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| Squatina leae Weigmann, Vaz, Akhilesh, Leeney & Naylor, 2023 |
Abstract
Sampling efforts on the Saya de Malha Bank (part of the Mascarene Plateau, western Indian Ocean) unveiled three unusual small juvenile angel shark specimens, that were a much paler color than the only known western Indian Ocean species, Squatina africana Regan, 1908. However, it took many years before further specimens, including adults of both sexes, and tissue samples were collected. The present manuscript contains a redescription of S. africana based on the holotype and additional material, as well as the formal description of the new species of Squatina. All specimens of the new species, hereafter referred to as Squatina leae sp. nov., were collected in the western Indian Ocean off southwestern India and on the Mascarene Plateau at depths of 100–500 m. The new species differs from S. africana in a number of characteristics including its coloration when fresh, smaller size at birth, size at maturity, and adult size, genetic composition, and distribution. Taxonomic characteristics include differences in the morphology of the pectoral skeleton and posterior nasal flap, denticle arrangement and morphology, vertebral counts, trunk width, pectoral–pelvic space, and clasper size. A key to the species of Squatina in the Indian Ocean is provided.
Keywords: Chondrichthyes; Elasmobranchii; angel sharks; systematics; taxonomy; diversity; morphology; PCA; mCT scans; genetics; NADH2; CO1
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| Squatina leae sp. nov., holotype, CMFRI GA. 15.2.5.4, adult male, 671 mm TL, in (a) dorsolateral, (b) dorsal, and (c) ventral views in fresh condition. Photographs kindly provided by P. U. Zacharia (ICAR-CMFRI). Scale bar: 5 cm. |
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| Squatina leae sp. nov., holotype, CMFRI GA. 15.2.5.4, adult male, 671 mm TL, head in (a) dorsal and (b) ventral views, (c) clasper region in dorsal view, (d) anterior pectoral-fin margin in dorsofrontal view, (e) dorsal fins in dorsal view, and (f) caudal fin in dorsolateral view. Photographs (a–d,f) kindly provided by P. U. Zacharia (ICAR-CMFRI) show the holotype in fresh condition, photograph (e) shows the holotype in preserved condition. |
Family Squatinidae Bonaparte, 1838
Genus Squatina Duméril, 1806
Squatina leae sp. nov.
English name: Lea’s angel shark
Spanish name: Angelote de Lea
German name: Leas Engelhai
Diagnosis. A small angel shark species (maximum size 870 mm TL) with the following characteristics: dorsal coloration conspicuously bright, beige to light grayish-brown, with many light yellowish flecks on trunk, and pectoral and pelvic fins, as well as countless densely set, minute dark spots, partially forming pseudocelli, all over the dorsal surface; no median row of scute-like denticles on trunk; anterior nasal flap with two lateral, elongate barbels and a medial rectangular barbel, all with ventral margins slightly fringed to almost smooth; concave between eyes; posterior nasal flap with an additional barblet; pectoral-pelvic space 10.0–14.9% TL; pectoral-fin apex angular; pelvic-fin free rear tips not reaching level of first dorsal-fin origin; tail moderately long, its length from cloaca 50.2–58.5% TL; pectoral fins moderately long, length 31.1–35.2% TL; dorsal fins not lobe-like; first dorsal-fin base somewhat longer than second dorsal-fin base; caudal fin of adults with angular apices; monospondylous centra 43–46; diplospondylous precaudal centra 55–58; total precaudal centra 100–104; total vertebral centra 130–136; and pectoral-fin skeleton with propterygium articulating with four radials.
Geographic distribution—The new species is currently known from the western Indian Ocean on the Mascarene Plateau and off southwestern India in 100–500 m depths (Figure 10).
Etymology—The name is dedicated to the memory of Lea-Marie Cordt, the late sister of the first author’s fiancée.
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| Squatina leae sp. nov., paratypes ZMH 26097, juvenile male, 298 mm TL fresh (in dorsal view) and ZMH 26098, juvenile male, 259 mm TL fresh (in ventral view) taken directly after catching. The photograph was taken and kindly provided by Matthias F. W. Stehmann. Scale bar: 5 cm. |
Conclusions:
The recognition of a new species, Squatina leae sp. nov., with the redescription of S. africana, clarifies the taxonomic status and distribution of these two western Indian Ocean angel shark species. This is essential for improved data collection and research and for more effective conservation and management policy decisions. Accordingly, this information must be incorporated into future conservation and management plans of sharks in the western Indian Ocean. The current lack of conservation plans at all scales in this ocean area, as well as the need for more research, will likely jeopardize the populations of western Indian Ocean angel sharks in the future.
Simon Weigmann, Diego F. B. Vaz, K. V. Akhilesh, Ruth H. Leeney and Gavin J. P. Naylor. 2023. Revision of the Western Indian Ocean Angel Sharks, Genus Squatina (Squatiniformes, Squatinidae), with Description of a New Species and Redescription of the African Angel Shark Squatina africana Regan, 1908. Biology. 12(7), 975. DOI: 10.3390/biology12070975
Simple Summary: Angel sharks (genus Squatina) are small- to medium-sized sharks with flattened bodies, that live on the seafloor. Until now, 23 valid species of angel sharks have been identified around the world, of which over half are thought to be facing a moderate to severe risk of extinction. Several juvenile angel sharks were collected by researchers working on the Mascarene Plateau, an elevated area of seabed in the Indian Ocean, in 1988 and 1989. They appeared different in coloration and in body shape and structure to a species known from East Africa and Madagascar, the African angel shark. Additional angel sharks were caught off the western coast of India in 2016 and in the central western Indian Ocean in 2017, including adult individuals. Information on body measurements and skeleton structure were collected, and genetic analyses were also conducted on these sharks and on museum specimens previously identified as African angel sharks. The results indicated that the specimens collected from the Mascarene Plateau and off southwestern India were a species that is new to science. It is genetically and morphologically distinct from the African angel shark; is smaller when born and when fully grown; and lives in a distinctly different area. The newly described species has been named Lea’s angel shark.
