Microtopsis takedai Komai, Ng & Yamada, 2012

Ng, Peter K. L. & Castro, Peter, 2016, Revision of the family Chasmocarcinidae Serène, 1964 (Crustacea, Brachyura, Goneplacoidea), Zootaxa 4209 (1), pp. 1-182 : 85-86

Microtopsis takedai Komai, Ng & Yamada, 2012

( Figs. 18 A; 27A; 48A, B; 55B; 62A; 80A, B; 81A–F; 88E; 92A)

Microtopsis takedai Komai, Ng & Yamada, 2012: 149 , figs. 1‒5 [type localilty: Japan, Ryukyu Is.].

Type material. Holotype male (2.4 × 3.1 mm) (CBM-ZC 10491), Japan, Ryukyu Is , Okinawa, Nago.

Paratype: female (2.8 × 3.4 mm) (CBM-ZC 10492), male and female (ZRC 2012.0146), type locality.

Other material examined. Japan. 1 male (damaged) , 1 female (3.6 × 2.7 mm) ( ZRC 2012.0146 ), Awa, Nago , Okinawa, 13 m, scuba diving, Y. Yamada coll., 0 2.01.2011.

Diagnosis. Carapace ( Fig. 18 A; Komai et al. 2012: figs. 1; 2A; 2B) subtrapezoidal, 1.2‒1.3 wider than long; front nearly straight; anterolateral margins arcuate, minutely dentate, without distinct lobes or teeth; dorsal surface almost smooth except for minute granules on lateral surfaces. Epistome ( Fig. 27 A; Komai et al. 2012: fig. 2C) slightly depressed; posterior margin with widely semicircular median lobe with median fissure, semicircular lateral margins without fissures. Eye peduncle ( Fig. 27 A; Komai et al. 2012: fig. 2B) filling orbit, long, mobile; cornea reduced, pigmented. Third maxillipeds ( Fig. 80 A; Komai et al. 2012: fig. 3A) not filling buccal cavern when closed; merus subcircular, anteroexternal angle rounded, narrower than ischium; ischium quadrate, widened inner margin, about same length as merus ( Fig. 80 A; Komai et al. 2012: 3A). Chelipeds ( Figs. 18 A; 48A, B; Komai et al. 2012: figs. 3B, D; 5A, B) subequal in length, slightly dissimilar in female, heteromorphic in males; cutting margins of both chelipeds of females, minor in males with dense row of short setae ( Fig. 48 B; Komai et al. 2012: figs. 3D, 5A, B), largest chela of male ( Fig. 48 A; Komai et al. 2012: 3B) high, with broad teeth on pollex, dentate dactylus. Inner margin of cheliped carpus ( Fig. 18 A; Komai et al. 2012: 3C, E) with short tooth. Ventral surface of cheliped merus with short row of low microscopic tubercles on posterior outer margin in both sexes. Meri of ambulatory legs unarmed; P5 merus 0.5 cl in paratype female. Fused thoracic sternites 1, 2 ( Fig. 55 B; Komai et al. 2012: fig. 2D) broadly triangular, proportionally long, short; fused sternites 3, 4 ( Figs. 88 E; 92A; Komai et al. 2012: fig. 2E) relatively broad. Male pleon ( Figs. 55 B; 62A; 80B; Komai et al. 2012: fig. 2D; 2H) with lateral margins of somite 6, fused somites 3‒5 convex; telson proportionally short; postero-lateral regions slightly swollen. Sterno-pleonal cavity deep. Press-button for pleonal holding ( Komai et al. 2012: fig. 2G) as small, short tubercle posterior to thoracic sternal suture 4/5 near edge of sterno-pleonal cavity. G1 ( Fig. 81 A‒E; Komai et al. 2012: fig. 4A‒E) stout, short, median part distinctly twisted, distal part slightly twisted, distal segment with short spinules. G2 ( Fig. 81 F); Komai et al. 2012: fig. 4F) slightly curved, slender, pointed distal segment, almost as long as G1. Somites of female pleon ( Fig. 88 E; Komai et al. 2012: fig. 5D) with convex lateral margins; telson proportionally short. Sterno-pleonal cavity of female ( Fig. 92 A; Komai et al. 2012: fig. 5C) moderately deep, vulvae far apart from each other on outer margins of cavity close to suture 5/6.

