Research Article |
Corresponding author: Jin Hee Wi ( sumiae425@hotmail.co.kr ) Academic editor: Ingo S. Wehrtmann
© 2018 Jin Hee Wi, Man-Ki Jeong, Chang-Keun Kang.
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:
Wi J, Jeong M, Kang C (2018) A new species of the genus Hexapleomera Dudich, 1931 from the South Korea, with molecular evidence (Crustacea, Tanaidacea, Tanaididae). ZooKeys 739: 1-28. https://doi.org/10.3897/zookeys.739.21580
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Two populations of new species are described for Hexapleomera Dudich, 1931 from the southeastern coast and Jeju island of South Korea (north west Pacific). The specimens were collected using a light trap set overnight at the entrance near a pier or harbour. Hexapleomera ulsana sp. n. is clearly differentiated from other species in the genus by the uropod with five articles, a maxillule palp with four distal setae, the maxilliped coxa with three proximal setae, the epignath with short and blunt spiniform seta, the propodus of pereopods 2–3 with three ventral setae, and the maxilla with a rugged shape of the distal margin. Differences of mitochondrial cytochrome c oxidase subunit I (mtCOI) gene observed between two populations of H. ulsana from different regions (Ulsan and Jeju Island) and between H. ulsana and H. urashima (Japan) were 1.1 % and 32.4 %, respectively. Two genetically-close populations differed in the setae on pleopod 3, the proximal setae on the maxilliped coxa, and the ventral setae on pereopods 2–3, which showed that geographical distance affected the morphological divergence. In addition, a comprehensive comparison with previous records of Hexapleomera was conducted and close examinations on the appendages, known to have morphological variations between the individuals of one species and/or between different genders, were carried out based on new species and discussed herein.
genetic analysis, Hexapleomera , sexual dimorphism, Tanaidacea , Tanaidomorpha
Tanaidaceans are represented by almost 1,200 mostly marine species, and these are distributed from almost any type of marine habitat (
The genus Hexapleomera was defined by
The material was obtained from the bottom of entrances near two harbours of South Korea: Ulsan (35°22'7.47"N; 129°35'25.47"E) in January 2016 and Jeju Island (33°14.0'N; 126°22.6'E) in May 2016, using a light trap set. The light trap set was made with a PVC pipe (10 cm in diameter, 50 cm long) and a LED lamp on the mouth, placed on mud-sandy bottom of 3m in depth at the seawalls in harbors after sunset. The samples caught overnight in the light trap were filtered through a plankton net with 350 μm mesh at dawn. The specimens were preserved in 99 % alcohol solution. The individuals were dissected under a dissection microscope (Nikon SMZ745T) in CMC-10 aqueous mounting medium (Masters, Wood Dale, IL, USA), mounted on slides, and then sealed with high-quality nail varnish. Drawings were generated using a differential interference contrast microscope (Nikon Y-IM) that was equipped with a drawing tube. The total body length was measured from the tip of the rostrum to the pleotelson apex in the dorsal view. Scale bars are given in mm. The morphological terminology follows
DNA extraction, amplification, sequencing, and analysis
The total genomic DNA was extracted from five specimens of Hexapleomera (H. ulsana: two females MABIK CR00240699, MABIK CR00240701, and one male MABIK CR00240704; Jeju population of H. ulsana: one female MABIK CR00240707, and one male MABIK CR00240710). To extract genomic DNA, a centrifuge tube (1.5 mL) each containing 90 μL of 10 % Chelex suspension (Bio-Rad Laboratories Inc.), 10 μL of Proteinase K (10 mg/ml, iNtRON Biotechnology, Inc.) and grinded tissues were incubated at 56 °C for 3 hours. The extracted genomic DNAs were used as templates to amplify the target regions on the mtCOI gene. Polymerase chain reaction (PCR) was performed on a Mastercycler PCR thermal cycler (Eppendorf Co.). A pair of primer for COI was jgLCO1490 and jgHCO2198 (
Holotype. (MABIK CR00235364) ovigerous female dissected and mounted in eight slides, collected from the Ulsan of Korea (35°22'7.47"N, 129°21'25.47"E) in January 2016. Allotype. (MABIK CR00235366) male dissected and mounted in four slides, same locality as for holotype. Paratypes. Four females partially dissected and mounted in three slides (MABIK CR00235365), two slides (MABIK CR00240699), five slides (MABIK CR00240700), and two slides (MABIK CR00240701); two intact females in one vial (MABIK CR00240702); four males partially dissected and mounted in two slides (MABIK CR00235367), four slides (MABIK CR00240703), one slide (MABIK CR00240704), one slide (MABIK CR00240705); two intact males in one vial (MABIK CR00240706). Same locality as for holotype.
