Research Article |
Corresponding author: Jimin Lee ( leejm@kiost.ac ) Academic editor: Danielle Defaye
© 2023 Kyuhee Cho, Jong Guk Kim, Jimin Lee.
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:
Cho K, Kim JG, Lee J (2023) Two new species of Cerviniella Smirnov, 1946 (Copepoda, Harpacticoida, Aegisthidae) from the Yellow Sea, Korea. ZooKeys 1178: 165-189. https://doi.org/10.3897/zookeys.1178.105407
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Two new species, Cerviniella bisegmenta sp. nov. and C. permixta sp. nov., are described in detail with illustrations based on females from the Korean Yellow Sea. These species lacking the fourth leg endopod belong to the mirabilipes group, one of two species groups within the genus Cerviniella Smirnov, 1946. Both species can be distinguished from each other by the surface ornamentation of the cephalothorax, shape of the rostrum tip, antennule segments, armature formula of thoracic legs 1–4, and length ratio of the caudal rami. Cerviniella bisegmenta sp. nov. is characterized by a short caudal ramus and a two-segmented antennary exopod, which are unique within the genus. Cerviniella permixta sp. nov. differs from other congeners of the mirabilipes group by the seven-segmented antennule, the armature formulae of the exopod of the antenna and thoracic legs 1–4, and the modified apical inner element of the second endopodal segment of the second leg. The present study is the first to identify the genus Cerviniella in Korean waters, resulting in extension of its distribution area to East Asia.
Cerviniellinae, Crustacea, Korean fauna, meiofauna, Yellow Sea
The genus Cerviniella Smirnov, 1946 was established by
In the 20th and 21st centuries, eight and five additional species of Cerviniella were described, respectively; therefore, 13 species have been identified thus far (
During a biodiversity study of benthic harpacticoids in Korea, we found two new species of the genus Cerviniella in the sublittoral zone of the Yellow Sea. Here, we discuss the morphological characteristics of the newly found species and provide a key to species of the genus Cerviniella.
Sediments were collected from the Yellow Sea using a Smith-McIntyre grab (0.1 m2) aboard R/V Eardo and R/V Onnuri of the Korea Institute of Ocean Science & Technology (KIOST). The upper sediment surface (0–5 cm) was subsampled and treated with 7.5% magnesium chloride (MgCl2) to anesthetize the benthic organisms. After 30 min, the samples were preserved in a 10% formalin/seawater solution. The Ludox centrifugation method was used to separate benthic organisms from sediments (
The descriptive terminology was followed by
Order Harpacticoida Sars, 1903
Family Aegisthidae Giesbrecht, 1893
Subfamily Cerviniellinae Khodami, Mercado-Salas & Martínez Arbizu, 2020
Cerviniella mirabilipes Smirnov, 1946.
Cerviniella abyssalis Apostolov, 2011, C. arctica Kihara & Martínez Arbizu, 2012, C. bodini Coull, 1973, C. brodskayae Por, 1969, C. danae Kihara & Martínez Arbizu, 2012, C. hamata Coull, 1973, C. hitoshii Kihara & Martínez Arbizu, 2012, C. lagarderei Bodin, 1968, C. langi Bodin, 1968, C. longifurcata Apostolov, 2011, C. peruana Becker, 1974, and C. talpa (Por, 1964).
The Yellow Sea; 34°59'40.14"N, 125°00'2.82"E; 88 m depth.
Holotype. One ♀ preserved in a vial with 80% ethanol (MABIK CR00253873); collected from the type locality, 20 April 2019. Paratypes. One ♀ (MABIK CR00253868) dissected on 11 slides, three ♀♀ (MABIK CR00253869–00253871) each dissected on 10 slides, six ♀♀ (MABIK CR00253874) and eight ♀♀ (MInRB-Hr88-L001) preserved in a vial with 80% ethanol, collection data as in holotype; S.L. Kim leg.
Female (based on the holotype and paratypes). Body length from anterior margin of rostrum to posterior margin of caudal rami (paratype, MABIK CR00253868, in lateral view, telescoping of somites not considered) 797 μm (range: 694–797 μm, n = 11, holotype: 765 μm).
Habitus
(Fig.
Urosome
(Figs
Caudal rami
(Figs
Rostrum
(Fig.
Antennule
(Fig.
Antenna
(Fig.
Mandible
(Fig.
Paragnaths
(Fig.
Maxillule
(Fig.
Maxilla
(Fig.
Maxilliped
(Fig.
P1
(Fig.
P2
(Fig.
P3
(Fig.
P4
(Fig.
Armature formulae of P1–P4 as follows:
P5
(Fig.
Male. Unknown.
The morphological variation in Cerviniella bisegmenta sp. nov. appears in the armature formula of thoracopods. P2 enp-2 presumably has four inner setae in the normal condition, but the P2 enp-2 of some specimens (four of 18 specimens) has two or three inner setae.
