Parablennius tentacularis, commonly known as ‘horned blennid’ is a marine fish belonging to the family Blenniidae and the order Blenniiformes. The genus name ‘Parablennius‘ is derived from the Greek, where ‘para‘ means ‘close‘ and ‘blennios‘ refers to a mucus or slime fish, alluding to the mucous secretion that covers its skin. The epithet ‘tentacularis‘ comes from the Latin ‘tentaculum‘, meaning ‘tentacle‘, in reference to the long protrusions or tentacles above its eyes. Parablennius tentacularis is distributed in the northeast Atlantic, from the southern coasts of England to Morocco, and is also common in the Mediterranean and Black Seas. This fish inhabits coastal waters, preferably in rocky areas, reefs and seaweed beds, generally at depths of between 1 and 20 meters.
Parablennius tentacularis is a small fish, measuring between 10 and 13 centimeters in length. Its body is elongated and laterally compressed, with a large and robust head, characteristic of blennids. Its most distinctive feature is the long, thin tentacular extensions over the eyes, which can vary in length and shape among individuals. Its coloration is variable, ranging from shades of brown, green and gray, with irregular darker spots and bands that allow it to camouflage itself effectively in its rocky environment or among the algae. It has a unique dorsal fin, with anterior spiny rays shorter than the posterior soft ones, giving it a distinctive ‘sail‘ shape. Unlike other similar species, such as Parablennius gattorugine, Parablennius tentacularis is distinguished by having longer and thinner tentacles over the eyes, and a shorter overall body length.
As for its diet, Parablennius tentacularis is omnivorous, with a diet consisting mainly of small benthic invertebrates such as crustaceans, molluscs and worms, as well as algae. It uses its small mouth, equipped with short, sharp teeth, to scrape algae from rocks and capture small prey. This type of feeding allows it to adapt to diverse environments and contributes to its ecological role in controlling invertebrate populations and cleaning algae.
Reproduction of Parablennius tentacularis generally occurs in spring and summer. This species is oviparous, and males become highly territorial during the breeding season, aggressively defending small shelters in crevices or under rocks where females deposit their eggs. After laying, the male fertilizes the eggs and takes care of protecting them until they hatch, ventilating them with his flippers to maintain a constant flow of oxygenated water. The eggs are small and clingy, and once hatched, the larvae are pelagic and spend some time in the water column before settling on the seafloor.
A curiosity about Parablennius tentacularis is its ability to change color depending on its environment and emotional state, which gives it an advantage both for camouflage against predators and for communicating with other individuals, especially during reproduction. Its curious and often bold behavior makes it an attractive subject of study for marine biologists and a point of interest for divers exploring the rocky areas of the Mediterranean and Atlantic.
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