Uropod endopod 4-articulate. Pleopods 1–3 endopod with one seta on inner margin. Pleopod 3 basal article with four outer setae and no inner seta; pleopods 1–2 each with six outer setae and one inner seta on basal article. Pereopod 1 coxa lacking apophysis and having two dorsal setae. Pereopods 2–3 propodus with two simple setae and one bifurcated pinnate spiniform seta on ventral margin. Mandible setal row consists of two pinnate setae. A maxillule palp with four distal setae. Maxilliped coxa with three proximal setae; endite bearing two long plumose setae, two short plumose spiniform setae, and two simple spiniform setae. Dactylus of male cheliped with spinules along cutting edge.
Body (Fig.
Cephalothorax (Fig.
Pereon (Fig.
Pleon (Fig.
Antennule (Fig.
Antenna (Fig.
Labrum (Fig.
Left mandible (Fig.
Labium (Fig.
Maxillule (Fig.
Maxilla (Fig.
Maxilliped (Fig.
Epignath (Fig.
Cheliped (Fig.
Pereopod 1 (Fig.
Pereopod 2 (Fig.
Pereopod 3 (Fig.
Pereopod 4 (Fig.
Pereopod 5 (Fig.
Pereopod 6 (Fig.
Pleopod 1 (Fig.
Pleopod 2 (not figured): Similar to pleopod 1, except for outer margin of exopod with smaller plumose setae (26).
Pleopod 3 (Fig.
Uropod (Fig.
Body (Fig.
Pereon (Fig.
Pleon (Fig.
Appendages similar to those of female except for antennule, antenna, mandible, maxilliped, cheliped, and uropod:
Antennule (Fig.
Antenna (Fig.
Left mandible (Fig.
Cheliped (Fig.
Uropod (Fig.
Cheliped of smaller male (Body length 2.1 mm) (Fig.
The specific name refers to Ulsan, a harbour city near the type locality.
Hexapleomera ulsana sp. n. can be differentiated from other species of the genus by the following combination of characteristics (Table
Morphological comparison between nine species within the genus Hexapleomera.
