Too close for comfort? Are these Striped Catfish (Plotosus lineatus) oblivious to the danger the predator presents? Haven’t they noticed him? And is the Tasseled Scorpionfish (Scorpaenopsis oxycephala) aware of the deadly spines these catfish possess and therefor doesn’t strike? For one or another reason the Scorpionfish doesn’t attack and the catfish don’t flee. Maybe the Scorpionfish is more interested in the Cardinalfishes and doesn’t want to give its position away by moving?
One can only speculate what’s behind both fish species’ motivation for not fleeing of for not striking. Let’s look at a few known facts regarding both fish species.
Although Striped Catfish don’t look dangerous at all, they really are. Almost all catfish species have a defensive, hollow, spine-like ray on their dorsal and both pectoral fins. Catfishes can lock these spines into place to inflict severe wounds when they feel threatened. Around half of all catfish species have glandular cells in the skin covering their sharp rays. These cells produce a venomous protein, which is released into the wound when the membrane surrounding the venom gland is torn. Of most catfish species this venom may be painful, but a sting from the Striped Catfish can even result in death! A sting of the catfish’s spine inside the scorpionfish’s mouth could be devastating and life-threatening for the bigger scorpionfish.
The Tasseled Scorpionfish also possess highly venomous spines. Here however the venomous spines of the scorpionfish are insignificant to the catfish as the chance of being eaten by the catfish is non-existent for the scorpionfish. The scorpionfish however has the ability to swallow several catfish in one go. The scorpionfish possess an enormous mouth and an appetite to match.
How do we know that fish are aware of these dangers? In the animal kingdom there is something called “aposematism” and this can explain why it is that fish are aware of their powers, abilities and weaknesses. Aposematism is advertising using bright colours (such as red, orange, and yellow in combination with white and/or black, and high-contrast patterns such as stripes and dots) to signal to potential predators that the animal is toxic, distasteful, or dangerous. For this to be an efficient deterrent, fish must be able to reed this signalisation, understand it and apply it in order not to eat something venomous or poisonous. The black and white high-contrasted stripes of the Striped Catfish are more than probable a form of aposematism.
In this scene we see a single catfish coming extremely close to the scorpionfish’s mouth, but when he suddenly realises what he’s up to the little catfish makes a hasty retreat.
The most interesting scenes to film or document under water are the ones that show marine life behaviour. Scenes like these ones are also the most challenging ones for the videographer as it is often very difficult to anticipate wild animals’ next moves. When you think what will happen next you’re often in for a surprise. Way too often lying on the bottom filming a scene like this one I think to myself “come on little fish, do something…” and way too often nothing happens. To catch something great on video requires besides your anticipation a good doses of luck. Film and let the camera roll, you’ll never know what comes next (and often nothing comes next).
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