Tripterygion tripteronotum is a species of threefin blennies belonging to the class Actinopteri, the order Blenniiformes and the family Tripterygiidae. It is a species found mainly in the Mediterranean Sea, although it is also possible to observe it on the Atlantic coast of Morocco. Generally associated with waters no deeper than 6-8 meters. It is a benthic species, which inhabits on sinuous rocky bottoms, preferably on somewhat dark places and with the presence of algae.
The body of Tripterygion tripteronotum is elongated (up to 8 cm in total length) and thin, presenting a conical and somewhat pointed head. Also prominent on its head are somewhat prominent lips and present but poorly developed supraocular appendages. Its eyes are round and relatively large for the size of the head. It has 3 distinct dorsal fins, a characteristic feature of the threefin blennies. The first dorsal fin is small in size, triangular in shape and black in color. The second dorsal fin has 15-18 spines, the first spines being much longer, giving this second dorsal fin the appearance of a sail. This feature is much more pronounced in males than in females. The third dorsal fin is formed by 11 to 13 soft rays. The anal fin has 2 spines and 23-26 soft rays. The pectoral fins are large and their shape ends in a point. The pelvic fins are forked and the caudal fin is somewhat rounded. As for the coloration of Tripterygion tripteronotum, the base color is reddish-brown, with a dark cephalic mask that extends over the belly and along the pectoral fins to their apical ends. They also have oblique dark bands along their flanks. There is a clear sexual dimorphism in Tripterygion tripteronotum, males of reproductive age, during the months of May to August intensify the black color of the cephalic mask and have a dark spot behind the first dorsal fin. On the contrary, females and non-breeding males are more yellowish-brown and have dark bands on their flanks, the last band being just in front of the caudal fin and not very pronounced in terms of coloration.
Tripterygion tripteronotum is a species whose male specimens are very territorial. Those male specimens that are in breeding season intensify the coloration of their cephalic mask being much darker. Females and non-breeding males, the cephalic mask tends to be of a less intense and more grayish color. During the breeding season, the male takes a rocky territory of a few tens of centimeters, in an area protected from the waves and currents. During this time he will not stop courting as many females as pass through his territory. To these females he performs a zig-zag dance with all his fins fully deployed and at the same time making rapid movements up and down with his head. After this ritual, and after the eggs have been laid by the female and immediately fertilized by the male, it will be the latter who will take care of the eggs.
Although there are clear differences, there is frequent confusion between Tripterigion tripteronotum, Tripterygion melanurum (subspecies Tripterygion melanurum minor and Tripterygion melanurum melanurum), and Tripterygion delaisi (subspecies Tripterygion delaisi delaisi and Tripterygion delaisi xanthosoma). To summarize, these are the main characteristics that differentiate them:
- Tripterygion melanurum minor. The spines of the second dorsal fin gradually decrease in height. Absence of black spot on the upper dorsal part of the caudal peduncle. Reddish color.
- Tripterygion melanurum melanurum. The rays of the second dorsal fin gradually decrease in height. Presence of black spot on the upper dorsal part of the caudal peduncle.
- Tripterygion tripteronotum. First spines of the second dorsal fin much longer than the following ones. Cephalic mask extends to pectoral fins. Color reddish-brown or yellowish-brown with dark bands on the flank (the last one, located on the caudal peduncle is very faint).
- Tripterygion delaisi delaisi. First spines of the second dorsal fin much longer than the following ones. Cephalic mask does not reach the pectoral fins. Absence of black spot on the upper dorsal part of the caudal peduncle. Bright yellow color without bands on the flanks or if present very faint.
- Tripterygion delaisi xanthosoma. First spines of the second dorsal fin much longer than the following ones. Cephalic mask does not reach the pectoral fins. Presence of black spot on the upper dorsal part of the caudal peduncle. Bright yellow color with dark bands on the flanks, the last of them, located on the caudal peduncle is much darker than the rest.