Research Article |
Corresponding author: Cheon Young Chang ( cychang@daegu.ac.kr ) Academic editor: Danielle Defaye
© 2015 Jimin lee, Cheon Young Chang.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Lee J, Chang CY (2015) A new marine cyclopoid copepod of the genus Neocyclops (Cyclopidae, Halicyclopinae) from Korea. ZooKeys 520: 131-146. https://doi.org/10.3897/zookeys.520.6006
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A new cyclopoid species of the genus Neocyclops Gurney, 1927 is described. Type specimens were collected from a beach on south-western coast of the Korean Peninsula by rinsing intertidal coarse sandy sediments. Neocyclops hoonsooi sp. n. is most characteristic in showing the conspicuous chitinized transverse ridges originating from the medial margins of the coxae of all swimming legs. The new species is most similar to N. vicinus, described from the Brazilian coast, and N. petkovskii, from Australia. All three species share a large body size (more than 750 µm long), the presence of an exopodal seta on the antenna, two setae on the mandibular palp, the same seta/spine armature on the third endopodal segment of leg 3 (3 setae + 3 spines), and the fairly long inner distal spine on the third endopodal segment of the female leg 4. However, N. hoonsooi sp. n. differs from both species by the much shorter caudal rami (less than 1.7 times as long as wide) and the shorter dorsal caudal seta VII. Furthermore, N. hoonsooi is clearly distinguished from N. vicinus by the 10-segmented antennule (vs 12 segments in N. vicinus), and from N. petkovskii by the elongate inner distal spine on leg 5 exopod and the 3-segmented leg 5 in male (vs 4-segmented in N. petkovskii). A tabular comparison of characters separating N. hoonsooi from its closest allies and a key to Neocyclops species from the Indo-Pacific Ocean are provided. This is the first record of the genus Neocyclops from the northern Pacific.
Beach, description, interstitial, meiofauna, northwest Pacific, taxonomy
Members of the genus Neocyclops Gurney, 1927 (Cyclopidae, Halicyclopinae) typically inhabit marine epibenthic or interstitial environments. The genus is widely distributed in coastal, surface and subterranean (anchialine) habitats of the Northeast and Tropical Atlantic, the Mediterranean, the Black and Red Seas and the Indo-Pacific (West Australia, Papua New Guinea), with an endemism index of about 95% (
Although cyclopoid copepods constitute an important component of the marine epibenthic and interstitial fauna, our knowledge of their taxonomy and diversity is relatively very poor in comparison with freshwater cyclopoids, especially in the northwest Pacific region (
Collections were made at Holtong beach, located along the south-western coast of the Korean Peninsula, in shallow littoral (about 0.5–1 m deep) by scooping the surface layer of a coarse sand bottom with a long-handled dipper. Sediment samples were gathered into a bucket, subjected to freshwater shock and filtered through a conical plankton net or plankton hand-nets (mesh size 64 µm). Samples were immediately fixed in the field by adding a few drops of 35% formaldehyde. Copepods were sorted in the laboratory, using a micropipette under a zoom-stereomicroscope (Zeiss SV-11, Germany), and transferred to 80% ethanol or to 4% buffered formaldehyde for long-term preservation.
Methods for dissection, double-coverglass preparation using H-S slides (see
Type specimens are deposited in The Natural History Museum, London (NHMUK) and the specimen room of the Department of Biological Science, Daegu University (DB), Korea.
General terminology for the description of the new species follows
Holtong beach (35°03.68'N, 126°19.87'E), South Korea, Jeollanam-do Province, Muan-gun County, Hyeongyeon-myeon, Oryu-ri; western coast of the Dadohae Oceanic National Park, South Korea.
Holotype ♀ (DB20046), allotype ♂ (DB20047), both dissected on slides. Paratypes: 1♀ (NHMUK reg. no. 2015. 3056), 1♂ (NHMUK reg. no. 2015. 3057), both undissected, ethanol-preserved; 2♀♀ (DB20048, 20049), 1♂ (DB20050), dissected on slides; 2♀♀ (DB20051), 2♂♂ (DB20052), in ethanol. All specimens were collected from the type locality by J. Lee on 21 August 2008.
