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Epaulette shark
The epaulette shark (/ɛpəlɛt ʃɑːrk/, Hemiscyllium ocellatum) is a species of longtailed carpet shark of the family Hemiscylliidae, found in shallow, tropical waters off Australia and New Guinea (and possibly elsewhere). The common name of this shark comes from the very large, white-margined black spot behind each pectoral fin, which are reminiscent of military epaulettes. A small species (usually under 1 m (3.3 ft) long), the epaulette shark has a slender body with a short head and broad, paddle-shaped paired fins. The caudal peduncle (to which the tail fin is attached) comprises over half the shark's length. Adults are light brown above, with scattered darker spots and indistinct saddles.
Epaulette sharks have nocturnal habits and frequent shallow water on coral reefs or in tidal pools. This shark has evolved to cope with the severe night time oxygen depletion (hypoxia) in isolated tidal pools by increasing the blood supply to its brain and selectively shutting down non-essential neural functions. It is capable of surviving complete anoxia for two hours without ill effects, and at a much higher temperature than most other hypoxia-tolerant animals. Rather than swim, epaulette sharks often "walk" by wriggling their bodies and pushing with their paired fins. This species feeds on a wide range of small benthic invertebrates and bony fishes. Epaulette sharks are oviparous, with females depositing pairs of egg capsules around every 14 days from August to December. Due to their hardiness and small size, epaulette sharks are popular with both public and home aquaria. The International Union for Conservation of Nature (IUCN) has assessed this species as of Least Concern, as outside of the small aquarium trade it is of little interest to fisheries.
The epaulette shark was originally described as Squalus ocellatus by the French naturalist Pierre Joseph Bonnaterre in the 1788 Tableau encyclopédique et méthodique des trois règnes de la nature. The name was later changed to the currently valid Hemiscyllium ocellatum. The type specimen was a 35 cm (14 in) long immature male caught near Cooktown, Queensland, Australia. Other common names for this species are the itar shark and the blind shark (also used for Brachaelurus waddi). Goto's 2002 morphological analysis of the carpet sharks showed the genus Hemiscyllium as a polytomy, meaning that the phylogenetic relationships between the epaulette shark and its sister species could not be resolved.
The range of the epaulette shark extends from the southern coast of New Guinea to the northern coast of Australia, as far south as Sydney. The Capricorn-Bunker Group of the Great Barrier Reef contains a particularly large population, with thousands estimated to inhabit the reefs around Heron Island alone. The estimated population density of these reefs is approximately 0.3 to 1.2 individuals per 100 square meters. Additionally, there are unsubstantiated reports of this species from Malaysia, Sumatra, and the Solomon Islands. Epaulette sharks are found in shallow water to a maximum depth of 50 m (160 ft), and are often seen in water barely deep enough to cover their bodies. They prefer tidal pools, coral flats, and stands of staghorn coral.
The epaulette shark has an elongated body, over half of which is comprised by the slender caudal peduncle. The snout is short and rounded, with the nares placed almost at the tip along with a pair of tiny barbels; there are grooves running from the nares to the mouth. There are 26–35 tooth rows in the upper jaw and 21–32 tooth rows in the lower jaw. The teeth are small, with broad bases and triangular cusps. The eyes are oval in shape and elevated, with a large spiracle below each. The five pairs of gill slits are small, with the fourth and fifth very close together.
The pectoral and pelvic fins are broad and rounded and are thickly muscled. The two similarly sized dorsal fins are placed well back on the body. The anal fin is low and positioned just in front of the caudal fin. The caudal fin has only an upper lobe, which contains a prominent ventral notch near the tip and is angled almost horizontally relative to the body. Adult epaulette sharks are beige to brownish above with many widely spaced brown spots and subtle darker bands. There is a very large black spot ringed in white located behind each pectoral fin; this pair of spots are the origin of this shark's common name. Juveniles have alternating light and dark bands over their body and fins, which break up as they mature. Epaulette sharks are typically 70–90 cm (27.5–35.5 in) long; the maximum reported length is 107 cm (42 in).
