page_title: Sand devil
section_title: Biology and ecology
hierarchical_section_title: Sand devil / Biology and ecology
caption_attribution_description: English: Embryo of the sand devil (Squatina dumeril)
context_page_description: The sand devil or Atlantic angel shark is a species of angelshark, family Squatinidae, native to the northwestern Atlantic Ocean. It occurs off the eastern United States, in the northern Gulf of Mexico, and possibly in parts of the Caribbean Sea. This bottom-dwelling shark is found in shallow inshore waters in summer and fall, and deep offshore waters in winter and spring. The sand devil's flattened body and enlarged pectoral and pelvic fins give it a ray-like appearance. There is a band of enlarged thorns running along the middle of its back. It is gray or brown in color, with scattered small dark spots. This species reaches 1.2–1.5 m in length.
  The diet of the sand devil consists mainly of small teleost fishes and squid, which are captured via ambush attack. This species is viviparous, with the unborn young nourished by their yolk sacs. Females have a multi-year reproductive cycle and give birth to 4–25 pups in spring or early summer, following a 12-month gestation period. The sand devil is not aggressive, but may attempt to bite if harassed or captured. Though not valued economically, it is caught incidentally by commercial bottom trawl fisheries.
context_section_description: The sand devil is an ambush predator that spends much time buried in the bottom sediment. Its diet consists mainly of demersal teleost fishes such as croakers, goatfishes, and butterfishes. However, some types of demersal fishes such as jacks are rarely eaten, perhaps because they are more active and thus likely to escape attacks. Squid are a major secondary food source, particularly for smaller sharks. Crabs, shrimp, mantis shrimp, skates, and bivalves are infrequently eaten. This species feeds both during the day and at night. It tends to select prey approximately 50–60% as long as its mouth is wide; this size is consistent with what is predicted from optimal foraging theory to yield the most efficient rate of energy return. The variety of prey taken is greatest in fall and least in winter, and smaller sharks have a more varied diet than larger ones. In the northern Gulf of Mexico, the most important prey species are Atlantic croaker (Micropogonias undulatus), longspine porgy (Stenotomus caprinus), spot croaker (Leiostomus xanthurus), Gulf butterfish (Peprilus burti), red goatfish (Mullus auratus), dwarf goatfish (Upeneus parvus), and longfin inshore squid (Doryteuthis pealeii). The relative importance of each differs across seasons (for example, squid are more important in winter), perhaps due to seasonal variation in their availability. A known parasite of the sand devil is the copepod Eudactylina spinula.
  Like other angel sharks, the sand devil is viviparous with the developing embryos sustained by yolk. Mature females have one functional ovary, on the left, and two functional uteruses. Mating occurs in the spring; adult males have spines on the outer margins of their pectoral fins, which may help in gripping the female during copulation. Females reproduce no more than once every two years, perhaps longer. Litter size varies from four to 25 pups, and does not appear related to the size of the female. The gestation period lasts roughly 12 months, and birthing occurs between February and June at depths of 20–30 m (66–98 ft). The newborns measure 25–30 cm (9.8–11.8 in) in length. Males and females sexually mature at around 93 and 86 cm (37 and 34 in) long respectively; the fact that females mature at a smaller size than males is unusual among sharks.
caption: Sand devil embryo with external yolk sac.
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