta. Second
All these legs spiniferous. All legs with 1 segment triangular, greatly expanded prox-
large inner coxal seta; those of legs 1-3 plu- imally, strongly tapering, with a flat, thin
mose on one side and weakly spinulated on protrusion at inner proximal comer, and
the other side. Inner spine on basis of leg 1 armed with 2 rows ofthin, truncate spinules
shorter than first endopodal segment ofsame (one row shorter), 2 rows of epicuticular
leg. Posteromedian part of basis of legs 1-4 extensions and 2 small setae (one in the
ornamented with spinules. Each leg with en- middle, the other smaller one in distal part)
dopod distinctly longerthan exopod. Formula on inner margin. Third segment short and
of armature of these legs as follows: unarmed. Terminal segment forming a claw
bearing proximally 2 setae and 1 distal
Leg 1: coxa 0-1: basis l-I; membranous process.
exp. I-O; I-l; I, 7 Legs 1-4 as in female. Basal segment of
leg 5 completely fused with fifthpedigerous
enp. 0-1; 0-1; I, 5 somite, leaving only 1 distal seta. Free dis-
Leg 2 & 3: coxa 0-1: basis 1-0; tal segment broader and shorter than that of
female (Fig. 3D). Leg 6 represented by 1
exp. I-O; I-l; II, 7
stiff seta on t—erminal corner of genital flap.
enp. 0-1; 0-2; III, 3 Etymology. The specific name cucullus
Leg 4: coxa 0-1: basis 1-0; (=hood in Latin) alludes to the hood-like
dorsal coverture on the fifth pedigerous so-
exp. I-O; I-l; I, 7 mite of the female.
enp. 0-1; 0-2; III, 2
Discussion
Leg 5 2-segmented (Fig. IB, C). Basal
segment articulating with fifth pedigerous The genus Hemicyclops best illustrates
somite, distally armed with 1 small seta and general features of the family Clausidiidae
spinules. Distal segment elongate, tapering, (Humes, 1987). The new genus Foliomol-
armed with 1 outer lateral and 3 terminal gus belongs to the Clausidiidae, because it
setae; all setae naked, and as long as or shares with Hemicyclops the important
shorter than distal segment. Leg 6 not seen. characters such as the 7-segmented anten-
—
Male. Body (Fig. 3C) similar to that of nule, 3-segmented rami on legs 1-4, inner
female. Length 2.20 mm. Urosome (Figure spine on the basis of leg 1, 4-segmented
3D) 6-segmented. Genital somite 175 X 317 antenna armed with four and seven ele-
|xm, distinctly narrower than fifth pedigerous ments respectively on the third and terminal
somite, withoutdorsal hood. Genital flapwith segments, and 5+3 setae on the maxillule.
numerous spinules near inner margin. Four Humes & Huys (1992) recognized seven
664 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
Fig. 2. Foliomolgus cuciiUus, new genus, new species, female. A, antenna; B, labrum; C, mandible; D,
mouth area, including paragnaths; E, maxillule; F, maxilla; G, distal part ofmaxilla; H, leg 1. Scale bars: A-C,
E-E 0.05 mm; D, 0.02 mm; H, 0.1 mm.
VOLUME NUMBER
114, 3 665
Fig. 3. Foliomolgus cucullus, new genus, new species. Female: A, leg 2; B, leg 4. Male: C, habitus, dorsal;
D, urosome, ventral; E, mandible; F, maxilla; G, maxilliped. Scale bars: A, B, 0.1 mm; C, 0.5 mm; D, 0.2 mm;
E, 0.02 mm; E G, 0.05 mm.
