Family members have the usual carcharhiniform characteristics. Their eyes are round, and one or twogill slits fall over thepectoral fin base. Most species areviviparous, the young being born fully developed. They vary widely in size, from as small as 69 cm (2.26 ft) adult length in theAustralian sharpnose shark, up to 4 m (13 ft) adult length in theoceanic 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 theISAF, requiem sharks are among the top five species involved inshark 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 namerequiem shark may be related to the French word for shark,requin, which is itself of disputed etymology. One derivation of the latter is from Latinrequiem ("rest"), which would thereby create a cyclic etymology (requiem-requin-requiem), but other sources derive it from the Old French verbreschignier ("to grimace while baring teeth").
The scientific nameCarcharhinidae was first proposed in 1896 byD.S. Jordan andB.W. Evermann as a subfamily of Galeidae (now replaced by "Carcharhinidae").[6][7] The term is derived from Greekκάρχαρος (karcharos, sharp or jagged), and ῥί̄νη (rhinē, rasp); both elements describe the jagged, rasp-like skin.[8] Rasp-like skin is typical ofshark skin in general, and is not diagnostic to Carcharhinidae.
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, includingbony fish,squid,octopus,lobster,turtles,marine mammals,seabirds, other sharks andrays; smaller species tend to select a narrow range of prey, but some very large species, especially thetiger shark (Galeocerdo cuvier), are virtually omnivorous.[7] They are often considered the "garbage cans" of the seas because they will eat almost anything, even non-food items like trash.[7] They are migratory hunters that follow their food source across entire oceans. They tend to be most active at night time,[7] where their impressive eyesight can help them sneak up on unsuspecting prey. It is worth mentioning that the tiger shark, however, possibly belongs to theGaleocerdidae family.[12] Most requiem sharks hunt alone, however some species like thewhitetip reef sharks andlemon 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.[7]
^Pollerspöck, J.; Straube, N. Bibliography Database of Living/Fossil Sharks, Rays and Chimaeras (Chondrichtyes: Elasmobranchii, Holocephali)—List of Valid Extant Species; List of Described Extant Species; Statistic, World Wide Web Electronic Publication, Version 10/2021;ISSN2195-6499. Available online: www.shark-references.com (accessed on 23 November 2021).
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