Social connections and pair-bonding between conspecifics are widespread forms of love among humans, primates, mammals, dogs, and birds. What about fish? Here we’ll talk about the simple form of how zebrafish love their conspecifics.
Is Love Simply a Connection?
Some scholars consider love as a positive social connection, as a way of social bonding between individuals. It is perfectly true. I believe that many forms of human love evolve from a basic need to positively connect, bond, and belong. Human life depends on having a positive connection with other people. People need other people, whether they are close or far from us, to live and do well (see for review, Karandashev, 2022a, in press).
Love Is Social Bonding
According to evolutionary and cultural theories, community bonding was the earliest form of love. This type of love stemmed from basic survival needs in the ecological, economic, and social conditions under which people lived in specific environments and societies. The varieties of historically evolved cultures determined specific forms of love.
It’s well known that humans are “social animals.” It is possible, however, that many animals are also “social.” Studies show that not only humans, but also other animals have evolved the psychological mechanisms of prosocial behavior, cooperation, and social bonding that have helped them survive in the natural and social worlds (e.g., Germonpré, Lázničková-Galetová, Sablin, & Bocherens, 2018; Marshall-Pescini, Virányi, & Range, 2015; Hare, 2017; 2006; Fisher, 2004; Rosenblum & Plimpton, 1981, see for review Karandashev, 2022a in press).
Humans are not alone in their propensity to cooperate with members of their own species to meet their needs and to survive and thrive. For example, in nature, herds of mammals, flocks of birds, or shoals of fish abundantly exhibit prosocial tendencies. There is plenty of evidence of social bonding in dogs and primates (see for review, Karandashev, 2022a, in press).
Throughout thousands of years of biological evolution, special physiological and neural mechanisms of social connection and love have evolved in animals and humans (e.g., Buss, 2006; Eastwick, 2009; Esch & Stefano, 2005; Fisher, Aron, & Brown, 2006; Fletcher et al., 2015; Gonzaga & Haselton, 2008; Lampert, 1997; Zeki, 2007, see for review Karandashev, 2022a, in press).
Social connections necessitate that an individual recognize others as belonging to their own sort. How does the brain of an animal recognize other members of its own species?
Connections and Attractions of Zebrafish
Johannes Kappel, Johannes Larsch, and their colleagues at the Max Planck Institute for Biological Intelligence investigated this process in juvenile zebrafish. They found a neural circuit that mediates the social attraction of zebrafish. This path, which goes from the retina to the brain, lets zebrafish detect and approach neighboring conspecifics.
Recent studies by scientists at the Max Planck Institute for Biological Intelligence have discovered the neural processes in young zebrafish that enable zebrafish to detect and approach nearby conspecifics. Researchers found that zebrafish social attraction is mediated by a neuronal circuit—the specialized pathway that runs from the retina all the way into the brain.
Shoaling Behavior of Zebrafish
Scientists investigated the role of the visual system and neuronal processing of the stimulus in the social interactions of zebrafish. Experiments demonstrated that a moving dot activates a particular collection of neurons in the thalamus region of the brain. The thalamus is the brain’s sensory control center, integrating and relaying sensory information.
When another zebrafish larva is nearby, the same region of the thalamus becomes active. On its way to the thalamus, sensory information is processed first in the retina and then in the tectum, a key visual center of the vertebrate brain. When information gets to the thalamus, it has already been checked for social cues, like jerky movements from a possible conspecific.
The Brain Regions for Social Behavior Are Connected with the Visual System of Zebrafish
These nerve cells connect the visual system of the zebrafish to other brain regions that are active during social behavior. Researchers thus discovered the visual triggers of this brain activation.
When researchers were able to inhibit newly found neurons, zebrafish larvae lost interest in both conspecifics and moving dots and no longer followed them around. Thus, it was proven that these neurons regulate social approach and affiliation in zebrafish.
These findings increased our understanding of the brain region whose activation provides the basic “glue” for the connection of two zebrafish. These small-scale interactions collectively form shoals of fish. And all this social behavior is governed by neural networks of this kind.
What about human social behavior?
Humans also have a thalamus, and their numerous neural processes have been conserved throughout evolution. The role of these regions in people’s social behavior has yet to be investigated.