SPINY BUTTERFLY RAY|
Order - Myliobatiformes
Family - Gymnuridae
Genus - Gymnura
Species - altavela
Linnaeus first described the spiny butterfly ray in 1758. The genus Gymnura of the currently accepted scientific name
is derived from the Greek word gymnos meaning naked. Synonyms for Gymnura altavela include
Pteroplatea altavela, Raja altavela, Dasyatis altavela, Raja maclura, Dasyatis canariensis,
Pteroplatea canariensis, Pteroplata valenciennii, Pteroplatea binotata, and Pteroplatea vaillantii.
Common English names for this species include spiny butterfly ray, butterfly ray, and the giant butterfly ray.
Other names include aeroplanke (Albanian), altavela (Italian), avejão (Portuguese), bâsternâk (Arabic),
doornvlinderrog (Dutch), farfett (Maltese), isoperhosrausku (Finnish), kazikkuyruk baligi (Turkish), khop
(Wolof), mariposa (Spanish), marmorerad fjärilsrocka (Swedish), motýlovec trnitý (Czech), pastenague ailée
(French), peitschenrochen (German), pilrokke (Norwegian), platyselacho (Greek), ptaszyca (Polish), raia-borboleta
(Portugese), raya mariposa (Spanish), and stor sommerfuglerokke (Danish).
The spiny butterfly ray is found in the western and eastern Atlantic Ocean. In the western Atlantic it occurs
from southern New England to Brazil. It is rarely recorded in the Gulf of Mexico. In the eastern Atlantic it occurs from Portugal to Ambriz, Angola (including
the Mediterranean, Black Sea, and the Madeira and Canary islands).
World distribution map for the spiny butterfly ray
The spiny butterfly ray is a demersel species that prefers brackish and coastal waters and is known to
occur in depths ranging from five to 100 meters. This ray generally occurs over sand and mud bottoms.
Spiny butterfly ray
© George Burgess
- · Distinctive Features
This is a broad, diamond-shaped ray with a short tail armed with a dorsal spine. This ray has a protruding snout.
The front edges of the disk are concave. The tail has low dorsal and ventral finfolds. The spiny butterfly ray has a
slender tentacular structure on the inner posterior margin of each spiracle. These structures are lacking in the smooth butterfly ray (G. micrura). G. altavela has a more obtuse anterior angle than G. micrura. The keeled shape of the upper surface
of the tail of G. altavela separates it from G. hiruno.
The spiny butterfly ray is typically dark brown
© Christina Conrath
- · Coloration
The spiny butterfly ray is typically dark brown dorsally with a grayish or reddish cast or coffee brown shading to
cinnamon at the margins sometimes with pale rimmed ocular spots. They have also been known to be dorsally brown
with small darker spots or light spots and blotches (usually marbled) and white ventrally. The tail of small
specimens is marked with pale crossbars, which usually fade over time.
The upper jaw generally has 98 to 138 teeth with each tooth having a high conical cusps. The lower jaw generally has
78 to 110 teeth. Teeth tend to get larger as the ray itself grows but remain as sharp throughout development to
adulthood. In both the upper and lower jaw there are about 10 to 12 rows of functional teeth and each dental band
takes up about 70% the width of the jaw.
The skin is relatively smooth in small or medium specimens but is described as rough in the larger specimens.
The maximim disk width of the spiny butterfly ray
is a little over 13 feet
© Christina Conrath
- ·Size, Age, and Growth
The maximum recorded disk width of the species is 13.1 feet (4.0 m) and the maximum published weight is 132 pounds (60.0 kg).
The maximum reported total length is 4.6 feet (1.4 m). Off the Tunisian coast of northern Africa females are larger than
males with the size at first maturity of males estimated at 2.6 feet (0.78 m) disc width.
- · Food Habits
Feeds on fishes, crustaceans, mollusks and plankton.
- · Reproduction
G. altavela is an aplacental viviparous species (ovoviviparous), with two functional uteri. Gestation likely lasts
four to nine months. One reproductive cycle occurs per year. Average disc width and weight of fully developed
embryos have been reported as 11.6 inches (29.4 cm) and 2.2 pounds (269.3 g) in Tunisian waters. Fecundity ranges from two to six embryos
per litter with an average of approximately four in western Atlantic waters. Embryos are symmetrically distributed
in each uterus.
- · Predators
Potential predators include larger fishes and marine mammals. Great hammerhead sharks likely are predators of gymnurid rays.
- · Parasites
A three-year study done in 1995 collected seven spiny butterfly rays and tested them for parasites. A phyllobothriid cestode
new to science was found in the spiral intestine of all host specimens. In addition, Heteronchocotyle gymnurae,
a gill parasite, is often seen in these rays.
This ray is being landed as part of a scientific study
Importance to Humans
© Christina Conrath
These rays are of minor commercial importance and in some places are listed as a game species.
Danger to Humans
The spiny butterfly ray is harmless to humans as it is not aggressive but if stepped on, it
will utilize its spine as a defense. The wound will most likely be painful but not lethal.
This ray is not listed as endangered or vulnerable with the World Conservation Union (IUCN). The IUCN is a
global union of states, governmental agencies, and non-governmental organizations in a partnership that
assesses the conservation status of species.
Christina Conrath and Rebecca Scarbrough