Johora Bott, 1966

Ng, Peter K. L., 2020, Revision of the freshwater crabs of the Johora tahanensis (Bott, 1966) species group (Crustacea, Brachyura, Potamidae), with a key to the genus, ZooKeys 994, pp. 1-34 : 1

publication ID	https://dx.doi.org/10.3897/zookeys.994.56810
publication LSID	lsid:zoobank.org:pub:DB1879C9-1904-4320-BE67-4D9F863F6775
persistent identifier	https://treatment.plazi.org/id/A9062979-ED11-52B1-8751-6DC9D8AB3C57
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scientific name	Johora Bott, 1966
status

Treatment

Genus Johora Bott, 1966

Type species.

Potamon (Potamon) johorense Roux, 1936, by original designation.

Comparative material.

Johora johorensis (Roux, 1936): 1 male, 1 female, 1 juvenile (ZRC 2019.1054), Sungei Pulai, Gunung Pulai, Pulai, clear waters, sandy, and large rock substrate; shallow to waist deep waters with low vegetation cover on sides, in forest, 1°35'31.1"N, 103°31'10.7"E, Johor, coll. BY Lee et al., 23 June 2019. Johora intermedia Ng, 1986b: holotype male (19.8 × 15.1 mm) (ZRC 1984. 6529), stream near Bentong, Pahang, ca. 3°27'36"N, 101°53'31"E, ca. 600 m a.s.l., coll. Tweedie MWF, 12 July 1935; paratypes 26 males, 13 females, 17 juveniles (ZRC 1984. 6530-6585), same data as holotype; 7 males, 4 females, 1 juvenile (ZRC 1989.2171-2182), Gombak Forest, Selangor, coll. Ng PKL, 9 June 1987; 2 males, 2 females, 1 juvenile (ZRC 2001.1002), stream at Engkabau Trail, river tract, Forest Research Institute of Malaysia (FRIM), forest reserve, Kepong, Selangor, coll. Leong TM et al., September 2000; 3 males (ZRC 2003.0327), Sungei Kroh and Engkabau Trail, stream in Forest Research Institute of Malaysia (FRIM), Kepong, Selangor, coll. Leong TM & Lim KKP, 22-27 November 2002; 3 males (ZRC 2001.2283), Genting Highlands, Pahang, coll. Leong TM, 24 October 2001; 1 female (ZRC 2013.1819), Genting Highlands, Pahang, coll. Barlow HS, 9 April 2013; 2 males, 2 females (ZRC 2018.0690), Genting Tea Estate, Pahang, 3°21'24.9"N, 101°47'42.2"E, 670 m, coll. Barlow HS, 2000s; 4 males (ZRC 2002.242), in roadside seepage, on road to Jeriau Falls, Fraser’s Hill, Pahang, coll. Leong TM, 24 February 2002; 2 males (ZRC 2016.003), under rocks, first stream on road towards Raub, descending from Fraser’s Hill, Pahang, coll. Lai JCY, 6 December 2015; 2 males (ZRC 2020.0073), shaded stream along road, Fraser’s Hill, Jalan Telekom, Pahang, 3.715485, 101.747604, coll. Lai JCY, December 2015; 1 male, 1 juvenile female (ZRC 2016.0002), Jeriau Falls, Fraser’s Hill, Pahang, coll. Lai JCY & Hogg AH, 5 December 2015; 1 male (ZRC 2020.0354), Jeriau Falls, Fraser’s Hill, Pahang, coll. Hogg AH, 30 May 2016. Johora gapensis (Bott, 1966): 2 males, 2 females (ZRC 1995.349), in shallow leaf litter stream, The Gap, Fraser’s Hill, coll. Lim KKP, 9 June 1990; 1 male (ZRC 2002.0587), Gunung Bunga Buah, Genting Highlands, 3°22'30.0"N, 101°44'23.7"E, Pahang, coll. Lim KKP, 4 July 2002; 1 male (ZRC 2020.0074), along path to main waterfall, Jerijau Waterfall, Fraser’s Hill, Pahang, 3.724534, 101.714471, coll. Lai JCY, December 2015. All locations in Peninsular Malaysia. For material of other Johora species, see Ng (1985, 1987, 1990), Ng and Takeda (1992), Yeo et al. (1999), Yeo (2001) and Leelawathanagoon et al. (2005).

