Chiloscyllium plagiosum ( Bennett, 1830 )

Cabebe-Barnuevo, Roxanne, Penuela, Dianne Frances, Delloro Jr., Emmanuel S., Babaran, Ricardo P., Motomura, Hiroyuki & Malay, Maria Celia D., 2025, Cartilaginous fish diversity in the Western Visayas, Philippines, including two putative unidentified species and the first record of Carcharhinus plumbeus (Elasmobranchii: Carcharhiniformes: Carcharhinidae), Acta Ichthyologica et Piscatoria 55, pp. 51-75 : 51-75

Chiloscyllium plagiosum ( Bennett, 1830)

IUCN standard name :: Whitespotted Bambooshark Fig. 4 , Table 1

Material examined.

UPVMI 3123, 441 mm TL, male, fish landing site, Cabalagnan, Nueva Valencia, Guimaras Province, Philippines, October 2021, coll. J. Tubillara.

Morphological description.

Body small, elongated, moderately slender, with lateral dermal ridges. Eyes relatively small without nictitating eyelids; spiracles large and located below eyes. Snout rounded and broad. Mouth small, positioned closer to eyes than to snout tip. Nostrils small, partially covered by broad nasal flap; nasal flap reaching mouth; sensory barbels on each nostril very short. Teeth on both jaws small with single small cusp. Both dorsal fins fully erect, equal in size; posterior margin straight; first dorsal fin originating behind pelvic-fin origin. Anal fin short, originating behind free rear tip of second dorsal fin; positioned just anterior to caudal-fin origin; anal-fin base length shorter than base of lower caudal-fin lobe (9 % vs. 16 % TL, respectively). Pectoral fin slightly larger than dorsal fins, originating just below third gill opening; posterior margin straight. Pelvic fin approximately similar in size to dorsal fins, located just behind pectoral fin and front of first dorsal fin insertion. Caudal fin asymmetrical; subterminal notch well developed; ventral lobe absent. Precaudal pits absent. Gill slits on both sides five, small; fourth and fifth gill slits situated extremely close to one another.

Color of fresh specimen. Body and head surface area light brown with darker transverse bands and covered of numerous white and black spots; underside light brown with numerous white spots and few black spots. Fins brown with numerous white spots.

Color of preserved specimen. Transverse dark brown bands, white and black spots still visible on the body, head, and fins.

Distribution.

Indo – Pacific. western Indian Ocean: Madagascar, India, and Sri Lanka; western Pacific: Indonesia, Philippines, Japan, and New Guinea ( Human 2022).

DNA barcode.

The COI sequence of 617 bp was submitted to GenBank under accession number OR 614480.

Conservation status.

Near Threatened

Remarks.

Chiloscyllium plagiosum has a maximum recorded length of 950 mm ( Compagno and Niem 1998 a). This species can be found at depths ranging from 0–50 m ( Weigmann 2016). Sightings have been reported in Philippine waters, particularly in Cavite, Cebu, Guimaras Island, Manila Bay, Negros Occidental, Negros Oriental, Oriental Mindoro (Calapan), and Palawan ( Compagno et al. 2005; Gonzales 2013).

The specimen was identified as C. plagiosum based on its slender body and tail, anal-fin base shorter than the base length of lower caudal-fin lobe (9 % vs. 16 % TL, respectively), presence of lateral dermal ridges, transverse dark bands, and small white spots. According to Compagno and Niem (1998 a), C. plagiosum is frequently misidentified as Chiloscyllium griseum Müller et Henle, 1838 , Chiloscyllium hasselti Bleeker, 1852 , Chiloscyllium indicum ( Gmelin, 1789) , or Chiloscyllium punctatum Müller et Henle, 1838 . These species all exhibit transverse dark bands on their bodies, especially when young, which often leads to misidentifications. However, C. plagiosum can be distinguished from C. indicum by its shorter anal-fin base compared to the base length of lower caudal-fin lobe (vs. base lengths of anal-fin and lower caudal fin lobe equal in C. indicum ) ( Compagno and Niem 1998 a). Additionally, C. plagiosum is differentiated from C. griseum , C. hasselti , and C. punctatum by the presence of lateral dermal ridges (Fig. 4 B ), which are absent in the latter three species ( Compagno and Niem 1998 a). The identity of the collected specimen was further verified using COI data, which showed it forming a distinct clade with a sequence of C. plagiosum , separate from the clades of the aforementioned closely related species (Fig. 3 ).

Figures

Figure 3. Maximum likelihood phylogenetic tree of partial COI sequences from chimaeras and sharks, constructed using the Kimura 2 - parameter model. Philippine sequences are identified by UPVMI voucher codes, with related genera color-coded. Bootstrap support values (1000 replicates) are shown at nodes, and the scale bar represents evolutionary distance in substitutions per site.

Figure 4. Chiloscyllium plagiosum from Western Visayas, Philippines, UPVMI 3123, 441 mm TL. A body in lateral view B head in dorsal view C oronasal region.