Research Article 
Corresponding author: Wonchoel Lee ( wlee@hanyang.ac.kr ) Academic editor: Kai Horst George
© 2017 Jinwook Back, Wonchoel 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:
Back J, Lee W (2017) Two new species of the genus Emertonia Wilson, 1932 from Korean waters (Copepoda, Harpacticoida, Paramesochridae). ZooKeys 718: 3564. https://doi.org/10.3897/zookeys.718.19959

Two new species of the genus Emertonia were found from the west coast of Korea. The first new species, E. koreana sp. n., is closely related to E. acutifurcata. However, the new species is clearly distinguished by the presence of two modified pinnate setae on the P5 baseoendopodal lobe. All body somites of the new species except for the last two urosomites have strongly developed hyaline frills forming quadrilateral lappets. The second new species, E. simplex sp. n., superficially resembles E. mielkei in the structure of antennary exopod (with five setae), and the shape of P5. However, this new species differs from its congener mainly by having a caudal ramus 3.5 times as long as width, and P1 enp2 with two clawlike setae. In addition, a key to the worldwide species of Emertonia is provided.
Crustacea, Jeju Island, Kliopsyllus, Taxonomy, Yellow Sea
The family Paramesochridae consists of 13 genera and more than 150 species distributed worldwide. Within the family, the genus Emertonia Wilson, 1932 is seen to be the most speciesrich genus. Despite the rich diversity, there are still many unidentified species to be regarded as new species within the genus (
In Korea, taxonomic studies on coastal benthic copepods are underway.
The sediment samples for Emertonia koreana sp. n. were collected from the Chulripo Beach in the west coast of the Korean peninsula. The sediment samples for E. simplex sp. n. were collected from a subtidal zone of Jeju Island. Samples were fixed with 5% buffered formalin and dissected specimens were mounted on several slides separately using lactophenol as mounting medium. Slides were sealed with transparent nail varnish. Observations of the specimens were carried out using an LEICA DM 6000 equipped with a drawing tube. Specimens were deposited in the Marine Biodiversity Institute of Korea (MABIK).
To prepare specimens for scanning electron microscope analysis (SU3500; Hitachi, in National Marine Biodiversity Institute of Korea), specimens were transferred to 100 % ethanol, dehydrated by tBuOH freeze dryer (VFD21S; Vacuum Device), mounted on stubs using doublesided tape, coated with goldpalladium, and then photographed.
The descriptive terminology was adopted from
A1 antennule;
A2 antenna;
ae aesthetasc;
exp exopod;
enp endopod;
exp (enp)1 (2, 3) to denote the proximal (middle, distal) segment;
P1–P6 first to sixth thoracopod;
benp baseoendopod.
The Chulripo Beach, intertidal zone in the west coast of Korea, Yellow Sea (36°48'11.46"N, 126°08'58"E) by sand rinsing collected by J. Back on 14 May 2010 (
Holotype 1♀ dissected on 4 slides (MABIK CR00241565). Paratypes: 1♂ on 3 slides (MABIK CR00241566), and 5 ♀♀ (MABIK CR00241570 – 00241574), 3 ♂♂ (MABIK CR00241567 – CR00241569) in 70 % ethanol. 1♀ and 1♂ dried, mounted on stub, and coated with goldpalladium for SEM.
Female P5 deeply divided into two parts in the center of both P5 baseoendopods. Two setae of baseoendopod swollen near the base. Innermost seta of P5 exopods somewhat swollen at base, similar to setae of baseoendopod. Urosomites armed with rectangular frills, except for the last two segments.
Body. Length 330 µm (n = 6, mean = 325 µm); largest width measured at cephalic shield; 55 µm; cylindrical, slightly depressed dorsoventrally; whole body very hyaline; sensilla and pores on dorsal surface as figured (Fig.
Prosome (Fig.
Urosome (Fig.
Caudal ramus (Figs
Rostrum (Fig.
Antennule (Fig.
Antenna (Fig.
Mandible (Fig.
Maxillule (Fig.
Maxilla (Fig.
Maxilliped (Fig.
P1 (Fig.
P2, P3 (Fig.
P4 (Fig.
Armature formula as follows:
Exopod  Endopod  
P1  0.121  0.011 
P2  0.0.112  010 
P3  0.0.112  010 
P4  0.0.011  010 
P5 (Figs
Body (Fig.
Antennule (Fig.
legs P1–P4 shape and setae formulae as in female (Fig.