Female habitus large, about 830 µm long. Genital double-somite with lateral expansions in anterior quarter. Caudal rami about 1.7 times as long as wide, with 7 caudal setae, including vestigial ventrolateral seta I; inner caudal seta VI well developed, about 1.7 times longer than outer caudal seta III; dorsal seta VII slightly shorter than caudal ramus. Antennule 10-segmented. Antenna with exopodal seta. Exp-3 of legs 1–4 with setal formula 5,5,5,5 and spine formula 3,4,4,3; enp-3 of leg 3 bearing 3 spines and 3 setae; inner distal spine on enp-3 of leg 4 distinctly longer than enp-3 and outer distal spine. Leg 5 exopod subpyriform, about twice as long as wide; inner distal spine 1.2 times longer than outer spine, about 1.4 times as long as lateral spine, about 0.9 times as long as exopod. Male caudal rami 1.36 times longer than wide, with 7 caudal setae. Male leg 5 3-segmented, comprising coxa, basis and exopod.
Female (Holotype). Body (Fig.
Prosome oval, about 1.2 times longer than urosome, a little protruding anteriorly. Rostrum reflexed downwards, not discernible in dorsal view, with blunt apex in ventral aspect. Nauplius eye not discernible. Cephalothorax not strongly protruding anteriorly, slightly longer than 4 free thoracic somites combined; first pedigerous somite completely incorporated into cephalosome. Prosomites not showing pronounced lateral expansions, with narrow and nearly smooth hyaline fringe along posterior; ornamented with one pair of minute sensilla medially on dorsal surface of second to fourth pedigerous somites, and a few integumental pores near posterior margin of each prosomite.
Urosomites (Figs
Caudal rami (Fig.
Antennule (Fig.
Antenna (Fig.
Labrum (Fig.
Mandible (Fig.
Maxillule (Fig.
Maxilla (Fig.
Maxilliped (Fig.
Legs 1–4 (Fig.
coxa | basis | exopod | endopod | |
Leg 1 | 0-1 | 1-1 | I-1, I-1, III,2,3 | 0-1, 0-2, I,I+1,3 |
Leg 2 | 0-1 | 1-0 | I-1, I-1, III,I+1,4 | 0-1, 0-2, II,I,3 |
Leg 3 | 0-1 | 1-0 | I-1, I-1, III,I+1,3 | 0-1, 0-2, II,I,3 |
Leg 4 | 0-1 | 1-0 | I-1, I-1, II,I+1,4 | 0-1, 0-2, I,II,2 |
Leg 5 (Fig.
Male (allotype): Body (Fig.
Antennule (Fig.
Leg 5 (Fig.
The proposed specific name is dedicated to the late Professor Hoon Soo Kim in honor of his contribution to the development of invertebrate taxonomy in Korea.
This species was found at Holtong beach along the western coast of the Dadohae Oceanic National Park, which is located along south-western coast of the Korean Peninsula. The beach is exposed and fringed with rocks on both sides. The intertidal, coarse to medium sandy sediments contained a little mud. Salinity: 27–32 ‰. The new species co-occurred with other interstitial ones: Cerconeotes japonicus (Itô, 1968), Cyclopina spp. (Copepoda), Xenotrichula sp. (Gastrotricha), and Echinoderes sp. (Kinorhyncha).
The genus Neocyclops currently accommodates 24 nominal species (
Neocyclops species typically possess 12-segmented antennules in the female but a few members are known to show fewer segments: 11-segmented in N. improvisus and N. geltrudeae Pesce & Galassi, 1993, 10-segmented in N. petkovskii De Laurentiis, Pesce & Halse, 1997, and only 8-segmented in N. salinarum (Gurney, 1927). Neocyclops hoonsooi sp. n. shares the 10-segmented condition with N. petkovskii, showing traces of subdivision in compound segments 3 and 4. Neocyclops hoonsooi sp. n. also shares with N. petkovskii an exopodal seta on the antenna, which is absent in N. parvus, N. medius Herbst, 1955, N. affinis (Pleşa, 1961), N. improvisus, N. australiensis Karanovic, 2008, and N. dussarti Karanovic, 2008 [= nomen novum for N. affinis Dussart, 1974, a junior homonym of N. affinis (Pleşa, 1961), for details, see
The new species is most characteristic in having large scar-like integumental ridges originating from the medial margins of the coxae in all swimming legs. The transverse chitinized reinforcements are very conspicuous, and consistently occurred in all specimens examined. Similar structures have been illustrated for three species that were recently described from Australia by
The new species is also unusual in bearing a small setule on the anteroventral surface of the caudal ramus in both sexes. This setule is here identified as the anterolateral accessory seta I. As far as we can ascertain, it was recorded only once before in the genus Neocyclops, i.e. in the description of the female caudal ramus of N. pilbarensis Karanovic, 2008, where it was interpreted as a “sensillum at anterior part ventrally”. While the caudal seta I is rarely expressed and usually lacking in members of the Cyclopoida, it can sometimes be quite conspicuous in some marine, and especially ancestral, genera, such as Heterocyclopina Pleşa, 1968.
