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Three Aetideid Species of Copepods (Copepoda: Calanoida: Aetideidae) from East Sea of Korea
Three Aetideid Species of Copepods (Copepoda: Calanoida: Aetideidae) from East Sea of Korea
Animal Systematics, Evolution and Diversity. 2011. Mar, 27(1): 35-46
Copyright ©2011, The korean Society of Systematic Zoology
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License(http://creativecommons.org/licenses/by-nc/3.0/)which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
  • Received : December 12, 2010
  • Accepted : March 03, 2011
  • Published : March 31, 2011
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About the Authors
Byung-Jin Lim
Department of Biological Sciences, Inha University, Incheon 402-751, Korea
Sung Joon Song
Institute of Environment and Ecology, Korea University, Seoul 136-701, Korea
Gi-Sik Min
Department of Biological Sciences, Inha University, Incheon 402-751, Korea
mingisik@inha.ac.kr
Abstract
Three aetideid copepods collected from the East Sea of Korea are described: Bradyidius angustus (Tanaka,1957), Gaetanus minutus (Sars, 1907), and Aetideus acutus Farran, 1929. The former two species are new to the Korean copepod fauna. The sequences of cytochrome c oxidase subunit 1 were determined to be the molecular characteristics of these three species.
Keywords
INTRODUCTION
Aetideid copepods are relatively large-sized marine calanoids with most found in the deep sea between the mesopelagic and bathypelagic depths, even though a few species are known to be epipelagic (Boxshall and Halsey, 2004). Copepods in this group are mixed feeders and their mouthparts are well adapted for seizing and filtration (Arashkevich, 1969).
The family Aetideidae consists of 213 known species in 30 genera worldwide (Razouls et al., 2010) whereas only three species have been reported from Korea: Aetideus acutus Farran, 1929, Gaetanus brevirostris Brodsky, 1950 and G. minor Farran, 1905 (see Kim, 1985).
In this study, the following three aetideid species are reported from the East Sea of Korea, based on the samples collected by vertical towing of a plankton net from the surface level up to 300 m depth: Bradyidius angustus (Tanaka, 1957), Gaetanus minutus (Sars, 1907), and Aetideus acutus Farran, 1929. Among them, B. angustus and G. minutus are new records of Korean fauna and are known as mesopelagic species (Tanaka, 1957; Park, 1975; Markhaseva, 1996). Korean Aetideus acutus was first reported by Kim (1985) with a short description. This paper redescribes this species to provide additional taxonomical information.
The sequences of the mitochondrial cytochrome c oxidase subunit 1 (CO1) for these three species are also provided as supplementary data for their molecular characteristics.
MATERIALS AND METHODS
- Morphological taxonomy
The samples were collected by vertical tows (0-300 m) using a plankton net (45 cm mouth diameter, 330㎛ mesh) at three sites in the East Sea. The specimens were preserved in 95% ethanol immediately after collection. The appendages of the specimens were dissected in glycerol on a cavity slide glass under a stereomicroscope (Olympus SZX-7; Olympus, Tokyo, Japan) and observed using a microscope (Leica DM 2500; Leica Microsystems, Wetzlar, Germany). All drawings and measurements were made using a drawing tube. Voucher specimens were deposited in the Department of Biological Sciences, Inha University, South Korea.
The Roman and Arabic numerals in the armature formula represent spines and setae, respectively.
- Molecular taxonomy
Single antennas were removed from each specimen for genomic DNA extraction. The other body parts were used for the morphological observation. The genomic DNA was extracted using a RED Extract-N-Amp Tissue PCR kit (Sigma, St.Louis, MO, USA) according to the manufacturer’s instructions. Mitochondrial CO1 was amplified by PCR using universal primers of LCO1490 and HCO2198 (Folmer et al., 1994). PCR amplification was carried out under the following conditions: 3 min at 94℃, 35 cycles of 95℃ for 15 sec, 48℃ for 30 sec, and 72℃ for 90 sec, with a final 72℃ extension reaction for 7 min. The PCR products were gel-purified using a QIAquick ® Gel Extraction Kit (Qiagen, Valencia, CA, USA) and sequenced with an ABI PRISM ® 3700 DNA Analyzer using a BigDye Terminator Cycle Sequencing Ready Reaction Kit (Applied Biosystems, Foster City, CA, USA).