P5 (Figs
P6 (Figs
The species name refers the type locality of new species, Republic of Korea.
The new species Emertonia koreana sp. n. is closely related with E. acutifurcata (Mielke, 1985). They share similar shape of caudal ramus. E. koreana sp. n. and E. acutifurcata only have subtriangular caudal ramus. Within the genus Paramesochra, similar morphology of caudal ramus is observed in P. acutata acutata Klie, 1935, P. acutata hawaiiensis Kunz, 1981, and P. taeana Back & Lee, 2010. They also have same setal formula of P1–P5. E. koreana sp. n. can be easily distinguished from those species based on the following unique characteristics: 1) female P5 is deeply divided into two parts in the center of both P5 baseoendopods. 2) Two setae at the end of baseoendopod are swollen near the base. In addition, the base of the innermost seta of P5 exopods is swollen, similar to setae of baseoendopod. 3) There are rectangular frills, except for the last two segments of urosomite. This structure is similar to that of P. taeana, but has not been reported in the genus Emertonia yet.
A subtidal zone near the Seogwipo Port in Jeju Island, Korea (33°13'33"N, 126°34'39"E), and sampled by using a grab (surface area: 0.1 m^{2}) on a fishing boat (
Holotype 1♀ dissected on 7 slides (MABIK CR00241575), and paratypes: 1♂ on 5 slides (MABIK CR00241576). Additional paratypes represented by 3 ♀♀ (MABIK CR00241577 ~ CR00241579) and 2 ♂♂ (MABIK CR00241580, CR00241581) in 70 % ethanol. 2♀♀ dried, mounted on stub, and coated with goldpalladium for SEM. All samples were collected from the type locality by J. Back on 4 June 2010.
Emertonia simplex sp. n. with four setae at P5 exopod in male, and one short Inner seta at P5 baseoendopod in female. Caudal rami rectangular, approximately 3.8 times as long as its width. Body armed with long dorsal sensilla.
Body cylindrical, slightly depressed dorsoventrally (Figs
Prosome (Fig.
Urosomites (Fig.
Caudal rami (Figs
Rostrum (Fig.
Antennule (Fig.
Antenna (Fig.
Mandible (Fig.
Maxillule (Fig.
Maxilla (Fig.
Maxilliped (Figs
P1 (Fig.
P2, P3 (Figs
P4 (Fig.
Armature formula as follows:
Exopod  Endopod  

P1  0.121  0.011 
P2  0.0.112  010 
P3  0.0.112  010 
P4  0.0.011  010 
P5 (Figs
Smaller than female, body length 345 µm (n = 3, mean = 344 µm) (Fig.
Antennule (Fig.
P5 (Fig.
P6 (Fig.
The species name refers to the simple somites without hyaline frills forming quadrilateral lappets.
The second new species, Emertonia simplex sp. n., shares the general characteristics of other species like E. holsatica holsatica (Klie, 1929) and E. major (Nicholls, 1939), including segmentation and setal formula of swimming legs, rectangular caudal rami, and a welldeveloped P5 baseoendopod and separated exopod. However, E. simplex sp. n. has a combination of all the following characteristics: 1) exopod of antenna has five setae. This characteristic is found in eleven species of Emertonia, for instance E. regulexstans (Mielke, 1984b), and E. diva (VeitKöhler, 2005), and 2) Two clawlike setae are present on the second segment of P1, which can be found in E. brevicaudata (Kornev and Chertoprud, 2008), E. californica (Kunz, 1981), E. insularis (Kunz, 1981), E. holsatica s. str., E. longifurcata (Scheibel, 1975), and E. unguiseta (Mielke, 1984). Of these, E. unguiseta is the species closest to E. simplex sp. n. since they share all of the characteristics mentioned above. However, differences between E. simplex sp. n. and E. unguiseta are as follows: 1) E. simplex sp. n. has four setae at P5 exopod in male, whereas E. unguiseta bears only three setae, 2) the new species has a shorter inner seta at P5 baseoendopod in female, whereas E. unguiseta bears two subequal setae, 3) the length of caudal rami is approximately 3.8 times as long as its width, whereas that of E. unguiseta is 3.2 times of the width. In addition, the new species has long dorsal sensilla. The major morphological characteristics of the genus Emertonia, including the two new species were summarized in Table
Species list and morphological comparison of the species in genus Emertonia Wilson, 1932 based on female.
