Raising Nemo: Parental care in the clown anemonefish

Clown anemonefish caring for their eggs.

Clown anemonefish caring for their eggs.

The activities are as follows:

When animals are born, some offspring are able to survive on their own, while others rely on parental care. Parental care can take many forms. One or both parents might help raise the young, or in some species other members of the group may help them out. The more time and energy the parents invest, the more likely it is that their offspring will survive. However, parental care is costly for the parents. When a parent invests time, energy, and resources in their young, they are unable to invest as much in other activities, like finding food for themselves. This results in a tradeoff, or a situation where there are costs and benefits to the decisions that must be made. Parents must balance their time between caring for their offspring and other activities.

Environmental conditions may change the severity of the tradeoff between parental care and other activities. For example, if there is a lot of food available, parents may spend more time tending to their young because finding food for themselves takes less time and energy. Based on this tradeoff in how parents spend their time, scientists wonder if parents adjust their parental care strategies in response to environmental changes.

Photo of Tina (left) with other members of her lab. The glowing blue tanks around them all contain anemonefish!

Photo of Tina (left) with other members of her lab. The glowing blue tanks around them all contain anemonefish!

Tina is a scientist studying the clown anemonefish (Amphiprion percula). She is interested in how parental care in this species changes in response to the environment. She chose to study anemonefish because they use an interesting system to take care of their young, and because the environment is always changing in the coral reefs where they live. Anemonefish form monogamous pairs and live in groups of up to six individuals. The largest female is in charge of the group. Only the largest male and female get to mate and take care of the young. Both parents care for eggs by tending them, mouthing the eggs to clean the nest and remove dead eggs, and fanning eggs with their fins to oxygenate them. A single pair may breed together tens or even hundreds of times over their lifetimes. But here is the crazy part – anemonefish can change their sex! If the largest female dies, the largest male changes to female, and the next largest fish in line becomes the new breeding male. That means that a single parent may have the opportunity to be a mother and a father during its lifetime.

Parents will fan the eggs to increase oxygen by the nest, or mouth them to remove dead eggs and clean the nest.

Parents will fan the eggs to increase oxygen by the nest, or mouth them to remove dead eggs and clean the nest.

On the reef, anemonefish groups also experience shifts in how much food is available. In years with lots of food, the breeding pair has lots of young, and in years with little food they do not breed as often. Tina presumed that food availability determines how much time and energy the parents invest in parental care behaviors. She collected data from 20 breeding pairs of fish, 10 of which she gave half rations of food, and 10 of which she gave full rations. The experiment ran for six lunar months. Every time a pair laid a clutch of eggs, Tina waited 7 days and then took a 15-minute video of the parents and their nest. She watched the videos and measured three parental care behaviors: mouthing, fanning, and total time spent tending for both males and females. Some pairs laid eggs more than once, so she averaged these behaviors across the six months of the experiment. Tina predicted that parents fed a full ration would perform more parental care behaviors, and for a longer amount of time, than parents fed a half ration.

Watch videos of the experimental trials, demonstrating the mouthing and fanning behaviors:

Featured scientist: Tina Barbasch from Boston University

Flesch–Kincaid Reading Grade Level = 9.4


barbasch_photoAbout Tina: I first became interested in science catching frogs and snakes in my backyard in Ithaca, NY. This inspired me to major in Biology at Cornell University, located in my hometown. As an undergraduate, I studied male competition and sperm allocation in the local spotted salamander, Ambystoma maculatum. After graduating, I joined the Peace Corps and spent 2 years in Morocco teaching environmental education and 6 months in Liberia teaching high school chemistry. As a PhD student in the Buston Lab, I study how parents negotiate over parental care in my study system the clownfish, Amphiprion percula, otherwise known as Nemo.

Dangerously bold

An aquarium filled with young bluegill sunfish. Bluegills are a common type of fish that live in freshwater lakes in the eastern United States.

An aquarium filled with young bluegill sunfish. Bluegills are a common type of fish that live in freshwater lakes in the eastern United States.

The activities are as follows:

1

Just as each person has their own personality, animals in the same species can behave very different from one another! For example, pets like dogs have different personalities. Some have lots of energy, some are cuddly, and some like to be alone. Boldness is a behavior that describes whether or not an individual takes risks. Bold individuals take risks, while shy do not. The risks animals take have a big impact on their survival and the habitats they choose to search for food.

Bluegill sunfish are a type of fish that live in freshwater lakes and ponds across the world. Open water and cover are two habitats where young bluegill are found. The open water habitat in the center of the pond is the best place for bluegill to eat lots of food. However, the open water is risky and has very few plants or other places to hide. Predators can easily find and eat bluegill in the open water. The cover habitat at the edge of the pond has many plants and places to hide from predators, but it has less food that is best for bluegill to grow fast. Both habitats have costs and benefits – called a tradeoff.

To determine their personality, Melissa observed bluegill sunfish in the aquarium lab.

To determine their personality, Melissa observed bluegill sunfish in the aquarium lab.

Melissa is a scientist who is interested in whether differences in young bluegill behavior changes the habitats they choose to search for food. First, she looked at whether young bluegill have different personalities by bringing them into an aquarium lab and watching their behavior. She saw that just like in humans and dogs, bluegill sunfish had different personalities. Some bluegill took more risks and were bolder than others. Melissa wanted to know if these differences in behavior changed how the fish behaved back in the pond. She thought that bold fish would take more risks and use the open water habitat more than shy fish. Bold fish would then have more food and grow faster and larger. She thought that shy fish would play it safe and not take risks, so they would use the cover habitat. Shy fish would then eat less food and not be able to grow as large. Because the bold fish would be in the open water habitat, they might get eaten by predators more because shy fish would avoid predators. These differences in the habitats that the fish use would create a tradeoff based on personality.

Melissa designed a study to test the growth and survival of bold and shy fish. When she was watching the fish’s behavior in the lab, she determined if a fish was bold or shy. If a fish took the risk of leaving the safety of the vegetation in a tank so that it could eat food while there was a predator behind a mesh screen, they were called bold. If it did not eat, it was called shy. She marked each fish by clipping the right fin if it was bold or the left fin if it was shy. She placed 100 bold and 100 shy bluegill into an experimental pond with two largemouth bass (predators). The shy and bold fish started the experiment at similar lengths and weights. After two months, she drained the pond and found every bluegill that survived. She recorded survival and size (length and weight) for each fish and noted if it was bold or shy.

Featured scientist: Melissa Kjelvik from Michigan State University

Flesch–Kincaid Reading Grade Level = 7.3

Photo Jul 23, 5 41 38 PM

A view of the aquarium tank used to determine fish personality. A largemouth bass is placed to the left of the barrier, while 3 bluegill sunfish are placed to the right. If a sunfish swims out of the vegetation and eats a bloodworm dropped near the predator, it is considered bold.

A view of the aquarium tank used to determine fish personality. A largemouth bass is placed to the left of the barrier, while 3 bluegill sunfish are placed to the right. If a sunfish swims out of the vegetation and eats a bloodworm dropped near the predator, it is considered bold.

Average Rating