Sesarmops mora, Li & Shih & Ng, 2020

Li, Jheng-Jhang, Shih, Hsi-Te & Ng, Peter K. L., 2020, Paralbunea dayriti, Zoological Studies 59 (16), pp. 1-32 : 17-29

publication ID	https://doi.org/ 10.6620/ZS.2020.59-16
persistent identifier	https://treatment.plazi.org/id/816BA245-7E2D-FFBD-33DD-FBABFD98F8AF
treatment provided by	Felipe
scientific name	Sesarmops mora
status

Treatment

Sesarmops mindanaoensis ( Rathbun, 1914) View in CoL ( Figs. 11A, B View Fig , 12–14 View Fig View Fig View Fig )

Sesarma (Sesarma) mindanaoense Rathbun, 1914: 75 View in CoL .

Sesarmops mindanaoensis View in CoL – Serène and Soh 1970: 401, 406; Ng et al. 2008: 223; Liu 2013: 32, fig. 2.

Material examined: Holotype female (19.6 × 18.2) ( USNM 45765 About USNM ), small stream south side of Cotabato, Mindanao, Philippines, coll. 20 May 1908. Philippines: Kawasan, Cebu: 1 male (34.1 × 31.6), 1 female (35.6 × 32.4) ( ZRC 2014.0285 View Materials ), coll. H.-C. Liu, 3 December 2001; 5 males (30.8 × 29.9, 30.7 × 28.7, 31.6 × 29.1, 24.1 × 21.8, 23.5 × 21.6), 2 females (33.7 × 30.7, 29.0 × 26.7) ( ZRC 2019.1658 View Materials ), coll. P. K. L. Ng, 30 July 2003; 1 male (36.4 × 35.0) ( ZRC 2019.1657 View Materials ), 1 male (31.2 × 31.3) (NCHUZOOL 16333), 2 females (27.9 × 26.4, 26.0 × 24.9) ( ZRC 2019.1657 View Materials ), coll. J.- J. Li, 6 September 2018; Loboc R., Bohol: 1 male (24.1 × 23.5), 3 females (18.6 × 17.5, 18.1 × 16.9) ( ASIZ 72948 ), 1 male (22.5 × 21.7), 1 female (18.8 × 17.8) ( ZRC 2019.1110 View Materials ), 1 female (16.4 × 15.4) ( ASIZ 72948 ), Philippines: Loboc R., Bohol, coll. H.-C. Liu et al., 19 February 2003. Taiwan: 1 female (25.6 × 23.3) (NCHUZOOL 16334), 1 female (24.8 × 23.5) (NCHUZOOL 15858), Gangkou R. estuary, Pingtung, coll. J.-J. Li, 18 May 2017.

Diagnosis of male: Carapace ( Figs. 12A, E View Fig , 14A, B View Fig ) nearly square in dorsal view, 1.0 ± 0.04 times broader than long (n = 4); regions well defined, separated by shallow grooves; postfrontal region distinct, separated into 4 lobes by deep grooves; front deflexed downwards, margin distinctly concave in dorsal view. Anterolateral margin with large triangular, exorbital angle and smaller, acutely triangular, epibranchial tooth; lateral margin straight, slightly divergent posteriorly. Cornea reaching edge of external orbital tooth. Chelipeds ( Figs. 12F, G View Fig , 16C, D View Fig ) robust, outer surface with numerous rounded granules, with a prominent line of tubercles along inner palm surface; dactylus curved, dorsal margin with numerous granules; proximal part of fixed-finger slightly concave, smooth. Ambulatory legs ( Fig. 12A, E View Fig ) slender; P3 and P4 subequal, longer than others, about 2.4 ± 0.1 times carapace width (n = 4). P3 merus 2.8 ± 0.1 times as long as broad (n = 4); upper margin with acute subdistal spine. Propodus of P3 3.0 ± 0.1 times as long as broad (n = 4), with accessory stria on inferior proximal portion of outer surface, dorsal and ventral margins with short stiff setae. Dactylus of P3 0.6 ± 0.1 times length of propodus (n = 4), slightly curved, terminating in acute calcareous tip; dorsal and ventral margins with short stiff setae. Pleon ( Fig. 12B View Fig ) relatively broad, all somites free. Telson semicircular, evenly rounded, as long as preceding somite, base of telson not inserted in somite 6. G1 ( Figs. 16H, I View Fig , 17B, C View Fig ) straight, relatively stout; apical process short, chitinous part short, ending in truncate tip; setae long, simple, originating at base of apical process. G2 shorter than quarter length of G1.

