Conchoecetes chanty, Naruse, 2019

Naruse, Tohru, 2019, Revision of the shell-carrying crab genus Conchoecetes Stimpson, 1858 (Crustacea: Brachyura: Dromiidae), Zootaxa 4706 (1), pp. 1-47 : 18-21

Conchoecetes chanty n. sp.

( Figs. 6A , 9 , 10 )

Conchoecetes artificiosus —Ng et al 2000: 156, figs 1 a, b (only specimens from Taiwan);— Ng et al 2001: 5 (list) (part);—Tsang et al 2003: 362 (DNA);— Ahyong et al 2009: 31, figs 6–8;— Ng et al 2017: 24, fig. 1d. [Not Conchoecetes artificiosus ( Fabricius, 1798].

Type: Taiwan: ZRC 2019.1630 , holotype, female, 31.6 × 30.2 mm , ZRC 2019.1664 , paratype, ovig. female, 24.9 × 25.9 mm, Dasi Fish Port , Yilan, 9 Jan. 2012 .

Material examined. Taiwan: NTOU, ovig. female 26.4 × 25.6 mm, Dasi Fish Port , Yilan County, 21 Jul. 2005 [China DNA Jan 2007. 2009.0838 B00005, T-YC] ; NTOU, ovig. female 41.4 × 38.6 mm, Dasi Fish Port , Yilan County, 14 Mar. 2011 ; ZRC 2019.1628 , male, 31.6 × 30.34 mm, female, 29.3 × 27.7 mm, Ezailiao , Kaohsiung, 22 Jan. 2013 .

East China Sea: NSMT Cr-15047, 2 males 9 × 9 mm, 11.2 × 10.8 mm, 2 females 10.7 × 10.8 mm, 11.5 × 10.6 mm, stn 12, 29°59.12’N, 126º29.25’E, 90–92 m, 15 Oct. 2001, coll. by G. Shinohara & H. Saito, Yoko-Maru ; ZRC 2019.1629 , 8 males, 13.4 × 13.2 mm, 14.0 × 13.9 mm, 18.4 × 18.2 mm, 20.0 × 19.8 mm, 20.5 × 20.2 mm, 21.5 × 21.4 mm, 25.2 × 24.0 mm, 26.0 × 25.9 mm, 7 females, 12.3 × 12.2 mm, 18.2 × 18.1 mm, 18.8 × 18.4 mm, 19.9 × 19.5 mm, 20.2 × 19.5 mm (with shell Venus cassinaeformis (Yokoyama, 1926)) , 21.7 × 21.0 mm, 23.5 × 23.3 mm, + 20 others in same size range unmeasured, East China Sea , 29°29.18’N, 123°35.40’E, 60 m, 7 Jan. 2008; Ondrej Radosta personal collection, dried female 36.3 × 35.5 mm ,, collected by Chinese fisherman .

Description. Carapace width approximately equal to length, surface evenly convex, smooth, covered by soft fine tomentum; cervical, cardiac and branchial grooves well marked. Deep frontal groove extends posteriorly to gastric region. Rostrum tridentate, edges carrying small granules, median tooth shorter on lower level, not deflexed so that all 3 teeth directed anteriorly; margin continues as supraorbital margin interrupted by prominent blunt supraorbital tooth, no post-orbital tooth; infra-orbital margin also has prominent blunt infraorbital tooth, shielded from view dorsally by supraorbital tooth. Anterolateral margin complex, sculptured, granulate: sinuous, initially concave then gently convex until reaching point where cervical groove meets the edge, marked by prominent shoulder-like anterolateral tooth, at widest point of carapace. Margin between orbital corner and anterolateral tooth adorned by 12–14 small irregular granules. Subhepatic area mostly smooth, sloping outwards to form granular margin at lower level; margin begins beneath and anterior to anterolateral tooth curving downwards and under subhepatic area. Posterior to anterolateral tooth, margin begins to converge, interrupted by blunt tooth behind branchial groove, then converging to posterior corner to meet concave posterior carapace margin.

Sternal sutures 7/8 end apart on prominent tube-like scrolls, between coxae of P2. These are directed posteriorly towards adjacent gonopores opening on coxae of P3.

Third maxilliped operculate, crista dentata armed with 8 to 10 well developed teeth.