SYSTEMATIC ACCOUNTS
  • Order Calanoida Sars, 1903
  • Family Aetideidae Giesbrecht, 1893
  • 1*Genus AetideusBrady, 1883
2* Aetideus acutus Farran, 1929 (Figs. 1-3)
  • Aetideus acutusFarran, 1929: 228, fig. 5; Tanaka, 1957: 36, fig. 25; Bradford and Jillett, 1980: 14, fig. 5.
Leg 2 ( Fig.3 B). Coxa with inner hairs and 1 inner seta. Basis unarmed. Endopod incompletely 1-segmented, with 6 setae. Exopod 3-segmented; first and second segments with 1 inner seta and 1 outer spine respectively; distal segment with 3 spines, 4 setae and 1 serrated spine bearing 12 teeth on outer edge.
Leg 3 ( Fig.3 C). Coxa with 1 inner seta. Endopod 3-segmented; first segment with 1 inner seta; second and third segments with 1 inner seta, 5 setae, respectively. Exopod 3-segmented; distal segment with 3 spines, 4 setae and 1 serrated spine bearing 13 outer teeth.
Leg 4 ( Fig.3 D) similar to leg 3 except for coxa with 1 inner seta and 5 small spines ( Fig.3 E) and distal segment of exopod with 14 outer teeth. Armature formula of swimmimg legs 1-4 as follows:
  • Leg 1 coxa 0-0 basis 0-1 exp 0-0; Ⅰ-1; I,2,2 enp 0,2,3
  • Leg 2 coxa 0-1 basis 0-0 exp Ⅰ-1; Ⅰ-1; Ⅲ,Ⅰ,4 enp 1,2,3
  • Leg 3 coxa 0-1 basis 0-0 exp Ⅰ-1; Ⅰ-1; Ⅲ,I,4
  • enp 0-1; 0-1; 1,2,2
  • Leg 4 coxa 0-1 basis 0-0 exp Ⅰ-1; Ⅰ-1; Ⅲ,Ⅰ,4
  • enp 0-1; 0-1; 1,2,2
- Male:
Not found.
- Distribution.
East Sea (Korea), New Zealand, South Atlantic, Izu region (Japan), and tropical Pacific Ocean.
- Remarks.
This species is quite rare and with only a few specimens have been reported (Chen and Zhang, 1965; Tanaka and Omori, 1970; Kim, 1985). Only a single female specimen was found.
The genus Aetideus Brady, 1883 consists of 11 species. Aetideus acutus is quite similar to A. giesbrechti Cleve, 1904 in terms of the following characteristics: the anterior part of the cephalosome bears a crest and the coxa of leg 4 has 5 short spines. On the other hand, in the dorsal view, the base
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Aetideus acutus Farran female. A Habitus dorsal; B Habitus lateral; C Rostrum; D Antenna. Scale bars: A-C=0.5 mm D=0.1 mm.
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Aetideus acutus Farran female. A Mandible; B Maxillule; C Maxilla; D Maxilliped; E Gnathobase of the mandible. Scale bar: A-D=0.1 mm.
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Aetideus acutus Farran female. A Leg 1; B Leg 2; C Leg 3; D Leg 4; E Posterior coxal margin of leg 4. Scale bar: AD=0.1 mm.
of the rostrum is not protruded from the top of the head in the female of A. giesbrechti , whereas it is protruded in A.acutus .
The Korean specimen is congruent with that of the original description with minor differences: the last pedigerous somite of the present specimen has a process that reaches the 2/3 region of the second abdominal somite, but that of the type specimen is longer than the Korean specimen and extends beyond the second abdominal somite.
The CO1 sequence of the Korean specimen showed 99% similarity to that of the previously known sequence of A.acutus (Genbank accession no: EU599526).
  • 1*GenusBradyidiusGiesbrecht, 1897
- 2*Bradyidius angustus(Tanaka, 1957) (Figs. 4, 5)
  • Undinopsis angustusTanaka, 1957: 45, fig. 29.
  • Bradyidius angustus: Markhaseva, 1996: 70, fig. 49.
- Material examined. Korea:
1♂, East Sea, 36°05′N, 131°40′E, Jun 2009.
