, the nurse shark, resides in coastal waters in the Pacific and Atlantic Oceans. In the Pacific Ocean, nurse sharks are found in waters off the coast of Estero de La Bocana, Baja California Sur (26.8159°N latitude and -113.7945°W longitude) in Central America along the Pacific coast and completely inhabiting the Gulf of California, and to just south of the coast of Nazca, Peru (-15.2830°S latitude and -75.6732°W longitude) in South America.
In the western Atlantic Ocean, nurse sharks are found in coastal waters ranging from Portsmouth, New Hampshire, United States of America (43.0691°N latitude and -70.6227°W longitude) and southern Belize (16.4254°N latitude and -87.8582°W longitude). They are also found in the waters off Cuba, the Bahamas, the Dominican Republic, and Puerto Rico. Nurse sharks are found along South America starting from Guyana (8.2830°N latitude and -58.7204°W longitude) and spanning south to the State of Sao Paulo (-23.8261°S latitude and -44.6038°W long).
In the eastern Atlantic Ocean, nurse sharks live in the Bay of Biscay between France and Spain near the coast (45.2637°N latitude and -4.2776°W longitude) as well as from the Strait of Gibraltar (35.9421°N latitude and -5.6754°W longitude) south to Luanda, Angola (-8.7699°S latitude and 13.1463°E longitude) in Africa. (Rosa, et al., 2006)
Nurse sharks inhabit coastal saltwater coral reefs in tropical and subtropical climates. Juvenile nurse sharks are found at depths ranging from 1 to 4 meters, older juveniles and adults range from depths of 1 to 75 meters during the day. At night both juveniles and adults stay between 1 and 20 meters in depth. Juveniles are more often found in crevices in shallow lagoons. Adults are more wide-ranging, inhabiting deeper reefs, around bridges, rocky areas, and boulders. The lowest recorded depth was at 130 meters. This species is not migratory and shows strong site fidelity. (Castro, 2000; Ebert, et al., 2013; Ferreira, et al., 2013)
Nurse sharks are yellow to grayish-brown in color. Adult mass ranges from 70.45 to 114.5 kg. A nurse shark at birth is 27 to 30 cm in length, while an adult is 107 to 300 cm long with an average length of 193 cm. Sizes do not vary significantly between sexes. Masses recorded vary greatly with only the largest of the sexes being reported in literature. Castro (2000) writes of the exaggerated weights in previous literature. The largest he examined was one female weighing near 114.5 kg. Not surprisingly, Castro (2000) reports that females with eggs have the greatest mass. Nurse sharks have five gills located between the head and first dorsal fin. The fifth gill almost overlaps the fourth. The dorsal and second dorsal fins are rounded. The first dorsal fin is 25% larger than the second. The anal fins are similar in size to the second dorsal fins and precede the tail. Nurse sharks have nasoral grooves and long barbels that surround the mouth. The eye location is dorsolateral approximately 20 cm from the mouth in adults. Between the eyes and gills is a spiracle which is a vestigial gill slit that takes in oxygen from the surrounding water while the shark is stationary. A juvenile nurse shark can be identified by small, dark, ocellar spots covering its body. These sharks have 30 to 42 upper teeth and 28 to 34 lower teeth in single rows. (Allaby, 2014; Castro, 2000; Ebert, et al., 2013; Ferreira, et al., 2013; Santander-Neto, et al., 2011)
Nurse sharks have a single litter, which often includes multiple paternities. Carrier and Luer (1990), found that growth rates in the population averaged 13.1 ± 9.5 cm per year and 2.3 ± 1.3 kg per year in the wild, but a nurse shark kept in captivity grew slightly faster at 19.1 ± 4.9 cm per year and 4.0 ± 1.7 kg per year. Nurse sharks exhibit indeterminate growth, but the rate of growth slows as they age. (Carrier and Luer, 1990; Ebert, et al., 2013)
Male nurse sharks begins mating by nudging the female into position with their head. Often he will bite a pectoral fin or flank in order to hold on. The male then inserts its clasper until sperm transfer is complete. Like other sharks, the purpose of the male's siphon sac is to assist in sperm competition and to flush rival sperm out. The siphon sac is a pair of bladders attached to the claspers of the male that uses seawater to inject its sperm into the cloaca from the clasper. The action of contracting the bladder and force from the seawater flushes competing sperm out of the female nurse shark. This happens just prior to copulation. During copulation, the female nurse shark remains quite motionless. Biting behavior in males has been noted as being a possible