Female: Carapace ( Figs. 12C View Fig , 13A, B View Fig , 15A View Fig ) more convex and broader than male, 1.1 ± 0.4 times broader than long (n = 6). Chelipeds ( Figs. 13E View Fig , 14D View Fig , 15C View Fig ) smaller than male. P3 merus slightly stouter than male, 2.7 ± 0.1 times as long as broad (n = 6). Pleon ( Figs. 13H View Fig , 14G View Fig , 15B View Fig ) wide, rounded, telson semicircular, base partially inserted in somite 6. Vulva ( Figs. 16G View Fig , 17D View Fig ) near anterior edge of sternite 5, central operculum tubular, oval shaped, directed anteriorly; posterior and anterior sternal vulvar covers low.

Colouration in life: Carapace and legs dark or light brown, without prominent spots; male chelipeds purple or reddish purple, cornea greenish yellow ( Figs. 11A, B View Fig , 12 View Fig ; Liu 2013). Preserved small specimens with some speckling on legs.

Distribution: Taiwan (Pingtung) and Philippines (Cebu and Bohol).

Ecology: Similar to Sesarmops impressus (H. Milne Edwards, 1837) in Taiwan and Philippines, but it has sometimes been found to climb large rocks and trees in the Philippines (J-J Li, personal observation).

Remarks: Rathbun (1914: 75–76) described Sesarma (Sesarma) mindanaoensis from a relatively small but adult female specimen (19.6 × 18.2 mm) from a stream in Cotabato in Mindanao, Philippines. No figures were provided, but the author compared it to Pseudosesarma modestum (De Man, 1902) and Sesarmoides longipes (Krauss, 1843) . On the basis of the description, Serène and Soh (1970: 401) transferred the species to their new genus, Sesarmops , without discussion. Liu (2013) mentioned there is a population of “ Sesarmops mindanaoensis ” in Kawasan, Cebu, Philippines, but did not elaborate on the matter. In the ZRC and/or ASIZ contain many specimens from the Philippines and Indonesia that were identified as Sesarmops mindanaoensis by the third author, Christoph Schubart and H-C Liu. This identification was based on comparisons with the holotype female almost 20 years ago, but none of the data have been published.