Another unusual characteristic of N. hoonsooi sp. n. is the very short caudal ramus, being slightly less than 1.7 times as long as wide. Caudal rami of Neocyclops species are generally more than twice as long as wide, being about 2.0–2.5 times in N. affinis, N. parvus, N. australiensis and N. ferrarii Rocha, 1995, 2.7–3.0 times in N. magnus and N. vicinus (Herbst, 1955), and even reaching to 3.5–4.0 times in N. remanei (Herbst, 1952). However, in a few species the caudal ramus is much shorter, and less than twice as long as wide, being about 1.8–2.0 times in N. medius and N. dussarti, and slightly less than 1.7 times in N. hoonsooi sp. n. Two genuinely interstitial species from beaches in southern Australia, have extremely short caudal rami (1.5 times in N. tropicus Karanovic, 2008, and 1.3 times in N. trajani), however, these species differ clearly from N. hoonsooi sp. n. by the much smaller body size (546–565 µm long), the 12-segmented antennule, the presence of 3 setae on the mandibular palp, and the very long dorsal caudal seta (1.5–2.4 times longer than caudal rami). The caudal seta VII in N. hoonsooi sp. n. is slightly shorter or nearly as long as the caudal ramus. This condition is shared with N. ferrarii, N. improvisus, N. magnus, N. mediterraneus (Kiefer, 1960), N. remanei and N. vicinus, while most other species have a much longer dorsal seta (more than twice longer than the caudal ramus): N. geltrudeae, N. pilbarensis, N. sharkbayensis and N. tropicus. Neocyclops papuensis Fiers, 1986 clearly differs from all its congeners, including the present new species, by bearing an extremely short dorsal seta (0.4 times as long as the caudal ramus). Seta VI (innermost caudal seta) of N. hoonsooi sp. n. is much longer than seta III (outermost caudal seta), and thus differs from those species that display the reverse condition (seta III longer than seta VI) such as N. affinis, N. vicinus, N. improvisus, N. monchenkoi Karanovic, 2008 and N. australiensis.
Neocyclops hoonsooi sp. n. displays the typical seta/spine armature pattern on legs 1–4 found in the majority of species in the genus Neocyclops. The setal formula of the third exopodal segments of the new species is 5,5,5,5, which differs from the 5,5,5,4 pattern in N. herbsti Petkovski, 1986 and the 4,5,5,5 condition in N. wellsi Petkovski, 1986. The spine formula of the third exopodal segments of N. hoonsooi sp. n. is 3,4,4,3, and differs only from the 2,4,4,3 pattern of N. sharkbayensis. The setal formula on the distal endopodal segments of the new species is 4,3,3,2, and differs from the 4,3,4,2 pattern displayed by N. affinis, N. dussarti and N. improvisus (
Taking into consideration the characters mentioned above, N. hoonsooi sp. n. appears to be most similar to N. vicinus, described from the Brazilian coast, and N. petkovskii, from Australia. All three species share a large body size (more than 750 µm long), the presence of an exopodal seta on the antenna, two setae on the mandibular palp, the same seta/spine armature on the third endopodal segment of leg 3 (3 setae + 3 spines), and the fairly long inner distal spine on the third endopodal segment of the female leg 4. However, N. hoonsooi sp. n. clearly differs from N. vicinus by the following characters: (1) 10-segmented antennule (vs 12 segments in N. vicinus); (2) shorter caudal rami (less than 1.7 times as long as wide, while about three times longer in N. vicinus); and (3) much shorter dorsal caudal seta VII (about 2/3 times shorter than inner caudal seta VI, while 1.4 times longer in N. vicinus), and much longer inner caudal seta VI (more than 1.5 times longer than outer caudal seta III, while slightly shorter than outer one in N. vicinus). Furthermore, N. hoonsooi sp. n. also clearly differs from N. petkovskii by the much shorter caudal rami (vs 2.4 times as long as wide in N. petkovskii), the shorter inner distal spine on the female leg 5 (vs slightly shorter than the outer distal and lateral spines, and about half the length of the exopod in N. petkovskii), and the 3-segmented leg 5 in male (vs 4-segmented in N. petkovskii). Table