indicator of a sexual hierarchy and is maintained through such behavior. Nurse sharks repeatedly use the same mating locations. They also stay in the same group after copulation. Nurse sharks are polygynandrous and both sexes have multiple partners through a several week mating period in June and July. Other specific courtship and mating behaviors include the male and female swimming parallel and synchronously side-by-side. If the female is avoiding copulation she will lie on her back, float in the water, or rest motionlessly on the ocean floor. The female might also pivot and roll on her back when a male bites her pectoral fin. If the female is receptive, she will arch her body toward the male, cupping her pelvic fins. (Pratt Jr. and Carrier, 2001)
Nurse sharks are ovovivoparous or aplacental viviparous (Compagno, 2002). Nurse shark litters range from 20 to 30 pups arising from multiple paternities. Breeding season, copulation, and fertilization occurs in June and July and lasts 2 to 4 weeks. Gestation takes 5 to 6 months. Litters form a nursery in areas of shallow turtle-grass (Thalassia testudinum) beds and coral reefs. Nurse sharks reach sexual maturity at certain lengths depending on sex. When the male reaches 200 to 210 cm in length after 10 to 15 years of age they have reached sexual maturity, while the female reaches sexual maturity between 240 and 260 cm after 15 to 20 years. Female nurse sharks only reproduce every other year. New born pup length range is 27 to 30 cm long. Nothing is recorded on initial pup weight or age of independence. (Carrier and Luer, 1990; Compagno, 2002; Ebert, et al., 2013; Pratt Jr. and Carrier, 2001; Rosa, et al., 2006)
Nurse shark parental investment is limited past the juvenile nursery in the local habitat. Research does not indicate whether or not it is currently known for parents to have specificity towards caring for specific pups. The promiscuous nature of both sexes and multiple paternity in a litter is likely to attribute to the community raising effort in the nursery. It is not outwardly apparent that there are distinguishing features to identify paternity among the litter. The litter is involved in the social group of the local nurse shark population and as such inherits the local territory. (Compagno, 2002; Ebert, et al., 2013; Pratt Jr. and Carrier, 2001)
Carey and Judge (2000) report that the longest known living nurse shark was 25 years old in the wild, which is sourced from an aquarium publication from 1963. Maximum or average longevity in captivity has not been reported. There is also no established expected age in the wild. (Carey and Judge, 2000; Rosa, et al., 2006)
Nurse sharks are social and nocturnal. They stay in groups and return at dawn to the same location for rest in groups or piles. The social hierarchy may be correlated with the same biting as performed during mating. Nurse sharks use olfaction to find prey. They use the snout to push the mouth against small crevices and suck prey out. These sharks are territorial and will bite competing sharks for prey. (Castro, 2000; Ebert, et al., 2013; Pratt Jr. and Carrier, 2001)
The home range is very limited, sources not listing specific territory sizes. Multiple studies had the same tagged specimen return over the course of multiple years. It often returns from feeding during the night to the same shallow water or cave locations by dawn to rest in groups or piles. Nurse sharks have high territorial fidelity and do not travel more than several square kilometers from their point of origin. (Castro, 2000; Compagno, 2002; Ebert, et al., 2013)
Nurse sharks are very social and use sight, sound, electroreception, touch, and smell to detect its surroundings. Sight is solely from vision but is almost always accompanied by other senses. Sight is limited to 10 meters. Nurse sharks do not identify prey with sight. Sound is in the form of an acoustic near and far-field perception. Gardiner et al. (2014) report that the near-field perception can acquire sound pressure signals at distances 0.4 to 2 body lengths of the nurse shark, while far-field perception can be detected in low frequency signals over multiple kilometers away. This is slightly different than reported by Casper and Mann (2006), who found that the nurse shark's most sensitive hearing is between 300 Hz and 600 Hz which is in the ultra low frequency spectrum. Olfaction, or smell, is used to detect odor plumes of prey. The variables that determine the distance an odor plume is detectable is the source strength, wavelength, and environmental signal-to-noise ratio. Smell is used for prey identification. Gardiner et al. (2014) found that by blocking olfaction, nurse sharks neither detect nor feed on nearby prey. Electroreception is through the ampullae of Lorenzini located in the shark's snout. This electroreception is used for precise directional locating of prey or other creatures. This is used at distances less than 1 meter. (Casper and Mann, 2006; Ebert, et al., 2013; Gardiner, et al., 2014)
