Jellyfish Scientist - Perfect Picture Book Friday #PPBF

Maria Marshall
Apr 25
4 min read

This week's #PPBF book is an intriguing STEM biography about a self-taught and determined female marine biologist who was the first person to ever raise a jellyfish in a lab and record their unusual life cycle.

Book cover - woman looking through a clear tank and studying a jellyfish.

Jellyfish Scientist: Maude Delap and Her Mesmerizing Medusas

Author: Michelle Cusolito

Illustrator: Ellen Rooney

Publisher: Charlesbridge (4/22/2025)

Ages: 7-10

Nonfiction Biography

Themes:

Biography, marine life, naturalist, jellyfish, and sea life.

Synopsis:

Meet scientist Maude Delap in this riveting STEM biography that details her biggest experiment—her observations of and research about jellyfish.

Maude scoops a jellyfish out of the water and embarks on more than a year of observation of the animal, accomplishing something countless other scientists were unable to do: trace the life cycle of a jellyfish and understand the creature’s metamorphosis from larva to adult.

Maude’s story must be told. Her painstaking observations of a compass jellyfish in 1899-1900 laid the foundation for research still ongoing today.

Opening Lines:

June 21, 1899 (Day 1)

Welcome to the craggy coast of Ireland. The lady

rowing her currach into the surf is Maude Delap.

She’s a scientist collecting specimens.

Her clothes aren’t designed for barging into the

North Atlantic Ocean, but Maude doesn’t let that

stop her.

Maude didn’t attend school, because she was

expected to become a wife and mother. She’s

neither. Instead, she’s an expert in the marine

life on Valentia, her island home.

What I LOVED about this book:

Using a wonderfully conversational tone, Michelle Cusolito explores the research of a talented and determined

naturalist and marine biologist. Fascinated by ocean life, Maude Delap decided to discover the life cycle of a jellyfish. Something no one else had done. Doubling amazing, because she was entirely self-taught.

Internal spread - on the left, a notebook and pencil under the text. On the right, a woman in a row boat (with four large glass conainers) paddling among a bunch of jellyfish.

Text © Michelle Cusolito, 2025. Image © Ellen Rooney, 2025.

On June 21, 1899, using the jars seen in the boat on the opening spread, Maude scooped up a jelly fish and took it back to her home lab - "the Department" (as she called it). The use of date headers and a running day count is a great way to show the passage of time over the year - ultimately 383 days - that Maude observed, recorded, and experimented to discover how a jellyfish developed into an adult. Giving the feeling of the text being 'notes' within a research journal. It's an ingenious way to bring the reader into Maude's grand experiment.

Internal spread - on the left a notebook and pencil under the text. A woman and boy tend the garden as a dog sniffs algae in a bucket. On the right, a woman and her niece set up a tank to examine a jellyfish.

Text © Michelle Cusolito, 2025. Image © Ellen Rooney, 2025.

Luckily Maude had captured a jellyfish with "larvae called planulae." Maude's determination and ability to watch teeny, tiny specs in the water for 7 days paid off when she noticed changes and recorded the development of the larvae into polyps - "ghostly white tubes with waving tentacles."

Internal spread - on the left, a close-up view of the polyps as the attached to the jars side and pebbles on the bottom. On the right, a life-size view of a woman looking through a magnifying glass at tiny, white specs in a water filled jar.

I adore the way Ellen Rooney not only highlights Maude's scientific methods (earlier seen with a magnifying glass and thermometer) using the microscope and creating detailed drawings, but also subtly gives the reader an impressive zoomed-in look at the polyps next to an actual sized view. For the next 262 days (about nine months), Maude cared for the polyps. Maude braved all kinds of weather to fetch fresh seawater in buckets and, through trial and error, discover what her polyps eat.

Finally, she noticed and recorded a change. Tiny pulsing snowflake-like shapes moving in the water. Watching closely, Maude observed five rings form and then seaerate into "pinhead-sized jellyfish called an ephyra." She had done it! Maude had raised baby jellyfish. As beautifully detailed in her notebook! Now, to discover what they eat? More trial and error. Including the discovery that the ephyra shouldn't be in an aquarium together at this stage. Survival of the biggest.

Internal spread - on the left, an open journal with detailed drawings and observations of jellyfish stages of development. On the right, a woman carrying buckets of seawater joins her neice to stare in wonder into a tank with only one remaining young jellyfish.

I adore the great expressions of Maude and her niece highlighting their wonder, curiosity, and surprise associated with this grand experiment. In addition to chronically the remainder of Maude's research with jellyfish, the book's excellent back matter explains a bit more about jellyfish, Maude's unusual life and the importance, accuracy, and general acceptance of her research by the wider scientific community, and how the author discovered Maude's story. In addition to explaining some specific choices made by the author in writing the book.

This is a stunningly beautiful and thoroughly engaging biography of a self-trained marine biologist who was the first person ever to raise a jellyfish through its entire life cycle.

Resources:

check out all these ways to make your own jellyfish.

participate in your own citizen science project - such as Project Squirrel, Project Feeder Watch, or Tracking Seasonal Changes in Plants and Animals.
Check out the book's Activity Guide.

If you missed my interview with Michelle Cusolito on Monday, find it (here).

This post is part of a series of blog posts by authors and KidLit bloggers called Perfect Picture Book Fridays. For more picture book suggestions and resources see Susanna Leonard Hill's Perfect Picture Books.

1 Comment

Leslie Goodman

Apr 25

It was probably five or more years ago when I went with my family to the aquarium in the city. I still have the photos on my phone of the jelly fish I couldn't stop photographing. Watching them pulse and gracefully move was mezmerizing. I'm thrilled to see this book about Maude's accomplishments and can't wait to read it. The illustrations are clever, showing a excerpt from Maude's journal beside the main illustration.