Key characters \ species | H. bultidactyla | H. edgari | H. moverleyi | H. robustasensu Moore | H. robustasensu Sieg | H. satella | H. ulsana | H. urashima | H. wombat |
---|---|---|---|---|---|---|---|---|---|
F/M | F/M | F/M | F/M | F/M | F/M | F/M | F/M | F/M | |
Number of uropod articles | 4/4 | 4/4 | –/5 | 4/– | 4/4 | 4/4 | 5/5 | 4/4 | 5/5 |
Number of inner seta on pleopod 3 basal article | 0/0 | 1/1 | –/1 | – | 0/0 | 0/0 | 0/0 | 0/0 | 0/0 |
Pereopod 1 coxa with apophysis | yes | yes | yes | – | no | yes | no | yes | no |
Number of seta on maxillule palp | 4 | 5 | 5 | 8 | 8 | 4 | 4 | 6 | 5 |
Maxilliped | |||||||||
Basis setae | 2 | 2 | 1 | – | 2 | 2 | 1 | 1~2 | 1 |
Coxa setae | 2 | 3 | 2 | – | 2 | 2 | 3 | 2 | 3 |
Endite with distal plumose setae | yes | yes | yes | – | yes | no | yes | yes | no |
Right/Left Mandibles | |||||||||
Setae number of setal row | 1 | 1 | 1 | – | 2 | 1 | 2 | 2 | 1 |
Pereopods 2–3 | |||||||||
Ventral setae on propodus | 2, 2 | 4, 4 | 2, 2 | – | 3, 2 | 1, 2 | 3, 3 | 3, 3 | 2, 3 |
Habitat | aquaculture fouling | turtles | epifaunal | turtles | turtles | benthic/epifaunal | benthic/epifaunal | turtles | yacht hulls |
Figs
Yerae (33°27'30.0"N, 126°20'18.0"E), Jeju Island of Korea in May 2016. Ovigerous female dissected and mounted in five slides (MABIK CR00235368). Male dissected and mounted in five slides (MABIK CR00235370). Three females partly dissected and mounted in five slides (MABIK CR00235369), one slide (MABIK CR00240707), three slides (MABIK CR00240708); two partly dissected females in one vial (MABIK CR00240709); three males dissected and mounted in one slide (MABIK CR00235371), one slide (MABIK CR00240710), one slide (MABIK CR00240711); two partly dissected males in one vial (MABIK CR00240712).
Description of female (with a budding of oostegites). Body (Fig.
Pereon (Fig.
Pleon (Fig.
Antennule (Fig.
Antenna (Fig.
Labrum (Fig.
Left mandible (Fig.
Labium (Fig.
Maxillule (Fig.
Maxilla (Fig.
Maxilliped (Fig.
Cheliped (Fig.
Pereopod 1 (Fig.
Pereopod 2 (Fig.
Pereopod 3 (Fig.
Pereopod 4 (Fig.
Pereopod 5 (Fig.
Pereopod 6 (Fig.
Pleopod 1 (Fig.
Pleopod 2 (not figured): Basal article and exopod similar to those of pleopod 1. Endopod with one inner and eleven outer plumose setae and one robust seta.
Pleopod 3 (Fig.
Uropod (Fig.
Description of male.Body (Fig.
Pereon (Fig.
Pleon (Fig.
Appendages similar to those of female except for antennule, antenna, mandibles, cheliped, and uropod:
Antennule (Fig.
Antenna (Fig.
Left mandible (Fig.
Labium (Fig.
Cheliped (Fig.
Uropod (Fig.
Two populations of Hexapleomera ulsana from the Ulsan and Jeju Island exhibited a morphological divergence in the number of the setae on the maxilliped coxa (3 vs. 2), setae on the maxillule palp (4 vs. 6), setae on the pleopod basal article (absence vs. presence), pattern of pigmentation of cephalothorax, and the number of ventral setae on the pereopods 2–3 propodus (3 vs. 2). On the other hand, specimens of both populations coincided in the number of uropod articles (5), the presence of apophysis on the pereopod 1 coxa, the number of setae on the mandible setal row, and the number of setae on the maxilliped endite. Little morphological variation was found in each population. These results show that the geographical isolation can affect the morphological divergence between two populations of H. ulsana.
The mtCOI gene sequences between two populations of H. ulsana from Ulsan and Jeju Island showed somewhat low molecular divergence (1.1 %). The divergence values are genetically indicative of the same species when compared with other taxa of Tanaididae(
The family Tanaididae Nobili, 1906 consists of five subfamilies, 19 genera, and 87 species (
Nine species of Hexapleomera were compared based on the combination of morphological characteristics (Table
We would like to thank Dr. Larsen and Dr. Ingo Wehrtmann who made constructive and invaluable suggestions and useful comments. This study was a part of the project titled “Long-term change of structure and function in marine ecosystems of Korea”, funded by the Ministry of Oceans and Fisheries, Korea. This work was supported by the National Marine Biodiversity Institute Research Program (2018M01200), funded by the National Marine Biodiversity Institute of Korea (MABIK).