Research Article |
Corresponding author: Hsi-Te Shih ( htshih@dragon.nchu.edu.tw ) Academic editor: Sameer Pati
© 2023 Hsi-Te Shih, Tohru Naruse, Christoph D. Schubart.
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:
Shih H-T, Naruse T, Schubart CD (2023) Molecular evidence and differences in gonopod morphology lead to the recognition of a new species of the freshwater crab genus Candidiopotamon Bott, 1967 (Crustacea, Brachyura, Potamidae) from eastern Taiwan. ZooKeys 1179: 169-196. https://doi.org/10.3897/zookeys.1179.106718
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A new freshwater crab of the potamid genus Candidiopotamon Bott, 1967, is described from eastern Taiwan. Candidiopotamon penglai sp. nov. is morphologically similar to C. rathbuni (De Man, 1914) from western Taiwan, but can be distinguished by the morphology of the male first gonopod (G1), as well as by their mitochondrial DNA (16S rRNA and COI genes). In the G1 of C. rathbuni, the subterminal segment shows a cline from robust in northern populations to slender in southern populations. In the G1 of C. penglai sp. nov., a distinctly larger and more distally directed keel-like projection is found on the distal inner edge of the terminal segment, with northern populations having an inward-curving subterminal segment and southern populations a straight subterminal segment. The genetic differentiation of the two species of Candidiopotamon within Taiwan is discussed, and morphological differences are compared. A key to the species of Candidiopotamon is also provided.
16S rDNA, Candidiopotamon penglai, Candidiopotamon rathbuni, cytochrome oxidase subunit I, Decapoda, morphology, new species, taxonomy
Taiwanese freshwater systems are populated by three genera of potamid freshwater crabs, viz., Candidiopotamon Bott, 1967, Geothelphusa Stimpson, 1858, and Nanhaipotamon Bott, 1968, with the former two often occurring in sympatry. Recent molecular studies suggested that the colonization of Candidiopotamon and Geothelphusa to Taiwan took place shortly after Taiwan was geologically shaped as an island, ca 5–6 mya (
Despite sharing the same evolutionary history and the same habitat, the taxonomic situation of these two genera is quite different. In the case of Geothelphusa, nearly 40 species have been described from Taiwan, many of them recently (
In the present study, we describe a new pseudocryptic species, C. penglai sp. nov., for the eastern populations of Taiwanese Candidiopotamon. We also conduct detailed morphological examinations, and molecular analyses using 16S rDNA and cytochrome oxidase subunit I (COI), with additional samples of Taiwanese representatives of Candidiopotamon, to test whether external characters related to reproduction correspond to genetic differences. The two Taiwanese species of Candidiopotamon are also compared with three congeners from the Ryukyu Islands in Japan, viz., C. kumejimense Minei, 1973, C. okinawense Minei, 1973, and C. tokashikense Naruse, Segawa & Aotsuka, 2007.
Specimens of the Taiwanese Candidiopotamon species were collected from mountain streams and coastal plains (Fig.
Haplotypes of 16S and COI of Candidiopotamon rathbuni (De Man, 1914) and Candidiopotamon penglai sp. nov. collected from different populations of Taiwan, as well as the outgroups from the Ryukyus. Numbers within square brackets correspond to localities in Fig.
