Opecarcinus cathyae, Van Der Meij, 2014

Van Der Meij, Sancia E. T., 2014, A new species of Opecarcinus Kropp & Manning, 1987 (Crustacea: Brachyura: Cryptochiridae) associated with the stony corals Pavona clavus (Dana, 1846) and P. bipartita Nemenzo, 1980 (Scleractinia: Agariciidae), Zootaxa 3869 (1), pp. 44-52 : 45-51

publication ID	https://doi.org/ 10.11646/zootaxa.3869.1.4
publication LSID	lsid:zoobank.org:pub:7A119F04-0C0D-4A08-AC35-77125DBCE566
DOI	https://doi.org/10.5281/zenodo.5514186
persistent identifier	https://treatment.plazi.org/id/9A61262D-F151-FFA8-FF41-078C5F6EFE66
treatment provided by	Felipe
scientific name	Opecarcinus cathyae
status	sp. nov.

Treatment

Opecarcinus cathyae View in CoL sp. nov.

( Figs 1A–E View FIGURE 1 , 2A–E View FIGURE 2 , 3A–F View FIGURE 3 , 4A–E View FIGURE 4 , 5A–D View FIGURE 5 )

Type locality. Creach Reef , Semporna district, Sabah, Malaysia (04°18′58.8"N, 118°36′17.3"E) GoogleMaps

Type material. Holotype (female) and allotype (male). RMNH. Crus.D. 53648a, 10–14 m, host Pavona clavus ( Dana, 1846) , 05.xii.2010, ovig. female (5.5 × 3.8), male (3.3 × 2.6), leg. Z Waheed. Paratypes. RMNH. Crus.D. 53648b, from the same lot as holotype and allotype, 1 ovig. female (3.7 × 3.0), 1 juvenile male (1.6 × 1.1). A damaged male from this lot was used for DNA barcoding .

DNA barcoding. A COI sequence (partially, Folmer et al. 1994) of one of the paratypes (damaged male) has been deposited in GenBank under accession number KM 396420 View Materials .

Additional material. Indonesia. RMNH.Crus.D.53923, S Lela, Gura Ici, Halmahera (00°01′51.2"S 127°15′03.1"E), 10.xi.2009, 3 males, one with epicaridean parasite ( Carcinione platypleura Bourdon, 1983 ) under carapace, host Pavona clavus , leg. SET van der Meij.— RMNH.Crus.D.53916, 3 ovig. females, 1 male, host Pavona clavus , leg. SET van der Meij (same lot as RMNH.Crus.D.53923); RMNH.Crus.D.54202, Baturiri, Lembeh Strait (01°27'34.7"N 125°14'23.1"E), 10 m, 6.ii.2012, 1 male, host Pavona bipartita , leg. SET van der Meij;— RMNH.Crus.D.54214, Teluk Walemetodo, Lembeh Strait (01°24'11.3"N 125°10'20.3"E), 6 m, 15.ii.2012, 1 ovig. female, 1 male, host Pavona bipartita , leg. SET van der Meij. Malaysia (Borneo). RMNH.Crus.D.53656, Mataking I., Semporna district (04°34'57.6"N 118°56'46.5"E), 8.xii.2010, 1 ovig. female, 1 non-ovig. female, host Pavona clavus , leg. BW Hoeksema.— RMNH.Crus.D.53768, Hanging Gardens, Sipadan I., Semporna district (04°06'45.3"N 118°37'29.3"E), 18.xii.2010, 2 ovig. females, host Pavona clavus , leg. Z Waheed.— RMNH.Crus.D.54297, SW Mangsee Great Reef, Kudat (07°27′24.8"N 117°13′21.6"E), 9 m, 22.ix.2012, 1 ovig. female, 1 male, host Pavona clavus , leg. SET van der Meij.— RMNH.Crus.D.54275, Paliuk, Kudat (07°03'17.4"N 117°22'32.6"E), 10.ix.2012, 2 ovig. females, 2 non-ovig. females, 2 males, host Pavona clavus , leg. SET van der Meij.

Description female holotype Carapace vase-shaped, CL 1.4 CW; widest posterior to midlength; anterior third of carapace deflected by about 40°, not sharply set off from posterior carapace, with shallow transverse depression across protogastric region; dorsal surface convex in lateral view, median third concave with scattered small conical tubercles. Mesogastric region slightly inflated with tubercles, cardiointestinal region outlined. Carapace surface ornamented with rounded, conical tubercles; posterior carapace smooth, tubercles most numerous at anterior, lateral carapace; anterolateral margins of carapace granular; anterolateral angle without prominent tubercle; margin inner orbital angle with tubercle. Front slightly concave with small tubercles, width about half of carapace at anterolateral angle. Orbit broadly V-shaped. Pterygostomial region fused to carapace ( Fig. 1A–B View FIGURE 1 ). Brood pouch swollen (ovigerous), many short setae on distal margin (ventral view) ( Fig. 1E View FIGURE 1 ). Posterior carapace, brood pouch margins fringed with many setae ( Fig. 1A, E View FIGURE 1 ).