- Redescription. Male:
Body as Fig.4 A. Body length 1.57 mm. Prosome about 2.3 times as long as urosome. Cephalosome and first pedigerous somite fused forming cephalothorax.Posterior corners of last pedigerous somite extending to distal margin of first abdominal somite. Rostrum ( Fig.4 B) bifurcate and weakly divergent. Caudal rami about 1.3 times longer than width.
Antennule ( Fig.4 C). 22-segmented, reaching posterior
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Bradyidius angustus (Tanaka) male. A Habitus dorsal; B Rostrum; C Antennule; D Antenna; E Mandible; F Maxillule; G Maxilliped. Scale bars: A C=0.5 mm D E G=0.1 mm B F=0.05 mm.
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Bradyidius angustus (Tanaka) male. A. Leg 1; B Leg 2; C Leg 3; D Leg 5. Scale bar: A-D=0.1 mm.
border of genital somite.
Antenna ( Fig.4 D). Coxa with 1 long seta and hairs; basis with 2 setae. Endopod 2-segmented; first segment unarmed; second segment with 6 inner and 6 outer setae. Exopod 7-segmented; first segment unarmed; second to sixth segments with 1 seta each; distal segment with 3 setae.
Mandible ( Fig.4 E). Basis with 2 short setae. Endopodal segment with 8 setae. Exopod indistinctly 4-segmented; first segment unarmed; second and third segments with 1 seta, respectively; distal segment with 3 plumose setae.
Maxillule ( Fig.4 F). Arthrite unarmed. Coxal endite degenerate. Coxal epipodite with 4 large and 1 minute setae. Basal endites with 1, 2 setae respectively. Endopod with 9 setae. Exopod with 7 setae.
Maxilla strongly reduced in size and structure.
Maxilliped ( Fig.4 G). Coxa with 1 distal seta. Basis with 2 medial setae. Endopod 6-segmented; first segment with 1 seta; second to sixth segments with 4, 3, 2+1, 2, and 4 setae respectively.
Leg 1 ( Fig.5 A). Coxa with hairs along outer margin and distal part of inner margin. Basis with hairs and 1 distal seta on inner margin. Endopod 1-segmented; outer margin swollen with 1 row of spinules and 5 setae. Exopod 3-segmented; first segment with inner hairs and 1 outer spine; second segment with 1 inner seta and 1 outer spine; distal segment with 4 setae and 1 outer spine.
Leg 2 ( Fig.5 B). Coxa with hairs on both margins and 1 inner seta. Basis unarmed. Endopod 2-segmented; first segment with 1 inner seta; second segment with minute spinules on posterior surface and 5 setae. Exopod 3-segmented; first and second segments with 1 inner seta and 1 outer spine, respectively; distal segment with 3 spines, 4 setae, and 1 serrated spine bearing 22 teeth on outer edge.
Leg 3 ( Fig.5 C). Coxa and basis same as in leg 2. Endopod 3-segmented; first segment with 1 inner seta; second and third segments with 1 inner seta and 5 setae, respectively and minute spinules on posterior surface. Exopod 3-segmented; first and second segments with 1 inner seta and 1 outer spine; distal segment with 3 spines, 4 setae, and 1 serrated spine with 17 outer teeth. Armature formula of swimming legs 1-4 as follows:
  • Leg 1 coxa 0-0 basis 0-1 exp Ⅰ-0; Ⅰ-1; Ⅰ,1,3 enp 0,2,3
  • Leg 2 coxa 0-1 basis 0-0 exp Ⅰ-1; Ⅰ-1; Ⅲ,Ⅰ,4 enp 0-1; 1,2,2
  • Leg 3 coxa 0-1 basis 0-0 exp Ⅰ-1; Ⅰ-1; Ⅲ,Ⅰ,4
  • enp 0-1; 0-1; 1,2,2
  • Leg 4, missing.
Leg 5 ( Fig.5 D) uniramous and asymmetrical; right and left exopod without seta and spine; third segment of right exopod spiniform, about 2.4 times longer than second segment; third segment of left exopod forming a sharp process with 1 subdistal seta.
- Female:
Not found.
- Distribution.
The East Sea (Korea), Sagami, and Suruga (Japan).
- Remarks.