Species and clades | Localities | Catalog no. of |
Sample size | 16S | Access. nos. | COI | Access. nos. |
---|---|---|---|---|---|---|---|
C. rathbuni | |||||||
NW clade | |||||||
New Taipei City (Wulai [1]) | 13146 | 1 | NW1 | AB208590 | NW1-C | AB625764 | |
New Taipei City (Wulai [1]) | 15189 | 1 | NW2 | AB208589 | NW2-C | OR344947 | |
New Taipei City (Sansia [2]) | 12956 | 2 | NW3 | OR346841, OR346842 | NW3-C | OR344948, OR344949 | |
New Taipei City (Wulai [1]); Hsinchu Co. (Guansi [5]; Jianshih [6]; Wufong [8]) | 13146; 12927; 12915; 12914 | 5 | NW4 | AB208591, AB208591, AB208591, AB208591, AB208591 | NW4-C1 | OR344950, OR344951, AB433579, OR344952, OR344953 | |
Taoyuan (Dongyanshan, Fusing [3]) | 12955 | 2 | NW4 | OR346843, OR346844 | NW4-C2 | OR344954, OR344955 | |
Taoyuan (Baling, Fusing [4]) | 12954 | 1 | NW4 | OR346845 | NW4-C3 | OR344956 | |
Hsinchu Co. (Beipu [7]); Miaoli (Baguali, Tai-an [9]) | 12917; 12916 | 2 | NW4 | AB208591, AB208591 | NW4-C4 | OR344957, OR344958 | |
Hsinchu Co. (Beipu [7]) | 12917 | 1 | NW4 | AB208591 | NW4-C5 | OR344959 | |
Miaoli (Erbensong [10]) | 15193 | 1 | NW4 | AB208591 | NW4-C6 | OR344960 | |
Hsinchu Co. (Jianshih [6]) | 12904 | 1 | NW5 | AB208592 | NW5-C | OR344961 | |
Miaoli (Baguali, Tai-an [9]) | 12916 | 1 | NW6 | AB208593 | NW4-6 | OR344962 | |
Taichung (Dongshih [11]) | 12918 | 1 | NW7 | AB208594 | NW7-C1 | OR344963 | |
Taichung (Dongshih [11]) | 12918 | 1 | NW7 | AB208595 | NW7-C2 | OR344964 | |
Taichung (Dongshih [11) | 12918 | 1 | NW7 | AB208596 | NW7-C3 | OR344965 | |
Taichung (Guguan [12]) | 12941 | 1 | NW8 | AB208597 | NW8-C | OR344966 | |
W clade | |||||||
Taichung (Caohu, Dali [13]; Taiping [13]); Nantou (Shueili [15]) | 12944; 12924; 12902 | 3 | W1 | AB208598, AB208598 | W1-C | OR344967, OR344968, OR344969 | |
Nantou (Shueili [15]) | 17185 | 2 | W2 | OR346846, OR346847 | W2-C | OR344970, OR344971 | |
Nantou (Shueili [15]) | 12902 | 1 | W3 | AB208599 | W3-C1 | OR344972 | |
Nantou (Lianhua Pond, Yuchih [14]) | 12903 | 1 | W3 | AB208599 | W3-C2 | OR344973 | |
Nantou (Lianhua Pond, Yuchih [14]) | 12903 | 1 | W3 | AB208599 | W3-C3 | OR344974 | |
Nantou (Shueili [15]) | 15187 | 1 | W4 | AB208600 | W4-C | OR344975 | |
Nantou (Yapingshan, Sinyi [16]) | 12393 | 1 | W5 | OR346848 | W5-C | OR344976 | |
Chiayi Co. (Guanhua, Jhuci [17]) | 12942 | 1 | W6 | AB208601 | W6-C1 | OR344977 | |
Chiayi Co. (Dabang, Alishan [18]) | 13609 | 1 | W6 | AB208601 | W6-C2 | OR344978 | |
Kaohsiung (Mincyuan, Sanmin [19]) | 12921 | 2 | W6 | AB208601, AB208601 | W6-C3 | OR344979, OR344980 | |
Kaohsiung (Baolai, Liouguei [20]) | 12920 | 1 | W6 | AB208601 | W6-C4 | OR344981 | |
Kaohsiung (Baolai, Liouguei [20]) | 12920 | 1 | W6 | AB208601 | W6-C5 | OR344982 | |
Kaohsiung (Daganshan, Alian [24]) | 12919 | 2 | W6 | AB208601, AB208601 | W6-C6 | OR344983, OR344984 | |
Kaohsiung (Tianliao [23]) | 12923 | 1 | W6 | AB208601 | W6-C7 | OR344985 | |
Kaohsiung (Tianliao [23]) | 12923 | 1 | W6 | AB208601 | W6-C8 | OR344986 | |