As an adaptation for navigating its complex reef environment, the epaulette shark moves by seemingly walking, bending its body from side-to-side and pushing off of the substrate with its paddle-shaped pectoral and pelvic fins. Its gait is similar to that of salamanders, an example of convergent evolution. The shark is capable of swimming, but often prefers to walk along the sandy or coral bottom even when the water is deep enough to allow it to swim freely. The cartilaginous supports of the epaulette shark's paired fins are reduced and separated when compared to other sharks, allowing them to be rotated for use as limbs. This mode of locomotion even enables the shark to crawl out of the water to access isolated tidal pools. The gait of the epaulette shark is convergently similar to those of tetrapods such as salamanders, suggesting that the movements needed for walking on land may predate, and perhaps contributed to the evolution of, the first terrestrial vertebrates. Epaulette sharks are largely nocturnal and are most active in low water. They often hide inside or below coral heads, though it is enough for the head to be covered even if the rest of the body is exposed. Sometimes they perch in the open on sandy flats or atop reefs facing into the current, a form of orientation known as rheotaxis that may improve respiration or predator awareness.
Epaulette sharks are preyed upon by larger fishes such as other sharks. Its coloration provides protective camouflage, while its epaulette is speculated to be an eyespot for distracting or deterring predators. Epaulette sharks are almost all parasitized by the praniza (parasitic) larval stage of gnathiid isopods. The larvae feed on blood and mostly attach to the skin around the cloaca and the claspers, though they are also found inside the mouth and on the gills. These parasites cause little damage and are not believed to adversely affect the health of the shark. Other parasites of this species include a species of myxosporean in the genus Kudoa, which infests the skeletal muscles, the hemogregarine protozoan Haemogregarina hemiscyllii, which infects the blood, the ostracod Sheina orri, which attaches to the gills, and the nematode Proleptus australis, which infests the stomach.
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Epaulette shark
The epaulette shark (/ɛpəlɛt ʃɑːrk/, Hemiscyllium ocellatum) is a species of longtailed carpet shark of the family Hemiscylliidae, found in shallow, tropical waters off Australia and New Guinea (and possibly elsewhere). The common name of this shark comes from the very large, white-margined black spot behind each pectoral fin, which are reminiscent of military epaulettes. A small species (usually under 1 m (3.3 ft) long), the epaulette shark has a slender body with a short head and broad, paddle-shaped paired fins. The caudal peduncle (to which the tail fin is attached) comprises over half the shark's length. Adults are light brown above, with scattered darker spots and indistinct saddles.
Epaulette sharks have nocturnal habits and frequent shallow water on coral reefs or in tidal pools. This shark has evolved to cope with the severe night time oxygen depletion (hypoxia) in isolated tidal pools by increasing the blood supply to its brain and selectively shutting down non-essential neural functions. It is capable of surviving complete anoxia for two hours without ill effects, and at a much higher temperature than most other hypoxia-tolerant animals. Rather than swim, epaulette sharks often "walk" by wriggling their bodies and pushing with their paired fins. This species feeds on a wide range of small benthic invertebrates and bony fishes. Epaulette sharks are oviparous, with females depositing pairs of egg capsules around every 14 days from August to December. Due to their hardiness and small size, epaulette sharks are popular with both public and home aquaria. The International Union for Conservation of Nature (IUCN) has assessed this species as of Least Concern, as outside of the small aquarium trade it is of little interest to fisheries.
The epaulette shark was originally described as Squalus ocellatus by the French naturalist Pierre Joseph Bonnaterre in the 1788 Tableau encyclopédique et méthodique des trois règnes de la nature. The name was later changed to the currently valid Hemiscyllium ocellatum. The type specimen was a 35 cm (14 in) long immature male caught near Cooktown, Queensland, Australia. Other common names for this species are the itar shark and the blind shark (also used for Brachaelurus waddi). Goto's 2002 morphological analysis of the carpet sharks showed the genus Hemiscyllium as a polytomy, meaning that the phylogenetic relationships between the epaulette shark and its sister species could not be resolved.