Sixteen species have been recorded in the genus Bradyidius Giesbrecht, 1897 thus far (Boxshall and Halsey, 2004). The male of B. angustus is most similar to B. hirsutus Bradford, 1976 and B. spinifer Bradford, 1969 in having uniramous leg 5 with almost equal lengths of the left and right exopods. On the other hand, B. angustus can be distinguished from the two congeners by the following characteristics: first outer spine on leg 1 exopod of B. hirsutus is short, whereas that of B. angustus is long, exceeding half of the length of the next segment; the endopod of legs 2-4 of B.spinifer has extremely dense spinules, whereas B. angustus has moderately dense spinules.
The Korean specimen coincides well with the Japanese specimen of the original description (Tanaka, 1957). Nevertheless, the Korean and Japanese specimens show the following differences: 1) Tanaka’s specimen has a short outer spine on the first exopodal segment of leg 1, whereas the same spine of our specimen extends to the middle of the second segment; 2) according to Tanaka’s description, the serrated spines of legs 2 and 3 each have 24 and 25 outer teeth, whereas the specimen in the present study has 22 and 18, respectively; and 3) the original illustration shows that the first endopodal and exopodal segments of the antenna have a distal seta, respectively, but no seta was found in the present specimen. These differences are considered variations within the species.
The partial CO1 sequence of genus Bradyidius was determined for the first time and registered at GenBank (Genbank accession no: GU319976).
  • 1*GenusGaetanusGiesbrecht, 1888
- 2*Gaetanus minutus(Sars, 1907) (Figs. 6-8)
  • Gaidius minutusSars, 1907: 10, 1924-1925: 49, Pl. 14, figs. 14-18; Tanaka, 1957: 64, fig. 39a-f.
  • Gaidius variabilisBrodsky, 1950: 160, fig. 74; Tanaka and Omori, 1970: 127, fig. 6a-k.
  • Gaetanus moderatusTanaka, 1957: 66, fig. 40.
- Material examined. Korea:
1♀, East Sea, 37°05′N, 131°20′E; 5♀ ♀, 36°30′N, 131°20′E, Jun 2009.
- Redescription. Female:
Body as Fig.6 A. Body length 4.46 mm. Prosome about 3.7 times as long as urosome. Cephalosome and first pedigerous somite fused forming cephalothorax. Posterior corners of last pedigerous somite ( Fig.6 B) with short spine on each side. Rostrum ( Fig.6 C, D) short and acute, but slightly notched at apex ( Fig.6 E).
Antennule ( Fig.6 H). 24-segmented, reaching end of caudal rami. Endopod of antenna ( Fig.7 A) slightly shorter than exopod; coxa with 1 seta; basis with 2 setae. Endopod 2-segmented; first segment with 2 distal setae; second segment with 8 inner and 7 outer setae. Exopod 7-segmented; first segment without seta; second segment with 2 setae; third to sixth segments with 1 seta each; distal segment with 3 terminal setae and medial seta.
Mandible ( Fig.7 B, C). Gnathobase with 6 large and 5 small teeth, 1 long seta and 2 rows of setules. Basis with 2 setae. Endopod 2-segmented; first segment with 1 seta; second segment with 9 setae. Exopod 5-segmented; first to fourth segments with 1 seta each; distal segment with 2 setae.
Maxillule ( Fig.7 D). Arthrite with 4 posterior setae, 9 spines and 1 medial seta. Coxal epipodite with 9 setae. Coxal endite with 4 setae. Basal endites with 4+5 setae. Endopod with 14 setae. Exopod with 11 setae.
Maxilla ( Fig.7 E). First and second praecoxal endites with 3 setae and row of spinules on one side. First coxal endite with 2 long setae and row of spinules on one side. Second coxal endite with 2 setae and 1 thickened seta and with a proximal border spinulose on one side. Basal endite with 3 setae, one of them thickened. Endopod with 5 setae.
Maxilliped ( Fig.7 F). Coxa with 3 groups (from proximal to distal end of segment) of 2, 3 and 3 setae (distal group with small spinules). Basis with spinules on proximal edge and 3 medial setae. Endopod 6-segmented; first segment with 2 setae; second to sixth segments with 4, 4, 3, 3+1, and 4 setae, respectively.
Leg 1 ( Fig.8 A). Coxa with hairs on inner border. Basis with hairs on inner border and 1 inner distal seta on anterior surface. Endopod 1-segmented; outer margin swollen with 1 row of spinules. Exopod 2-segmented; first and second segments incompletely fused with 1 outer spine and 1 inner seta; third segment with 1 outer spine and 4 inner setae.