Kaohsiung (Chuyunshan, Taoyuan [21]) | 12922 | 1 | W7 | AB208602 | W7-C | OR344987 | |
Kaohsiung (Meinong [22]) | 13368 | 1 | W8 | AB208603 | W8-C | OR344988 | |
Pingtung (Ila, Wutai [25]; Jiamu, Wutai [25]) | 12928; 12949 | 2 | W9 | AB208604 | W9-C | OR344989, OR344990 | |
SW clade | |||||||
Pingtung (Wutai [26]) | 12945 | 1 | SW1 | AB208607 | SW1-C1 | OR344991 | |
Pingtung (Haocha, Sandimen [27]) | 12947 | 1 | SW1 | AB208607 | SW1-C2 | OR344992 | |
Pingtung (Haocha, Sandimen [27]) | 15201 | 1 | SW2 | AB208606 | SW2-C | OR344993 | |
Pingtung (Haocha, Sandimen [27]) | 15200 | 1 | SW3 | AB208608 | SW3-C1 | OR344994 | |
Pingtung (Liangshan, Majia [28]) | 17184 | 1 | SW3 | OR346849 | SW3-C2 | OR344995 | |
Pingtung (Taiwu [29]) | 12907 | 1 | SW4 | AB208605 | SW4-C1 | OR344996 | |
Pingtung (Taiwu [29]) | 15219 | 1 | SW4 | AB208605 | SW4-C2 | OR344997 | |
Pingtung (Taiwu [29]) | 15219 | 1 | SW4 | AB208605 | SW4-C3 | OR344998 | |
Pingtung (Laiyi [30]) | 12925 | 3 | SW4 | AB208605, AB208605, AB208605 | SW4-C4 | OR344999, OR345000, OR345001 | |
Pingtung (Lili, Chunrih [31]) | 12908 | 1 | SW4 | AB208605 | SW4-C5 | OR345002 | |
C. penglai | |||||||
S clade | |||||||
Pingtung (Jioucijia, Chunrih [32]) | 13074 | 1 | S1 | AB208609 | S1-C1 | OR345003 | |
Pingtung (Jioucijia, Chunrih [32]) | 13074 | 1 | S1 | AB208609 | S1-C2 | AB290649 | |
Pingtung (Nanshihhu R., Shihzih [33]; Cili R., Shihzih [33]) | 12939; 12948 | 2 | S1 | AB208610, AB208609 | S1-C3 | OR345005, OR345006 | |
Pingtung (Fangshan R., Shihzih [34]) | 12910 | 1 | S1 | AB208611 | S1-C4 | OR345007 | |
Pingtung (Maozaikengnei, Hengchun [37]) | RUMF-ZC-57 | 1 | S1 | AB208615 | S1-C5 | OR345008 | |
Pingtung (Nanrenshan, Manjhou [38]) | 12940 | 1 | S1 | AB208615 | S1-C6 | OR345009 | |
Taitung (Dawu [39]) | 15220; 12943 | 2 | S1 | AB208616, AB208616 | S1-C7 | OR345010, OR345011 | |
Pingtung (Jioucijia, Chunrih [32]) | 13074 | 1 | S2 | AB208613 | S2-C3 | OR345012 | |
Pingtung (Fangshan R., Shihzih [34]) | 12910 | 1 | S3 | AB208612 | S1-C3 | OR345013 | |
Pingtung (Nanshihhu R., Shihzih [33]) | 12939 | 1 | S4 | AB208614 | S4-C1 | OR345014 | |
Pingtung (Danlu, Shihzih [35]) | 12912 | 1 | S4 | AB208614 | S4-C2 | OR345015 | |
Pingtung (Danlu, Shihzih [35]) | 15207 | 1 | S4 | AB208614 | S4-C3 | OR345016 | |
Pingtung (Sihchong R., Checheng [36]) |
|
1 | S4 | AB208614 | S4-C4 | OR345017 | |
Pingtung (Nanrenshan, Manjhou [38]) |
|
1 | S4 | AB208614 | S4-C5 | OR345018 | |
Pingtung (Nanrenshan, Manjhou [38]) | 15215 | 1 | S4 | OR346850 | S4-C6 | OR345019 | |
SE clade | |||||||
Taitung (Taiban, Daren [40]) |
|
1 | SE1 | AB208617 | SE1-C1 | OR345020 | |
Taitung (Taiban, Daren [40]) | 15218 | 1 | SE1 | AB208617 | SE1-C2 | AB551394 | |
Taitung (Taiban, Daren [40]) | 15218 | 1 | SE1 | AB208617 | SE1-C3 | OR345022 | |
Taitung (Jhihben [42]; Taimali [41]) | 12929; 12931 | 2 | SE1 | AB208617, AB208617 | SE1-C4 | OR345023, OR345024 | |