Abnormal exopod and endopod of P2 were observed in one specimen (paratype, MABIK CR00253869) (Fig.
The specific name bisegmenta is derived from a combination of the Latin prefix bi-, meaning ‘having two parts’ and the Latin noun segmentum, meaning ‘cutting’ or ‘piece’, and refers to the two-segmented antennary exopod, which is an autapomorphy of this species. It is a noun in the nominative plural.
Based on the presence or absence of the P4 endopod,
The segmentation of the female antennule is useful for differentiating among species of Cerviniella. Cerviniella bisegmenta sp. nov. has an advanced five-segmented antennule, shared in C. danae and C. hitoshii, but the latter species is in the brodskayae group. The other 11 Cerviniella species have a six- or seven-segmented antennule (see discussion below).
Cerviniella bisegmenta sp. nov. can be easily distinguished differs in several characters from the same group, C. danae. First, the antenna of C. bisegmenta sp. nov. has a two-segmented exopod, compared with the four-segmented antennary exopod of C. danae. Second, the mandibular endopod of C. bisegmenta sp. nov. has two lateral setae, whereas the mandibular endopod of C. danae has three lateral setae. Third, the basis and endopod of the maxillule of C. bisegmenta sp. nov. have a total of 13 setae, compared with 14 setae in C. danae. Fourth, the syncoxa of the maxilliped of C. bisegmenta sp. nov. has nine setae and spines, compared with the seven elements of C. danae. Fifth, the P1 endopod of C. bisegmenta sp. nov. has four setae, compared with six setae in C. danae. Sixth, the P3 exopod of C. bisegmenta sp. nov. has three inner setae, compared with two inner setae in C. danae. Finally, the caudal ramus of C. bisegmenta sp. nov. is short with a 1.7-fold length relative to width, compared with a 3.5-fold length for C. danae. The first and seventh aforementioned characteristics provide conclusive evidence for the identification of C. bisegmenta sp. nov. In all species of Cerviniella, except C. bisegmenta sp. nov., the antennary exopod is four-segmented, and the length of the caudal rami is > 3-fold to width and longer than the length of the anal somite.
The Yellow Sea; 35°00'05.44"N, 125°59'44.49"E; 88.1 m depth.
Holotype. One ♀ preserved in a vial with 80% ethanol (MABIK CR00253875); collected from the type locality, March 02, 2022. Paratypes. One ♀ (MABIK CR00253872) dissected on 10 slides, two ♀♀ (MABIK CR00253876) preserved in a vial with 80% ethanol, collection data as in holotype; J.G. Kim leg.
Female (based on the holotype and paratypes). Body length from anterior margin of rostrum to posterior margin of caudal rami (paratype, MABIK CR00253872, in lateral view, telescoping of somites not considered) 857 μm (range: 857–886 μm, n = 4, holotype: 861 μm).
Habitus
(Fig.
Prosome
(Fig.
Urosome
(Figs
Caudal rami
(Figs
Rostrum
(Fig.
Antennule
(Fig.
Antenna
(Fig.
Mandible
(Fig.
Paragnaths
(Fig.
Maxillule
(Fig.
Maxilla
(Fig.
Maxilliped
(Fig.
P1
(Fig.
P2
(Fig.
P3
(Fig.
P4
(Fig.
Armature formulae of P1–P4 as follows:
P5
(Fig.
Male. Unknown.
The specific name permixta is derived from the Latin adjective permixtus, meaning ‘mixed’ or ‘confused’, and refers to the fact that several diagnostic characteristics of Cerviniella species are mixed in this species. It is in the nominative singular. Gender: feminine.
Cerviniella permixta sp. nov. lacks a P4 endopod and is placed in the mirabilipes group as C. bisegmenta sp. nov. described above. This new species can be distinguished from C. bisegmenta sp. nov. on the basis of several morphological differences. Cerviniella permixta sp. nov. is characterized by the presence of numerous minute pits on the cephalothorax surface, whereas C. bisegmenta sp. nov. is characterized by numerous minute dots or denticles. Cerviniella permixta sp. nov. has a blunt rostral tip, whereas C. bisegmenta sp. nov. has a concave tip. The antennule has seven segments in C. permixta sp. nov. and five segments in C. bisegmenta sp. nov. The P1 enp-1 lacks the inner seta and P3 enp-2 has two setae in C. permixta sp. nov., whereas the P1 enp-1 has an inner seta and P3 enp-2 has one seta in C. bisegmenta sp. nov. The caudal ramus of C. permixta sp. nov. is relatively long, with a 4-fold length relative to width, compared with a 1.7-fold length for C. bisegmenta sp. nov.
In the mirabilipes group, the species with a seven-segmented antennule are C. lagarderei, C. langi (but illustrated as six-segmented in the original description (
A classification key for the 14 Cerviniella species (excluding C. peruana) is presented, including the two new species described from the Yellow Sea.
