The Frilled Shark (Chlamydoselachus anguineus) is a deep-sea dwelling freak of a fish. Due to their preferred habitat, humans rarely get to see this shark species. However, whenever there is an encounter, it always makes headlines. This is because only the appearance of this fish will drop anyone’s jaw.
With the frilled shark’s body of a snake and its movement to feeding habits, it is obvious that this shark is a “sea serpent” existing in the physical. Sometimes referred to as the “living fossil”, researchers believe this shark barely changed from what its ancestors looked like in prehistoric times.
The frilly-looking gills of this shark gave it its common name. Thus, the frilled shark has six-gill slits which form a red fringe around the shark’s neck. The first pair of gills cut all across the throat, unlike other shark species with separate gills.
From the family Chlamydoselachidae, the frilled shark is one of the only two extant shark species in the family. Their occurrence encompasses a wide area, however, they have a patchy distribution across the Atlantic and Pacific Oceans.
Other sharks may have interesting features, but none is with extraordinary features as the frilled shark. Hence, learning about the frilled shark will thrill you.
Naming and Identity
The species name of the frilled shark is Chlamydoselachus anguineus given by Samuel German an American zoologist. He combined three Greek words chlamy which means “frill”, idos which means “cape” and selachus which means “shark” to form the genus name. While on the other hand, he chose a Latin word anguineus which stands for “eel-like” as the specific name.
Chlamydoselachus anguineus belongs to the family Chlamydoselachidae and the order Hexanchiformes with the cow sharks. Although, there was a suggestion to place the frilled shark in its own order Chlamydoselachiformes. But, it was just a proposal.
Other common names to identify the frilled shark include frill shark, silk shark, scaffold shark, and lizard shark. It all depends on locality trying to describe this shark species.
Frilled Sharks Appearance
Head and Body
This shark species has an elongated body that looks more like an eel than a shark. The midsection (the body part between the head and the tail) is relatively longer in female frilled sharks than in males. Also, running along the belly is a pair of thick folds of skin in which the functions are not yet clear.
The frilled shark has small dermal denticles with shapes like the tip of a chisel and on the dorsal margin of the caudal fin, they tend to be larger and sharp. This shark species has a uniform body color of dark brown or gray.
Its head is broad and appears flattened with a snout short and rounded. The nostrils are vertical slits that have a flap of skin separating them into openings for the inward and outward flow of current. Frilled sharks have moderately large oval eyes tilting to the horizontal direction. Also, their eyes lack a nictitating membrane present in most sharks to serve as a protective eyelid.
Jaws and Teeth
The frilled shark has obvious long jaws situated at the end of the snout which is different from that of most other shark species that have their jaws suspended below. Also, the mouth sides of this shark species are without the usual folds or furrows common in sharks.
Frilled sharks have widely spaced rows of teeth. In the upper jaw, there are about 19 to 28 rows, while the lower jaw has about 21 to 29 rows. This shark generally has around 300 teeth in number and each tooth is small with three slender cusps like a needle that alternates with two cusplets.
Gills
This shark possesses six pairs of gill slits, long with a frilly appearance formed from the extension of the tips of the gill filaments. Thus, giving the shark its common name. Also, the first pair of gill slits from the head joined across the throat and forms a collar
Fins.
Frilled sharks have a single dorsal fin quite small with a rounded margin situated far back on the shark’s body. The anal fin is broad and about the same position as the dorsal fin, however on the opposite side. Their pectoral fins appear rounded and short. Also, there is the pelvic fin which broad and large positioned on the same side as the anal fin, but just before. At the tail end is the caudal fin roughly in the shape of a triangle. And, unlike most other sharks, the caudal fin has no lower lobe or a ventral notch on the upper lobe.
Growth Size
The female frilled sharks tend to grow larger than the male sharks. As such, the females grow to a maximum length of 6.6 feet (2 m), while the males will grow to 5.6 feet (1.7 m).
Lateral Line
While most fish have a lateral line on the sides of their body, the frilled shark has its lateral line located in a groove that is open to the sea. This is very unusual when compared to other shark species. As such, other sharks have their lateral line embedded in their skin and connected through pores to the outside.
the lateral line is a row of sense organs containing hair cells stimulated by movements and low-frequency vibrations in the water. More so, the hair cells are sensitive to mechanical pressure, therefore said to be mechanoreceptive.