Taitung (Taimali [41]) | 12953 | 2 | SE1 | OR346851, OR346852 | SE1-C5 | OR345025, OR345026 | |
Taitung (Jhihben [42]) | 12929 | 1 | SE1 | AB208617 | SE1-C6 | OR345027 | |
Taitung (Lijia, Beinan [43]) | 15160 | 1 | SE1 | AB208617 | SE1-C7 | OR345028 | |
Taitung (Lijia, Beinan [43]) | 12933 | 1 | SE1 | AB208617 | SE1-C8 | OR345029 | |
Taitung (Jhihben [42] | 12986 | 1 | SE2 | OR346853 | SE2-C | OR345030 | |
Taitung (Taimali) [41] | 12931 | 1 | SE3 | AB208618 | SE3-C1 | OR345031 | |
Taitung (Taimali) [41] | 12931 | 1 | SE3 | AB208618 | SE3-C2 | OR345032 | |
Taitung (Taimali) [41] | 12931 | 1 | SE3 | AB208618 | SE3-C3 | OR345033 | |
Taitung (Taimali) [41] | 12931 | 1 | SE3 | AB208618 | SE3-C4 | OR345034 | |
Taitung (Hongye, Yanping [44]) | 12937 | 1 | SE4 | AB208619 | SE4-C | OR345035 | |
Taitung (Hongye, Yanping [44]) | 12937 | 1 | SE5 | AB208620 | SE5-C | OR345036 | |
Taitung (Hongye, Yanping [44]) | 12937 | 1 | SE6 | AB208621 | SE6-C | OR345037 | |
E1 clade | |||||||
Taitung (Luming R., Yanping [45]); Hualien (Jingpu, Fengbin [50]) | 12934; 12909 | 3 | E1 | AB208626, AB208626, AB208622 | E1-C1 | OR345038, OR345039, OR345040 | |
Taitung (Taiyuan, Donghe [48]) | 12936 | 1 | E1 | AB208622 | E1-C3 | OR345041 | |
Taitung (Luanshan, Yanping [47]) | 15212 | 1 | E1 | AB208624 | E1-C4 | OR345042 | |
Taitung (Chenggong, Sansian [49]) | 17183 | 1 | E1 | OR346854 | E1-C5 | OR345043 | |
Taitung (Jiafeng, Beinan [45]) |
|
1 | E2 | AB208625 | E2-C | OR345044 | |
Taitung (Chenggong, Sansian [49]) | 15206 | 1 | E3 | AB208623 | E3-C | OR345045 | |
Taitung (Wulu, Haiduan [50]) | 12950 | 1 | E4 | OR346855 | E4-C | OR345046 | |
Hualien (Fuyuan, Rueishuei [51]) | 12935 | 1 | E1 | AB208622 | E1-C2 | OR345047 | |
Hualien (Jili Lake, Guangfu [52]) | 15228 | 1 | E1 | OR346856 | E1-C6 | OR345048 | |
Hualien (Jili Lake, Guangfu [52]) | 15227 | 1 | E1 | OR346857 | E1-C7 | OR345049 | |
E2 clade | |||||||
Hualien (Shueiyuandi, Shoufeng [53]; Liyu Lake, Shoufeng [54]; Ji-an [55]) | RUMF-ZC-8165 (paratype); 12952 (paratype); 15213 (paratype); 12932 (paratype); RUMF-ZC-8164 (paratype); 12951 (holotype) | 6 | E5 | OR346858, OR346859, OR346860, OR346861, OR346862, OR346863, OR346864 | E4-C | OR345050, OR345051, OR345052, OR345053, OR345054, OR345055, OR345056 | |
All localities | 112 | ||||||
Outgroups | |||||||
C. okinawense | Ryukyus, Japan (Okinawa [R1]) | 1 | Co | AB208627 | Co-C | OR345057 | |
Amamiku amamense Naruse, Segawa & Shokita, 2004 | Ryukyus, Japan (Amami [R2]) | 1 | Aa | AB428457 | Aa-C1 | OR345058 | |
Ryukyus, Japan (Amami [R2]) | 1 | Aa | OR346865 | Aa-C2 | OR345059 |
Collection sites for Candidiopotamon rathbuni (De Man, 1914) (circles) and Candidiopotamon penglai sp. nov. (squares) in Taiwan, as well as other congeners from the Ryukyus, Japan. Different colors indicate sampling sites of clades. Dotted lines indicate the possible biogeographic boundaries between clades NW, W, SW, S, SE, E1, and E2, corresponding to the color in Fig.