Remarks. The third maxilliped merus is incorrectly described and illustrated by Komai et al. (2012: fig. 3A). It is not subtriangular, but rather more subcircular, with the anterior margin even rather than distinctly produced. The “supplementary plate” ( Fig. 62 A), which is about the same short length along thoracic sternite 8 and reaches episternite 7 in the paratype male (ZRC 2012.0146), is not as narrow and not reaching the posterior edge of the pleon as depicted in the holotype by Komai et al. (2012: fig. 3E).

Distribution. Known only from Japan. Depth: 13 m.

Figures

FIGURE 18. Overall dorsal view of species of Microtopsis. A, M. takedai, Japan: paratype female 3.6 × 2.7 mm (ZRC 2012.0146); B, M. teschi n. sp., Indonesia: holotype male 1.5 × 2.1 mm (NNM-ZMA); C, M. teschi n. sp., Indonesia: paratype male 1.5 × 1.9 mm (NNM-ZMA).

FIGURE 27. Frontal view of species of Megaesthesius and Microtopsis. A, Microtopsis takedai, Japan: paratype female 3.6 × 2.7 mm (ZRC 2012.0146); B, Megaesthesius sagedae, Singapore: male 2.5 × 3.0 mm (ZRC 1995.883); C, Megaesthesius migmus n. sp., Philippines: holotype male 4.4 × 4.9 mm (NMCR); D, Alainthesius signatus n. sp., Madagascar: paratype female 2.7 × 3.0 mm (MNHN-IU- 2013 - 9471); E, Alainthesius bertrandi n. sp., New Caledonia: holotype male 3.3 × 4.1 mm (MNHN-IU- 2013 - 9073); F, Alainthesius bertrandi n. sp., Papua New Guinea: female 5.6 × 6.9 mm (MNHN-IU- 2013 - 9012).

FIGURE 48. Chelae of species of Megaesthesius, Alainthesius n. gen. and Microtopsis. A, B, Microtopsis takedai, Japan: holotype male 2.4 × 3.1 mm (after Komai et al. 2012: fig. 3 B, D); C, Megaesthesius sagedae, Singapore: male 2.5 × 3.0 mm (ZRC 1995.883); D, Megaesthesius migmus n. sp., Philippines: holotype male 4.4 × 4.9 mm (NMCR); E, Megaesthesius yokoyai, Japan: male (after Takeda & Miyake 1969: fig. 4 d); F, Alainthesius signatus n. sp., Madagascar: holotype male 3.5 × 3.8 mm (after Crosnier 1975: fig. 1 d); G, Alainthesius bertrandi n. sp., New Caledonia: holotype male 3.3 × 4.1 mm (MNHN- IU- 2013 - 9073); H, Alainthesius bertrandi n. sp., Papua New Guinea: female 5.6 × 6.9 mm (MNHN-IU- 2013 - 9012).

FIGURE 55. Anterior thoracic sternum and male pleon of species of Statommatia n. gen., Microtopsis and Megaesthesius. A, Statommatia granulosa n. sp., New Caledonia: holotype male 4.1 × 4.7 mm (MNHN-IU- 2013 - 9454); B, Microtopsis takedai, Japan: paratype male, carapace damaged (ZRC 2012.0146); C, Megaesthesius sagedae, Singapore: male 2.5 × 3.0 mm (ZRC 1995.885); D, Megaesthesius migmus n. sp., Philippines: holotype male 4.4 × 4.9 mm (NMCR); E, Alainthesius signatus n. sp., Madagascar: holotype male 2.5 × 3.3 mm (MNHN-IU- 2013 - 9472); F, Alainthesius bertrandi n. sp., New Caledonia: holotype male 3.3 × 4.1 mm (MNHN-IU- 2013 - 9073).

