Scott Hanko
Polka Dot Stingray
Potamotrygon leopoldi
Family
Potamotrygonidae
Distribution
Known only from the Rio Xingu basin and Rio Fresco in central Brazil.
Habitat
Like other members of the genus it inhabits a variety of biotopes. These include sand banks, the shallows of major rivers and slow-moving tributaries with substrates of mud or sand. It also move into areas of flooded forest during the annual wet season and can later be found in terrestrial lakes and ponds formed by the receding flood waters.
Maximum Standard Length
A large female can measure 24"/60cm across the disc. Males tend to be smaller.
Diet
Wild rays feed chiefly on other fish and aquatic invertebrates, including worms and crustaceans. They're active fish with a high metabolic rate and as such will need feeding at least twice a day. They're also notoriously big eaters and it's going to cost you a considerable amount of money to keep even a single specimen in good health. In general an exclusively meaty diet is preferable, although some will also learn to accept dried foods.
Juveniles (often sold simply as "teacup" rays regardless of species) relish live or frozen bloodworm, Tubifex, Artemia, krill and suchlike. Adults should be fed correspondingly larger foods, such as whole mussels, cockles, prawns, squid, whitebait (or other fresh fish) and earthworms. A varied diet is needed to keep the fish in top condition.
They're often a little reluctant to feed when initially imported, and usually arrive in quite a skinny state. It's very important to get them feeding as quickly as possible due to their metabolic requirements. Frozen foods may be refused at first, so bulk them up on live foods until they have enough weight to be safely weaned onto dead alternatives. Live bloodworm or earthworms (the latter can be chopped for small specimens) are generally considered to be among the best foods for conditioning newly imported rays.
Rays should not be fed the meat of mammals such as beef heart or chicken. Some of the lipids contained in these meats cannot be properly metabolised by the fish, and can cause excess deposits of fat and even organ degeneration. Similarly there is no benefit in the use of 'feeder' fish such as livebearers or small goldfish. Risks involved with these include the possible introduction of disease or parasites.
Breeding
Potamotrygon species utilise a breeding strategy known as matrotrophic viviparity. The young fish (often referred to as "pups") develop inside the mother and are born live and fully-formed. Inside the uterus of the female specialised filaments or villi develop. These secrete a milky substance known as histotrophe, from which the growing pups derive their nourishment once their yolk sacs have been used up. Litter size usually varies between 1-8 and gestation can take between months. Interestingly this period seems to be significantly shorter with rays breeding in aquaria, possibly due to the abundance of food they receive compared to wild fish. Successful captive breeding of several species has occured regularly in recent years, .
Rays can be picky when it comes to selecting a mate. Simply buying a pair of fish and putting them together will not guarantee a successful pairing. The ideal way to obtain a pair is to buy a group of juveniles, housing them in a huge tank and allowing them to select their own partners. However this is probably beyond the means of most hobbyists. It can also take several years for rays to become sexually mature, so a good degree of patience is required when starting with young fish.
If selecting a single pair try to choose similarly patterned specimens, and a bigger female than male. The comparative size of the pair is particularly important as courtship can be a somewhat violent affair, particularly if the female is unwilling to spawn. It's therefore essential that the she is large enough to defend herself. When in spawning condition the male will chase her incessantly, often biting her on the body and around the edge of the disc. He does so as in order to mate the pair must position themselves so that their bellies are facing each other. The male uses his mouth to take hold of the female and slide underneath her. If this behaviour continues for too long with no successful mating event real physical damage can occur. Keep a close eye on developments if your rays begin to show signs of mating behaviour, and have the facilities on hand to separate them if need be. You can try reintroducing them a few days later if necessary.
The spawning act itself is quite brief, lasting only a few seconds. Fertilisation occurs internally, the male inserting one of his claspers into the cloaca of the female before releasing his milt. Following a successful mating event the male should stop harassing his partner.
Gestation in captive rays generally takes between 9-12 weeks. During the latter stages the developing young can sometimes be seen as a visible (sometimes moving!) lump rising from the posterior end of the female's back, although in well-fed specimens this can be tricky to spot. It's essential to feed the female in sufficient quantities during this period as she will expend a lot of energy providing for her pups, and her appetite will increase significantly. Pregnant females are generally safe to be left in situ, although once the pups are born they're best removed to avoid predation by other tankmates. If the rays are being maintained alone the adults won't usually harm them although the chance is always there. Most breeders prefer to remove the pups for the sake of safety. The water in the tank is usually cloudy following a birth (this is thought to be caused by fluids released as the pups leave the body of the female), and a large water change is recommended once they've have been removed.
The pups usually have a small yolk sac attached at birth, and they will feed from this for anything up to a week. After the sac has been absorbed they should be offered high quality live and frozen foods several times a day. Some may initially refuse dead foods, but they can usually be weaned quite easily by mixing in a little live food when feeding. Growth is quite rapid with a stringent regime of water changes and the correct amount of food.
If you're lucky enough to own a pair of rays that are breeding regularly, give the female a break from the male after every 2-3 litters. Females use up a lot of energy in producing young and it may drastically shorten their lifespan if they're forced to mate continuously.
Successful captive breeding of Potamotrygon leopoldi has occured fairly regularly in the hobby. The pups don't exhibit the eye-catching colouration of the adults, having an overall mottled brown patterning (the spots are visible, but are also brownish in colour at this stage). In nature this probably serves to camouflage the pups from would-be predators.