We used the following abbreviations for morphological description:
CW, carapace width;
CL, carapace length;
G1, male first gonopod; and
G2, male second gonopod.
The terminology follows
Genomic DNA was isolated from the muscle tissue of the legs by using the Sigma mammalian genomic DNA miniprep kit (Sigma-Aldrich, St. Louis, MO, USA) or the GeneMark tissue and cell genomic DNA purification kit (Taichung, Taiwan). A region of approximately 510 to 550 basepairs (bp) of the 5’-end of the mitochondrial large ribosomal subunit (16S rRNA) gene was selected for amplification with polymerase chain reaction (PCR) using the primers 1471, 1472 (
For the combined 16S and COI dataset, the best-fitting models for sequence evolution of individual datasets were determined by PartitionFinder (v. 2.1.1,
A 553 bp segment of the 16S rDNA and a 658 bp segment of COI from 112 specimens of C. rathbuni and C. penglai sp. nov. were amplified and aligned. A total of 36 haplotypes of the 16S gene and 83 haplotypes of COI were found (Table
A Bayesian inference (BI) tree for Candidiopotamon rathbuni (De Man, 1914) and Candidiopotamon penglai sp. nov., as well as outgroups, based on the combined 16S rDNA and cytochrome oxidase I. Probability values at the nodes represent support values for BI and maximum likelihood (ML). For haplotype names, see Table
The pairwise nucleotide divergences and the total bp number differences of COI within and between clades and species are shown in Table
Matrix of percentage pairwise nucleotide divergences with K2P distance and the number of bp differences based on COI within and between clades of Candidiopotamon species from Taiwan (see Table
Within clade | Between clades | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Nucleotide divergence | bp difference | C. rathbuni | C. penglai | C. rathbuni | C. penglai | |||||||
NW | W | SW | S | SE | E1 | E2 | ||||||
C. rathbuni | NW | 0.59 (0–1.54) | 3.85 (0–10) | 33.86 (25–43) | 38.64 (35–44) | 73.55 (69–80) | 74.67 (72–81) | 72.4 (69–78) | 72.73 (71–76) | |||
W | 1.96 (0–3.93) | 12.6 (0–25) | 5.37 (3.92 –6.92) | 37.17 (29–46) | 70.93 (65–76) | 72.1 (66–79) | 69.75 (67–75) | 70.63 (68–73) | ||||
SW | 0.89 (0–1.85) | 5.83 (0–12) | 6.16 (5.54 –7.07) | 5.95 (4.58 –7.45) | 73.05 (66–79) | 73.22 (68–78) | 71.62 (69–75) | 72.58 (70–74) | ||||
C. penglai | S | 1.36 (0–2.16) | 8.81 (0–14) | 12.25 (11.41 –13.48) | 11.83 (10.72 –12.79) | 12.19 (10.89 –13.34) | 22.14 (18–28) | 18.19 (15–21) | 12.81 (11–15) | |||
SE | 1.12 (0–2.17) | 7.25 (0–14) | 12.45 (11.93 –13.65) | 12.05 (10.9 –13.32) | 12.23 (11.26 –13.13) | 3.46 (2.79 –4.41) | 22.18 (17–27) | 21.83 (20–25) | ||||
E1 | 0.54 (0–1.07) | 3.55 (0–7) | 12.04 (11.41 –13.09) | 11.61 (11.1 –12.6) | 11.93 (11.44 –12.57) | 2.83 (2.32 –3.28) | 3.47 (2.64 –4.24) | 13.83 (12–16) | ||||
E2 | 0 | 0 | 12.11 (11.79 –12.72) | 11.79 (11.3 –12.24) | 12.11 (11.62 –12.38) | 2.06 (1.7 –3.28) | 3.41 (3.12 –3.92) | 2.15 (1.86 –2.49) | ||||
C. rathbuni | 4.18 (0–7.45) | 26.34 (0–46) | 72.34 (65–81) | |||||||||
C. penglai | 2.53 (0–4.41) | 16.26 (0–28) | 12.06 (10.72 –13.65) |
Family Potamidae Ortmann, 1896
Subfamily Potamiscinae Ortmann, 1896 (sensu
Candidiopotamon
Bott, 1967: 210;
Potamon (Potamon) rathbuni De Man, 1914.