Species  A1  A2  P1  P2  P3  P4  P5  Caudal rami  

number of seg.  exp setae  exp1  exp2  enp2  exp2  exp3  exp2  exp3  enp1  exp2  exp3  enp1  enp2  exp  benp  shape  
setae  setae  width:lenth  
gracilisgroup  
E. gracilis Wilson, 1932  8  3  023  ·  011  0  011  0  011  010  0  011  010  3  2  square  
1:2  
E. pseudogracilis Krishnaswamy, 1957  7  2  122  ·  011  0  012  0  012  010  0  011  010  3  1  square  
1:2.5  
laurenticagroup  
E. laurentica (Nicholls, 1939)  7  ?  0  121  011  221  ·  221  ·  010  112  ·  010  3  2  square  
1:2  
andeepgroup  
E. andeep (VeitKöhler, 2004)  8  5  0  121  011  0  112  0  112  110  0  011  1  011  3  2  square 
1:4  
E. minor (Vasconcelos, VeitKöhler, Drewes & Parreira dos Santos, 2009)  7  4  0  121  011  0  112  0  112  010  0  011  0  010  ?  ?  square 
1:5  
coelebsgroup  
E. coelebs (Monard, 1935)  7  4  0  121  011  0  112  0  112  010  1  011  110  ·  3  ?^{1}  square 
1:5  
E. psammophila (Noodt, 1964)  8  3  0  121  011  0  112  0  112  010  1  011  010  ·  3  2  square 
1:2.5  
E. furcavaricata Kunz, 1974  8  ?  0  121  011  1  112  1  112  010  1  011  010  ·  3  2  square 
1:2.5  
E. atlantica (Kunz, 1983)  7  3  0  121  011  0  112  0  112  010  1  011  110  ·  3  1  square 
1:3  
holsaticagroup  
E. holsatica holsatica (Klie, 1929)  7  4(5)^{2}  0  121  011  0  112  0  112  010  0  011  010  ·  3  2  square 
1:2  
E. holsatica varians (Kunz, 1951)  7  5  0  121  011  0  112  0  112  010  0  011  110  ·  3  2  square 
1:3.5  
E. holsatica longicaudata (Galhano, 1970)  7  2(3)^{3}  0  121  011  0  112  0  112  010  0  011  010  ·  3  2  square 
1:3.5  
E. constricta constricta (Nicholls, 1935)  7  2(1)^{4}  0  121  011  0  012  0  012  010  0  012 (011)^{4}  010  ·  3  ?  square 
1:3  
E. constricta orotavae (Noodt, 1958)  7  2(3)^{5}  0  121  011  0  012  0  012  010  0  011  010  ·  3  2  square 
1:2  
E. constricta pacifica (Mielke, 1984a)  8  4  0  121  011  0  012  0  012  010  0  011  010  ·  3  2  square 
1:3  
E. constricta egyptica (Mittwally & Montagna, 2001)  8  4  0  121  011  0  012  0  012  010  0  011  010  ·  3  2  square 
1:4  
E. major (Nicholls, 1939)  9  3  0  121  011  0  112  0  012  010  0  011  010  ·  3  2  square 
1:3  
E. pygmaea (Nicholls, 1939)  7  3  0  121  011  0  112  0  112  010  0  011  010  ·  5  2  square 
1:2  
E. longisetosa (Krishnaswamy, 1951)  7  2  0  121  011  0  112  0  112  010  0  011  010  ·  3  2  square 
1:3  
E. arenicola (Krishnaswamy, 1957)  7  2  0  121  011  0  112  0  112  010  0  011  010  ·  3  2  square 
1:3  
E. capensis Krishnaswamy, 1957  7  1  0  121  011  0  012  0  012  010  0  011  010  ·  3  0  square 
1:2  
E. minuta Krishnaswamy, 1957  7  3  0  122  011  0  012  0  012  010  0  011  010  ·  3  0  square 
1:2  
E. enalia (Krishnaswamy, 1957)  8  1  0  022  011  0  112  0  112  010  0  011  010  ·  3  2  square 
1:4(?)^{6}  
E. wilsoni (Krishnaswamy, 1957)  7  3  0  121  011  0  112  0  112  010  0  011  010  ·  3  2  square 
1:3  
E. pontica (Serban, 1959)  9  3  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ·  3  2  square 