Leg 2 ( Fig.8 B). Coxa with hairs on inner border and 1 inner seta. Basis unarmed. Endopod 2-segmented; first seg-
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Gaetanus minutus (Sars) female. A Habidus dorsal; B Urosome lateral; C Rostrum lateral; D E Rostrum ventral; FGenital segment; G Urosome ventral; H Antennule. Scale bars: A-D=1 mm F G=0.25 mm H=0.5 mm.
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Gaetanus minutus (Sars) female. A Antenna; B Mandible; C Gnathobase of the mandible; D Maxillule; E Maxilla; F Maxilliped. Scale bars: A-C E F=0.25 mm D=0.1 mm.
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Gaetanus minutus (Sars) female. A Leg 1; B Leg 2; C Leg 3; D Leg 4. Scale bar: A-D=0.25 mm.
ment with 1 seta; second segment with 5 setae. Exopod 3-segmented; first and second segments with 1 outer spine and 1 inner seta, respectively; third segment with 3 spines and 1 terminal spine bearing 17 teeth on outer edge.
Leg 3 ( Fig.8 C). Coxa with hairs on inner border and 1 inner seta. Basis unarmed. Endopod 3-segmented; first and second segments with 1 seta, respectively; distal segment with 5 setae. Exopod 3-segmented; first and second segments with 1 outer spine and 1 inner seta; distal segment with 3 spines, 5 setae and 1 serrated spine bearing 16 teeth on outer edge.
Leg 4 ( Fig.8 D). Coxa with thin spines similar to setae. Basis unarmed. Endopod and exopod same as leg 3. Distal segment of exopod with serrated spine bearing 18 teeth on outer edge. Armature formula of swimming legs 1-4 as follows:
  • Leg 1 coxa 0-0 basis 0-1 exp 0-0; Ⅰ-1; Ⅰ,1,3 enp 0,2,3
  • enp 0-1; 0-1; 1,2,2
  • Leg 4 coxa 0-1 basis 0-0 exp Ⅰ-1; Ⅰ-1; Ⅲ,Ⅰ,4
  • enp 0-1; 0-1; 1,2,2
  • Leg 5 absent.
- Male:
Not found.
- Distribution.
East Sea (Korea), Sea of Okhotsk, Bering Sea, Izu (Japan), Gulf of Mexico, New Zealand, Kurile-Kamchatka and Mariana Trench.
- Remarks.
Gaetanus minutus is a morphologically highly variable species and is distributed worldwide (Markhaseva,1996). The species was reported first as Gaidius minutus by Sars (1907), but Park (1975) incorporated Gaidius into the genus Gaetanus based on the inconsistency of the cephalic process and similarity of other morphological features.
Female Gaetanus minutus is similar to G. brevirostris (Brodsky, 1950) in having a cephalosome without a spine and posterior corners of the last pedigerous somite with a short spine on each side. On the other hand, G. brevirostris has 3-segmented leg 1 exopod, which is fused incompletely in G. minutus .
The specimen (4.46 mm) examined in this study is larger than those of other previous records (Tanaka, 1957; Tanaka and Omori, 1970; Park, 1975). The Korean specimen is congruent with the Japanese one described by Tanaka (1957). However, the present specimen shows some minor differences from Tanaka’s specimen as follows: 1) the maxilliped does not have a small lamellous process on the distal margin of the basis; 2) the terminal spines of legs 2, 3, and 4 were recorded to have 19, 17, and 20 outer teeth (Tanaka, 1957), respectively, whereas there were 15, 16, and 18, respectively, in the present specimen. These differences variations were considered to be within the species.
The CO1 sequence of the Korean specimen showed 99.8% similarity to the previous sequence of the same species (Genbank accession no: AB379980).
Korean name: 1*참수리노벌레속(신칭), 2*참수리노벌레
Korean name: 1*두갈래이마뿔노벌레속(신칭), 2*두갈래이마뿔노벌레(신칭)
Korean name: 1*이마노벌레속(신칭), 2*꼬마이마노벌레(신칭)
Acknowledgements
The authors wish to thank Dr. Seok Hyun Youn (National Fisheries Research and Development Institute) for providing the samples. This study was supported by an Inha University grant.
References
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