Antennular peduncle dorsal surface with small tubercles, slightly inflated distally, scarcely inflated mesially; apex of distal projection slightly extending beyond tip of eyestalk; spines on distal margin larger than those on mesial margin. Basal segment strongly tapering anteriorly in ventral view, length 1.5 times width; ventral surface relatively smooth ( Fig. 1E View FIGURE 1 ).

Eyestalk partly exposed dorsally, slightly granular. Cornea anterolateral. Lateral margin of stalk not extending beyond anterolateral angle; distal margin with small spines ( Fig. 1A, E View FIGURE 1 ). Distal segment of antennules with protruding segment, visible from ventral side ( Fig. 1D–E View FIGURE 1 ).

MXP3 with exopod; mesial margin of ischium slightly crenulated; merus with distolateral projection, carpus to dactylus decreasing in size, latter with bundle of setae ( Fig. 1C View FIGURE 1 ).

P1 (chelipeds) slender; merus length 2.8 times height; carpus granular on dorsal margin; propodus with stronger granulation on dorsal margin than carpus; cutting edge fingers entire, tips of fingers slightly crossing when closed ( Fig. 2A View FIGURE 2 ).

P2 stout; merus length 1.8 times height, dorsal margin evenly convex, entire length crenulated, ventral margin straight, smooth; carpus, propodus of similar length with rows of conical tubercles; dactylus smooth, sharp, curved ventrally ( Fig. 2B View FIGURE 2 ).

P3 stout; merus length 1.6 times height, dorsal margin slightly convex, entire length with scattered conical tubercles, ventral margin straight, smooth; carpus, propodus of similar length with conical tubercles on dorsal margin; carpus with small anterior lobe; dactylus smooth, sharp, curved ventrally ( Fig. 2C View FIGURE 2 ).

P4 relatively slender; merus length 1.4 times height, entire length dorsal margin with scattered conical tubercles, ventral margin straight, smooth; carpus, propodus of similar length; carpus with slight anterior lobe; propodus with conical tubercles on dorsal margin; dactylus smooth, sharp, curved ventrally ( Fig. 2D View FIGURE 2 ).

P5 slender; merus length 2.0 times height, straight, smooth margins; carpus, propodus of similar length, margins smooth; dactylus smooth, sharp, curved ventrally ( Fig. 2E View FIGURE 2 ).

Thoracic sternum 1–3 with transverse row of rounded tubercles at midlength, thoracic sternum 4 with fewer tubercles ( Fig. 5B View FIGURE 5 ).

Gonopore (vulva); elliptical, lateral margin with small vulvar cover (examined in paratype).

Description male allotype. Generally similar to holotype, differences outlined hereafter. Carapace vaseshaped, CL 1.3 longer than CW; median third concave with few scattered small conical tubercles. Carapace surface ornamented with few rounded to conical tubercles, fewer than holotype, most numerous at lateral margins; anterolateral margins of carapace with row of small conical tubercles; anterolateral angle without prominent tubercle; inner orbital angle marked with tubercle. Orbit broadly V-shaped, margin somewhat crenulated. ( Fig. 3A–B View FIGURE 3 ). Posterior carapace margins fringed with numerous setae ( Fig. 3A View FIGURE 3 ).

Antennular peduncle dorsal surface with numerous spiny tubercles, slightly inflated distally, scarcely inflated mesially. Basal segment tapering anteriorly in ventral view, length 2.3–2.4 times width; surface relatively smooth ( Fig. 3F View FIGURE 3 ).

Eyestalk partly exposed dorsally. Cornea anterolateral. Lateral margin of stalk not extending beyond anterolateral angle; distal margin with two small spines ( Fig. 3F View FIGURE 3 ). Distal segment of antennules with small protruding segment, visible from ventral side ( Fig. 3D View FIGURE 3 ).

MXP3 with exopod; mesial distal margin of ischium very slightly crenulated; merus with distolateral projection; carpus, propodus dactylus of similar length, dactylus with tuft of setae ( Fig. 3C View FIGURE 3 ).

P1 (chelipeds) somewhat stout; merus length 1.4 times height; carpus granular on dorsal margin; propodus with stronger granulation on dorsal margin than carpus; cutting edge fingers entire, tips of fingers crossing ( Fig. 4A View FIGURE 4 ).

P2 stout; merus length 1.8 times height, dorsal margin slightly convex, entire length with tubercles, slightly larger distally, ventral margin straight, smooth ( Fig. 4B View FIGURE 4 ).

P3 stout; merus length 1.5 times height, dorsal margin evenly convex, entire length with scattered conical tubercles, ventral margin rounded smooth; carpus with anterior lobe ( Fig. 4C View FIGURE 4 ).

P4 stout; merus length 1.1 times height, dorsal margin slightly convex, entire length with scattered conical tubercles, ventral margin straight, smooth; carpus, propodus of similar length with conical tubercles on dorsal margin; carpus with anterior lobe ( Fig. 4D View FIGURE 4 ).