Taiwan and the Ryukyu Islands (Okinawa, Kumejima, and Tokashiki islands) of Japan.
The genus Candidiopotamon was erected by
1 | Distal part of G1 opening outwards, terminal segment relatively slender | 2 |
– | Distal part of G1 opening distally, terminal segment relatively stout | 3 |
2 | Subterminal segment of G1 straight or curving inwards; distal inner edge of terminal segment of G1 with proportionally larger keel-like projection directed more distally | C. penglai sp. nov. (eastern Taiwan) |
– | Subterminal segment of G1 straight; distal inner part of terminal segment of G1 with proportionally smaller keel-like projection directed more laterally | C. rathbuni (De Man, 1914) (western Taiwan) |
3 | Outer angle of frontal margin of carapace not touching first segment of endopod of antenna | C. okinawense Minei, 1973 (Okinawa Island, Japan) |
– | Outer angle of frontal margin of carapace touching first segment of endopod of antenna | 4 |
4 | Outer dorsal margin of second ambulatory propodus with 1 row of spines; subdistal carina of G1 directed dorsally | C. tokashikense Naruse, Segawa & Aotsuka, 2007 (Tokashiki Island, Japan) |
– | Outer dorsal margin of second ambulatory propodus without spines; subdistal carina of G1 directed inwards | C. kumejimense Minei, 1973 (Kumejima Island, Japan) |
Potamon (Potamon) rathbuni
De Man, 1914: 128, pl. 3(4–4d) [type locality: Sun Moon [Rihyuetan], Nantou, Taiwan];
Thelphusarubra Nakagawai Nakagawa, 1915a: 1036 (nomen nudum); 1915b: 322.
Potamon (Geothelphusa) obtusipes
–
Potamon obtusipes
–
Potamon rathbuni
–
Candidiopotamon rathbuni
–
Candidiopotamon
sp. –
Candidiopotamon guangdongense Dai, 1999: 156, fig. 81, pl. 19(8).
Candidiopotamon rathbunae
–
Taiwan — 3 males, CW 25.6 × CL 22.6–28.6 × 25.6 mm, 1 female, 38.0 × 32.8 mm,
Carapace subtrapezoidal, CW 1.10–1.21× CL (mean 1.16, n = 5), dorsal surface almost flat, relatively rough, epigastric and postfrontal cristae distinct, both cristae represented by 1–3 oblique lines of granules, lateral end of postfrontal cristae far apart from epibranchial tooth; external orbital and epibranchial teeth distinct, sharp, directed anteriorly. G1 terminal segment proportionally longer, more slender, distal opening directed laterally, distal inner edge with keel-like projection in dorsal view, projection proportionally small, directed more laterally; G1 subterminal segment straight.
Carapace (Figs
Candidiopotamon rathbuni (De Man, 1914): male (44.6 × 36.8 mm) from Chiayi, western Taiwan (RUMF-ZC-86) (A–E); male (35.4 × 31.2 mm) from Miaoli, northwestern Taiwan (
Color in life of Candidiopotamon rathbuni (De Man, 1914) (A, B) and Candidiopotamon penglai sp. nov. (C–F). A, C, E overall dorsal view B, D, F overall ventral view A, B
Antenna (Fig.
Eye (Fig.
Chelae of large males unequal, females or young specimens with subequal chelae; palm of major chela (Fig.
Ambulatory legs moderately long; propodus cross-section oblong, each of 2 inner and 1 ventral outer longitudinal margins with 1 spine-row.
Male pleonal somites elongate trapezoidal, sixth pleonal somite length ~ 1/2 of its width; telson obtusely triangular, length ~ 1/2 of its width, distal end reaching imaginary line joining lower hinges of cheliped coxae. Female pleon of adult wide, covering ventral surface of thoracic sternum except for part of thoracic sternites 1 and 2.
G1 (Fig.
Vulvae close to each other, obliquely oblong, occupying proximal two-thirds of thoracic sternite 6.
(Figs
Color in life of Candidiopotamon rathbuni (De Man, 1914) (A–D) and Candidiopotamon penglai sp. nov. (E–H). A, B
(Fig.
Most large specimens were found under large stones within streams. Sometimes adults move outside the water at night.
