The genus Carcharhinidae, commonly known as requiem sharks. The genus contains two extant species: the lemon shark, Negaprion brevirostris, and the sicklefin lemon shark, Negaprion acutidens. The genus also includes one extinct species, Negaprion eurybathrodon. Species in this genus inhabit coastal water in the Atlantic, Pacific, and Indian Oceans and. They can measure between 150 and 300 cm and weigh up to 180 kg, and use their grayish yellow coloring to blend in to the sandy ocean floor (Morgan 2018). Lemon sharks are apex predators, but they are regularly hunted for their fins and are now listed as vulnerable on the IUCN Red List. (Morgan, 2018)is one of 12 genera in the family
N. brevirostris) is found in the nearctic and neotropical regions of the Atlantic Ocean, from the northern coast of the United States all the way to southern Brazil, including the Caribbean and the Gulf of Mexico. There is a relict population of N. brevirostris in the eastern Pacific along the coast of Central America (Morgan, 2018). In this population, there is evidence of allopatric speciation corresponding with the formation of the Panama land bridge (Schultz, 2008). The sicklefin lemon shark (N. acutidens) is found in the Indian Ocean along the eastern coast of Africa, around the Sinai Peninsula, and throughout the Indonesian Archipelago to Australia. g. Negaprion species were previously common throughout the tropical and subtropical Indo-West Pacific, but overfishing and habitat destruction has led to their disappearance from the coasts of India and Thailand. (Morgan, 2018; Schultz, 2008)species inhabit tropical temperate regions around the world. The common lemon shark (
Maturity is reached at 225cm for males and 235cm for females, or around 13 years of age. Lemon sharks measure between 55 and 60 centimeters at birth and grow at a rate of approximately four centimeters per month (Gruber, 1981). Some studies have recorded much faster growth rates. This is likely because captive individuals have four times faster growth rates than those in the wild, meaning that food availability is a limiting factor. (Stevens, 1984; Sundström, 2015)
Information about shark breeding behavior is very limited, but it is known that they exhibit internal fertilization. Males have paired claspers used for sperm transfer by attaching to the female. The mating process involves males grasping onto females with their teeth, causing females to often exhibit lacerations during mating season (Feldheim, Gruber, and Ashley, 2002). Females can mate with several males in one mating season and also may store sperm from several males which results in multiple paternity of the litters. (Feldheim, et al., 2002; Feldhiem, et al., 2001)
Lemon sharks are viviparous, giving birth to between 4 and 17 live young in each litter. Females reach sexual maturity between 12 and 16 years of age and then follow a two-year reproductive cycle. Mating usually occurs in spring, with gestation lasting between 10 and 12 months. Females exhibit strong site fidelity for parturition, and their young maintain this strong attachment for several years after their birth. (Feldheim, et al., 2002; Filmalter, et al., 2013; Gruber, et al., 1988)
Lemon sharks can live up to 25 years in captivity. There have been no ongoing studies of lifespan in the wild. ("Lemon Shark", 2018)species are estimated to live between 27 and 30 years based on growth rate information
Lemon sharks are usually solitary but can found in groups of up to 20 individuals, often around fishing docks or protected atolls. These sharks are active throughout the day but are most active around dusk and dawn. Juvenile ("Lemon Shark", 2018; Morgan, 2018; Sundström, 2015)species remain in the nursery areas until they are mature enough to begin their migrations. Little is known about the patterns or distances of these movements, but females will return to the same areas biannually to give birth to their young.
These sharks can orient themselves based on sound at a distance of about two meters, which is less than most large sharks.They can hear low frequencies best, with a low threshold of 40 hertz, but are also receptive to higher frequencies up to 320 Hertz. (Nelson, 1967)
Smell plays an important role for lemon sharks in food localization, predator detection, homing and navigation, and also likely in mating. It enables them to detect chemical cues at great distances because those cues can be transported on currents much farther than electric signals. (Tricia and Kajiura, 2010)
Lemon sharks have laterally mounted eyes with little overlap between their monocular fields of vision. They have vertically slit pupils which contract under bright light, and retinas with cones which allow them to see in color. (Hueter and Gruber, 1982)
Young feed mostly on teleost fishes, crustaceans, and octopods. Older sharks eat mostly teleosts and cartilaginous fishes (other sharks), and sometimes even seabirds. Lemon sharks use sight, smell, hearing, and electrical sensitivity in order to locate food. (Fields, 2007; Stevens, 1984)
Adult lemon sharks have no predators. Juvenile sharks are occasionally eaten by adults or by other shark species. (Sundström, 2015)
Lemon sharks are hosts to a variety of endo- and ectoparasites, including copepod species and tapeworms. Remoras (Echeneis naucrates) are also commonly found on lemon sharks, though these two organisms share a symbiotic relationship. Remoras latch onto sharks for transportation and eat scraps from their meals. In return, Remoras eat dead skin and dermal parasites, keeping the sharks healthy.
Historically, many parts of the lemon shark were used and sold, including the hide for leather and the liver which was used to produce liver oil with a high vitamin content. The flesh was sometimes used for fertilizer or chicken feed, or dried for human consumption (Baughman and Springer, 1950). More recently, (Baughman and Springer, 1950; Sundström, 2015)are hunted for their use in shark fin soup, a highly profitable practice.
Due to its relative abundance in coastal water, its adaptability to laboratory conditions, and their phyletic position, sharks in the genusare some of the most commonly studied sharks (Hueter and Gruber, 1982). They are well suited for experimental conditions because of their ability to ventilate their gills while stationary, which is an unusual trait among sharks.
Lemon sharks pose a very minimal threat to humans. There have been only 10 reports of unprovoked lemon shark attacks, none of which were fatal. (Sundström, 2015)
There are currently no conservation measures in place for any (Sundström, 2015)species. Lemon sharks from the Atlantic and Pacific Oceans are listed as near threatened on the IUCN Red List. Sicklefin lemon sharks from the Indian Ocean is listed as vulnerable due to overfishing and habitat loss and isolation. Sicklefin lemon sharks are popular in shark fin soups and are occasionally still caught for meat. Their population is declining, but no conservation efforts have been initiated yet.
Elena Haverluk (author), Colorado State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.
the body of water between Europe, Asia, and North America which occurs mostly north of the Arctic circle.
the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.
uses sound to communicate
Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
active at dawn and dusk
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
uses electric signals to communicate
parental care is carried out by females
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
fertilization takes place within the female's body
makes seasonal movements between breeding and wintering grounds
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
found in the oriental region of the world. In other words, India and southeast Asia.
An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).
an animal that mainly eats fish
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.
mainly lives in oceans, seas, or other bodies of salt water.
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
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