Hexanchus griseus (Bonnaterre, 1788)

Del Moral-Flores, Luis Fernando, Lozano-Quiroz, Sergio Alejandro, Escartín-Alpizar, Viridiana R., García-Mercado, Eduardo & Hernández-Ortiz, Rolando, 2025, First record of the bluntnose sixgill shark, Hexanchus griseus (Elasmobranchii, Hexanchiformes, Hexanchidae), from the southwestern Gulf of Mexico, Acta Ichthyologica et Piscatoria 55, pp. 115-121 : 115-121

Hexanchus griseus (Bonnaterre, 1788)

English common name: bluntnose sixgill shark Spanish common name: tiburón leche (Figs 2 , 3 ; Table 1 )

Material examined.

CIFI-2400 , 3260 mm TL, male; ca. 20.4 km to the North of Salinas Roca Partida , Veracruz, Mexico (Fig. 1 ); 21 Jul. 2024; Armando Campos Pérez leg.

Description.

Table 1 . Robust body, large and broad head, head length (HL) 14.7 % of TL. Snout wide (27 % HL), big mouth and ventral arched with symphyseal tooth on both jaws and six rows of large, serrated comb-shaped teeth on each side of lower jaw. Ten teeth on each side of upper jaw with hooked cusp, not counting smallest and molariform ones. Six large gill slits not inserted on pectoral fins. Eye small (13.3 % HL), pupil dark with white rim, prominent tapetum lucidum giving a fluorescent greenish coloration in life. Single dorsal fin originating ahead of anal fin insertion. Short caudal peduncle (8.3 % TL). Asymmetric caudal fin. For all measurements see Table 1 . Specimen sexually mature, testes elongated, vascularized, with well-developed vas deferens and, along with seminal vesicles, filled with sperm. Clasper calcified, mobile, and presented several hematomas.

Coloration.

The live specimen had green eyes, the dorsolateral region greyish in color with brown tones, and pale grey in the ventrally (Fig. 2 ). After its capture, while frozen and fresh, the dorsolateral coloration was darker brown, and the ventral region grayish (Figs 3 , 4 ).

Figures

Figure 1. Previous records (yellow circles) based on GBIF records (GBIF 2024) and new record (red triangle) of Hexanchus griseus in the southwestern Gulf of Mexico.

Figure 2. Stills from the video of the Hexanchus griseus captured in the southwestern Gulf of Mexico.

Figure 3. Male Hexanchus griseus (CIFI- 2400) from the southwestern Gulf of Mexico. A) Lateral view; B) cephalic dorsoventral view; C) pelvic fins and claspers.

Figure 4. Head of Hexanchus griseus (CIFI- 2400) from the southwestern Gulf of Mexico. A) Lateral cephalic view; B) front cephalic view; C) oral view.