Fish

Can clownfish count?

Clownfish, also known as anemonefish, are feisty critters that vigorously defend their anemone homes from intruders, particularly those of their own species, displaying aggressive behaviour. Anemonefish species living in the same areas exhibit a variety of stripe patterns, ranging from three vertical bars to none, as observed by Kina Hayashi from the Okinawa Institute of Science and Technology, Japan.

A Matter of Sentience

Fish feel pain, or don’t they? Despite a growing body of sound evidence that fish do indeed feel pain and are sentient beings capable of all the types of cognition found in the “higher” mammals, with the possible sole exception of the ability to imitate, a group of critics seems to systematically seek to discredit this research. But for what reasons? Ila France Porcher takes a closer look at the stakes involved.

An electric eel in a tank
The electric eel in the research study

Electric eels can genetically modify cells of nearby animals

In a recent study, researchers from Nagoya University in Japan have demonstrated that electric eels can release electricity potent enough to induce genetic modifications in small fish larvae. 

This ground-breaking study challenges the conventional belief that electroporation, a gene delivery technique in which an electric field is generated to create temporary pores in cell membranes to enable the entry of molecules like DNA or proteins into the  cells, is confined to laboratory settings.

In 2023, DNA analysis found the houting to be genetically indistinguishable from Coregonus lavaretus, the common European Whitefish,and therefore not extinct.
In 2023, DNA analysis found the houting to be genetically indistinguishable from Coregonus lavaretus, and therefore not extinct.

The Houting's Remarkable Return: Not Extinct After All

The Houting fish, believed to have vanished from our waters, has made an unexpected return. Previously listed as 'extinct' on the IUCN Red List of Species, recent research has unveiled that this fish is not only thriving but is also not a distinct species as once thought.

The initial classification of its extinction was centred on morphological differences, especially the number of gill rakers. However, a detailed study published on bmcecolevol.biomedcentral.com contradicts this.

The hogfish, also known as boquinete, doncella de pluma or pez perro in Mexico is a species of wrasse native to the Western Atlantic Ocean
The hogfish, also known as boquinete, doncella de pluma or pez perro in Mexico is a species of wrasse native to the Western Atlantic Ocean

Light-sensing Skin Cells Make Hogfish a Master of Camouflage

Hogfish, Lachnolaimus maximus, possess an uncanny ability to alter their skin colour, transitioning from a mottled white to a deep coral orange within mere seconds. This remarkable transformation is a survival mechanism, allowing them to seamlessly blend with their environment, evading potential predators.

When the trumpetfish swims alongside another species, it either remains hidden or is not recognised as a threat due to its altered shape
When the trumpetfish swims alongside another species, it either remains hidden or is not recognised as a threat due to its altered shape.

The trumpetfish's unique hunting strategy

The trumpetfish, with its long, slender body, shadows non-threatening species like the parrotfish. This allows it to get closer to its prey, such as damselfish, without being detected. Dr Sam Matchette, a leading researcher from the University of Cambridge, explains that when the trumpetfish swims alongside another species, it either remains hidden or is not recognised as a threat due to its altered shape.

Tetra fish
Tetra fish

Neon tetra fish wait their turn when evacuating through narrow opening

Scientists have observed neon tetra fish queuing up when exiting through a narrow opening, according to a study in the journal Scientific Reports.

In the study, Aurélie Dupont, a biological physicist in the Laboratoire Interdisciplinaire de Physique at University Grenoble Alpes, and her team set up two fish tanks connected to each other by a narrow opening. The diameter of the passageway varied from 1.5 to 4 centimeters.

A research team has demonstrated that fish think "it's me" when they see themselves in a mirror or picture.

Fish recognises itself in photographs

A new study demonstrates how animals recognise self-images.

Some animals have the remarkable capacity for mirror self-recognition (MSR), yet any implications for self-awareness remain uncertain.

In a test of MSR ability in cleaner fish, mirror-naive fish initially attacked photograph models of both themselves and unfamiliar strangers. In contrast, after all fish had passed the mirror mark test, they did not attack their own (motionless) images, but still frequently attacked those of unfamiliar individuals.

Why damselfish chasing away cleaner fish's customers is bad for reefs

Many of us are familiar with the scenes at cleaning stations, where cleaner fish and cleaner shrimp feed on the parasites and dead tissues of their “clients.”

Under normal circumstances, sharknose gobies (Elacatinus evelynae) would set up a cleaning station at a coral reef, and use it as a base to attend to their “clients”—usually the parrotfish, surgeonfish, butterflyfish, etc— by eating the parasites and dead body tissue off their client's skin, fins and mouth. 

However, at reefs with damselfish, things are not always so peaceful.