Cebudonus poppeorum, Ng, Peter K. L., 2014

Ng, Peter K. L., 2014, Cebudonus poppeorum, a new genus and new species of eumedonine crab (Crustacea: Decapoda: Brachyura: Pilumnidae) from the Philippines, Zootaxa 3815 (1), pp. 94-102 : 96-101

publication ID	https://doi.org/ 10.11646/zootaxa.3815.1.6
publication LSID	lsid:zoobank.org:pub:51A13505-C327-49F7-8FCC-0C407927C76C
DOI	https://doi.org/10.5281/zenodo.6131212
persistent identifier	https://treatment.plazi.org/id/523B87B7-FF96-2703-06D6-2558FC1BD05F
treatment provided by	Plazi
scientific name	Cebudonus poppeorum
status	gen. nov.

Treatment

Cebudonus poppeorum View in CoL n. gen., n. sp.

( Figs. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Material examined. Holotype: male (10.8 × 11.9 mm) ( NMCR), Punta Engaño, Mactan Island, Cebu, Visayas, 180–250 m, coll. local trawler, 2013. Paratypes: 1 dried female (10.6 × 12.5 mm) ( ZRC 2014.0211), same data as holotype; 1 female (8.1 × 9.2 mm) ( ZRC 2014.0212), Punta Engaño, Mactan Island, Cebu, Visayas, 180–210 m, coll. local trawler, 2012; 1 dried male (8.3 × 9.2 mm) ( ZRC 2014.0213), Talingting, Siquijor, Visayas, 120 m, coll. local fishermen, tangle nets, 2013; 1 female (10.9 × 12.4 mm) ( ZRC 2014.0214), Talingting, Siquijor, Visayas, 120 m, coll. local fishermen, tangle nets, 2013; 1 female (12.5 × 14.5 mm) (GTP), Talingting, Siquijor, Visayas, 150 m, coll. local fishermen, April 2013; 1 male (9.9 × 10.3 mm) (GTP), Basul Island, Surigao, northern Mindanao, 80- 100 m, coll. local trawlers, January 2013. All locations in central Philippines.

Comparative material. See ZRC material examined in Chia & Ng (1998, 2000), Chia et al. (1995, 1999) and Ng & Chia (1999). In addition: Zebrida adamsii White, 1847: 1 dried female (9.8 × 9.7 mm) ( ZRC), Molocaboc area, north of Negros Island, Philippines 10–25 m, coll. local fisherman, 2014; 1 dried female (12.9 × 12.0 mm) ( ZRC), Molocaboc area, north of Negros Island, Philippines, 10–25 m, coll. local fisherman, 2014.

Diagnosis. As for genus.

Description. Carapace pentagonal; dorsal surface gently convex, covered with numerous small pits, otherwise smooth; regions poorly demarcated, cardio-gastric groove shallow ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 ). Front with 2 long pseudorostral spines, subparallel, ca. 0.4 times total carapace length; surface finely pitted; tip straight, rounded; spines separated by broad, U-shaped cleft; spines confluent with supraorbital margin ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 , 3 View FIGURE 3 C). Orbit small, rounded; cornea protrudes beyond edge of carapace when retracted ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 , 3 View FIGURE 3 A–C). Anterolateral margin concave, entire, demarcated by small, sharp external orbital tooth, large, broadly triangular, sharp lateral tooth, projecting laterally, not upturned, dorsal surfaces adjacent to it gently convex, not flattened ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 , 3 View FIGURE 3 A, 4A). Posterolateral margin almost straight to gently convex; converging strongly to slightly sinuous posterior carapace margin ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 , 3 View FIGURE 3 E). Suborbital margin short, concave; inner tooth short, rounded ( Fig. 3 View FIGURE 3 B). Pteryogostomial, subhepatic regions pitted, not pubescent ( Fig. 3 View FIGURE 3 A–C).

Antennae short; basal article free, subrectangular, twice as long as wide; flagellum enters orbit but not extending across length ( Fig. 3 View FIGURE 3 B). Antennules large, folding at ca. 45°; basal article subtrapezoidal, filling about two-thirds of fossa ( Fig. 3 View FIGURE 3 B). Epistome relatively broad longitudinally, covered with small pits except for depressed median part; posterior margin crenulate, with distinct median triangular lobe, separated by distinct fissure ( Fig. 3 View FIGURE 3 A–C).

Outer surfaces of third maxilliped densely covered with small pits ( Figs. 3 View FIGURE 3 C, 4A). Ischium subrectangular, with deep submedian longitudinal sulcus; inner margin dentate ( Figs. 3 View FIGURE 3 C, 4A). Merus subquadrate; anteroexternal angle subauriculiform ( Figs. 3 View FIGURE 3 C, 4A). Carpus short; propodus rectangular; dactylus elongated ( Fig. 4 View FIGURE 4 A). Exopod relatively stout, with distinct flagellum ( Fig. 4 View FIGURE 4 A).

Ambulatory legs long, slender; second leg longest, fourth leg shortest ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 ). Merus elongated, slender; surface with scattered pits; margins rounded, not cristate, almost entire, not distinctly granular except for distal margin; dorsal distal tooth distinct but may be low ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 , 4 View FIGURE 4 E). Carpus smooth, with scattered pits on outer surface ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 , 4 View FIGURE 4 E). Propodus elongated, dorsoventrally flattened; margins entire, ventral margin with numerous short stiff setae; outer surface with scattered pits ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 , 4 View FIGURE 4 D, E). Dactylus gently curved; ventral margin with dense mat of short, stiff setae except for corneous tip; forming distinct dactylo-propodal lock ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 , 4 View FIGURE 4 D, E).