—
666 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
genera as valid in the Clausidiidae: Clausi- one of the diagnostic features of the new
&
dium Embleton, Conchyliurus Bocquet genus, is a general feature observed in the
Stock, Doviella Rocha, Hemicyclops Boeck, Clausiidae, Nereicolidae and Serpulidicoli-
Hippomolgus Sars, Hyphalion Humes, and dae, the copepods generally associated with
Leptinogaster Pelseneer. In the same year. the polychaetes. Therefore the similarity of
Ho & Wardle (1992) added a new genus the maxilla in these copepods may be a
Pholadicola to this family. Because one of convergence resulting from the association
these genera, Doviella, is a junior synonym with similar hosts.
of Clausia of the Clausiidae (Kim, 2001),
the Clausidiidae currently consists of seven Acknowledgement
genera. In the absence ofa maxilliped in the The field survey of this work was sup-
female and having a claw on the third seg- ported by the Korea Science and Engineer-
ment of the antenna, Foliomolgus is com- ing Foundation (2000-1-20200-003-3).
parable to the genera Leptinogaster and
Pholadicola. However the latter two genera, Literature Cited
both associates of bivalves, carry a 6-seg-
Gooding, R. U. 1963. External morphology and clas-
mented antennule, and fewer setae on the
sification ofmarine poecilostome copepods be-
antenna, maxillule and legs. longingtothefamiliesClausidiidae,Clausiidae,
The morphology ofthe mandible, bearing Nereicolidae, Eunicicolidae, Synaptiphilidae,
the rudimentary dorsal (posterior) element Catiniidae, Anomopsyllidae, and Echiurophili-
(claw) and three well-developed foliaceous dae. Unpublished Ph.D. thesis. University of
Washington, Seattle, 276 pp.
ventral (anterior) elements, is a unique fea- Ho, J.-S. & W. J. Wardle. 1992. Pholadicola intestin-
ture of the new genus Foliomolgus. As far alis, new genus and species, a clausidiid cope-
as the Clausidiidae and related families, the pod pa—rasitic in a deep-burrowing clam from
nereicoliform copepods of Gooding (1963), Texas. Bulletin ofMarine Science 51:37-44.
Humes, A. G. 1987. Copepoda from deep-sea hydro-
are concerned, the size reduction ofmandib- —
thermal vents. Bulletin ofMarine Science41:
ular elements usually involves the ventral 645-788.
ones. The extreme case of this armature re- , & R. U. Gooding. 1964. A method fo—r study-
duction, where only the dorsal claw-like el- ing the external anatomy of copepods. Crus-
eermaenotfiCsarteitnaiiindeade,,iCsleaxuhsiibiidtaeed, bayndsoSmyenagpetni-- t,ac&eaRn.a 6H:u2y3s8.-214909.2. Copepoda (Poecilostoma-
toida and Siphonostomatoida) from deep-sea
philidae. In contrast to this general trend of hydrothermal vent areas off British Columbia,
armature reduction, a mandible similar to including Amphicrossus altalis, a new species
that of the new genus may be seen in co- ofErebonasteridae, with note on thetaxo—nomic
pepodid I of Conchyliurus (see Kim, 1994; position of the genus Tychidion Humes. Ca-
nadian Journal ofZoology 70:1369-1380.
only three ventral elements are retained in Imajima,M., & O. Hartman. 1964.Thepolychaetousan-
the adult) and the adult of Myzomolgus nelidsofJapan,Partn.AUanHancockFoundation
where the dorsal claw is reduced and the Publications, Occasional Paper 26, 452 pp.
ventral elements are developed. Kim, I.-H. 1994. Copepodid stages of Conchyliurus
^Mm?M5Tanaka, 1961 (Poecilostomatoida,Clau-
In addition to the mandible, the antenna
sidiidae) associated with bivalve moUusks.
also is characteristic within the Clausidiidae Hydrobiologia 292/293:161-169.
and related families. In this appendage the . 2000. Poecilostomatoid copepods—from an in-
third segment is produced distally along the tertidal mud flat in the Yellow Sea. Journalof
main axis of the appendage; the fourth seg- Natural History 34:367-432.
ment is displaced laterally. . 2001. A new species of Clausia (Copepoda,
Poecilostomatoida, Clausiidae) associated with
The transformation of the maxilla in thepolychaeteArenicolabrasilliensisNonatain
—
which the distal segment is a spatulatelobe. Korea. Hydrobiologia (in press).