- Marine Record
- Open Access
New record of Zameus squamulosus (Chondrichthyes: Squaliformes: Somniosidae) in the Southern Gulf of Mexico
Marine Biodiversity Records volume 9, Article number: 61 (2016)
Zameus squamulosus is a somniosid shark with a patchy world-wide distribution that has been reported throughout the Atlantic, Indian, western, north, central and south-eastern Pacific Oceans. In the Northern Gulf of Mexico Zameus squamulosus is occasionally captured by longlines in deep waters off the coast of Florida, but until now there were no records of the species in the Southern Gulf of Mexico. Four specimens of Zameus squamulosus were collected in 2004 and 2009 on the continental slope of the Gulf of Mexico. Collections were made at depths of 698 m and 701 m. These specimens constitute the first records of this species for the southern Gulf of Mexico and, as they were captured with bottom associated trawls, we infer that this species is more commonly found at the bottom ocean.
Zameus squamulosus was first described as Centrophorus squamulosus in 1877 by Günther from a female specimen collected in Japan. Barbosa du Bocage & de Brito Capello 1864 reassigned this species to the genus Scymnodon. Later Jordan & Fowler in 1903 designated this species as the type for their newly described genus Zameus, but Bigelow & Schroeder (1957) concluded that Zameus was a junior synonym of Scymnodon. After morphological studies Taniuchi & Garrick (1986) resurrected the genus Zameus and redefined Scymnodon as a monotypical genus from the North Atlantic. White et al. (2014) placed Zameus as a monotypical genus excluding the species Zameus ichiharai (Yano & Tanaka 1984), now assigned to Scymnodon.
Zameus differs from Scymnodon, among other characters, in the presence of a medial tooth in the lower jaw (Fig. 1) and of dermal denticles with transverse ridges (Fig. 2). Recent molecular studies have confirmed the distinctiveness of the genus Zameus from Scymnodon, and place it closer to the genus Centroselachus (Naylor et al. 2012).
Zameus squamulosus is a poorly known somniosid shark that has a patchy world-wide distribution and has been reported throughout the Atlantic, Indian, western, north, central and south-eastern Pacific Oceans (Compagno et al. 2005; Akhilesh et al. 2013 and Ebert et al. 2014). This shark is epipelagic and bathypelagic, and is usually found off continental and insular slopes, on or near the bottom at depths of 550 to 1,450 m, but also found well off the bottom at depths between 0 and 580 m in waters up to 2,000–6,000 m deep (Ebert et al. 2014).
In the Northern Gulf of Mexico Zameus squamulosus is occasionally captured by longlines in deep waters off the coast of Florida (Castro 2011), but until now there were no records of the species in the Southern Gulf of Mexico.
Four female specimens of Zameus squamulosus were captured during two separate collecting trips, conducted by the Research Vessel (RV) ‘Justo Sierra’ in the continental slope of Campeche and Veracruz. These records represent evidence of the presence of Zameus squamulosus in the Southern Gulf of Mexico.
Materials and methods
The identification of the specimens was based on McEachran & Fechhelm (1998), Castro (2011) and Ebert et al. (2013). Measurements (Table 1), were presented as a percentage of the total length (TL), were taken after Ebert & Stehmann (2013) and were made in preserved specimens. Specimens were fixed in 10 % formalin and subsequently preserved in 70 % ethanol. All of the specimens were deposited in the Colección Nacional de Peces of the Instituto de Biología, Universidad Nacional Autónoma de México (CNPE-IBUNAM).
Two specimens (CNPE-IBUNAM 14608) were captured on 2004–07–27 at a depth of 689 m, using a 12 m long, 9 m wide and 1.5 m tall semi-balloon otter trawl with a 6.35 cm mesh, during the Sigsbee VII project (22.41722 – 96.61110). The other two specimens (CNPE-IBUNAM 16547) were captured on 2009–08-23 at a depth of 701 m, using a 12 m long, 9 m wide and 1.5 m tall semi-balloon otter trawl with a 6.35 cm mesh, during the COBERPES III project (18.97537–94.12077). Both campaigns were conducted over the continental slope in the Gulf of Mexico (Fig. 4.).
Specimens were identified as Zameus squamulosus in laboratory. All of them show the distinctive transverse ridges on their dermal denticles (Yano & Tanaka 1984; Taniuchi & Garrick 1986) (Fig. 2). Specimens are also dark colored and low-flat headed (Head height 5.1–7.6 % TL) with a short-narrow snout (Preoral length 8.2–9.6 % TL). Their mouths are nearly transverse and narrow (Mouth wide 6.8–7.7 % TL) with well-developed labial furrows (length of upper labial furrow 3–3.6 %TL and length of lower labial furrow 2–2.4 %TL). Teeth in the lower jaw are large, broad and with knife-shaped cusplets. Teeth in the upper jaw are small and lanceolate, without cusplets (Fig. 1). Both dorsal fins are preceded by a very minute spine. First dorsal fin is long (7.6–9.2 % TL), narrow at its base (4.4–5.5 %TL) and inserted posteriorly to the pectoral fin. Second dorsal fin is small (7.6–9.1 %TL) with a wide base (6.8–7.7 % TL). Rear tips of the pectoral fins are short and broadly rounded. Anal fin is absent and caudal fin lacks subterminal notch (see Table 1 for complete meristics of the four specimens).