1:3.5  
E. perharidiensis (Wells, 1963)  7  4  0  121  011  0  112  0  012  010  0  011  110  ·  3  2  square 
1:5  
E. psammobionta (Noodt, 1964)  7  3  0  121  011  0  112  0  112  010  0  011  010  ·  3(2)  ?  square 
1:2  
E. idiotes (Wells, 1967)  6  3  0  121  011  0  112  0  112  010  0  111  010  ·  3  2  square 
1:2.5  
E. paraholsatica (Mielke, 1975)  7  4  0  121  011  0  112  0  112  010  0  011  010  ·  3  2  square 
1:3  
E. longifurcata (Scheibel, 1975)  7  4  0  121  011  0  112  0  112  010  0  011  010  ·  3  2  square 
1:2.5  
E. spiniger spiniger (Wells, Kunz & Rao, 1975)  7  5  0  022  020  0  112  0  112  010  0  011  110  ·  3  2  square 
1:6.5  
E. spiniger ornata (Kunz, 1981)  7  5  0  022  020  0  112  0  112  010  0  011  110  ·  3  2  square 
1:9  
E. masryi (Bodin, 1979)^{7}  8  2  0  121  011  0  012  0  012  010  0  011  010  ·  3  3  square 
1:2  
E. californica (Kunz, 1981)  7  3  0  121  011  0  112  0  112  010  0  020  010  ·  3  2  square 
1:3  
E. debilis (Kunz, 1981)  8  3  0  121  011  0  112  0  112  010  0  011  010  ·  3  2  square 
1:2  
E. insularis (Kunz, 1981)  8  4  0  121  011  0  112  0  112  010  0  011  010  ·  3  2  square 
1:3  
E. miguelensis (Kunz,1983)  ?  3  0  121  011  0  112  0  112  010  0  011  010  ·  ?  ?  square 
1:3.5  
E. panamensis (Mielke, 1984a)  8  2  0  121  011  0  112  0  112  010  0  111  010  ·  3  1  square 
1:2  
E. regulexstans (Mielke, 1984b)  8  5  0  121  011  0  112  0  112  010  0  011  010  ·  3  2  square 
1:2.3  
E. similis (Mielke, 1984b)  8  5  0  121  011  0  112  0  112  010  0  011  010  ·  3  2  square 
1:3  
E. unguiseta (Mielke, 1984b)  8  5  0  121  011  0  112  0  112  010  0  011  010  ·  3  2  square 
1:3.2  
E. acutifurcata (Mielke, 1985)  ?  4  0  121  011  0  112  0  112  010  0  011  010  ·  3  2  subtriangular 
1:4  
E. chilensis (Mielke, 1985)  8  4  0  121  011  0  112  0  112  010  0  011  010  ·  3  2  square 
1:2  
E. diva (VeitKöhler, 2005)  8  5  0  121  011  0  112  0  112  010  0  011  011  ·  3  2  square 
1:5.5  
E. brevicaudata (Kornev & Chertoprud, 2008)  7  4  0  121  011  0  112  0  112  010  0  011  010  ·  3  2  square 
1:1.6  
E. schminkei (VeitKöhler & Drewes 2009).  8  5  0  121  011  0  112  0  112  010  0  011  010  ·  3  2  square 
1:9  
E. clausi Pointner & VeitKöhler, 2013  7  5(6)^{8}  0  121  010  0  112  0  112  010  0  011  010  ·  3  2  square 
1:5.5  
E. ingridae Pointner & VeitKöhler, 2013  8  5  0  121  010  0  112  0  112  010  0  011  010  ·  3  2  square 
1:4.5  
E. koreana sp. n. (This study)  8  2  0  121  011  0  112  0  112  010  0  011  010  ·  3  2  subtriangular 
1:3  
E. simplex sp. n. (This study)  8  5  0  121  011  0  112  0  112  010  0  011  010  ·  3  2  square 
1:3.8 
The family Paramesochridae is divided into nine genera based on segmentation, and setal formula of swimming legs. Two new species clearly belongs to the genus Emertonia, because of: 1) onesegmented endopods of P2–P4 with one seta each, 2) threesegmented exopods of P2–P4, and 3) the onesegmented exopod of antenna.
