Family: Squatinidae – Angel Sharks
Common Name– Angel Sharks or Angelsharks
Status: IUCN Red List DATA DEFICIENT
Average Size and Length: They are known to reach at least 4.4 feet. One small male was measured at 4.1 feet. One female was measured at 1.5 feet, more than likely juvenile.
Current Rare Mythical Sightings: The Indonesian angelshark was first described by Commonwealth Scientific and Industrial Research Organisation (CSIRO) researchers Peter Last and William White in a 2008 volume of the scientific journal Zootoxa, based on specimens found at several Indonesian fish landing sites. One of the specimens, a 47 cm (19 in) long female from the Cilacap landing site in central Java, was designated the holotype. The origin of the word legnota is from the Greet word legnotos meaning “having a colored border”, which refers to the dark leading margins of the pectoral fins.
Teeth and Jaw: They have expendable necks and trap-like jaws that can rapidly snap upwards and hinge shut. They have long, but small, needle-like teeth in the upper and in the lower jaws used for gripping. The large, terminal, curved mouth is placed at the front of the head. There are long, deep furrows extending from the mouth corners onto and away from the lower jaw. The teeth number around 18 rows in both jaws; each is small and dagger-like, with a single sharp cusp.
Head: The broad, laterally extended, flattened head has a very short, blunt snout and small, widely spaced eyes placed somewhat on top. The eyes are followed by much larger, crescent-shaped spiracles. The nostrils are large and preceded by well-developed flaps of skin that reach the mouth. Each flap has two prominent barbels, which are smooth rather than fringed; the Indonesian angelshark lacks fringe on its nasal barbels. The five pairs of gill slits are long and placed on the sides of the head.
Denticles: It does not have thorns down the midline of its back. The dorsal surface is covered by small, roughly conical dermal denticles. They are less dense or absent on posterior borders of fins.
Tail: It has a well-developed long tail and caudal fin. The caudal peduncle is moderately flattened and expanded laterally into keels. The lower lobe of the short and triangular caudal fin is larger than the upper, and there is a notch in the upper lobe trailing margin.
Demographic, Distribution, Habitat, Environment and Range: The Indonesian angelshark can be found in the Indian Ocean off of southern Indonesia. The known specimens of the Indonesian angelshark have come from fish landing sites at Palabuhanratu in West Java, Cilacap in Central Java, Kedonganan in Bali, and Tanjung Luar in Lombok (6°S – 8°S). It is thought to inhabit the deep waters of the continental slope. They are considered benthopelagic, preferring tropical climates.
Ram-Suction Index: They have an RSI more towards the suction end of the scale. They lay flat and still on the bottom, when the time comes, they lung at prey and suck it into their mouths with negative pressure.
Aesthetic Identification: The Indonesian angelshark has a flattened, ray-like shape with an anteriorly depressed body, depressed trunk, greatly elongated pectoral and pelvic fins that look like wings, giving it the appearance of an angel. The Indonesian angelshark is plain grayish-brown dorsally with dark saddles beneath the dorsal fin bases and a black leading margin on the underside of the pectoral fins. There is darkening around the eyes and on the snout and becoming translucent at the trailing fin margins. There are sometimes large, dark blotches and ocelli scattered over the dorsal surface. The underside is almost completely white. The pectoral fins are angular, with the anterior lobes of their bases free from the head, and their outer tips forming an angle of slightly under 120°. The tips of the pelvic fins are rounded. The two dorsal fins are close in shape and size, with rounded to angular apexes and slightly convex trailing margins. The first dorsal fin originates over the pelvic fin’s rear tips and the second dorsal fin is placed close to the first. There is no anal fin.
Biology and Reproduction: The Indonesian angelshark is presumably ovoviviparous.
Björn Stelbrink and colleagues’ 2010 phylogenetic analysis, based on mitochondrial DNA, found that the sister species of the Indonesian angelshark is the Taiwan angelshark (S. formosa); the two were the closest genetically of all the species examined. The pair additionally formed a clade with the Japanese angelshark (S. japonica) and the Ocellated angelshark (S. tergocellatoides). (Stelbrink, B.; T. von Rintelen; G. Cliff & J. Kriwet (2010). “Molecular systematics and global phylogeography of angel sharks (genus Squatina)“. Molecular Phylogenetics and Evolution. 54: 395–404)
Behavioral Traits, Sensing and Intelligence: The Indonesian angelshark lies semi-buried in the sand or on the muddy bottom waiting and ready to ambush prey. They can remain still on the bottom for extremely long and extended periods of time.
Indonesian angelsharks have a unique way of breathing compared to most other benthic sharks and fish. They do not pump out water from the oropharyngeal cavity. Instead, they use gill flaps located on the sides of their body to pump out water during respiration. Doing so also allows them to be more unnoticeable and prevent detection from unwanted predators.
Indonesian Angelshark Future and Conservation: The Indonesian angelshark is rarely caught on demersal longlines and marketed for meat and fins. If the Indonesian deepwater fisheries were to expand, this species may be threatened as other Angel shark species have shown themselves to be particularly susceptible to fishing depletion due to their high value, and low reproduction rates. The International Union for Conservation of Nature has listed this shark under Data Deficient.
Indonesian Angelshark Recorded Attacks on Humans: Indonesian angelsharks aren’t dangerous to humans unless provoked. Because of their powerful jaws and sharp teeth, they can inflict injury on anyone or anything that may pose a threat to them. There have been cases of Angel sharks biting divers that have tried to restrain them, approach too close to the head, corner them, or grab their tails.
(Last, P.R.; W.T. White (March 28, 2008). “Three new angel sharks (Chondrichthyes: Squatinidae) from the Indo-Australian region“. Zootaxa. 1734: 1–26.)