<b>Rostral anomaly in a juvenile Spiny Butterfly Ray <I>Gymnura altavela</I> (Linnaeus, 1758) (Elasmobranchii: Myliobatiformes: Gymnuridae) from the Canary Islands</b>

Abstract

The present communication documents the first observation of a morphologic anomaly in a juvenile Spiny Butterfly Ray Gymnura altavela. This observation is interesting for its similarity with a rostral abnormality in an adult G. altavela from the Canary Islands 10 years earlier and with the one from a juvenile Long-tailed Butterfly Ray G. poecilura from the Western Indo-Pacific. Although no firm conclusions can be drawn from these records, it reinforces the hypothesis of a congenital disorder for this type of malformation within the genus. The individual appeared to have successfully adapted for its anomaly, suggesting that these instances are not of major conservation concern. Hence, long-term studies are required to monitor anomaly occurrences and to evaluate their potential threats.

Great Blue Heron (Ardea herodias) Predation on an Abnormal California Butterfly Ray (Gymnura marmorata) and its Ecological Implications

“…Predator-prey relationships between species of butterfly rays and large predatory sharks has previously been inferred from fisheries data (Myers et al 2007) but no direct observation of a predator targeting this group of batoids has previously been documented. The ray's morphological abnormalities are consistent with rostral anomalies observed on similar species (Bennet 1964; Easwaran 1967; Suresh and Raffi 2012; Narvaéz and Osaer 2016; Osaer and Narvaéz 2018), however this is the first documenting of this kind of malformation in this species. Butterfly rays have previously demonstrated the ability to compensate for these morphological disadvantages (Narvaéz and Osaer 2016; Osaer and Narvaéz 2018) and even though those likely hindered the affected individual's competency at survival, they should not be considered the primary reason of its capture by the heron.…”

“…The ray's morphological abnormalities are consistent with rostral anomalies observed on similar species (Bennet 1964; Easwaran 1967; Suresh and Raffi 2012; Narvaéz and Osaer 2016; Osaer and Narvaéz 2018), however this is the first documenting of this kind of malformation in this species. Butterfly rays have previously demonstrated the ability to compensate for these morphological disadvantages (Narvaéz and Osaer 2016; Osaer and Narvaéz 2018) and even though those likely hindered the affected individual's competency at survival, they should not be considered the primary reason of its capture by the heron. Although the Great Blue Heron and the California butterfly ray are both restricted to North American coastlines, the ranges of similar species of large herons are known to overlap with those of butterfly ray species, including those considered to be threatened with extinction.…”

“…Although the Great Blue Heron and the California butterfly ray are both restricted to North American coastlines, the ranges of similar species of large herons are known to overlap with those of butterfly ray species, including those considered to be threatened with extinction. As an example, the Grey Heron ( Ardea cinerea ) is present throughout the Canary Islands (Clarke 2020) where a potential (although unconfirmed) nursery habitat of the endangered spiny butterfly ray ( Gymnura altavela ) has recently been hypothesized (Tuya et al 2020) and similar cases of rostral anomalies have also been recorded on the species within this region (Narvaéz and Osaer 2016; Osaer and Narvaéz 2018). In this case, further research and observation of the heron's foraging behavior is recommended to gain further insight on the ecology of the species, which could inform future conservation and management decisions.…”