FIGURE 62. Thoracic sternites 7 and 8 and male pleon of species of Microtopsis and Megaesthesius. A, Microtopsis takedai, Japan: paratype male, carapace damaged (ZRC 2012.0146); B, Megaesthesius sagedae, Singapore: male 2.5 × 3.0 mm (ZRC 1995.885); C, Megaesthesius migmus n. sp., Philippines: holotype male 4.4 × 4.9 mm (NMCR); D, Alainthesius bertrandi n. sp., New Caledonia: holotype male 3.3 × 4.1 mm (MNHN-IU- 2013 - 9073).

FIGURE 80. Third maxilliped and male pleon of species of Microtopsis. A, B, M. takedai, Japan: holotype male 2.4 × 3.1 mm (after Komai et al. 2012: figs. 3 A, 2 H, respectively); C, D, F, M. teschi n. sp., Indonesia: holotype male 1.5 × 2.1 mm (NNM- ZMA); E, M. teschi n. sp., Indonesia: paratype 1.5 × 1.9 mm (NNM-ZMA). A, left third maxilliped; B, F, male pleon; C, right third maxilliped (denuded, exopod not drawn); D, left third maxilliped (denuded, exopod not drawn); E, right third maxilliped (denuded). Scales = 0.5 mm.

FIGURE 81. Gonopods of species of Microtopsis. A ‒ F, M. takedai, Japan: holotype male 2.4 × 3.1 mm (after Komai et al. 2012: fig. 4); G ‒ N, M. teschi n. sp., Indonesia: holotype male 1.5 × 2.1 mm (NNM-ZMA). A ‒ C, G ‒ I, left G 1; D, E, J ‒ L, distal part of left G 1; F, M, left G 2; N, distal part of left G 2. Scales: G ‒ I, M = 0.1 mm; J ‒ L = 0.05 mm; N = 0.01 mm.

FIGURE 88. Female thoracic sternum and pleon of species of Statommatia n. gen., Tenagopelta n. gen., Microtopsis and Megaesthesius. A, Statommatia apta, Philippines: female 8.5 × 10.6 mm (ZRC 2015.238); B, Statommatia malagasy n. sp., Madagascar: paratype female 9.4 × 8.1 mm (ZRC 2015.215); C, Tenagopelta pacifica n. sp., Philippines: female 9.2 × 10.4 mm (ZRC 2015.187); D, Tenagopelta brachyphallus n. sp., Australia: female 6.9 × 7.6 mm (NMV J 61680); E, Microtopsis takedai, Japan: paratype female 3.6 × 2.7 mm (ZRC 2012.0146); F, Megaesthesius sagedae, Singapore: female 3.0 × 3.6 mm (ZRC 2013.1804); G, Megaesthesius migmus, Philippines: paratype female 3.9 × 4.5 mm (ZRC 2015.245); H, Alainthesius bertrandi n. sp., Papua New Guinea: female 5.6 × 6.9 mm (MNHN-IU- 2013 - 9012). Vulvae exposed in E.

FIGURE 92. Vulvae of species of Microtopsis and Megaesthesius. A, Microtopsis takedai, Japan: paratype female 3.6 × 2.7 mm (ZRC 2012.0146); B, Megaesthesius sagedae, Singapore: female carapace length 2.9 mm, sides damaged (ZRC 1995.883); C, Megaesthesius migmus n. sp., Philippines: paratype female 3.9 × 4.5 mm (ZRC 2015.245); D, Alainthesius bertrandi n. sp., Papua New Guinea: female 5.6 × 6.9 mm (MNHN-IU- 2013 - 9012).