Remarks.

Members of the J. tahanensis species group are distinct from the nominate species group ( J. johorensis , J. gapensis , J. tiomanensis , J. counsilmani , J. intermedia , J. murphyi and J. singaporensis ) (sensu Yeo et al. 2007) and can be distinguished by the following suite of characters: the epibranchial tooth is prominent, clearly demarcated from the external orbital tooth by a distinct cleft (Fig. 2B-H View Figure 2 ); the frontal margin is relatively wide (Fig. 2B-H View Figure 2 ); the epigastric cristae are prominently anterior of the postorbital cristae (Fig. 2B-H View Figure 2 ); the postorbital crista is sharp and prominent, with the lateral part clearly reaching at least the beginning of the cervical groove (Fig. 2B-H View Figure 2 ); the lateral margins of the posterior margin of the epistome are obliquely sloping (Fig. 3B-H View Figure 3 ); the third maxilliped is covered with dense, long setae, and the merus and ischium are proportionately longer (Figs 3B-H View Figure 3 , 4B View Figure 4 ); the male pleon is proportionately more elongate with somite 3 relatively less wide (Figs 5B-H View Figure 5 , 6D View Figure 6 , 7D View Figure 7 ); the G1 terminal segment is long to very long and often covered with numerous setae (e.g., Fig. 8A View Figure 8 ); and the adult female pleon is ovate (Fig. 13B-H View Figure 13 ). For members of the J. johorensis species group, the epibranchial tooth is usually lower and demarcated from the external orbital tooth by a shallow or narrow cleft (Fig. 2A View Figure 2 ); the frontal margin is relatively less wide (Fig. 2A View Figure 2 ); the epigastric cristae are only slightly anterior of the postorbital cristae (Fig. 2A View Figure 2 ); the postorbital crista is uneven and not sharp and do not clearly extend to the cervical groove (Fig. 2A View Figure 2 ); the lateral margins of the posterior margin of the epistome are horizontal and subparallel with the frontal margin (Fig. 3A View Figure 3 ); the setae on the third maxilliped are shorter and usually less dense, and in the smaller taxa, the merus and ischium are proportionately shorter (Figs 3A View Figure 3 , 4A View Figure 4 ); the male pleon is broadly triangular with somite 3 relatively wider (Fig. 5A View Figure 5 ); the G1 terminal segment is short to long (e.g., Ng 1987: figs 2F, I, 3A, 6D); and the adult female pleon is almost round (Fig. 13A View Figure 13 ).

In recent years, the structure of the vulva has proven useful in potamid taxonomy for some groups, but for Johora species, its morphology appears to be relatively conservative. The one exception is J. thoi , where the lateral sternal vulvar cover projects obliquely anteriorly as a large triangular plate (Fig. 14C View Figure 14 ), quite different from the simpler structures of congeners (Fig. 14A, B, D-H View Figure 14 ).

The molecular study by Yeo et al. (2007) tested three members of the J. tahanensis species group: " J. tahanensis " from Perak (ZRC 1995.268), J. hoiseni from Kelantan (ZRC1984.6674-6755, ZRC 1984.7683-7687), and J. thoi from Terengganu (ZRC 2001.1167), with the taxa coming out in one clade. The " J. tahanensis " from Perak (ZRC 1995.268) is here reidentified as a new species, J. erici sp. nov.

The last key to the genus was constructed in 1988 and in view of the additional species described since, there is a necessity to update this, and a revised key is presented here.