Bat Rays, Myliobatis californica
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Description & Behavior
Bat rays, Myliobatis californica (Gill, 1865), are members of the eagle rays or Myliobatidae family, and are light brown to black rays with white bellies. They grow up to 1.2-1.85 m in length and weigh up to 90 kg. Their wing span can reach up to 1.85 m from tip to tip. Males are typically smaller than females (sexually dimorphic).
These rays have at least one venomous spine located near the base of their tail behind their dorsal fin; some have up to 3 spines. Bat rays can live for up to 23 years. They have been observed both solitary and schooling, with some schools containing thousands of individuals.
One million year old bat ray fossils have been found in Pliocene deposits.
World Range & Habitat
They are native to the eastern Pacific from Oregon, US to the Gulf of California and the Galápagos Islands.
Feeding Behavior (Ecology)
Bat rays hunt for prey by lifting themselves up and down on their wings creating suction in the sand. This exposes invertebrates such as bivalves, mollusks, polychaetes, shrimps, and crabs. They have short flat teeth used to chew the shells of bivalves and snails.
As bat rays feed, they expose other buried organisms that are then often preyed upon by smaller fishes in the area.
Bat rays are an ovoviviparous species. Eggs are fertilized internally and litters of up to 10 are born live, usually in summer or fall, following a gestation period of 1 year.
Male bat rays select a mate then determine her reproductive state by swimming closely behind her to detect chemical signals. If a female is ready for mating, the male swims underneath her with his back to her belly, and rotates a clasper to position it near her cloaca. During copulation the pair swims together with synchronized beats of their wings. Females group together during mating season and assist the males in the selection of a suitable mate by protecting sexually immature females and females that have already mated.
Ovoviviparous: eggs are retained within the body of the female in a brood chamber where the embryo develops, receiving nourishment from a yolk sac. This is the method of reproduction for the "live-bearing" fishes where pups hatch from egg capsules inside the mother's uterus and are born soon afterward. Also known as aplacental viviparous.
Conservation Status & Comments
The spine(s) of these rays are venomous. Bat rays are not fished commercially; however, they are sometimes caught as bycatch.
References & Further Research
Research Myliobatis californica » Barcode of Life ~ BioOne ~ Biodiversity Heritage Library ~ CITES ~ Cornell Macaulay Library [audio / video] ~ Encyclopedia of Life (EOL) ~ ESA Online Journals ~ FishBase ~ Florida Museum of Natural History Ichthyology Department ~ GBIF ~ Google Scholar ~ ITIS ~ IUCN RedList (Threatened Status) ~ Marine Species Identification Portal ~ NCBI (PubMed, GenBank, etc.) ~ Ocean Biogeographic Information System ~ PLOS ~ SIRIS ~ Tree of Life Web Project ~ UNEP-WCMC Species Database ~ WoRMS
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