Nurse sharks are obligate ocean floor feeders. Nurse sharks are adapted to suction-feed within 3 cm of their mouth. The mode of hunting is foraging, stalking, and ambushing prey, most often at night. Rosa (2006) stated that stomach contents included small teleosts, cephalopods, gastropods, bivalves, sea urchins, and crustaceans as the main prey but contents also contained coral pieces and algae. The following is a breakdown of stomach contents included in stomach sampling from Castro (2000): Anthozoa 1.49%, Cephalopoda 4.46%, Crustacea 1.98%, Chondrichthyes 0.50%, Teleostei 89.11%, Other 2.48%. (Castro, 2000; Motta, et al., 2008; Rosa, et al., 2006)
Nurse sharks have few known predators. One juvenile nurse shark measuring 45 cm was found in the stomach of a 234 cm lemon shark (Negaprion brevirostris). Two nurse sharks of unstated lengths were recorded as being in a 224 cm tiger shark (Galeocerdo cuvier). Great hammerhead (Sphyrna mokarran) and bull sharks (Carcharhinus leucas) were observed attacking multiple nurse sharks on several occasions but failed to injure any and aren't listed as actual predators. (Castro, 2000; Rosa, et al., 2006)
Pedibothrium brevispine, Pedibothrium globicephalum, Prochristianella tenuispine, Grillotia similis, Pedibothrium maccalumi, Pedibothrium servattorum, Pedibothrium manteri, Pedibothrium lintoni, and Pedibothrium longispine. It is also host to the roundworm Lockenloia sanguinis. (Adamson and Caira, 1991; Borucinska and Caira, 1993; Caira and Pritchard, 1986; Caira, 1992)is host to the following tapeworms:
Nurse sharks are captured by humans (Homo sapiens) for private aquariums and the ornamental fish trade. They are typically docile in captivity. The skin is also used for leather. In Panama, thay are fished for fins and meat. The IUCN states the fins and meat are sold at a rate of US$ 0.75 per pound. Specifics on gross sales is not accounted for. Nurse sharks are important in some ecotourism ventures. (Castro, 2000; Ebert, et al., 2013; Rosa, et al., 2006)
Occasionally nurse sharks are unintentionally trapped in fish nets , which leads to increased worker time spent releasing them. If harassed while swimming, diving, or snorkeling, nurse sharks will bite but usually leave humans alone. (Rosa, et al., 2006)
The IUCN red list reports the nurse shark as a "Data Deficient" species. However, Columbia has several protected areas as part of a habitat protection campaign that the nurse shark coincidentally inhabits. The nurse shark is listed as "Vulnerable" in Brazil. The IUCN reports that there are little data on the migration habits and mating between shivers (pods or schools) of nurse sharks across different sites. Due to the strong site fidelity of the nurse shark, there have been cases of geographic population fragmentation and local extinctions. The vulnerability off the coast of South America, Central America, and Caribbean has caused it to be assessed as "Near Threatened" in these areas. The United States and Bahamas are reported as "Least Concern" status. (Rosa, et al., 2006)
Michael Barbour (author), Radford University - Fall 2015, Karen Powers (editor), Radford University, April Tingle (editor), Radford University, Cari Mcgregor (editor), Radford University, Zeb Pike (editor), Radford University, Jacob Vaught (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.
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.
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
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.
ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
uses electric signals to communicate
an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
Animals with indeterminate growth continue to grow throughout their lives.
fertilization takes place within the female's body
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
eats mollusks, members of Phylum Mollusca
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
reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.
the business of buying and selling animals for people to keep in their homes as pets.
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
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
uses sight to communicate
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