1 | Antennule 5-segmented | 2 |
– | Antennule different | 4 |
2 | P4 endopod 2-segmented | C. hitoshii Kihara & Martínez Arbizu, 2012 |
– | P4 without endopod | 3 |
3 | P1 endopod with 4 setae; P3 exopod with 10 setae/spines; antennary exopod 2-segmented; caudal rami < 2× as long as wide | C. bisegmenta sp. nov. |
– | P1 endopod with 6 setae; P3 exopod with 9 setae/spines; antennary exopod 4-segmented; caudal ramus 3.5× as long as wide | C. danae Kihara & Martínez Arbizu, 2012 |
4 | P1 endopod 2-segmented | 5 |
– | P1 endopod 1-segmented | 6 |
5 | P2 exopod with 10 setae/spines; caudal ramus 6.2× as long as wide | C. bodini Coull, 1973 |
– | P2 exopod with 11 setae/spines; caudal ramus 4.3× as long as wide | C. abyssalis Apostolov, 2011 |
6 | P4 exopod 2-segmented | C. lagarderei Bodin, 1968 |
– | P4 exopod 1-segmented | 7 |
7 | P3 endopod 1-segmented | 8 |
– | P3 endopod 2-segmented | 9 |
8 | P3 endopod with 2 setae; P3 exopod with 8 setae/spines | C. longifurcata Apostolov, 2011 |
– | P3 endopod with 3 setae; P3 exopod with 11 setae/spines | C. brodskayae Por, 1969 |
– | P3 endopod with 4 setae; P3 exopod with 9 setae/spines | C. hamata Coull, 1973 |
9 | P2 enp-1 without inner seta; P2 exopod with 10 setae/spines | C. talpa (Por, 1964) |
– | P2 enp-1 with 1 inner seta; P2 exopod with 11 setae/spines | 10 |
10 | P1 exopod with 10 setae/spines; P3 exopod with 11 setae/spines | C. langi Bodin, 1968 |
– | P1 exopod with 9 setae/spines; P3 exopod with 10 setae/spines | 11 |
11 | P4 exopod with 2 setae/spines; P5 exopod with 2 setae; P1 endopod with 3 setae | C. permixta sp. nov. |
– | P4 exopod with 4 setae/spines; P5 exopod with 3 setae; P1 endopod with 4 setae | C. arctica Kihara & Martínez Arbizu, 2012 |
– | P4 exopod with 5 setae/spines; P5 exopod with 3 setae; P1 endopod with 3 setae | C. mirabilipes Smirnov, 1946 |
Recently,
The female antennule of Cerviniella is typically five- or seven-segmented. The five-segmented antennule has an aesthetasc on the second segment, whereas the primitive antennule with seven segments has an aesthetasc on the third segment. The aesthetasc on the second segment is derived from the fusion of the second and third segments. Recently,
Intraspecific variability is common in the thoracic legs of harpacticoids, as observed in multiple benthic species, such as Argestes angolaensis George, 2008, Mesocletodes elmari Menzel, 2011 (Argestidae), Normanella spinosa Kim, Cho & Lee, 2014 (Normanellidae), and Quinquelaophonte enormis Kim, Nam & Lee, 2020 (Laophontidae) (
To establish the exact diagnosis of Cerviniella, it will be necessary to re-examine the ambiguous characteristics, including interspecific variability. There are 13 known species of Cerviniella, including four Arctic, six Atlantic, one Mediterranean, one Indian, and one from the Pacific Ocean. The discovery of two new species in the Korean Yellow Sea suggests that Cerviniella has a wider distribution than previously known. With the discovery of these new species, the family Aegisthidae and genus Cerviniella are reported in the Korean fauna here for the first time.
We are grateful to the reviewers for their critical comments and help in improving the manuscript.
The authors have declared that no competing interests exist.
No ethical statement was reported.
This research was supported by the management of Marine Fishery Bio-resources Center (2023) funded by the National Marine Biodiversity Institute of Korea (MABIK) and the research program of the Korea Institute of Ocean Science &Technology (Contract No. PEA0111). This research was also conducted with the support of the Center for Women In Science, Engineering and Technology (WISET) and WISET Regional Agency of PKNU Grant funded by the Ministry of Science and ICT (MSIT) under the Program for Returners into R&D (Returners into R&D program of Dongnam regional agency No. 2020-008) to K Cho.
Kyuhee Cho conceived and designed the experiments, identified the specimens, wrote the manuscript, prepared figures, and approved the final draft. Jong Guk Kim collected the samples, helped in the identification, authored or reviewed drafts of the paper, and approved the final draft. Jimin Lee conceived and designed the experiments, authored or reviewed drafts of the paper, and approved the final draft.
Kyuhee Cho https://orcid.org/0000-0002-5006-5713
Jong Guk Kim https://orcid.org/0000-0001-5299-9838
Jimin Lee https://orcid.org/0000-0001-9004-8275
All of the data that support the findings of this study are available in the main text.