affinis | australiensis | improvisus | monchenkoi | petkovskii | vicinus | hoonsooi sp. n. | |
---|---|---|---|---|---|---|---|
♀, body length (µm) | 390–439 | 731 | 396–488 | 720–1,110 | 765 | 750 | 830 |
♀, antennule, no. of segments | 12 | 12 | 11 | 12 | 10 | 12 | 10 |
Antenna, exp seta | absent | absent | absent | present | present | present | present |
Mandible, no. of setae on palp | 1 | 3 | 1 | 2 | 2 | 2 | 2 |
Caudal rami, L/W ratio,♀ | 2.2–2.6 | 2.5 | 1.8–2.0 | 2.7–3.5 | 2.4 | ~ 3 | 1.6–1.7 |
Length ratio, caudal setae VI/III | ~ 1 | 0.7 | 0.9 | ~ 0.9 | ~ 1 | 0.9–1.0 | 1.5–1.6 |
Length ratio, caudal setae VII/VI | ~ 3 | ~ 3.5 | ~ 2.2 | ~ 3 | ≥ 1 | 1.4 | ~ 2/3 |
Length ratio, caudal seta V/ramus | ~ 1.6 | ~ 1.4 | ~ 1 | ~ 1.3 | ~ 0.7 | ~ 0.9 | ~ 0.9 |
Leg 3 enp-3 armature formula | 4,III | 3,III | 4,III | 3,II | 3,III | 3,III | 3,III |
Leg 4, length ratio of inner spine/enp-3 | 1.5–1.8 | ~ 1.3 | 1.6 | 1.6−1.7 | 1.2 | ~ 1.4 | ~ 1.2 |
♀ leg 5 exp, length ratio of inner/outer spines | 1.2–1.5 | ~ 1.1 | 1.2 | ~ 1.2 | 0.9 | 1.1 | 1.2 |
♀ leg 5 exp, length ratio of inner/lateral spines | 1.3 | 1.5 | 1.3 | ~ 1.3 | 0.9 | 1.3 | 1.4 |
♀ leg 5, length ratio of inner distal spine/exp | 0.9–1 | ~ 1.2 | 0.7 | 0.7–0.8 | 0.5 | 0.86 | 0.86 |
♂ leg 5, no. of segments | 3 | 3/4 † | - | 3 | 4 | 3 | 3 |
Distribution | Ghana1; West Indies2 | Australia3 | Cuba4 | Black Sea5 | Australia6 | Brazil7 | Korea8 |
Pacific Ocean: from Papua New Guinea, N. papuensis Fiers, 1986 by
Indian Ocean: from Australia, N. australiensis Karanovic, 2008, N. sharkbayensis Karanovic, 2008, N. trajani Karanovic, 2008 and N. tropicus Karanovic, 2008 by
1 | Female antennule 8-segmented | N. salinarum |
– | Female antennule 10-segmented | 2 |
– | Female antennule 12-segmented | 3 |
2 | Caudal rami not more than 1.7 times as long as wide in female; male leg 5 3-segmented | N. hoonsooi sp. n. |
– | Caudal rami about 2.4 times as long as wide in female; male leg 5 4-segmented | N. petkovskii |
3 | Caudal rami less than 1.5 times as long as wide in female | 4 |
– | Caudal rami about 2–2.7 times as long as wide in female | 5 |
– | Caudal rami 3–3.5 times as long as wide in female | N. papuensis |
4 | Dorsal caudal seta VII less than twice as long as ramus | N. trajani |
– | Dorsal caudal seta VII more than twice as long as ramus | N. tropicus |
5 | Exopodal seta on antenna lacking | 6 |
– | Exopodal seta on antenna present | 8 |
6 | Inner caudal seta VI longer than outer caudal seta III | N. parvus |
– | Inner caudal seta VI shorter than outer caudal seta III | 7 |
7 | Enp-2 of legs 1–3 with single inner seta; exp-3 of leg 1 with 2 spines | N. sharkbayensis |
– | Enp-2 of legs 1–3 with 2 inner setae; exp-3 of leg 1 with 3 spines | N. australiensis |
8 | Setal formula of exp-3 of legs 1–4 5,5,5,5 | N. magnus |
– | Setal formula of exp-3 of legs 1–4 5,5,5,4 | N. herbsti |
– | Setal formula of exp-3 of legs 1–4 4,5,5,5 | N. wellsi |
We are much obliged to Professor Rony J. Huys (The Natural History Museum, London) for his critical review, and also appreciate an anonymous reviewer for the critical comments that greatly improved the manuscript. We are deeply grateful to Dr. Janet W. Reid (Virginia Museum of Natural History, USA) and Dr. Chad Walter for providing many references. This work was supported in part by the research grant of Daegu University, Korea in 2011.