The Behaviors of the Frilled Shark
The behaviors of the frilled shark are observed in the sharks’ feeding pattern (hunting techniques) and its life cycle. But, most of the information about this shark’s behavior bases on speculations by the experts. This is because of the occurrence of this shark in deep waters making it difficult to study.
Feeding Pattern
The frilled shark has long jaws that can stretch out (from internal pressure) giving the shark a very wide gape. With this, the frilled shark can swallow whole prey over half of its size. But then, considering the jaw length and articulation of this shark, it cannot deliver a quite strong bite as other sharks of a more conventional build.
Researchers suggest this shark be either feeding between long intervals or have a fast digestion rate. This suggestion comes from the fact that most captured individuals are with stomach contents barely or not even identifiable at all.
The preys of the frilled shark include squid, cephalopods, bony fishes, and smaller sharks. Squids are fast-moving prey of most sharks, however, how the weak-swimming frilled shark is able to hunt them down is just something to imagine.
Of course, there are possible speculations of the shark taking advantage of injured and exhausted squid probably dying after spawning. Also, there is the possibility of the shark launching a quick attack just like a snake by curving its body and subsequently bracing it with its fins positioned behind.
Other possible techniques include the shark being able to create negative pressure to suck in its prey by temporarily closing its gill slits. The teeth of the frilled shark on observation lights against the dark mouth as it swims with its mouth open. This may deceive squids, making them attack while entangling themselves in the shark’s sharp, recurved teeth that function similarly to squid jigs.
Mating and Reproduction
The mating of frilled sharks involves the male inserting its claspers into the female to deposit sperm. Thus, this shark has internal fertilization and is Ovoviviparous in nature. The embryos get nourishment from the yolk sac. It is also believed that the mother shark provides additional nutrition due to the difference in the weight of the newborn and the egg, though the means are not clear.
The two ovaries of an adult female frilled shark are functional, with only one functional uterus positioned on the right. Egg ovulation into the uterus occurs once in two weeks. This shark produces an average of 6 litters but can range from 2 to fifteen. During pregnancy, the growth of new ovarian eggs and the formation of yolk (vitellogenesis) tend to stop, possibly due to insufficient space within the body.
Frilled sharks have no particular season for breeding. Of course, this does not come as a surprise because the depths they inhabit have very little to no seasonal influence. There is a possible mating aggregation as recorded of this shark species over a seamount on the Mid-Atlantic involving 19 female and 15 male frilled sharks.
A complete gestation period of the frilled shark may last up to three and a half years. This is the longest of any vertebrate. The male frilled shark attains sexual maturity at a length of 3.3 to 3.9 feet (1 to 1.2 m), while the females mature at 4.2 to 4.9 feet (1.3 to 1.5 m). At birth, the young sharks measure around 16 to 24 inches (40 to 60 cm).
Natural Habitat and Distribution Range
Frilled sharks mainly inhabit the upper toward the middle continental slope and on the outer continental shelf. They prefer depths ranging from 160 feet to 600 feet below the water surface, although, they can also be found as deep as 5,150 feet.
This shark species will mostly stay close to the seafloor, however, they may participate in vertical migration toward the surface to feed on prey migrating upwards. They make such movement mostly at night according to researchers studying the diets of this shark.
On very rare occasions will frilled sharks swim to the water surface or spotted close to the surface.
Their range of distribution encompasses a variety of locations scattered across the Atlantic and Pacific Oceans. More so, they live in fragmented and spotty areas. Thus, they occur in eastern Atlantic from France to Morocco including Madeira, also off Mauritania. And, in central Atlantic frilled sharks have been caught in various locations along the Mid-Atlantic Ridge, from the Azores to off southern Brazil.
There is also a report of this shark species in the Western Atlantic off New England, Suriname, and Georgia. In the western Pacific frilled sharks distribution crosses Japan to Taiwan, Australia, near New Zealand, and off New South Whales. This shark is also found in central and eastern Pacific off Hawaii and California in the United States and around northern Chile.
Note that there are frilled sharks extant off southern Africa that were described as different species Chlamydoselachus africana (southern African frilled shark).
Interaction with Humans
Even if you stay within the regions where the frilled shark occurs, it is unlikely that you will just see one swimming the water. In other words, it is a rare experience encountering frilled sharks especially the ones still alive. But, there are chances you might get to see captured ones which would be dead by then.
Due to their rare appearance, it is safe to say that this shark is no threat to humans. Of course, except for researchers who go to find this shark species, hence some get cuts accidentally while examining the teeth.