Cheliped carpus dorsal surface with 1 prominent tubercle and weak second tubercle on distal outer margin and few scattered granules sometimes scattered or tending to be aligned in rows; dorsal face of propodus with around a dozen large granules embedded in setae; outer face with similar granules roughly arranged to form 2 parallel rows. Fingers with 7 or 8 interlocking blunt teeth increasing in size distally, hollowed out internally. Walking legs (P2–P3) shorter than chelae, setose, without granules dactyli fringed with 2 rows of stouter setae. P4 shorter stouter, anterior margin of carpus with row of 2 to ( Fig5 small blunt granules; dactylus talon-like, as long as propodus, curved with tip opposing quadrangular process on proximal margin of propodus thereby completing shell-grasping mechanism. P5 shortest, flattened, sub-dorsal, dactyl short bent at right angles.

Male telson narrowly triangular, posterior margin convex, uropods visible externally, locking in front of tubercles on coxae of P 2 in male. Female telson, broadly triangular, posterior margin convex, uropods visible externally, but pleon locking mechanism absent in mature female; fringed with long setae and sometimes scattered granules on dorsal surface particularly on more anterior segments; vestigial first pleopods present as well as normal egg-bearing biramous pleopods.

Colours. Female from the East China Sea has carapace with pink beneath tomentum, fingers and dactyli of P2 and P3 also bright pink ( Fig. 6A ). Other specimens from the East China Sea have pink fingers ( Fig. 10 ).

Etymology. The name Conchoecetes chanty n. sp. is used to recognize the contribution to decapod biology of Chan Tin-Yam, Institute of Marine Biology, Keelung, Taiwan and alludes to the fact that these shell-carrying crabs only occupy their bivalve shell temporarily. The specific name “chanty” uses the letters of his name and has the same sound as the English word “shanty”, a rough dwelling used for a short time, alluding to the crab’s use of shells. It is used as a noun in apposition.

Habitat. Sandy mud and shells, 20– 100 m.

Distribution. Taiwan and East China Sea.

Remarks. Conchoecetes chanty n. sp., is one of two new species from the East China Sea, long confused under Conchoecetes artificiosus s. str. Conchoecetes chanty n. sp. can be distinguished by its more distinct, tuberculate anterolateral carapace margin (margin smooth somewhat obtuse in C. artificiosus ) and the prominent smooth swellings on the cheliped carpus and propodus (smaller and granulate swellings). The other species, Conchoecetes atlas n. sp. ( Fig 4 ) can be separated by having a sub-pentagonal carapace shape (sub-oval in C. chanty n. sp.; see Fig. 9 ); strong anterolateral tooth and no posterolateral tooth (having both teeth more or less equal in size); cheliped carpus with a pair of more or less equal distal tubercles on external margin (only one prominent tubercle and weak second tubercle). These two species are sympatric both occurring around Taiwan and in the East China Sea. However, the distribution of C. atlas n. sp. also includes Japan, mainland China, the South China Sea and Southeast Asia including the Philippines.

Figures

FIGURE 4. Conchoecetes atlas n. sp., ZRC 2019.1631, holotype, male, 32.5 × 31.1 mm, Camiguin Island, Bohol Sea, Philippines. A, dorsal view; B, frontal view; C, ventral view of anterior region.

FIGURE 5. Conchoecetes atlas n. sp., dorsal views. A, SUF Cat. No. 9161, male, 29.7 × 29.2 mm, Ohshima, Japan; B, ZRC1999.0463, male, 30.0 × 29.8 mm, Guangdong, Nanao Island, China; C, NHMB-87555 (was ZMUC-CRU-10110), male, 28 × 27.5 mm, Taiwan.

FIGURE 6. A, Conchoecetes chanty n. sp. showing fresh colours, female, 36.3 × 35.5 mm from East China Sea; B, Conchoecetes atlas n. sp., male, 30.5 × 29.0 mm, from Camiguin I., Philippines (photographs by Ondrej Radosta).

FIGURE 9. Conchoecetes chanty n. sp., ZRC 2019.1630, holotype, female, 31.6 × 30.2 mm, Dasi Fish Port, Yilan, Taiwan. A, dorsal view; B, ventral view; C, frontal view.

FIGURE 10. Conchoecetes chanty n. sp.., ZRC 2019.1629, female, 20.2 × 19.5 mm, carrying a shell Venus cassinaeformis (Yokoyama, 1926), East China Sea. A, frontal view; B, ventral view.