Johora michaeli, Ng, 2020

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/4CA305BB-71CF-49E5-9559-24BB4019660C
taxon LSID	lsid:zoobank.org:act:4CA305BB-71CF-49E5-9559-24BB4019660C
treatment provided by	ZooKeys by Pensoft
scientific name	Johora michaeli
status	sp. nov.

Treatment

Johora michaeli sp. nov. Figures 1H View Figure 1 , 2H View Figure 2 , 3H View Figure 3 , 4H View Figure 4 , 5H View Figure 5 , 9I-L View Figure 9 , 12H View Figure 12 , 13H View Figure 13 , 14H View Figure 14

Material examined.

Holotype: male (22.7 × 19.2 mm) (ZRC 2020.0361), waterfalls at rock pools, ca. 5 minutes walk upstream from chalets, Sekayu Waterfall, 4°59'35"N, 102°56'50"E, Terengganu, coll. Tan HH, 21 October 1998. Paratype: 1 female (29.9 × 25.0 mm) (ZRC 2010.0047), same data as holotype. Others: 1 female (30.8 × 25.2 mm) (ZRC 1984.6794), Gunung Padang, Terengganu, 4°50'55.7"N, 102°52'1.9"E, coll. Hislep JSA, 1952. All locations in Peninsular Malaysia.

Diagnosis.

Adult carapace width to length ratio 1.20-1.22 (Figs 1H View Figure 1 , 2H View Figure 2 , 12H View Figure 12 ); dorsal surface gently convex in frontal view, not inflated (Fig. 3H View Figure 3 ); frontal margin almost straight (Fig. 2H View Figure 2 ); suborbital, pterygostomial and sub-branchial regions rugose, pterygostomial region covered with dense setae (Fig. 3H View Figure 3 ); epigastric cristae distinct, distinctly anterior to sharp postorbital cristae, postorbital cristae with lateral edges low, not joining lateral margin (Fig. 2H View Figure 2 ); external orbital tooth separated from epibranchial tooth by distinct cleft, epibranchial tooth sharp, distinct (Fig. 2H View Figure 2 ); anterolateral margin distinctly convex (Fig. 2H View Figure 2 ); posterolateral margin with median concavity or sinuous, distinctly converging towards gently convex to almost straight, entire posterior carapace margin (Fig. 2H View Figure 2 ); posterior margin of epistome with triangular median triangle, lateral margin obliquely sloping (Fig. 3H View Figure 3 ); outer surfaces of third maxillipeds with long stiff setae; ischium subrectangular, with shallow median oblique groove (Figs 3H View Figure 3 , 4H View Figure 4 ); ambulatory legs not elongate, length to width ratio of merus of fourth ambulatory leg 2.7-2.8 (Figs 1H View Figure 1 , 12H View Figure 12 ); G1 subterminal segment gradually tapering from broad proximal part to slender distal part, without distinct shelf-like structure along gently concave outer margin; terminal segment almost straight, slightly curved outwards (from median part of sternum), ca. two-thirds length of subterminal segment, surfaces with scattered short setae (Fig. 9I-K View Figure 9 ); G2 subequal in length to G1, distal segment long, about one-third length of basal segment (Fig. 9L View Figure 9 ). Female pleon ovate; somites 3-6 progressively narrower; telson subtriangular (Fig. 13H View Figure 13 ). Vulvae large, on anterior half of sternite 6, adjacent to suture with sternite 5, lateral sternal vulvar cover subtruncate (Fig. 14H View Figure 14 ).

Etymology.

The species is named after the last director of the Raffles Museum (1946-1967), the late Michael Tweedie, an intrepid collector of interesting animals from Malaysia. The author had the pleasure of knowing him, finally meeting him when the refreshed museum opened as the ZRC in 1988; and even after many years since retiring, he retained his great passion for his crabs, snakes, and fish.

Remarks.

The holotype male of Johora michaeli sp. nov. is not fully adult and it is clear that it can grow larger, with the adult females reaching 30 mm in carapace width. The G1, however, remains diagnostic, with the terminal segment elongate and almost straight (Fig. 9I-K View Figure 9 ). While this somewhat resembles that of J. thoi which is known from the nearby island of Pulau Redang, that of J. michaeli is distinctly less elongate and slender, being only about two-thirds the length of subterminal segment. Specimens of J. thoi even smaller than the type of J. michaeli remain the same G1 terminal segment shape and proportions of adults (Fig. 9E-G View Figure 9 ) so the differences observed here are independent of size. The vulva of J. thoi is diagnostic, the lateral sternal vulvar cover being triangular in shape (Fig. 14C View Figure 14 ); it is subtruncate in J. michaeli (Fig. 14H View Figure 14 ). The general shape of the G1 terminal segment somewhat resembles that of J. tahanensis s. str. (Fig. 8A-C View Figure 8 ), it is clearly straighter and slenderer in J. michaeli (Fig. 9I-K View Figure 9 ). It is also unlike that of J. hoiseni which has a proportionately and even straighter G1 terminal segment (Fig. 8E-G View Figure 8 ).

The G1 of J. michaeli also resembles that of J. singaporensis but the terminal segment in this species is longer ( Ng 1987: fig. 8A, B). In any case, the carapace of J. singaporensis is quite different from that of J. michaeli as it is a member of the J. johorensis species group (see remarks for the species group under remarks for the genus).

One large female (ZRC 1984.6794) had been collected from Gunung Padang, which is relatively close to the type locality in Sekayu Falls. Both are part of the same mountain system east of Lake Kenyir in Terengganu.

Distribution.

Johora michaeli sp. nov. is known so far only from highland streams in central Terengganu (Fig. 15 View Figure 15 ).

Conservation.

The conservation status for J. michaeli should be regarded as vulnerable as it is known from a relatively well protected area that is not subject to development (see Cumberlidge et al. 2009).