Chelipeds slender, elongated ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 ). Basis-ischium elongated, covered with small pits ( Fig. 3 View FIGURE 3 C). Merus rounded in cross-section; surface covered with numerous small pits, otherswise unarmed ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 , 3 View FIGURE 3 C). Carpus surface with numerous small pits, subovate; long, gently curved, dorsoventrally flattened spine on distal inner angle ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 , 3 View FIGURE 3 F). Chela elongated, margins rounded, not cristate; outer surface strongly pitted; fingers stout, ca. half length of palm, not pigmented, cutting edges with low teeth on distal half, proximal half relatively smooth ( Fig. 3 View FIGURE 3 F).

Thoracic sternum relatively narrow transversely; surfaces distinctly pitted; sternites 1, 2 completely fused, forming triangular plate, separated from sternite 3 by distinct sinuous suture; sternites 3, 4 completely fused, demarcated only by lateral cleft, median depression, sutures otherwise not visible ( Figs. 3 View FIGURE 3 C, 4B). Male abdomen not spanning width of thoracic sternum; sternite 8 visible between abdominal somites 1, 2, coxae of last pair of ambulatory legs ( Fig. 4 View FIGURE 4 E).

Sternoabdominal cavity deep, reaching to median part of fused sternites 3, 4 ( Fig. 3 View FIGURE 3 D). Male abdominal locking mechanism present as knob-like tubercle on distal one-third of sternite 5. Male abdomen broadly triangular, all somites, telson free ( Figs. 3 View FIGURE 3 D, 4C). Somite 1 subrectangular, distal margin deeply concave; somite 2 transversely subovate ( Figs. 3 View FIGURE 3 E, 4C). Somite 3 broadest, subtrapezoidal; somites 4–6 trapezoidal, lateral margins gently concave to sinuous ( Figs. 3 View FIGURE 3 D, 4C). Telson triangular, lateral margins gently convex to sinuous, tip rounded ( Figs. 3 View FIGURE 3 C, D, 4B, C). Penis opening on condyle of coxa of fourth ambulatory leg.

G1 long, slender, sinuous; distal part elongated, straight; distal surfaces with rows of short, to long setae; basal part with plumose setae ( Fig. 4 View FIGURE 4 F, G). G2 short, sigmoid; distal segment short ( Fig. 4 View FIGURE 4 H).

Females and variation. The female specimens agree with the male in almost all non-sexual aspects. The pseudorostral spines in some specimens (e.g., a female 10.6 × 12.5 mm, ZRC 2014.0211) converge along the distal half rather than being subparallel. The female abdomen is subovate, broad, and covers the entire surface of the thoracic sternum; with all the somites and telson free ( Fig. 3 View FIGURE 3 G). The vulvae are large, ovate, without any opercular cover, with the outer margin forming a low rim; and positioned on the anterior half of thoracic sternite 6 ( Fig. 3 View FIGURE 3 H).

Colour. The striking colour of fresh specimens ( Fig. 1 View FIGURE 1 ) remains even in preserved specimens ( Fig. 2 View FIGURE 2 ). The carapace has two broad longitudinal stripes on a reddish-brown background, with the posterolateral margins also white. The broad reddish-brown median stripe extends to the first two abdominal somites. The frontal parts of the carapace (epistome, suborbital and subhepatic regions) are purplish-pink. The chelipeds are generally white to pinkish-white, with the proximal part of the merus, carpal spine, proximal part of the pollex pink. The ambulatory legs are white to reddish-white.

Etymology. It is a pleasure to name this new species after the intrepid father and son team of Guido and Philippe Poppe, renowned malacologists and ardent naturalists. Between the two, they have had a significant influence advancing our knowledge of Philippine natural history over the last decade.

Remarks. The specimens of Cebudonus poppeorum n. gen., n. sp. were collected from depths ranging from 80 to 250 m by trawlers and tangle nets. The general features and its close resemblance to Eumedonus and Gonatonotus strongly suggest that it is an obligate symbiont of urchins. Like species members of these genera, their dorsal carapace surface is also distinctively longitudinally striped in life (cf. Chia & Ng 2000). It is noteworthy that eumedonines that have their carapaces marked with transverse stripes at some stage of their lives are all associated with crinoids (cf. Chia & Ng 1998). The live colour pattern and host of Zebridonus (from northern Australia), which is closely allied to Eumedonus , are not known, but it is also believed to be associated with an echinoid because of its colour pattern. The unusual eumedonine Tauropus (from the South China Sea and Japan), known only from its type species T. egeriae (Gordon, 1947; Chia & Ng 1998) is also probably associated with echinoids but known specimens had no distinctive colour pattern (unpublished data). Guido Poppe commented (in litt. 23 April 2014) that large cidaroid sea urchins were collected together with the crab in Mactan Island. Most urchins belonged to Coelopleurus Agassiz, 1840 (family Arbaciidae ), with C. maillardi (Michelin, 1862) the most common one. It is therefore possible that C. poppeorum n. sp. is associated with this echinoid species.