New York Aquarium Coney Island NY
Polka Dot Stingray
Potamotrygon leopoldi
Family
Potamotrygonidae
Distribution
Known only from the Rio Xingu basin and Rio Fresco in central Brazil.
Habitat
Like other members of the genus it inhabits a variety of biotopes. These include sand banks, the shallows of major rivers and slow-moving tributaries with substrates of mud or sand. It also move into areas of flooded forest during the annual wet season and can later be found in terrestrial lakes and ponds formed by the receding flood waters.
Maximum Standard Length
A large female can measure 24"/60cm across the disc. Males tend to be smaller.
Diet
Wild rays feed chiefly on other fish and aquatic invertebrates, including worms and crustaceans. They're active fish with a high metabolic rate and as such will need feeding at least twice a day. They're also notoriously big eaters and it's going to cost you a considerable amount of money to keep even a single specimen in good health. In general an exclusively meaty diet is preferable, although some will also learn to accept dried foods.
Juveniles (often sold simply as "teacup" rays regardless of species) relish live or frozen bloodworm, Tubifex, Artemia, krill and suchlike. Adults should be fed correspondingly larger foods, such as whole mussels, cockles, prawns, squid, whitebait (or other fresh fish) and earthworms. A varied diet is needed to keep the fish in top condition.
They're often a little reluctant to feed when initially imported, and usually arrive in quite a skinny state. It's very important to get them feeding as quickly as possible due to their metabolic requirements. Frozen foods may be refused at first, so bulk them up on live foods until they have enough weight to be safely weaned onto dead alternatives. Live bloodworm or earthworms (the latter can be chopped for small specimens) are generally considered to be among the best foods for conditioning newly imported rays.
Rays should not be fed the meat of mammals such as beef heart or chicken. Some of the lipids contained in these meats cannot be properly metabolised by the fish, and can cause excess deposits of fat and even organ degeneration. Similarly there is no benefit in the use of 'feeder' fish such as livebearers or small goldfish. Risks involved with these include the possible introduction of disease or parasites.
Breeding
Potamotrygon species utilise a breeding strategy known as matrotrophic viviparity. The young fish (often referred to as "pups") develop inside the mother and are born live and fully-formed. Inside the uterus of the female specialised filaments or villi develop. These secrete a milky substance known as histotrophe, from which the growing pups derive their nourishment once their yolk sacs have been used up. Litter size usually varies between 1-8 and gestation can take between months. Interestingly this period seems to be significantly shorter with rays breeding in aquaria, possibly due to the abundance of food they receive compared to wild fish. Successful captive breeding of several species has occured regularly in recent years, .
Rays can be picky when it comes to selecting a mate. Simply buying a pair of fish and putting them together will not guarantee a successful pairing. The ideal way to obtain a pair is to buy a group of juveniles, housing them in a huge tank and allowing them to select their own partners. However this is probably beyond the means of most hobbyists. It can also take several years for rays to become sexually mature, so a good degree of patience is required when starting with young fish.
If selecting a single pair try to choose similarly patterned specimens, and a bigger female than male. The comparative size of the pair is particularly important as courtship can be a somewhat violent affair, particularly if the female is unwilling to spawn. It's therefore essential that the she is large enough to defend herself. When in spawning condition the male will chase her incessantly, often biting her on the body and around the edge of the disc. He does so as in order to mate the pair must position themselves so that their bellies are facing each other. The male uses his mouth to take hold of the female and slide underneath her. If this behaviour continues for too long with no successful mating event real physical damage can occur. Keep a close eye on developments if your rays begin to show signs of mating behaviour, and have the facilities on hand to separate them if need be. You can try reintroducing them a few days later if necessary.
The spawning act itself is quite brief, lasting only a few seconds. Fertilisation occurs internally, the male inserting one of his claspers into the cloaca of the female before releasing his milt. Following a successful mating event the male should stop harassing his partner.
Gestation in captive rays generally takes between 9-12 weeks. During the latter stages the developing young can sometimes be seen as a visible (sometimes moving!) lump rising from the posterior end of the female's back, although in well-fed specimens this can be tricky to spot. It's essential to feed the female in sufficient quantities during this period as she will expend a lot of energy providing for her pups, and her appetite will increase significantly. Pregnant females are generally safe to be left in situ, although once the pups are born they're best removed to avoid predation by other tankmates. If the rays are being maintained alone the adults won't usually harm them although the chance is always there. Most breeders prefer to remove the pups for the sake of safety. The water in the tank is usually cloudy following a birth (this is thought to be caused by fluids released as the pups leave the body of the female), and a large water change is recommended once they've have been removed.
The pups usually have a small yolk sac attached at birth, and they will feed from this for anything up to a week. After the sac has been absorbed they should be offered high quality live and frozen foods several times a day. Some may initially refuse dead foods, but they can usually be weaned quite easily by mixing in a little live food when feeding. Growth is quite rapid with a stringent regime of water changes and the correct amount of food.
If you're lucky enough to own a pair of rays that are breeding regularly, give the female a break from the male after every 2-3 litters. Females use up a lot of energy in producing young and it may drastically shorten their lifespan if they're forced to mate continuously.
Successful captive breeding of Potamotrygon leopoldi has occured fairly regularly in the hobby. The pups don't exhibit the eye-catching colouration of the adults, having an overall mottled brown patterning (the spots are visible, but are also brownish in colour at this stage). In nature this probably serves to camouflage the pups from would-be predators.
New York Aquarium Coney Island NY