With deepwater fishing techniques such as using trawls, longlines, and gillnets, only small numbers of frilled sharks are consequently caught. More so, fishermen in Japan consider this shark species as a nuisance when trapped in their net as it causes damage to the nets. Frilled sharks have very little to no economic value and not actively hunted by humans.
Threats and Conservation Status
There is not much information about the interaction of the frilled shark with other species in its environment. Researchers believe these fish have no much threat in their natural habitat and in general. Even humans rarely catch this fish and for the small number of times they were caught, it is usually a bycatch.
Currently, the International Union for Conservation of Nature (IUCN) lists this species as “Least Concern (LC)”. However, before now due to the very low rate of reproduction and expansion of deepwater fisheries that leads to bycatching of frilled sharks, they appeared on the list as “Near Threatened”.
In all, note that there is no information on the population size or trend of the frilled shark. It is rare in the general sense even in Japan where there are more common reports of this fish.
Are There Possible Domestication of the Frilled Shark?
No, there is no record of any frilled shark domesticated in any way. More so, no frilled shark has survived in any aquarium setting. Of course, there was the female shark found swimming at the surface of the water in Japan in 2007. There is video footage of this individual which was later taken to a marine park and died a few hours later.
Amazing Frilled Shark Facts in a Glance
1. Sea Serpent Mythology Linked to the Frilled Shark
Some researchers believe that the sea serpent mythology originated from probably a sight of the frilled shark. Certainly, these creatures have a frightening appearance and movement like the serpent. Moreover, there could have been larger specimens existing in previous times.
2. A Living Fossil Predating the Dinosaurs
From the fossils of frilled sharks, there is an indication that they may have lived before the mass extinction that wiped the dinosaurs in shallower water. And, swimming into deeper water to hunt prey.
3. Gestation Period is Longer than Any Vertebrate
Due to the rather slow embryonic growth rate of frilled sharks, their gestation period lasts up to three years and a half. Thus, making it the longest of any known vertebrate.
4. Frilled Sharks Poses No Threat to Humans
Except you are a researcher looking out for this shark species, you are unlikely to encounter frilled sharks. Even swimmers and divers rarely get to meet one. This is due to the great depths that this shark lives in. As such, they do not pose a threat to humans.
5. The Population of Frilled Sharks in Nature is Unknown
Even while the International Union for Conservation of Nature (IUCN) listed this species as Least Concern, their population is not known. So, what if they are threatened or endangered? However, we know that the expansion of deepwater fishing poses a threat to this shark species.
6. Looks More of an Eel than a Shark
This shark is elongated with the existing fins receding backward except for its small pectoral fins. Even more, the tail fin is different from other sharks.
7. Frilled Sharks Possesses Enormous Liver
The huge liver of this shark species is filled with low-density lipids that let the shark maintain its position in the water column effortlessly.
8. The Eyes Lack Nictitating Membrane
Sharks, in general, have a nictitating membrane that serves as an eyelid that helps to protect their eyes. However, the frilled shark lacks this membrane.
9. Chlamydoselachus africana is a Sibling Species of the Frilled Shark
The Southern African frilled shark (Chlamydoselachus africana) is a look-alike species of the frilled shark (Chlamydoselachus anguineus) with many similarities. But in 2009, it was classified its own species because of few differences in size, body, and snout proportions.
10. Has Its Lateral Line in a Groove
While others have their lateral line on each side of their body, the frilled shark has its lateral line in a groove open to the ocean.
Conclusion
This page contains information about the frilled shark, although most are what the experts and scientists think. It is difficult to study this shark species due to its rare appearance. Thus, leading to some unclear facts about this shark.
Facts such as the population size and trend are very relevant to accurately determine the conservation status of this shark. However, it is important that more conservation actions be put in place to protect this species.
Further Reading
- “Frilled Shark” Wikipedia, Wikipedia. Online here
- “Chlamydoselachus anguineus (Frilled Shark, Lizard Shark, Scaffold Shark)” IUCN Red List of threatened species. Online here
- “Chlamydoselachus anguineus (Frilled Shark)”, FishBase. Online here
- “Deep Sea: Frilled Shark”, ReefQuest Centre for Shark Research. Online here
- “35 Frilled Shark Facts: Snake Fish of the Deep (Chlamydoselachus anguineus)”, Drew Haines, everywherewild. Online here