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Purple Eagle Rays
Transcript of Purple Eagle Rays
One male, or sometimes several, will pursue a female. When one of the males approaches the female, he uses his upper jaw to grab her dorsum. The male will then roll the female over by grabbing one of her pectoral fins, which are located on either side of her body. Once she is on her ventral side, the male puts a clasper into the female, connecting them venter to venter, with both undersides together.The mating process lasts for 30–90 seconds.
Difference In Gender
Just like humans, male and female rays have different
sexual organs. Female have two pelvic fins that conform to the
contour of their body.
Male rays also have two pelvic fins, but in addition they have two claspers. Claspers start out as small
fins that grow beyond the pelvic fins and become hard and calcified as the male reaches sexual maturity.
Looking from either above or below the ray, if you spot two fins extending
beyond the main body, you’re looking at a male.
Juvenile mantas can be tricky. Young females look the same as mature females,
with nothing but two pelvic fins, but juvenile males are often mistaken for females. Claspers on young males are small and
undeveloped, and when viewed from above they’re not distinctive. Juvenile males can really only be identified from below,
where their small claspers can be seen growing underneath the pelvic fins.
Numbers of Individuals
Known from only a handful of specimens (15 individuals). Population sizes unknown but this species appears to be extremely rare. This species was affected early on by fishing activities and now we are seeing only a depleted population. They are ovoviviparous specimens.
Hermit crabs and other crustaceans including shrimp and prawns, abalone and other molluscs, and polychaete worms are components of the diet, and the Purple Eagle
Ray has specialized flat, plate-like teeth for crushing shellfish.
It also appears to be individually dispersed and not aggregating like some other Myliobatis. Consistent fishing activities Along the east coast of Australia this species is rarely encountered. Mainly stay on the east coast of Australia.
Adaptions to the Environment
These rays have the unique behavior of digging with their snouts in the sand of the ocean. While doing this, a cloud of sand surrounds the ray and sand spews from its gills. Purple eagle rays are commonly found in shallow inshore waters such as bays and coral reefs but may cross oceanic basins. They sometimes enters estuaries. They swim close to the surface, or close to the bottom.The purple eagle ray is distributed worldwide in tropical, coastal waters.
Class & Order
Commensalism & Mutualism
Restricted to eastern Australia. References to the species off Western Australia represent a separate species. Available habitat may be small, as its presently known area of occurrence on the outer shelf and upper slope is not a broad area.
Purple eagle rays, in common with many other rays, often fall victim to sharks such as the tiger shark, the lemon shark, the bull shark, the silver tip shark, and the great hammerhead shark. A great hammerhead shark has been observed attacking a purple eagle ray in open water by taking a large bite out of one of its pectoral fins, thus incapacitating the ray. The shark then used its head to pin the ray to the bottom and pivoted to take the ray in its jaws, head first. Sharks have also been observed to follow female rays during the birthing season, and feed on the newborn pups.
Class:CHONDRICHTHYES Order: RAJIFORMES
Purple eagle rays have flat disk-shaped bodies, deep blue or black with white spots on top with a white underbelly, and distinctive flat snouts similar to a duck's bill. Their tails are longer than those of other rays and may have 2–6 venomous spines,just behind the pelvic fins. The front half of the long and wing-like pectoral disk has five small gills in its underside.Mature spotted eagle rays can be up to 5 meters (16 ft) in length; the largest have a wingspan of up to 3 meters (10 ft) and a mass of 230 kilograms (507 lb). Their age structure is 4-6 years. Population sizes unknown.
When in shallow waters or outside their normal swimming areas the rays are most commonly seen alone, but they do also congregate in schools. One form of traveling is called loose aggregation, which is when three to sixteen rays are swimming in a loose group, with occasional interactions between them. A school commonly consists of six or more rays swimming in the same direction at exactly the same speed.
Purple Eagle Rays have powerful jaws which they use to crush open conchs and other shellfish, which they find living on sandy bottoms. Jacks have often been observed to follow rays around, hoping to make a meal of small fish that are flushed from under the sand, while the ray is digging for food.
Trematodes, including Thaumatocotyle pseudodasybatis, commonly infect the skin of the spotted eagle ray. Clemacotyle australis was reported in the branchial cavity of an individual caught in Australian waters and Decacotyle octona n. comb was found on the gills on another individual.
I didn't find much on their competition but I think their competition would be other eagle rays because they all have the same diet.