SLENDER SMOOTHHOUND OR GOLLUMSHARK
The Slender Smoothhound or Gollumshark (Gollum attenuatus) is a species belonging to the family Pseudotriakidae. It is endemic to the waters around New Zealand, where it is usually found close to the bottom over the continental slope at depths of 984–1,969 feet. It is a slim and plain shark reaching 110 cm/3.6 feet in length. This shark has a broad, flattened head with a bell-shaped snout. The mouth is angular with short furrows at the corners and contains a very high number of tooth rows in both jaws. Its two dorsal fins are roughly equal in size. This shark practices oophagy.
Family: Pseudotriakidae – False Catsharks and Gollumsharks
Common Name– Ground Sharks
Average Size and Length: They are born around 40 cm/1.3 feet. Mature males and females measure around 70 cm/2.3 feet. The maximum recorded is 110 cm/3.6 feet.
Current Rare Mythical Sightings: The first known specimen of the Slender Smoothhound was a 93 cm/3-foot-long adult male collected by the trawler Maimai in December 1953, at a depth of 722 feet off Cape Palliser on New Zealand’s North Island. It was preserved by the crew as a curiosity and given to ichthyologist Jack Garrick, who described it in a 1954 issue of the scientific journal Transactions of the Royal Society of New Zealand. Garrick named the species Triakis attenuata, in reference to its extremely slender body.
In 1973, Leonard Compagno proposed a separate genus for the Slender Smoothhound (Gollum), after the character in J. R. R. Tolkien’s The Lord of the Rings, “to whom this shark bears some resemblance in form and habits.” He placed Gollum with the Finback catsharks (Proscylliidae), but also noted its many anatomical similarities to the False catshark (Pseudotriakis microdon). At the time, Compagno chose to maintain Pseudotriakis as the sole member of the family Pseudotriakidae because of its numerous unique traits. More recently, he and other taxonomists have increasingly tended to group Gollum and Pseudotriakis together in the family Pseudotriakidae. This arrangement was corroborated by a 2006 phylogenetic study by Juan Andrés López and colleagues, which found that the two genera have a high degree of genetic similarity across four protein-coding genes and form a natural clade apart from Proscyllium (Compagno, L.J.V. (July 9, 1973). “Ctenacis and Gollum, two new genera of sharks (Selachii; Carcharhinidae)“. Proceedings of the California Academy of Sciences. Series 4. 39 (14): 257–272).
Teeth and Jaw: The mouth is angular, extending behind the eyes. The labial furrows are short. There are and abundance of small teeth. On average just under 120 rows per jaw. The upper and lower jaws contain 96–99 and 108–114 rows of very closely spaced teeth. Each tooth has a narrow upright central cusp flanked by smaller cusplets on both sides. The teeth seem to be pointed, jagged with 3-5 cusps, with the central cusp the longest.
Head: The head is broad and flattened. The snout is long and angular, with a bell shape in the dorsal-ventral view, and a wedge shape in the lateral view. The eyes are cat-like and elongated with nictitating membranes. Beneath each eye is a prominent ridge, and just behind those, the spiracles, which are small. The anterior nasal flaps are short.
Denticles: The skin is densely covered by small, overlapping dermal denticles. The crown of each denticle is mounted on a short stalk and has three horizontal ridges leading to marginal blade-like teeth, with the central tooth particularly long.
Tail: The tail is slender, short and narrow. The caudal fin makes up about one-sixth of the total length. The lower caudal fin lobe is indistinct, while the upper lobe has a strong ventral notch near the tip.
Demographic, Distribution, Habitat, Environment and Range: The Slender Smoothhound or Gollumshark can be found in New Zealand and the surrounding northern seamounts and ridges, including the Three Kings Ridge, the Challenger Plateau, and the Wanganella Bank (46°S). They have been found on the outer most continental shelf, upper slope, and adjacent seamounts between 423-2,375 feet. They are most commonly abundant between 984–1,969 feet on the seafloor. It prefers a temperature of around 50 °F and a salinity of approximately 34.8%.
Diet: The diet is diverse, but dominated by small, benthic bony fishes like lanternfish, and decapod crustaceans. It has been documented to scavenge. Human garbage has been reported among its stomach contents. Cephalopods, gastropods, isopods, brittle stars, dogfish sharks, and cartilaginous fish egg capsules may also be consumed. On the Challenger Plateau, cephalopods are an important food source for juveniles under 50 cm/1.6 feet long (Shimizu, T.; Taniguchi, N.; Mizuno, N. (February 15, 1993). “Distribution and food habits of the slender smoothhound Gollum attenuatus, from the waters around New Zealand” (PDF). Japanese Journal of Ichthyology. 39 (4): 345–356). They are considered bathydemersal.
Aesthetic Identification: The Slender Smoothhound or Gollumshark is greyish in color, without any patterns. The ventral side is lighter in color. It is somewhat small with a slender body. The five pairs of gill slits are short. The first dorsal fin is subtriangular and somewhat short. The second dorsal fin is just as high, or even a bit higher. The two dorsal fins are similar in size and shape, with narrowly rounded apexes and concave trailing margins. The pectoral fins originate below the fourth gill slit and have gently curved margins. The pelvic fins are small and angular. The first dorsal fin originates over rear of the pectoral fins, while the second dorsal fin originates between the pelvic and anal fins. A midline ridge is present between the dorsal fins. The anal fin is less than half as high as the first dorsal fin and has a nearly straight trailing margin. The males have pointed claspers.
Biology and Reproduction: They are ovoviviparous and oophagous, having two pups per litter. Mature females have a single functional ovary, on the right side, and two functional uteruses. The females produce a single capsule in each uterus that contains 30–80 ova, of which one ovum develops into an embryo that consumes the rest of the ova and stores the yolk material in its external yolk sac. The growing embryo is mainly sustained by this yolk sac during gestation, though it may be additionally supplied with histotroph produced by the mother. The oophagous process is completed by an embryonic length of 10–39 mm. Each ova measures 4–8 mm across, and are packed into a single rigid, amber-colored egg case. When it is time for the embryo to emerge from the egg case, the case becomes gelatinous and translucent, this process usually happens when the embryo is between 29-40 mm or 1.1-1.6 inches long. Embryos between 1.6-9.8 inches long have well developed external gill filaments. And between 34-42 cm/1.1-1.4 feet, the entire yolk sac is absorbed. Sexual maturity is reached by 70 cm/2.3 feet.
Behavioral Traits, Sensing and Intelligence: Unknown, but possibly a schooling species of shark.
Slender Smoothhound or Gollumshark Future and Conservation: They are currently of least concern. They are taken as bycatch, but fishing is low among its range. They are of no economic value. This shark has a low reproductive rate, so if commercial fishing were to increase in the future, this shark could be at risk.
Slender Smoothhound or Gollumshark Recorded Attacks on Humans: Not a threat to humans.