The range of the epaulette shark extends from the southern coast of New Guinea to the northern coast of Australia, as far south as Sydney. The Capricorn-Bunker Group of the Great Barrier Reef contains a particularly large population, with thousands estimated to inhabit the reefs around Heron Island alone. The estimated population density of these reefs is approximately 0.3 to 1.2 individuals per 100 square meters. Additionally, there are unsubstantiated reports of this species from Malaysia, Sumatra, and the Solomon Islands. Epaulette sharks are found in shallow water to a maximum depth of 50 m (160 ft), and are often seen in water barely deep enough to cover their bodies. They prefer tidal pools, coral flats, and stands of staghorn coral.
The epaulette shark has an elongated body, over half of which is comprised by the slender caudal peduncle. The snout is short and rounded, with the nares placed almost at the tip along with a pair of tiny barbels; there are grooves running from the nares to the mouth. There are 26–35 tooth rows in the upper jaw and 21–32 tooth rows in the lower jaw. The teeth are small, with broad bases and triangular cusps. The eyes are oval in shape and elevated, with a large spiracle below each. The five pairs of gill slits are small, with the fourth and fifth very close together.
The pectoral and pelvic fins are broad and rounded and are thickly muscled. The two similarly sized dorsal fins are placed well back on the body. The anal fin is low and positioned just in front of the caudal fin. The caudal fin has only an upper lobe, which contains a prominent ventral notch near the tip and is angled almost horizontally relative to the body. Adult epaulette sharks are beige to brownish above with many widely spaced brown spots and subtle darker bands. There is a very large black spot ringed in white located behind each pectoral fin; this pair of spots are the origin of this shark's common name. Juveniles have alternating light and dark bands over their body and fins, which break up as they mature. Epaulette sharks are typically 70–90 cm (27.5–35.5 in) long; the maximum reported length is 107 cm (42 in).
As an adaptation for navigating its complex reef environment, the epaulette shark moves by seemingly walking, bending its body from side-to-side and pushing off of the substrate with its paddle-shaped pectoral and pelvic fins. Its gait is similar to that of salamanders, an example of convergent evolution. The shark is capable of swimming, but often prefers to walk along the sandy or coral bottom even when the water is deep enough to allow it to swim freely. The cartilaginous supports of the epaulette shark's paired fins are reduced and separated when compared to other sharks, allowing them to be rotated for use as limbs. This mode of locomotion even enables the shark to crawl out of the water to access isolated tidal pools. The gait of the epaulette shark is convergently similar to those of tetrapods such as salamanders, suggesting that the movements needed for walking on land may predate, and perhaps contributed to the evolution of, the first terrestrial vertebrates. Epaulette sharks are largely nocturnal and are most active in low water. They often hide inside or below coral heads, though it is enough for the head to be covered even if the rest of the body is exposed. Sometimes they perch in the open on sandy flats or atop reefs facing into the current, a form of orientation known as rheotaxis that may improve respiration or predator awareness.
Epaulette sharks are preyed upon by larger fishes such as other sharks. Its coloration provides protective camouflage, while its epaulette is speculated to be an eyespot for distracting or deterring predators. Epaulette sharks are almost all parasitized by the praniza (parasitic) larval stage of gnathiid isopods. The larvae feed on blood and mostly attach to the skin around the cloaca and the claspers, though they are also found inside the mouth and on the gills. These parasites cause little damage and are not believed to adversely affect the health of the shark. Other parasites of this species include a species of myxosporean in the genus Kudoa, which infests the skeletal muscles, the hemogregarine protozoan Haemogregarina hemiscyllii, which infects the blood, the ostracod Sheina orri, which attaches to the gills, and the nematode Proleptus australis, which infests the stomach.