P5 slender; merus length 1.3 times height, margins crenulated, ventral margin relatively straight; carpus slightly shorter than propodus, margins smooth ( Fig. 4E View FIGURE 4 ).

Thoracic sternum 1–3 with transverse row of rounded tubercles at midlength, thoracic sternum 4 with fewer, somewhat scattered tubercles ( Fig. 5D View FIGURE 5 ). Abdomen widest at somite 3, somite 6 not visible in ventral view because of curvature; telson rounded ( Fig. 3E View FIGURE 3 ).

Gonopods; G1: slightly curved laterally, slightly cinched in the middle, apex blunt, distal margin with 6–7 simple, long setae; G2: almost straight, slightly cinched in the middle, apex blunt with two large non-plumose setae at distal margin of the same length as G2.

Variation. The tubercle on the margin of the inner orbital margin is prominent in some individuals only. The setae along the carapace margins are more numerous in large individuals, especially in females.

Colour. Carapace bright orange-red to rust, darker rust on the lateral sides. Cardio-intestinal region outlined by a lighter colouration, off-white in some specimens. Anterolateral region off-white, sometimes with tubercles of contrasting (dark) colour. MXP ischium, merus off-with with orange hue, carpus, propodus, dactylus rust-coloured. P1 to P5 opaque with fine orange network of lines, giving an orange hue. Cornea bright rust colour ( Fig. 5B, C View FIGURE 5 ). Some specimens are quite pale, and lack the intense orange-red colouration. These specimens do have the cardiointestinal region outlined by a lighter colouration and have black chromatophores visible on the carapace, predominantly on the lateral margins ( Fig. 5C View FIGURE 5 ).

Remarks. The orientation of the cornea on the eyestalk was used by Kropp (1989) to separate the species of Opecarcinus into two groups. Opecarcinus cathyae sp. nov. has anterolaterally oriented corneas, which places it in the same group as O. hypostegus , O. granulatus (Shen, 1936) and O. pholeter Kropp, 1989 . The five remaining species of Opecarcinus have terminally oriented corneas. In Opecarcinus hypostegus , an Atlantic species, and O. granulatus the anterior third of the carapace is sharply set off from the posterior carapace and the transverse depression confined to the protogastric region. In O. cathyae sp. nov. and O. pholeter the anterior third is not sharply set off from the posterior carapace and the transverse depression is shallow. The new species can, furthermore, be separated from O. granulatus by the smooth dorsal margin of the P5 carpus in females, and from O. pholeter by the smooth surface of MXP3 and the lack of depressions on the carapace. Opecarcinus cathyae sp. nov. can also be separated from its Indo-West Pacific congeners in this species group by its colour pattern: O. granulatus is opaque with black chromatophores and O. pholeter has nine amber-coloured bands ( Kropp, 1989), whereas O. cathyae sp. nov. is orange-red (rust) overall, with an off-white anterolateral region.

Coral hosts. The new species appears to be strictly associated with the Pavona clavus and P. bipartita , sister species that form a rather distinct lineage within the Agariciidae (F. Benzoni, pers. comm.). In his overview of the Pacific Opecarcinus species , Kropp (1989) does not mention P. clavus and P. bipartita as hosts, hence O. cathyae sp. nov. is the first species described in association with these corals. A figure of the dwelling of O. cathyae sp. nov. in P. clavus was provided by Hoeksema & van der Meij (2013: Fig. 1b, c View FIGURE 1 ). In P. bipartita the new species lives in tunnels on the coral surface. According to Kropp (1989) host specificity has been observed for O. aurantius Kropp, 1989 (host Pavona minuta Wells, 1954 ), O. peliops Kropp, 1989 (host P. duerdeni Vaughan, 1907 ), and O. lobifrons Kropp, 1989 (host Gardineroseris planulata ( Dana, 1846)) . Opecarcinus cathyae sp. nov. also seems to be host-specific by inhabiting two closely related species: P. clavus and P. bipartita .

Ecology. The carapace and pereiopods are fringed with numerous setae ( Fig. 1A, E View FIGURE 1 ; Fig. 2A–E View FIGURE 2 ), which, in case covered with trapped sediment, can give the crab a mucky appearance.

Distribution. So far known from Indonesia and Malaysian Borneo. The holotype of P. clavus , illustrated by Veron & Pichon (1980), appears to have a dwelling of a cryptochirid. This coral species was described by Dana (1846) from Fiji, which is therefore a possible distribution record for O. cathyae sp. nov. Pavona clavus is widespread, occurring from the Red Sea and East Africa to the eastern Pacific ( Veron & Pichon 1980; Veron 2000). Pavona bipartita also shows a wide range, occurring from the Red Sea and East Africa to the Central Pacific ( Veron 2000). It is thus possible that O. cathyae has a wider distribution based on the distribution ranges of its host corals. Opecarcinus cathyae sp. nov. can be very abundant locally, with estimated densities up to 200 per m -2 because its coral host can form large monospecific stands ( Veron & Pichon 1980; Hoeksema & van der Meij 2013).

Etymology. This species is named after Cathy [Catherine] DeGeorge to celebrate 15 years of Trans-Atlantic friendship.