The present study of the specimens, including new material from Taiwan as well as the type of S. mindanaoensis , confirms their conspecificity. Comparisons of similarly sized female specimens from the Philippines with the type of S. mindanaoensis show that they share many key characters, including the gentle convexity of the dorsal carapace surface (when viewed frontally); the shape of the external orbital angle (acutely triangular and directed obliquely outwards) ( Figs. 13B View Fig , 14B View Fig ); relatively more slender ambulatory meri and propodi where the dorsal and ventral margins of P4 and P5 are lined with dense short setae and scattered long setae ( Figs. 13F, G View Fig , 14E, F View Fig ); and the outer surface of the chela is smooth or almost so ( Figs. 13E View Fig , 14D View Fig , 15C View Fig ). The P2–P5 leg proportions may be slightly asymmetrical in some specimens. In the holotype female, the left P3 and P4 propodi are slightly longer ( Fig. 13F View Fig ) than those on the right P3 and P4 ( Fig. 13G View Fig ). There is one female specimen (21.5 × 19.7 mm, ZRC 2014.285) obtained from the Philippines which is similar in size to the holotype female and agrees with it in almost all aspects ( Fig. 14 View Fig ), except that its left P2 and P3 propodi are slightly shorter ( Fig. 14E View Fig ) than those on the right instead ( Fig. 14F View Fig ). The ambulatory leg characters, however, do vary slightly. In another similarly sized female from the Philippines (18.8 × 17.8 mm, ZRC 2019.1110), the P4 dactylus and propodus appear proportionately longer and more slender, and the setae lining the margins of the P2–P5 propodus and dactylus are distinctly sparser ( Fig. 15E, F View Fig ) compared to the holotype female. Examining the series of specimens on hand, however, the differences in P3 and P4 meri and propodi, are not significant at the species-level as they are too variable. That being said, none are ever as short and stout as those of S. impressus ( Fig. 18E, F View Fig ). The density of setae on the margins of the ambulatory propodus and dactylus varies in some specimens of S. mindanaoensis , sometimes appearing shorter and less dense; but it is always present ( Figs. 13F, G View Fig , 14E, F View Fig , 15E–H View Fig ).

C o m p a r i n g t h e h o l o t y p e f e m a l e o f S. m i n d a n a o e n s i s w i t h s i m i l a r l y s i z e d f e m a l e S. impressus , the dorsal surface of the later species is more prominently inflated, the external orbital tooth is clearly directed anteriorly, the ambulatory meri and propodi are distinctly shorter and the outer surface of the chela is distinctly granulated ( Fig. 18A–D View Fig ).

Sesarmops mora n. sp. ( Figs. 11C, D View Fig , 19–21 View Fig View Fig View Fig ) urn:lsid:zoobank.org:act:93C54D7B-2847-4A82-A9A2-D4A3CEC83A24

Sesarma frontalis – De Man 1892: 334, pl. 19(13). (not Sesarma frontale A. Milne-Edwards, 1869 View in CoL = Sesarma impressa H. Milne Edwards, 1837 View in CoL ).

Material examined: Holotype: 1 male (27.7 ×

25.5) (NCHUZOOL 16137), Gangkou R. estuary, Pingtung, Taiwan (21°59'17.3"N 120°50'01.6"E), coll. J.-J. Li, 18 May 2017. Paratypes: 2 females (28.0 × 25.8, 25.2 × 22.6) (NCHUZOOL 16335), same locality as holotype, coll. J.-J. Li, 18 May 2017; 1 female (25.8 × 23.5) (NCHUZOOL 16336), same locality as holotype, coll. J.-J. Li, 11 August 2017; 1 male (13.1 × 13.0) (NCHUZOOL 16337), same locality as holotype, coll. J.-J. Li, 25 September 2018; 1 male (26.0 × 24.2) ( ZRC 2019.1111), same locality as holotype, coll. J.- J. Li, 10 June 2019. Others: Philippines: Kawasan,

Cebu: 2 males (27.5 × 24.1, 22.4 × 20.7) ( ZRC 2019.1653), coll. H.-C. Liu, 2 December 2001; 5 males (33.3 × 30.4, 33.3 × 30.0, 27.7 × 25.6, 29.2 × 26.5, 22.2 × 20.4), 5 females (24.0 × 21.0, 19.6 × 17.1, 19.1 × 17.5, 16.0 × 14.2, 14.2 × 12.6) ( ZRC 2019.1655), coll. P. K. L. Ng and C. D. Schubart, 3 December 2001; 2 males (25.0 × 23.1, 21.7 × 19.6) ( ZRC 2019.1656), coll. N. K. Ng et al., 2 January 2002; 1 male (31.5 × 28.8), 1 female (27.2 × 24.8) ( ASIZ 72950), coll. H.-C. Liu et al., 14 February 2003; 1 male (27.7 × 25.3), 1 female (25.3 × 23.9) ( ZRC 2019.1654), coll. P. K. L. Ng et al., 30 July 2003; 1 male (27.3 × 25.1), 1 ovig. female (26.4 × 23.8) ( ZRC 2012.0434), coll. P. K. L. Ng and P. Y. C. Ng, December 2010; 1 male (28.6 × 28.1) (NCHUZOOL 14910), coll. J.-J. Li, 6 September 2018. Indonesia: Manado Murex Resort, Sulawesi: 1 female (22.3 × 20.3) ( ZRC 2019.1661), coll. P. K. L. Ng et al., 17 July 2003.