Based on one male (31.4 × 26 mm) and one female (37 × 31.3 mm) specimens,
In his papers on the life history of Paragonimus westermani,
Subsequently,
Potamon rathbuni
–
Candidiopotamon rathbuni
–
Candidiopotamon rathbunae
–
Taiwan — Holotype: male, 38.4 × 33.4 mm,
Taiwan — 1 male, 23.9 × 20.1 mm,
Carapace subtrapezoidal, CW 1.14–1.24× CL (mean 1.18, n = 45), dorsal surface almost flat, relatively rough, epigastric and postfrontal cristae distinct, both cristae represented by 1–3 oblique lines of granules, lateral end of postfrontal cristae far apart from epibranchial tooth; external orbital and epibranchial teeth distinct, sharp, directed anteriorly. G1 terminal segment proportionally longer and slender, distal opening directed laterally, distal inner edge with keel-like projection in dorsal view, projection proportionally large, directed more distally; G1 subterminal segment curving inwards (in eastern to southeastern Taiwan populations) or straight (in southern Taiwan populations).
The new species is named after Penglai, the ancient name of Taiwan. It also refers to the fact that the island of Taiwan was formed by the Penglai Orogeny (ca 5 million years ago) (
(Figs
(Fig.
Same as C. rathbuni.
A detailed morphological comparison reveals that specimens of C. rathbuni from western Taiwan and C. penglai sp. nov. from eastern Taiwan show differences in G1 structure. Candidiopotamon rathbuni has a smaller and more laterally directed keel-like projection on the distal inner part of the terminal segment (Fig.
Candidiopotamon penglai sp. nov., holotype male (38.4 × 33.4 mm) from Ji-an, Hualien (
Candidiopotamon penglai sp. nov., male (42.9 × 36.2 mm) from Shihzih, Pingtung (
This new species includes clades from eastern Taiwan (E1, E2, SE and S, see Fig.
The phylogenetic pattern of Candidiopotamon in Taiwan inferred by the combined 16S and COI (Fig.
The genetic distance between these two major clades from eastern and western Taiwan is ≥ 10.72% (K2P distance) (Table
The maximum intraspecific distances within the Taiwanese species of Candidiopotamon are large, with 7.45% in C. rathbuni and 4.41% in C. penglai sp. nov. (Table
In C. rathbuni, three clades are recognizable, NW, W and SW (Fig.
In a paper dealing with the freshwater decapod fauna of Yunlin, Chiayi, and Tainan counties of western Taiwan,
In this study, a new pseudocryptic species, Candidiopotamon penglai sp. nov., from eastern Taiwan is established based on minor morphological differences of the G1 and pronounced differences in mitochondrial 16S and COI sequences. Morphological variation of the G1 was found in both C. rathbuni and C. penglai sp. nov. In C. rathbuni, a tendency from robust G1 in the northwestern population to slender G1 in southwestern populations was observed. In C. penglai sp. nov., northern and southern populations show the bent and straight form in the subterminal segment of G1, respectively.
The authors thank Hsueh-Wen Chang (National Sun Yat-sen University, Taiwan), Shigemitsu Shokita (University of the Ryukyus, Japan), Chia-Hsiang Wang (National Taiwan Museum, Taiwan), Hung-Chang Liu (Taiwan Academy of Ecology, Taiwan), Peter K. L. Ng and Ngan-Kee Ng (National University of Singapore, Singapore), Hisakatsu Minei (Kyushu University, Japan), Jhy-Yun Shy (National Penghu University, Taiwan), and Dark Brandis (Senckenberg Research Institute, Germany) for their help on various work and suggestions, and Min-Wan Chen for measuring specimens and performing part of the molecular work. We acknowledge Peter K. L. Ng (
The authors have declared that no competing interests exist.
No ethical statement was reported.
This study was supported by a grant from the National Science and Technology Council (NSTC 112-2313-B-005-051-MY3), Executive Yuan, Taiwan, to HTS. TN was supported by the 21st Century COE program of the University of the Ryukyus.
HTS conceived this study, performed the molecular analysis, and drafted the manuscript. TN performed the morphological description, participated in the discussion and drafted the manuscript. CDS participated in the discussion and final touches to the manuscript. All authors read and approved the final manuscript.
Hsi-Te Shih https://orcid.org/0000-0003-1317-8783
Tohru Naruse https://orcid.org/0000-0001-9212-5246
All of the data that support the findings of this study are available in the main text.