| Dark shyshark | |
|---|---|
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Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Division: | Selachii |
| Order: | Carcharhiniformes |
| Family: | Pentanchidae |
| Genus: | Haploblepharus |
| Species: | H. pictus |
| Binomial name | |
| Haploblepharus pictus (J. P. Müller &Henle, 1838) | |
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| Range of the dark shyshark[2] | |
| Synonyms | |
Scyllium pictumMüller & Henle, 1838 | |
Thedark shyshark orpretty happy (Haploblepharus pictus) is a species ofshark belonging to thefamilyPentanchidae, the deepwater catsharks. This species isendemic to thetemperate waters off southernNamibia and westernSouth Africa. It isbenthic in nature and inhabits shallow,inshore waters and favors rockyreefs andkelp forests. Growing to 60 cm (24 in) long, this small, stocky shark has a wide, flattened head with a rounded snout and a large flap of skin extending from before the nostrils to the mouth. Its dorsal coloration is extremely variable and may feature black-edged orange to blackish saddles and/or white spots on a light brown to nearly black background.
When threatened, the dark shyshark curls into a ring with its tail covering its eyes, hence the name "shyshark". It preys mainly on smallcrustaceans,bony fishes, andmolluscs. Reproduction isoviparous and proceeds throughout the year. Females lay twoegg cases at a time, which hatch after 6–10 months. This harmless species is of littlecommercial significance due to its small size. It is frequently caught byrecreational fishers and persecuted as a pest. TheInternational Union for Conservation of Nature (IUCN) has listed the dark shyshark underLeast Concern, as it is common and does not appear to be substantially threatened by fishing orhabitat degradation.
German physicians and biologistsJohannes Peter Müller andFriedrich Gustav Jakob Henle originally described the dark shyshark in their 1838–41Systematische Beschreibung der Plagiostomen, based on five specimens caught off theCape of Good Hope and deposited in theRijksmuseum van Natuurlijke Historie inLeiden,The Netherlands. Because of the shark's ornate coloration, they gave it thespecific epithetpictum from theLatin for "painted".[3][4] Originally placed in the now-obsolete genusScyllium, subsequent authors moved this species to the genusHaploblepharus, coined by AmericanzoologistSamuel Garman in 1913.[5]
The dark shyshark was often regarded to be the same as thepuffadder shyshark (H. edwardsii) until 1975, with the publication of A.J. Bass, Jeanette D'Aubrey, and Nat Kistnasamy's review of southern African sharks. It continues to be confused for the other three shyshark species because of its extremely variable coloration.[4][6] Thecommon name "pretty happy" ("happy" refers to the genus nameHaploblepharus) was recently introduced to the public as an easily remembered alternative to the colloquial names "shyshark" and "doughnut", which can apply to several species and have confounded research efforts.[2][4] Brett Human's 2006phylogenetic analysis, based on threemitochondrial DNAgenes, found that the dark shyshark and thebrown shyshark (H. fuscus) aresister species, and that the two make up the morederivedclade within the genus.[7]
Reaching no more than 60 cm (24 in) long, the dark shyshark differs from other shysharks in that it is slender-bodied when juvenile and stocky-bodied when adult. Its head is short, wide, and flattened, with a bluntly rounded snout and very large nostrils. The anterior rims of the nostrils bear greatly enlarged lobes of skin, which are fused into a single flap that reaches the mouth; the flap conceals the nasal excurrent openings and a pair of grooves that run between them and the mouth. The large, horizontally oval eyes are equipped with rudimentarynictitating membranes (protective third eyelids), and have strong ridges beneath. The mouth is short but wide and bears furrows at the corners extending onto both jaws. There are 45–83 upper and 47–75 lower tooth rows; each tooth has a long central cusp flanked by a pair of smaller cusplets. The five pairs ofgill slits are located fairly high on the body.[4][5]
