Fish

Live photos of the Hades' snake moray

Newly Described Species of Moray Eel Prefers Dark, Murky Environments

The Hades’ snake moray (Uropterygius hades) is a slender, dark brown eel which stands out for its unique adaptations to and preference for dim, turbid environments.

Unlike most of its marine relatives, which thrive in coral reefs, it is at home in estuarine habitats, a characteristic that is unusual among the 230 known species of moray eels. It is distributed across the Central Indo-Pacific, and has been found in southern Japan, Taiwan, the Philippines, southern Java, and Fiji.

The "fountain effect" can be seen when a marlin attacks a sardine shoal

Outsmarting the Predator: Sardines vs Marlin

In a recent study, researchers investigated how sardines that find themselves on a predator's radar collectively employ collective evasive manoeuvres and how their predators respond to outsmart them.

Using computational modelling and aerial video footage, the team from the Cluster of Excellence “Science of Intelligence” (SCIol), the Humboldt-Universität zu Berlin, the Leibniz Institute of Freshwater Ecology and Inland Fisheries, and Cambridge University focussed on the predator-prey behaviour of striped marlins and sardine shoals in the open ocean. 

A zebrafish embryo. (Image credit: Dr. Deodatta Gajbhiye)

Fish Embryos Decide When to Hatch

When it comes to making its grand entrance into the world, fish embryos do not leave things to chance.

Researchers, led by Dr. Matan Golan of the Hebrew University of Jerusalem and the Agricultural Research Organization-Volcani Institute, have discovered that the hatching process of fish embryos is not a passive process. 

Squaretail coral grouper (Plectropomus areolatus)
Squaretail coral grouper (Plectropomus areolatus)

Fishing is Causing Fish to Flee When They Should Mate

Several times a year, squaretail groupers gather at spawning aggregation sites to mate, typically around the new and full moons between December and March. The males show up several days before to establish their territories, while the females arrive a day before the new moon. Then, both groups will attempt to pair and spawn in synchrony with the moon’s cycles.

For this species, these brief encounters are their only opportunities to reproduce.

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.