Spiny butterfly ray

Spiny butterfly ray (Gymnura altavela)

The spiny butterfly ray (Gymnura altavela)

The spiny butterfly ray Gymnura altavela is one of 10 species of butterfly rays known worldwide(1). This species has a broad distribution range and is present along the eastern and western coast of the Atlantic Ocean, including the Mediterranean Sea, the Black Sea and the Madeira and Canary Islands(2).

The spiny butterfly ray Gymnura altavela in the Canary Islands; photo credit Krupskaya Narváez.

Morphologic abnormality

Incomplete rostrum

Morphologic anomaly in the head of a spiny butterfly ray Gymnura altavela in the Canary Islands; source: Narváez K, Osaer F 2016 Morphological and functional abnormality in the spiny butterfly ray Gymnura altavela. Mar Biodivers Rec 9:95.

The first case of a morphologic abnormality in the spiny butterfly ray is reported for an individual in the Canary Islands. This is also the first time that an anomaly is reported for an elasmobranch species in its natural environment and for this class of fishes in the Canary Islands.

 

An adult female spiny butterfly ray with an incomplete developed rostrum was observed in the Port of Sardina (Gáldar, Gran Canaria) during 2 consecutive years. This anomaly was caused by the by the lack of fusion of its right pectoral fin to the cranium, leaving an opening in the anterior part of the disc which is normally closed.

Functional disadvantages

The lack of rostrum development makes that the individual has functional disadvantages in detecting and capturing preys, swimming, manoeuvrability and camouflage compared to normal developed individuals. Yet, it´s big size, and observations of preying, camouflage and locomotion during two years confirm that the individual was capable to compensate successfully for these handicaps.

Possible causes

The exact causes for the anomaly are unknown to us, but they might have a genetic origin or due to an obstruction during the embryonic development. However, there is insufficient knowledge about the early development processes of butterfly rays and the factors that can affect it. No matter how, the reported case is remarkable for its striking similarity with the one from a butterfly ray species from India; the long-tailed butterfly ray G. poecilura.

Video of an angelshark (Squatina squatina) startling a ray in the Port of Sardina del Norte; source: Narváez K, Osaer F 2016 Morphological and functional abnormality in the spiny butterfly ray Gymnura altavela. Mar Biodivers Rec 9:95.

Peer reviewed publication

The complete report is available at BioMed Central vía DOI 10.1186/s41200-016-0085-7 “Morphological and functional abnormality in the spiny butterfly ray Gymnura altavela”.


(1) Weigmann S (2016) Annotated checklist of the living sharks, batoids and chimaeras (Chondrichthyes) of the world, with a focus on biogeographical diversity. J Fish Biol 88, 837-1037. doi: 10.1111/jfb.12874

 

(2) Last P et al (2016) Rays of the world. CSIRO Publishing