The southernmost range limit for the hidden angelshark Squatina occulta
© Estalles et al. 2016
Received: 8 June 2016
Accepted: 10 June 2016
Published: 1 August 2016
Angelsharks (Genus Squatina) are distributed in the southern Southwest Atlantic Ocean between southeastern Brazil and central Patagonia. The endangered hidden angelshark Squatina occulta is reported in the literature as ranging from Espírito Santo, Brazil to Southern Uruguay. Its presence in Argentine waters has been suspected but not verified so far. This study describes and analyzes a specimen of S. occulta found in Puerto Quequén 38° 40′S - 58° 50′W, Buenos Aires Province, Argentina.
An immature male of 578 mm total length and 1,450 g was collected from commercial landings of the bottom trawl fishery of Puerto Quequén. The specimen exhibited the coloration pattern, dermal denticle distribution, and tooth formula characteristic of S. occulta.
Squatina guggenheim and S. argentina are already known to occur off Puerto Quequén. The present finding confirms the presence of a third species of angelshark in Argentina and constitutes the southernmost record of S. occulta.
KeywordsChondrichthyes Elasmobranchii Squatinidae Southwest Atlantic Ocean
The genus Squatina Dumeril 1806 is composed of 20 species of angelsharks (Weigmann 2016). The species of this genus are unique among sharks due to their ray-like features. Their bodies are flattened dorso-ventrally with broad pectoral fins, a terminal mouth, and eyes and spiracles located dorsally. They also have a long and flattened tail without an anal fin. Unlike rays, however, their gill slits are located laterally on the head and forward of the pectoral-fin origins (Last & White 2008).
Angelsharks are distributed in the southern Southwest Atlantic Ocean between southeastern Brazil and central Patagonia (Cousseau & Figueroa 2001; Vooren & Klippel 2005). They are found from the inshore to the upper continental slopes (Vooren & Klippel 2005). The similarity of external morphology among species led to different taxonomic hypothesis and misidentifications in previous literature (Cousseau & Figueroa 2001; Cousseau 1973; Vaz & de Carvalho 2013; Faria et al. 2014). Recently, the taxonomy of these species was revised and clarified and, Squatina guggenheim Marini 1936, S. argentina (Marini 1930) and S. occulta Vooren & da Silva 1991 are recognized as valid species in this area (Vaz & de Carvalho 2013). Genetic analysis supports the differentiation of these three species (Solé-Cava & Levy 1987; Solé-Cava et al. 1983; Furtado-Neto et al. 2002; Falcão et al. 2014).
Despite the recent clarifications of the taxonomy, problems concerning the distribution and occurrence of angelsharks in the region still persist, at least for S. occulta. The hidden angelshark S. occulta is reported in the literature as ranging from Espírito Santo State, Brazil to southern Uruguay in the Argentinean-Uruguayan Common Fishing Zone (Vaz & de Carvalho 2013; Milessi et al. 2001). Even though S. occulta’s presence was proposed along the Argentinean shelf (to 45° S), this could not be verified so far (Cousseau & Figueroa 2001; Vooren & Klippel 2005; Vaz & de Carvalho 2013). The present study reports and describes a specimen of this species found in the area of Puerto Quequén, Necochea, Buenos Aires Province, Argentina.
Squatina occulta was sampled on 15 March 2015 during fishery landings at Puerto Quequén. The specimen was preserved at -20 °C for 24 h and identified after defrosting. Identification and morphological measurements followed (Last & White 2008; Vaz & de Carvalho 2013). The specimen was deposited in the fish collection of the División Ictiología of the Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” and catalogued as MACN-Ict 10942.
Morphological measurements of Squatina occulta MACN-Ict 10942 collected at Puerto Quequén
Total length (TL)
Clasper inner length
Clasper outer length
Clasper base width
Orbital head width
Spiracular head width
Pelvic (origin)-caudal distance
Width at pectoral origins
Pectoral-fin anterior margin
Pectoral-fin base length
Pectoral-fin inner margin
Pelvic-fin inner margin
First dorsal-fin base length
First dorsal-fin anterior margin
First dorsal-fin height
First dorsal-fin inner margin
Second dorsal-fin base length
Second dorsal-fin anterior margin
Second dorsal-fin height
Second dorsal-fin inner margin
Dorsal caudal-fin margin
Preventral caudal –fin margin
Teeth smaller in the upper jaw than in lower jaw and arranged in 18 longitudinal upper rows and in 20 lower rows. Tooth formula: 9–9/10–10, respectively.
The specimen collected at Puerto Quequén confirms the presence of S. occulta in Argentina. The most distinctive characteristics of the individual found were its coloration pattern, the relative size of the spots, and the distribution pattern of enlarged dermal denticles. The morphological measurements were in the range of the values reported for S. occulta even though they were not useful for discriminating among Southwestern Atlantic species, as pointed out by the authors (Vaz & de Carvalho 2013).
This individual was distinguished from S. guggenheim and S. argentina by its brown background color with several rounded yellowish spots on the dorsal surface (spot size ranging from 0.54 to 0.81 eye-length), the larger spots surrounded by many small blackish dots; the slightly convex anterior margin of the pectoral fin; absence of enlarged dermal denticles and enlarged dermal denticles symmetrically distributed on the head with a pair of them located between spiracles.
TL, total length; g, grams; mm, milimeters; MACN, Museo Argentino de Cienicas Naturales “Bernardino Rivadavia”
We thank Roque Bruno, José Renaudo and David Iglesias, as well as their staff at the fish processing plants, for kindly allowing us to sample angelsharks. We also would like to acknowledge the fishermen of Puerto Quequén, Necochea for granting us access to their catch falta el verbo. We are grateful to Aspen Padilla for language review.
The study was performed during the Postdoctoral fellowship granted by Consejo Nacional de Investigaciones Científicas y Técnicas- CONICET to María Lourdes Estalles.
Availability of data and materials
The specimen analyzed in the present study is available in the fish collection of the División Ictiología of the Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”, catalogued as MACN-Ict 10942.
MLE and DCL collected the specimen, identified the specimen and performed the measurements, took the photograph and prepared the figures. MLE analyzed the data. MLE, VVF, GEC, JMDA prepared the manuscript. All the authors corrected the draft, read and approved the final manuscript.
The authors declare that they have no competing interests.
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
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