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Finding Nemo’s Clownfish, High school

Two clownfish in a purple sea anemone on a reef in Palau

In Finding Nemo, Nemo’s mom is lost at the start of the movie, and his dad, Marlin, raises him alone.

In a wild clownfish family, could a dad like Marlin become the mom?

Video 1. Finding Nemo got the clownfish wrong

Clownfish live in groups inside an anemone, and the biggest fish is the female. When the female is gone, the biggest male turns into a female. So after Nemo’s mom was gone, Marlin would have become the mom.

Video 2. Nemo is probably not Marlin’s son

Clownfish parents guard their eggs until the eggs hatch. Then the babies drift in open water for about a week and a half and usually settle in a different anemone. Scientists used DNA from clownfish on 310 anemones to build a family tree, and relatives shared an anemone only about 2% of the time.

A common clownfish in the tentacles of a sea anemone
A tadpole is the larva of a frog or toad. Video 2 uses the plural, larvae.

Your word of the day is

LAHR-vuh

larvaghost, maskfrom Latin larva

A young animal that hatches from an egg and looks far different from the adult it will become.

A group of clownfish swimming together

Wild breeding male clownfish carry testis tissue and immature ovary tissue at the same time.

How does a breeding male clownfish become the new breeding female?

A two-banded clownfish in a sea anemone

After a breeding male clownfish becomes the breeding female, what happens to the largest non-breeder and the smaller fish in line?

Fish swimming over a coral reef

Clownfish parents tend their eggs for about a week, but the larvae drift away on hatching night.

How could egg care raise the number of offspring clownfish parents produce?

Two clownfish on a sea anemone

Which experiment would best test whether clownfish egg care raises the number of eggs that hatch?

Clownfish swimming in and out of the tentacles of a sea anemone on a coral reef

On Kimbe Island, 56% of the young fish that settled had hatched from Kimbe Island parents, and the other 44% arrived as larvae from other reefs. Yet relatives shared an anemone only about 2% of the time.

What path does a clownfish larva take from hatching night to settling?

Two clownfish sharing a sea anemone, darting among its tentacles

On Kimbe Island, 56% of settlers had Kimbe Island parents, yet relatives shared an anemone only about 2% of the time.

How can most Kimbe Island settlers have Kimbe Island parents while relatives rarely share an anemone?

A clownfish swimming through the waving tentacles of its anemone home

The Kimbe team never followed a larva across open water. Divers clipped a tiny piece of fin from each fish, and the team read 22 DNA markers from each clip over six rounds of sampling between 2003 and 2013.

How can DNA markers link a young clownfish to one breeding pair?

Several clownfish crowded together in one sea anemone

Why would the Kimbe Island team sample clownfish six times over ten years instead of once?

The camera tilts across a coral reef full of corals and small fish

Claim, evidence, reasoning

Non-breeding clownfish skip breeding while they wait in line, and their groupmates are usually not relatives.

Which claim best explains why a non-breeding clownfish stays in its group instead of leaving for a different anemone?

Scuba divers gliding over a coral reef

Claim, evidence, reasoning

Which evidence best backs the claim that staying gives a non-breeding clownfish its best chance to breed later?

Blue-green ocean water rippling at the surface

Claim, evidence, reasoning

Which reasoning best links a non-breeding clownfish’s place in line to staying in the group?

Clownfish swimming among sea anemone tentacles on a reef in Bali

Kimbe Island has 310 anemones. Each anemone holds one breeding pair and up to four non-breeders.

What’s the most clownfish Kimbe Island could hold at one time?

A clownfish peeking out from between the tentacles of a sea anemone

Kimbe Island’s 310 anemones hold a limited number of clownfish at one time, but scientists identified 2,927 different fish over ten years.

Why could the Kimbe Island scientists identify more clownfish over ten years than the island holds at one time?

Two anemonefish swimming together on a reef off the coast of Kenya

Each Kimbe Island anemone holds one breeding pair, and the island has 310 anemones.

What limits how many clownfish can breed on Kimbe Island at once?

A few clownfish swimming among sea anemones in the ocean

In Finding Nemo, Marlin stays a dad after Nemo’s mom is gone, and Nemo grows up in Marlin’s anemone.

Which finding shows protandry in wild clownfish?

Close-up of a clownfish surrounded by sea anemone tentacles

Which Kimbe Island finding best describes clownfish philopatry?

A clownfish hovering over a patch of its eggs stuck to the reef

Lesson complete

Today’s word

larva

LAHR-vuh

A young animal that hatches from an egg and looks unlike the adult it will become.

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Sources
  1. Océane Salles, Benoit Pujol, Serge Planes and seven co-authors, led from the Université de Perpignan Via Domitia in France, PNAS, 2016
  2. Madison Pacaro, Tina Barbasch, Michaela Rogers, Juan Chavez, Peter Buston and John Majoris, Boston University, Ethology, 2023
  3. Peter Buston, Steven Bogdanowicz, Alex Wong and Richard Harrison, Molecular Ecology, 2007
  4. Peter Buston, Proceedings of the Royal Society B, 2004
  5. Theresa Rueger, Peter Buston and colleagues at Boston University and James Cook University, Proceedings of the Royal Society B, 2018
  6. Laura Casas, Xabier Irigoien and colleagues at King Abdullah University of Science and Technology in Saudi Arabia, Scientific Reports, 2016
  7. John Pearce, The Auk, 2007
  8. Vision and Change core concepts and competencies, as summarized in Brownell and others, CBE Life Sciences Education, 2014
  9. Word origins from Dictionary.com: larva, Lares, larvicide, philo-, patri-, proto-, proton, andro-, protandrous
  10. Spanish and French spellings from Wiktionary
  11. Instagram originals of video 1 and video 2, not linked because Instagram needs a login