Why do fish form schools? Swimming in groups is first and foremost a defense mechanism. Humankind has probably been aware of it since the dawn of our evolution, because we always did like to eat fish. The thinking goes: If you are one fish out of hundreds or thousands swimming with a seemingly magical coordination that would put Olympians to shame, you personally are less likely to be singled out and consumed by a passing predator. You’re also more likely to find a nice mate – or a terrible one, but a mate, you will find. Here is a photograph of fish schooling that won the 2021 BMC Ecology and Evolution Image Competition.
Taken by Kristen Brown from the University of Pennsylvania, the picture shows a school of jack fish in a spiral formation at Heron Island in the Great Barrier Reef, Australia. “This image represents both the beauty and bounty of our oceans as well as the spiraling crisis unfolding within the marine environment,” Brown said.
Let us distinguish between shoaling, which is when fish swim together for social reasons, and schooling, which is when the shoaling fish swim in the same direction. Shoals may form schools, which may break up back into shoals. Herring are famous shoalers: you will not find one swimming on its own. Even some shark species like to school.
Here, for instance, is a BBC video of hammerhead sharks forming a gigantic school for social purposes.
When a fish breaks ranks from the shoal or school, it may not be feeling well and is more likely to get eaten. In general, fish evidently prefer to shoal or school with fish that look like them and are healthy.
Not as warm and fuzzy as you might think
In second place, and winner in the category of Evolutionary Developmental Biology and Biodiversity, is a picture of Eulimnogammarus verrucosus. It looks like a furry shrimp, but it isn’t.
Normally Eulimnogammarus looks like all other amphipods – it has a smooth external skeleton. But this isn’t the Disney image competition for little kids, and this animal actually has a parasitic ciliate infection, BMC Ecology and Evolution explains. We shall not elaborate, but will just say that the amphipod and its passengers live in Lake Baikal in Siberia, the deepest lake in the world.
BMC explains that its competition celebrates “Earth’s biodiversity and its evolutionary origins, from how species learn and develop, to conflict, collaboration and parasitic relationships, both between and within species.”
Shame they can’t purr too
This image shows a giant gladiator frog escaping from a snake. They live in the forests of Suriname. It is a tree frog, though here it is shown in a stream, and can reach quite impressive sizes of some 13 centimeters (five inches) in length.
The gladiator frog’s fingers and toes are adapted to the arboreal lifestyle, but, being amphibians, they need land too, and make merry in little basins the males dig into the mud of the river banks. There, the males engage in battle. After that, the lady gladiator frogs they win over will spawn in the basins. According to Guyana’s Stabroek News, when the gladiator frog is startled, for instance by a snake or a nudnik, it will meow like a cat Here is a video of a gladiator frog making a truly extraordinary noise.
A spider inside her
This picture of a wasp eating a spider was taken in Tiputini, Ecuador, and it won the Behavioral Ecology category. It’s not easy to capture pictures like that. You decide whose side you’re on.
This picture of soldier termites moving along a stretch of abandoned rope in a Malaysian forest won the Population Ecology category.
Photographer Roberto García-Roa from University of Valencia, Spain, who also took the wasp-eating-a-spider picture, explains: “Thousands of soldier termites are able to migrate in a complex social environment where each individual has its own mission framed altogether in a global objective: the survivorship and reproduction of the colony. In this case, these termites used meters of an abandoned rope to move across the Malaysian forest. Once humans disappear, nature recovers its space and uses what is needed to survive.”
Soldier termites are in charge of protecting the termite colony. They typically have bigger jaws than the other classes of insect in their nest. There is not much they can do about the aardvark set, but they can put an end to ants attacking the colony – that is, unless the ants attack en masse. Soldier termites can’t eat, because their mandibles are specialized to attack, but they are fed by the worker termites. The ones eating your house are worker termites