These are the first confirmed records of Zameus squamulosus in the Southern Gulf of Mexico and therefore increase the number of known shark species in Mexico. Zameus squamulosus has been recorded in catches at midwater trawls (Cadenat & Blache 1981), on pelagic longlines (Taniuchi 1990; Last & Stevens 2009) and very close to the surface (Wetherbee & Crow 1996), but although the specimens reported here were captured in the depth range of the species already described (550–1,450 m), they were collected in a trawl associated to the bottom, which supports the idea of Last & Stevens (2009) and Wetherbee & Crow (1996) that this species is more commonly found at the bottom.
CNPE-IBUNAM, colección nacional de peces, Instituto Biología, Universidad Nacional Autónoma de México; RV, research vessel; TL, total lenght.
Akhilesh KV, Bineesh KK, Ganga U, Pillai NGK. Report of velvet dogfish, Zameus squamulosus (Günther, 1877) (Somniosidae: Squaliformes) from Indian waters. Indian Journal of Fisheries. 2013;60:127–129.
Barbosa du Bocage JV, de Brito Capello F. Sur quelques espèces inédites de Squalidae de la tribu Acanthiana, Gray, qui fréquentent les côtes du Portugal. Proc Zool Soc London 1864;(pt 2):260–263.
Bigelow HB, Schroeder WC. A study of the sharks of the suborder Squaloidea. Bulletin of the Museum of Comparative Zoology at Harvard College. 1957;117:1–150.
Castro JI. The Sharks of North America. United States of America: Oxford University Press; 2011.
Cadenat J, Blache J. Requins de Mediterranee et d' Atlantique (plus particulierement de la Cote Occidentale d' Afrique). Faune Tropicale. 1981;21:1–330.
Compagno LJV, Dando M, Fowler S. A field guide to the sharks of the world. London: Harper Collins Publishers. 2005. pp. 368.
Ebert DA, Fowler S, Compagno L. Sharks of the World a Fully Illustrated Guide. Plympton St. Maurice, United Kingdom: Wild Nature Press; 2013.
Ebert DA, Stehmann MFW. Sharks, Batoids and Chimaeras of the North Atlantic. FAO species catalogue for fishery purposes. No. 7. Roma: FAO; 2013.
Ebert DA, Knuckey JDS, Kamikawa DJ. First eastern North Pacific record of the velvet dogfish, Zameus squamulosus (Chondrichthyes: Squaliformes: Somniosidae). Mar Biodivers Rec. 2014;7:e48.
Günther A. Preliminary notes on new fishes collected in Japan during the expedition of H. M. S. Challenger. Ann Mag Nat Hist. 1877;20:433–46.
Jordan DS and Fowler HW. A review of the elasmobranchiate fishes of Japan. Proceedings of the United States National Museum. 1903;26:593–674.
Last PR, Stevens JD. Sharks and Rays of Australia. 2nd ed. Australia: CSIRO; 2009.
McEachran JD, Fechhelm JD. Fishes of the Gulf of Mexico. Volume 1: Myxiniformes to Gasterosteiformes. Austin: University of Texas Press; 1998.
Naylor GJP, Caira JN, Jensen K, Rosana KAM, White WT, Last PR. A DNA sequence-based approach to the identification of shark and ray species and its implications for global elasmobranch diversity and parasitology. Bull Am Mus Nat Hist. 2012;367:1–263.
Taniuchi T. The role of elasmobranchs in Japanese fisheries. In H. L. Pratt, Jr., S. H. Gruber and T. Taniuchi, (eds). Elasmobranchs as fishing resources: advances in the biology, ecology, systematics, and the status of the fisheries. NOAA Technical Report. NMFS. 1990;90:415–426
Taniuchi T, Garrick JAF. A new species of Scymnodalatias from the Southern Oceans, and comments on other squaliform sharks. Japanese J Ichthyology. 1986;33:119–34.
Wetherbee BM, Crow GL. First record of the squaloid shark Scymnodon squamulosus from the Hawaiian Islands. Ichthyological Res. 1996;43:334–9.
White WT, Vaz DF, Ho HC, Ebert DA, de Carvalho MR, Corrigan S, et al. Redescription of Scymnodon ichiharai Yano and Tanaka 1984 (Squaliformes: Somniosidae) from the western North Pacific, with comments on the definition of somniosid genera. Ichthyological Res. 2014;62:213–29.
Yano K, Tanaka S. Review of the deep sea squaloid shark genus Scymnodon of Japan, with a description of a new species. Japanese J Ichthyology. 1984;30:341–60.
We thank E. Escobar for the invitation to the expeditions, as well as the participants and specimen collectors on the cruise. Ship time of the research cruise Sigsbee VII and COBERPES III carried out onboard the RV ‘Justo Sierra’ was funded by Universidad Nacional Autónoma de México.
EV identified, determined and measured the specimens, elaborated the illustrations and drafted the manuscript. AM performed the map elaboration and participated in the measurement of the specimens and writting of the publication. CL participated in the measurement of the specimens and writting of the publication. HE participated in the writting of the publication and coordination of the manuscript. All authors read and approved the final manuscript.
The authors declare that they have no competing interests.