A cirrus is a short, flexible outgrowth of skin on a fish: a thread, flap or branched lobe with no bone or cartilage inside it, and the plural is cirri. In sharks they occur on the head — most visibly as the fringe of branched lobes around the jaw and snout of a wobbegong, and as the small flaps beside the nostrils of many species.
The word is borrowed from general zoology, where it also covers the feeding limbs of a barnacle and the arms of a sea lily. On a shark, a cirrus is passive: it breaks up the animal's outline, and where it carries nerve endings it works by contact, not by electricity.
- What it isA fleshy skin outgrowth
- Where on a sharkAround the head and nostrils
- Best exampleThe fringe of a wobbegong
On this page
What a cirrus is
In fish anatomy the term is deliberately loose. A cirrus is any small, soft projection of the skin that is not a fin, a spine or a scale: sometimes a single thread, sometimes a flap, sometimes a lobe divided into branches like a scrap of seaweed. It contains skin, connective tissue and blood vessels, and nothing stiff. Because it has no muscle worth the name, a fish cannot point one deliberately; cirri move only as the water and the animal's own motion move them.
The same word is used across the animal kingdom for structures that have nothing in common beyond being small and projecting. Barnacles feed by sweeping the water with cirri. Crinoids grip the sea floor with them. Polychaete worms carry them along the flanks. That is why a search for the word returns mostly invertebrates, and why it is worth stating plainly which meaning is in play on a page about sharks.
Among fishes, cirri are commonest in the small blennies and clingfishes of rocky shores, where a fringed head merges into weed and encrusting growth. Sharks use them for the same purpose, at a much larger scale, and in a much shorter list of species.
Where cirri appear on sharks and rays
The undisputed example is the wobbegong. A tasselled wobbegong carries a continuous fringe of branched dermal lobes around the entire front margin of its head, from the snout back past the corners of the jaw, each lobe splitting into finer filaments. Lying flat on a reef, marbled in brown and cream, the animal has no visible edge at all. The spotted wobbegong and its relatives carry simpler versions, and the angel sharks have a smaller pair beside the nostrils.
The second place they turn up is the nostril. Many sharks have a flap of skin at the front edge of each nostril, and in some species that flap is drawn out into a slender point — a nasal cirrus. Where it becomes long and finger-like it is usually called a barbel instead, which is why the boundary between the two words is blurred and why nurse sharks and bamboo sharks are described sometimes one way and sometimes the other.
Rays and skates have their own. The rim of a skate's mouth and the margins of some ray spiracles carry short cirri, and several deep-water species have them scattered on the disc. What all these have in common is position: on or around the head, close to where the animal makes contact with the bottom.
What cirri do
Camouflage comes first. An ambush predator lying on the sea floor is given away by its silhouette more than by its colour, and a fringe of irregular lobes destroys a silhouette very effectively. It also takes fouling — algae and small growth settle on the lobes, so the outline blends further as the animal stays put. A wobbegong waits for fish to swim within range of a very fast, very short strike, and that strategy depends entirely on not being seen.
Touch is the second function, and it is real but modest. Skin projections are well supplied with nerve endings, so a lobe that brushes something reports the contact, and in species where the projection is long enough to count as a barbel there are taste buds in it as well. The information is short-range and physical: what is there, and where.
Both jobs are unglamorous, which is probably why so much invented function has been attached to the word. A cirrus is a piece of skin in a useful shape. It does not detect prey at a distance, and it is not involved in anything a shark does at speed.
What cirri are not
A set of claims circulates about shark cirri that can be dismissed one by one. They are not found on the leading edge of the dorsal fin; no shark carries skin appendages there at all. They are not several inches long as a general rule; on a wobbegong the lobes are a few centimetres at most.
They are not electroreceptors and they are not covered in pores that read pressure or vibration. Electric fields are detected by the ampullae of Lorenzini, which are inward-going pores in the snout, and water movement is detected by the lateral line, a canal system running along the flank. Both are separate from anything projecting off the skin. Nor do sharks use cirri to communicate with each other; there is no evidence for signalling of any kind through them.
For the neighbouring structures on the same animal, see the placoid scales that make up shark skin and the spiracles behind the eye, or the shark terms glossary for the rest of the vocabulary.
Frequently asked questions
What are cirri on a shark?
They are small, soft outgrowths of skin on the head, with no bone or cartilage inside. The clearest example is the fringe of branched lobes around a wobbegong's snout and jaw. Smaller ones occur as flaps at the front edge of the nostrils in many species, and on the mouth margins of skates and rays.
What do cirri do?
Mostly they break up the outline of an ambush predator lying on the sea floor, which is what makes a wobbegong so hard to see against a reef. Where a cirrus is long enough to carry dense nerve endings, it also reports contact with the bottom, a short-range sense of touch rather than anything at a distance.
Are cirri the same as barbels?
They overlap. A barbel is a slender, whisker-like projection beside the nostril or mouth that carries touch receptors and taste buds. A cirrus is the broader term for any fleshy skin outgrowth, including flat lobes and branched fringes. Long thin ones tend to be called barbels and shorter branched ones cirri.
Do cirri detect electricity?
No. Electric fields are picked up by the ampullae of Lorenzini, a network of jelly-filled pores running inward from the surface of the snout. Cirri project outward and have no electrical function at all. The two are often confused on shark pages, but they are unrelated structures doing unrelated jobs.
Which sharks have cirri?
The wobbegongs have the most developed ones, particularly the tasselled wobbegong, whose head is fringed with branched lobes all the way round. Angel sharks have a smaller pair by the nostrils, and many catsharks, bamboo sharks and nurse sharks have nasal flaps drawn out into short points.
References
A small team focused on researching sharks and making marine biology easy to understand. Every page is reviewed against current species records and the SharkSider attack database, and updated when new incidents or research appear.
Published December 2, 2014 · Last updated September 23, 2026 · Part of the Shark Anatomy section.
