Requiem sharks are sharks of the family Carcharhinidae in the order Carcharhiniformes. They are migratory, live-bearing sharks of warm seas (sometimes of brackish or fresh water) and include such species as the bull shark, lemon shark, blacktip shark, and whitetip reef shark.
Family members have the usual carcharhiniform characteristics. Their eyes are round, and one or two gill slits fall over the pectoral fin base. Most species are viviparous, the young being born fully developed. They vary widely in size, from as small as 69cm (27inches) adult length in the Australian sharpnose shark, up to 4m (13feet) adult length in the oceanic whitetip shark.[1] Scientists assume that the size and shape of their pectoral fins have the right dimensions to minimize transport cost.[2] Requiem sharks tend to live in more tropical areas, but tend to migrate. Females release a chemical in the ocean in order to let the males know they are ready to mate. Typical mating time for these sharks is around spring to autumn.[3]
According to the ISAF, requiem sharks are among the top five species involved in shark attacks on humans;[4] however, "requiem shark" is not a single species, but refers, in this case, to an order of similar sharks that are often involved in incidents. ISAF prefers to use "requiem sharks" due to the difficulty in identifying individual species.[5]
The common name requiem shark may be related to the French word for shark, requin, which is itself of disputed etymology. One derivation of the latter is from Latin requiem ("rest"), which would thereby create a cyclic etymology (requiem-requin-requiem), but other sources derive it from the Old French verb reschignier ("to grimace while baring teeth").
The scientific name Carcharhinidae was first proposed in 1896 by D.S. Jordan and B.W. Evermann as a subfamily of Galeidae (now replaced by "Carcharhinidae").[6] The term is derived from Greek (karcharos, sharp or jagged), and ῥί̄νη (rhinē, rasp); both elements describe the jagged, rasp-like skin.[7] Rasp-like skin is typical of shark skin in general, and is not diagnostic to Carcharhinidae.
The oldest member of the family is Archaeogaleus lengadocensis from the Early Cretaceous (Valanginian) of France.[8] Only a handful of records of the group are known from prior to the beginning of the Cenozoic.[9] Modern carcharinid sharks have extensively diversified in coral reef habitats.[10]
Requiem sharks are extraordinarily fast and effective hunters. Their elongated, torpedo-shaped bodies make them quick and agile swimmers, so they can easily attack any prey. Some species are continually active, while others are capable of resting motionless for extended periods on the bottom. They have a range of food sources depending on location and species, including bony fish, squid, octopus, lobster, turtles, marine mammals, seabirds, other sharks and rays; smaller species tend to select a narrow range of prey, but some very large species, especially the tiger shark (Galeocerdo cuvier), are virtually omnivorous. They are often considered the "garbage cans" of the seas because they will eat almost anything, even non-food items like trash. They are migratory hunters that follow their food source across entire oceans. They tend to be most active at night time, where their impressive eyesight can help them sneak up on unsuspecting prey. It is worth mentioning that the tiger shark, however, possibly belongs to the Galeocerdidae family.[11] Most requiem sharks hunt alone, however some species like the whitetip reef sharks and lemon sharks are cooperative feeders and will hunt in packs through coordinated, timed attacks against their prey. Some of the species have been shown to give specialized displays when confronted by divers or other sharks, which may be indicative of aggressive or defensive threat.
The 59 species of requiem shark are grouped into 11 genera:[1]
† = extinct
Book: Compagno, Leonard J.V. . 1984 . Rome . FAO species catalogue Vol.4. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. Part 2. Carcharhiniformes. . 9251013837 .