The twodorsal fins are of nearly equal size and placed far back on the body, with the first originating over the latter third of thepelvic fin bases and the second over the latter half of theanal fin base. The pectoral and pelvic fins are broad and rounded; the males have stoutclaspers. The pelvic and anal fins are about as large as the dorsal fins. The broadcaudal fin comprises about a fifth of the total body length and has a strong notch near the tip of the upper lobe and an indistinct lower lobe. The skin is thick and covered by well-calcified arrowhead-shapeddermal denticles. The coloration of the dark shyshark is highly variable, and particular individuals can resemble any of the other shyshark species. The background color ranges from light brown to reddish to grayish to almost black above, transitioning abruptly to white or cream below, sometimes with dark blotches beneath the paired fins. There may be 6–8 orange, brown, or blackish variably shaped saddles along the back and tail, edged more or less obviously in black. There may also be white spots within or within and between the saddles.[4][5]
The range of the dark shyshark is restricted to the coastal waters of southern Africa, from north ofLüderitz in southernNamibia to east of theStorms River mouth in theEastern Cape Province ofSouth Africa. It is abundant, particularly west ofCape Agulhas.[4] This species is abottom-dweller found closeinshore, from theintertidal zone to a depth of 35 m (115 ft).[2] It prefers rocky reefs andkelp forests, but also presumably traverses sandy flats in between patches of more suitablehabitat. As this shark is not known to travel long distances, there is likely subpopulation differentiation across parts of its range.[1]
The dark shyshark is ageneralistpredator whose main food sources are, in descending order of importance, smallbenthiccrustaceans,bony fishes, andmolluscs. Larger sharks consume proportionately more crustaceans.[8]Polychaete worms andechinoderms are also taken on occasion, andalgae may be swallowed incidentally.[2] This species is preyed upon by thebroadnose sevengill shark (Notorynchus cepedianus), and potentially also other large fishes andmarine mammals.[9][10] When threatened, it adopts a characteristic defense posture in which it curls into a ring with its tail over its eyes; this behavior likely makes the shark harder to swallow and is the origin of the common names "shyshark" and "doughnut".[4][9] In captivity, thewhelksBurnupena papyracea andB. lagenaria have been documented piercing theegg cases of this species and extracting theyolk.[11] A knownparasite of the dark shyshark is thetrypanosomeTrypanosoma haploblephari, which infests theblood.[12]
Like other members of its genus, the dark shyshark isoviparous; adult females have a single functionalovary and two functionaloviducts.[13] There appears to be no distinctbreeding season and reproduction occurs year-round.[8] Females produce mature eggs two at a time, one per oviduct.[9] The eggs are enclosed in purse-shaped capsules measuring 5.5 cm (2.2 in) long and 2.5 cm (0.98 in) across; each capsule is plain amber to dark brown in color and bears thin, coiled tendrils at the four corners.[11] In one observation of an egg that hatched after 104 days, the developingembryo had external gill filaments until it was 50 days old, and completely absorbed itsyolk sac shortly before hatching.[13] Eggs in nature typically hatch in 6–10 months, with the newly hatched shark measuring 10–12 cm (3.9–4.7 in) long. Both sexes grow at approximately the same rate, reachingsexual maturity at around 15 years of age.[8] Mature males and females range from 40–57 cm (16–22 in) and 36–60 cm (14–24 in) long respectively.[4] Themaximum lifespan is 25 years.[8]
The dark shyshark poses no danger to humans and is too small to be of commercial importance. Many are hooked bysport fishers casting from the shore, who regard the shark as a pest and often kill it. It may also be caught bysubsistence fishers and inlobster traps andbottom trawls, though not in substantial quantities.[1][9] This shark occasionally finds its way into theaquarium trade, though there is no direct fishing for this purpose.[4] As the dark shyshark remains common and does not seem heavily threatened by human activity, it has been assessed asLeast Concern by theInternational Union for Conservation of Nature (IUCN).[1] Its small range does raise concerns that an increase in regional fishing pressure orhabitat degradation could impact the entire population.[9]
