Cebudonus poppeorum Ng, 2014, n. gen.
Creators: name: Ng, Peter K. L.
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Pilumnidae
Cebudonus
Cebudonus poppeorum

description: Cebudonus poppeorum n. gen., n. sp.
(Figs. 1–4)
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, 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, 2, 3 C). Orbit small, rounded; cornea protrudes beyond edge of carapace when retracted (Figs. 1, 2, 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, 2, 3 A, 4A). Posterolateral margin almost straight to gently convex; converging strongly to slightly sinuous posterior carapace margin (Figs. 1, 2, 3 E). Suborbital margin short, concave; inner tooth short, rounded (Fig. 3 B). Pteryogostomial, subhepatic regions pitted, not pubescent (Fig. 3 A–C).
Antennae short; basal article free, subrectangular, twice as long as wide; flagellum enters orbit but not extending across length (Fig. 3 B). Antennules large, folding at ca. 45°; basal article subtrapezoidal, filling about two-thirds of fossa (Fig. 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 A–C).
Outer surfaces of third maxilliped densely covered with small pits (Figs. 3 C, 4A). Ischium subrectangular, with deep submedian longitudinal sulcus; inner margin dentate (Figs. 3 C, 4A). Merus subquadrate; anteroexternal angle subauriculiform (Figs. 3 C, 4A). Carpus short; propodus rectangular; dactylus elongated (Fig. 4 A). Exopod relatively stout, with distinct flagellum (Fig. 4 A).
Ambulatory legs long, slender; second leg longest, fourth leg shortest (Figs. 1, 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, 2, 4 E). Carpus smooth, with scattered pits on outer surface (Figs. 1, 2, 4 E). Propodus elongated, dorsoventrally flattened; margins entire, ventral margin with numerous short stiff setae; outer surface with scattered pits (Figs. 1, 2, 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, 2, 4 D, E).
Chelipeds slender, elongated (Figs. 1, 2). Basis-ischium elongated, covered with small pits (Fig. 3 C). Merus rounded in cross-section; surface covered with numerous small pits, otherswise unarmed (Figs. 1, 2, 3 C). Carpus surface with numerous small pits, subovate; long, gently curved, dorsoventrally flattened spine on distal inner angle (Figs. 1, 2, 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 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 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 E).
Sternoabdominal cavity deep, reaching to median part of fused sternites 3, 4 (Fig. 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 D, 4C). Somite 1 subrectangular, distal margin deeply concave; somite 2 transversely subovate (Figs. 3 E, 4C). Somite 3 broadest, subtrapezoidal; somites 4–6 trapezoidal, lateral margins gently concave to sinuous (Figs. 3 D, 4C). Telson triangular, lateral margins gently convex to sinuous, tip rounded (Figs. 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 F, G). G2 short, sigmoid; distal segment short (Fig. 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 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 H).
Colour. The striking colour of fresh specimens (Fig. 1) remains even in preserved specimens (Fig. 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.
Distribution. Known so far from central and southern Philippines.
description: Published as part of Ng, Peter K. L., 2014, Cebudonus poppeorum, a new genus and new species of eumedonine crab (Crustacea: Decapoda: Brachyura: Pilumnidae) from the Philippines, pp. 94-102 in Zootaxa 3815 (1) on pages 96-101, DOI: 10.11646/zootaxa.3815.1.6, http://zenodo.org/record/226599