Diagnosis of male: Carapace ( Fig. 19A, E, F View Fig ) nearly trapezoid in dorsal view, 1.1 ± 0.04 times broader than long (n = 4); regions well defined, separated by shallow grooves; postfrontal region distinct, separated into 4 lobes by deep grooves; front deflexed downwards, margin distinctly concave in dorsal view. Anterolateral margin with large triangular, exorbital angle and smaller, acutely triangular, epibranchial tooth; lateral margin straight, divergent posteriorly ( Fig. 21A View Fig ). Chelipeds ( Figs. 19H View Fig , 20C, E View Fig ) robust, outer surface with numerous rounded granules; dactylus curved, dorsal margin with numerous granules; proximal part of fixed-finger slightly concave, smooth. Ambulatory legs ( Figs. 19A, E, F View Fig , 20G View Fig ) slender; P3 and P4 subequal, longer than others, about 2.3 ± 0.1 times carapace width (n = 4). P3 merus 2.6 ± 0.1 times as long as broad (n = 4); upper margin with acute subdistal spine. Propodus of P3 3.2 ± 0.1 times as long as broad (n = 4), with accessory stria on inferior proximal portion of outer surface, dorsal and ventral margins with short stiff setae. Dactylus of P3 0.8 ± 0.1 times length of propodus (n = 4), slightly curved, terminating in acute calcareous tip; dorsal and ventral margins with short stiff setae. Pleon ( Fig. 19B View Fig ) relatively broad, all somites free. Telson semicircular,

evenly rounded, as long as preceding somite, base of telson partially inserted in somite 6. G1 ( Figs. 20J, K View Fig , 21B–D View Fig ) straight, relatively stout; apical process very short, chitinous part short, ending in truncate tip; setae long, simple, originating at base of apical process. G2 shorter than quarter length of G1.

Females: Carapace ( Fig. 19D View Fig ) more convex and broader than male, 1.1 ± 0.1 times broader than long (n = 4). Chelipeds ( Fig. 19D, F View Fig ) smaller than male. P3 merus stouter than male, 2.2 ± 0.1 times as long as broad (n = 4). Pleon wide, rounded, telson semicircular, base partially inserted in somite 6. Vulva ( Figs. 20I View Fig , 21E View Fig ) on anterior edge of sternite 5, operculum low, oval shaped; posterior and anterior sternal vulvar covers low.

Etymology: The name is derived from the Latin “mora ” for delay and procrastination; alluding to the long time it has taken the third author to formally describe this species. The name is used as a noun in apposition.

Colouration in life: Carapace and legs dark brown, without speckling; chelipeds reddish purple to purple ( Figs. 11C, D View Fig , 19 View Fig ).

Distribution: Taiwan (Pingtung), Philippines (Cebu and Bohol) and Indonesia (Manado, Sulawesi).

Ecology: The habitats of Sesarmops mora n. sp. in Taiwan and Cebu are the river banks far above the high intertidal zone in river estuaries, with muddy substrate and sometimes mixed with some rocks. This species is sympatric with S. mindanaoensis , S. impressus , S. intermedius and Bresedium brevipes in Taiwan (Gangkou R. estuary); or with S. mindanaoensis and B. brevipes in the Philippines (Kawasan, Cebu).

