''Rostroraja texana'', the roundel skate or Texas clearnose skate, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

cartilaginous Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...

fish in the family Rajidae. It is found in the

Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...

, Southeast

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

and the Yucatan Peninsula.

Description

The disc of the roundel skate is diamond shaped. The short, rounded snout has a clear area of skin on either side. The rest of the dorsal surface is an unblotched chocolate brown colour, although sometimes there are darker patches. A pair of distinctive dark eyespots with pale pink rims lie on either side of the middle of the dorsal surface (these may confuse potential

predators Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

). A row of thorns runs along the midline of the back, but there are no venomous spines. The medium-length tail has a short dorsal fin near its tip and a small caudal fin. Males become mature at about 5 years old at a length of about , while females are mature a year later at a length of about .

Distribution and habitat

The roundel skate is native to the southeastern coast of Florida, the Gulf of Mexico and the

Campeche Bank Campeche Bank is part of the Gulf of Mexico and extends from the Yucatan Straits in the east to the Tabasco-Campeche Basin in the west. Campeche Bankin Geonames.org (cc-by)/ref> The Campeche ocean bank is from Mexico's geography of Campeche n ...

, a shallow area of sea off the northern coast of the Yucatan Peninsula. It usually occurs on sand, crushed shell or shingle to depths of about .

Biology

Adult roundel skates feed predominantly on

shrimp A shrimp (: shrimp (American English, US) or shrimps (British English, UK)) is a crustacean with an elongated body and a primarily Aquatic locomotion, swimming mode of locomotion – typically Decapods belonging to the Caridea or Dendrobranchi ...

(65%), but also take fish (25%) and sometimes

crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...

s and other

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s. The diet of juveniles is over 90% shrimp, with the rest composed of small fish. The roundel skate is sexually dimorphic, with the males usually being smaller than the females. In reproduction, the male's

claspers In biology, a clasper is a male anatomical structure found in some groups of animals, used in mating. Male cartilaginous fish have claspers formed from the posterior portion of their pelvic fin which serve to channel semen into the female's c ...

are inserted into the female's

cloaca A cloaca ( ), : cloacae ( or ), or vent, is the rear orifice that serves as the only opening for the digestive (rectum), reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles, birds, cartilagin ...

, and fertilisation is internal. As the fertilised egg passes down the uterus, albumen and yolk are added and it is placed in a rectangular

collagen Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a trip ...

ous egg case known as a

mermaid's purse An egg case or egg capsule, often colloquially called a mermaid's purse, is the casing that surrounds the eggs of oviparous chondrichthyans. Living chondricthyans that produce egg cases include some sharks, skates and chimaeras. Egg cases t ...

. This is pale brown, flat on one side and rounded on the other, with tendrils at the corners. The developing

embryo An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sp ...

feeds on the

yolk Among animals which produce eggs, the yolk (; also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo. Some types of egg contain no yolk, for example bec ...

, and some months later emerges as a fully formed juvenile fish about long.

Status

The

IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...

has classified this fish as "Least Concern" in its

Red List of Threatened Species The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is an inventory of the global conservation status and extinction risk of biological spe ...

References

{{Taxonbar, from=Q5845338 roundel skate Fauna of the Southeastern United States Fish of the Gulf of Mexico Least concern biota of North America Least concern biota of the United States roundel skate