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Barnacle Life Cycle — Reading Comprehension

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This audio-integrated reading passage, "Barnacle Life Cycle," delves into the intriguing growth and development of barnacles, marine invertebrates commonly found in ocean ecosystems. Aligned with NGSS Standard LS1.B: Growth and Development of Organisms, the passage describes the unique stages of a barnacle's life, from its free-swimming larval forms—the nauplius and cyprid—to its adult, sessile existence. Students will learn about barnacle reproduction, their remarkable ability to attach to surfaces, and how they adapt to their environment. Key terms like 'sessile,' 'larva,' and 'metamorphosis' are explained to enhance comprehension of this fascinating creature's journey. This passage is perfect for understanding diverse life cycles.

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Full-width barnacle life cycle from larva to adult with underwater visuals and labeled stages. — Barnacle grows from drifting larva to glued adult with cirri filtering food from ocean water.

Imagine a creature that spends its youth swimming freely, only to glue itself headfirst to a rock for the rest of its life. This fascinating journey belongs to the barnacle, a common marine invertebrate found clinging to rocks, ship hulls, and even whales around the world. Understanding the barnacle life cycle reveals an incredible story of growth, adaptation, and survival in the ocean.

The life of a barnacle begins as a tiny, free-swimming larva called a nauplius. This microscopic stage looks very different from an adult barnacle, resembling a small, oval-shaped creature with three pairs of legs and a single eye. The nauplius drifts in the ocean currents, feeding on plankton and growing. It undergoes several molts, shedding its outer skin as it gets larger. This period of growth is crucial for the barnacle to gather enough energy for its next transformation.

After several nauplius stages, the larva transforms into a second larval stage called a cyprid. The cyprid is still free-swimming but its main goal is no longer just eating; it's looking for a permanent home. It has complex antennae that it uses to explore surfaces, searching for the perfect spot to settle. These antennae are sensitive to chemical signals left by other barnacles, which helps them find safe and suitable places to attach. Once a good spot is found, the cyprid uses special glands in its antennae to produce a super-strong, natural biological glue.

With its glue applied, the cyprid attaches itself headfirst to the chosen surface. This is a critical moment of metamorphosis. Once attached, it will never move again, becoming sessile. Over the next few days, the cyprid transforms into its adult form. Its outer shell hardens into protective plates, and its feathery feeding legs, called cirri, emerge. These cirri sweep through the water, filtering out tiny food particles.

Barnacles are hermaphrodites, meaning each individual barnacle has both male and female reproductive organs. This allows them to reproduce even when isolated, though they usually cross-fertilize with neighbors. They release their fertilized eggs into the water, and the cycle begins anew with the hatching of new nauplius larvae. From a tiny swimmer to a firmly attached filter-feeder, the barnacle life cycle is a remarkable example of adaptation in marine environments.
Interesting Fact: Some barnacle species can live for over 10 years, continuously filtering food from the ocean currents.

What is the first free-swimming larval stage of a barnacle called?

NaupliusCypridAdultHermaphrodite

What does a barnacle cyprid use to explore surfaces?

LegsEyesAntennaeShell

Why is the cyprid stage crucial for barnacles?

Eating planktonFinding a homeGrowing largerShedding skin

What does 'sessile' mean for an adult barnacle?

Can swim freelyAttached permanentlyEats only plantsChanges color

How do adult barnacles typically feed?

By hunting fishSweeping waterEating seaweedDigging in sand

What advantage do barnacles gain from being hermaphrodites?

Swim fasterEat more foodReproduce aloneChange color