Paramesochridae. Body cylindrical, broad anteriorly, rather flattened; with distinct separation between prosome and urosome; rostrum small, fused at base. Operculum not developed. Caudal ramus with 6 or 7 setae, seta I small or obscure. Antennule 7 or 8segmented in female. Antennary exopod 1segmented with 1–5 setae. Mandible biramous; exopod 1segmented with 2–4 setae; distal segment of endopod with several basally fused setae at apex. Maxilla with 3 endites on syncoxa, first endite bilobed; endopod 1 or 2segmented. Maxilliped with elongate basis. P1 biramous, with 2segmented endopod and 1or 2segmented exopod. P2–P3 biramous, with 2 or 3segmented exopods and 1segmented endopods; P4 biramous, with 1 or 2segmented endopod and 2 or 3segmented exopod.
Five distinctive groups within genus Emertonia can be recognized based on segmentation and setal formula in swimming legs: 1) gracilisgroup, 1segmented exopod of P1; 2) laurenticagroup, 2segmented exopod of P2–P4; 3) andeepgroup, 2segmented endopod of P4; 4) coelebsgroup, P4 exp2 with one inner seta; 5) holsaticagroup, 2segmented exopod of P1, 3segmented exopod of P2–P4, 1segmented endopod of P2–P4, and P2–P4 exp2 without inner seta. However, more studies including the mouthparts, and the numbers and shapes of elements on the appendages will be necessary to confirm the phylogenetic relationships among the species of Emertonia.
1  P1 exopod 1segmented…(gracilisgroup)  2 
–  P1–P4 exopod 2segmented…(laurenticagroup)  E. laurentica 
–  P1 exopod 2segmented , P4 endopod 2segmented…(andeepgroup)  3 
–  P1 exopod 2segmented, P4 exopod 3segmented; P4 exp2 with 1 inner seta (coelebsgroup)  4 
–  Theses character not combined…(holsaticagroup)  7 
2  P2–P3 exp3 with 2 setae/spines  E. gracilis 
–  P2–P3 exp3 with 3 setae/spines  E. pseudogracilis 
3  P4 enp2 with 2 setae  E. andeep 
–  P4 enp2 with 1 seta  E. minor 
4  P2–P3 exp2 with 1 inner seta  E. furcavaricata 
–  P2–P3 exp2 without inner seta  5 
5  Length of caudal rami 5 times as long as wide; P4 enp1 with 2 setae  E. coelebs 
–  These characters not combined  6 
6  P4 enp1 with 1 seta; P4 baseoendopodal lobe with 2 setae  E. psammophila 
–  P4 enp1 with 2 setae; P4 baseoendopodal lobe with 1 seta  E. atlantica 
7  P2 exp3 with 3 setae/spines  8 
–  P2 exp3 with 4 setae/spines  14 
8  P1 exp2 with 5 setae/spines  E. minuta 
–  P1 exp2 with 4 setae/spines  9 
9  A2 exopod with 1 seta at most  E. capensis 
–  A2 exopod with 2 setae at least  10 
10  A2 exopod with 2 setae and P5 baseoendopodal lobe with 3 setae  E. masryi 
–  These characters not combined…(E. constrictus s. str.)  11 
11  A1 7segmented and A2 exp with 3 setae at most  12 
–  A1 8segmented and A2 exp with 4 setae  13 
12  P1 enp1 length 1.6 times longer than P1 exp, length of caudal rami 3 times as long as wide  E. constricta constricta 
–  P1 enp1 length 1.2 times longer than P1 exp, length of caudal rami 2 times as long as wide  E. constricta orotavae 
13  Vshaped baseoendopod of male P5 without setules  E. constricta pacifica 
–  Each side baseoendopodal lobe almost fused ornamented with row of setules  E. constricta egyptica 
14  P4 exp3 with 3 setae  15 
–  P4 exp3 with 2 setae  16 
15  A2 exp with 2 elements and P5 baseoendopod with 1 seta  E. panamensis 
–  A2 exp with 3 elements and P5 baseoendopod with 2 setae  E. idiotes 
16  P4 enp1 with 2 setae  17 
–  P4 enp1 with 1 setae  21 
17  P3 exp3 with 3 setae  E. perharidiensis 
–  P3 exp3 with 4 setae  18 
18–  Length of caudal rami more than 3.5 times as long as wide; penultimate somite normal  E. holsatica varians 
–  Length of caudal rami more than 5 times as long as wide  19 
19  Penultimate somite normal; endopod of P4 with 2 pinnate setae  E. diva 
–  Penultimate somite elongated and ornamented 2 dorsal processes/spines; endopod of P4 with 1 bare and 1 brushlike setae  20 
20  Length of caudal rami over 6–7 times as long as wide  E. spiniger spiniger 
–  Length of caudal rami over 9 times as long as wide  E. spiniger ornata 
21  P5 exopod with 5 setae  E. pygmaea 
–  P5 exopod with 3 setae  22 
22  Shape of caudal rami conical, subtriangular  23 
–  Shape of caudal rami square  24 
23  A2 exopod with 4 setae; median depression between baseoendopodal lobes shallow  E. acutifurcata 
–  A2 exopod with 2 setae; median depression between baseoendopodal lobes deeply  E. koreana sp. n. 
