Tank Tuesdays 4

Tompot Blenny (Parablennius gattorugine)

Today’s article is dedicated to a long-time member of the ARC Marine family, our  Tompot blenny (Parablennius gattorugine), who we recently had to say goodbye to. During his time here, he gained a reputation of being a bit of a bully as he has shown to be aggressive to a few of his tank mates during his time. Despite the bad attitude it is quite a beautiful fish with big frilly fins, a green/brown coloration with black bars running along the side and a pair of tentacles which resemble antlers on its head (see Figures 1 and 2). This species of blenny gets its name from its almost rusty appearance (gattorugine translates roughly from Latin to ‘rusty’).

ARC Marine Tank Tuesdays 4 tompot blenny
Figure 1: P.gattorugine resting on a natural reef 

P.gattorugine is commonly found around the south and west coasts of the UK as well as parts of Mediterranean and the North east Atlantic. It spends most of its time in shallow waters, around rocky areas and is never really observed deeper than twenty metres. While not the largest of fish (commonly around the 15 cm mark) it has been found to grow up to 30 cm in length, our blenny was about 10 cm in length so still had a bit of room for growth. Members of this species spends their time in shallow rocky waters where they hide in any cracks or holes within a rock face that they can find. When the blenny decides to leave the safety of his home it will spend its time searching for small crustaceans and gastropods. Additionally, it is one of the few predators of the anemone. We managed to see this first hand when we introduced a plumose anemone (Metridium dianthus) to the tank. This alone caused our blenny to get over excited.

P.gattorugine proceeded to approach the anemone and suck up its tentacles and immediately spit them back out. Our snake locks anemone managed to avoid being attacked, likely because it’s too large for P.gattorugine to take on. It has been found on occasion to attack larger anemones, but it will target them when they split (their method of reproduction) and therefore at their most vulnerable.

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Figure 2: P.gattorugine posing on a natural reef 

When not attacking anemones males of this species spend their time maintaining their homes by cleaning out mud and any unwanted guests as to impress the females of the species. When it is breeding season, females will enter the males burrow and assess the quality of the den and the male himself. If these are up to the standards of the female she will lay her eggs in the burrow and leave. This leaves the male to fertilise the eggs and then care for and guard the eggs until they hatch. Once the eggs have hatched the juvenile blennies migrate towards the shallow waters and hide amongst seaweed. Not only has our Tompot blenny been seen to be aggressive towards anemones but also to other species and in fact used to share a tank with our Ballan wrasse (see our last tank Tuesdays article for more information on this species). Unfortunately, they didn’t get along as well as the snake locks anemone and the leach’s spider crab. The blenny turned out to be quite the bully and chased our wrasse around the tank and nipping at his fins. So, our wrasse was moved out of the tank to avoid getting any major injuries. We expect that this aggressive behaviour is related to their method of breeding. As mentioned they guard dens as to encourage females to enter and lay their eggs with it, in real world examples organisms that hold territory will usually do so with aggressive means, as the cost and risk of losing a territory is higher than if they were to defend it. In this case our blenny seemed to settle itself in a small crack in between a Reef Cube and the tank wall. Due to this hyper aggressive behaviour of the Tompot blenny the wrasse was likely seen as a threat to his home and was chased away. Unfortunately, we did have to say goodbye to our blenny as we are currently moving some anemones over to our native tank and we didn’t want them eaten by our resident bully. So, we released him back home (after he was finally caught, he didn’t seem too keen on leaving the safety of his tank). He was released back to the waters around Brixham on the 5th of February 2019 and hopefully he can find a nice home to settle into where he can impress the ladies!

This article was written by Jamie Mathews and edited by James Murphy

Tank Tuesdays is a series of mini articles describing the marine life here at ARC Marine’s aquaria; and their interactions with our artificial habitats.