Remarks: Sesarmops mora n. sp. resembles Sesarmops impressus (H. Milne Edwards, 1837) in overall morphology, but differs markedly in having the dorsal surface of the carapace more prominently setose, with numerous clumps of short setae ( Fig. 16 View Fig ) (vs. carapace more glabrose in S. impressus ); the lateral margins of the carapace are more prominently diverging posteriorly ( Fig. 19A, E, F View Fig ) (vs. more quadrate in S. impressus ); the ambulatory merus is proportionately longer (length to width ratio ca. 2.4) ( Fig. 19A, E, F View Fig ) (vs. ambulatory merus relatively shorter in S. impressus , with the length to width ratio ca. 2.2); the length of the adult male telson is subequal to the width ( Fig. 19B View Fig ) (vs. telson length slightly less than the width in S. impressus ); the length of male pleonal somite 6 is proportionately shorter (length to width ratio ca. 2.3) (vs. somite 6 relatively longer, with length to width ratio ca. 2.6 in S. impressus ); and the elongated chitinous distal part of the G1 is less strongly bent obliquely outwards ( Fig. 20J, K View Fig ) (vs. bent more strongly in S. impressus ). Their colours in life differ markedly—the dorsal surface of the carapace of S. impressus is brown with the lateral margins cream or pale yellow; and the outer surface of the chela a uniform purple with white grains. In S. mora , the carapace is a uniform dark to purplish brown without any trace of light-coloured lateral margins ( Fig. 19A, E, F View Fig ), and the outer surface of the chela is dark purple on the dorsal two-thirds and white on the ventral one-third, without white grains ( Fig. 19C, H View Fig ). These differences are valid for the large series of specimens of S. impressus we have examined from Indonesia, Taiwan, Japan, Philippines and Guam.

Sesarmops mora n. sp. is superficially similar to the poorly known P. modestum (from Ternate Island, near Halmahera, Indonesia). Comparing the holotype of P. modestum with that of S. mora , the most obvious characters to distinguish the two species are the relatively narrower carapace, the male telson is distinctly inserted into somite 6 and the G1 is more elongate and slender in S. mora ( Figs. 19A, B, D– F View Fig , 20J, K View Fig , 21B–D View Fig ) (vs. carapace distinctly wider, the male telson is not inserted into somite 6 and the G1 is proportionately stout and shorter in P. modestum . Pseudosesarma modestum will be redescribed and figured at length in a separate paper revising the genus with allied new species by Schubart and Ng (2020).

DNA Analyses

A 579 bp segment of 16S and 658 bp segment of COI from 12 species (53 specimens) of the Sesarmidae were amplified and aligned ( Table 1). A phylogenetic tree of the combined markers was reconstructed using BI and ML analyses ( Fig. 22 View Fig ). There are clearly two major clades for most of the species studied, with one clade composed of Bresedium eurypleon n. sp., B. brevipes , Sesarmops impressus 1, S. impressus 2 and S. mora n. sp.; the second clade includes the Sesarmops intermedius complex [including S. sinensis (H. Milne Edwards, 1853) ], Pseudosesarma patshuni (Soh, 1978) and Chiromantes dehaani complex [including C. neglectum (De Man, 1887) and C. magnus Komai and Ng, 2013 ]. Sesarmops mindanaoensis is very different from other species on the tree, coming out far from all the other species. Pseudosesarma can be divided into three groups, (1) P. patshuni ; (2) P. bocourti (A. Milne-Edwards, 1869) and P. edwardsii ; and (3) P. crassimanum (De Man, 1887) . The phylogenetic tree shows that Sesarmops and Pseudosesarma are clearly polyphyletic. The two new species, B. eurypleon and S. mora , described in this study are supported genetically, some species cannot be separated successfully from their closely related species, including Sesarmops intermedius and S. sinensis ; as well as Chiromantes dehaani , C. neglectum and C. magnus .