24  A2 exopod with 1 seta  E. enalia 
–  A2 exopod with at least 2 setae  25 
25  A2 exopod with 2 setae  26 
–  A2 exopod with 3 setae  28 
–  A2 exopod with 4 setae  33 
–  A2 exopod with 5 setae  38 
26  Caudal rami with inwardly pointed spine and long seta V  E. longisetosa 
–  These characters not combined  27 
27  End of P2–P3 enp globular; A2 exopod with 2 or 3 setae  E. holsatica longicaudata 
–  Shape of P2–P3 endopods normal; A2 exopod with 2 setae  E. arenicola 
28  Distal segment of P3 exopod with 3 setae  E. major 
–  Distal segment of P3 exopod with 4 setae  29 
29  Seta V of caudal rami consisted of two type elements, proximal half stout and distal half slender seta  E. miguelensis 
–  Seta V of caudal rami normal  30 
30  A1 8segmented; P1 endopod 1.3 times longer than exopod; length of caudal rami twice as long as wide  E. debilis 
–  These characters not combined  31 
31  A1 7segmented; P2 and P3 endopod with a single tiny spinulelike seta each; length of caudal rami 3 times as long as wide  E. wilsoni 
–  These characters not combined  32 
32  Baseoendopod of P5 with two apical setae; male exp of P5 with 3 setae  E. californica 
–  Baseoendopod of P5 with one apical and one outer setae; male exp of P5 with four setae  E. psammobionta 
33  Baseoendopodal lobes fused forming large plate; A1 8segmented; male exp of P5 with four setae  E. insularis 
–  These characters not combined  34 
34  A1 8segmented; P1 enp1 ornamented with long setules; length of P1 enp1 1.6 times as long as P1 enp2; male P5 exp with three setae  E. chilensis 
–  These characters not combined  35 
35  Seta III of caudal rami blunt spine; apical seta of A2 exp stout comparison with other three setae; Caudal rami length approx. 2.5 times as long as wide  E. longifurcata 
–  These characters not combined  36 
36  Maxilliped enp 2segmented; Caudal rami length approx. 1.6 times as long as wide  E. brevicaudata 
–  These characters not combined  37 
37  Caudal rami length approx. 2 times as long as wide; length of P1 enp1 7 times as long as P1 enp2  E. holsatica holsatica 
–  Caudal rami length approx. 3 times as long as wide; length of P1 enp1 approx. 2.7 times as long as P1 enp2  E. paraholsatica 
38  Baseoendopodal lobes fused forming large plate; P1 enp1 and P1 exp equal in length  E. regulexstans 
–  These character not combined  39 
39  Caudal rami length more than 5 times as long as wide  40 
–  Caudal rami length under 5 times as long as wide  41 
40  Caudal rami length 9 times as long as wide; P5 exp with 1 pinnate and 2 bare setae, outermost longest  E. schminkei 
–  Caudal rami length 5.5 times as long as wide; P5 exp with 3 bare setae, innermost longest  E. clausi 
41  P2–P3 enp apical seta length longer than enp  42 
–  P2–P3 enp apical seta length shorter than enp  43 
42  P1 enp2 with 1 seta  E. ingridae 
–  P1 enp2 with 2 setae/spine  E. simplex sp. n. 
43  Length of P1 enp1 2.5 times as long as P1 exp; male P5 exp with 3 setae  E. unguiseta 
–  P1 enp1 and P1 exp same length; male P5 exp with 4 setae  E. similis 
This research was supported by Evaluation of Marine Invertebrate Bioresources (MABIK 2017M00600) sponsored by the National Marine Biodiversity Institute of Korea. Authors express a hearty thanks to Raehyuk Jung (Hanyang University) for his help in English correction of the early version of manuscript. We are also very grateful to subject editor, Dr. Kai Horst George and the two reviewers, Dr. Elena Chertoprud, and Dr. Sung Joon Song, for their help in greatly improving this manuscript.