Sea hare
A sea hare is a soft-bodied marine mollusc related to sea slugs, capable of releasing ink when threatened.
Also known as: Aplysia, sea slug
How big is it?
20 cm · defined body length
Also 7.874 in
Defined body length · defined specimen
Typical recorded range: 12 cm to 30 cm.
A little perspective
Sea hare vs Basket star: length comparison
The body length of a sea hare is approximately equal to the arm-tip span of a basket star.
A sea hare is a soft-bodied marine mollusc related to sea slugs, capable of releasing ink when threatened.
A basket star is a marine echinoderm related to brittle stars, with repeatedly branching arms adapted for filter feeding.
Both rulers start at the same zero and share one linear scale. Artwork keeps its original proportions.
Measurements, assumptions & sources +
Sea hare
Defined body length: 20 cm; defined specimen; range 12 cm–30 cm.
A defined 20 cm Aplysia sea hare measured along the relaxed body. Species, maturity and posture vary greatly; extended oral tentacles are excluded.
Monterey Bay Aquarium — California sea hare
The marked defined body length is calibrated. Unmeasured illustration details are representative.
Basket star
Defined arm-tip span: 20 cm; defined specimen; range 10 cm–50 cm.
A defined 20 cm expanded basket star measured across the branching arm tips. Species and posture alter the projected span dramatically; the central disc is much smaller.
Smithsonian Ocean — Basket stars
The marked defined arm-tip span is calibrated. Unmeasured illustration details are representative.
Use the visual comparison to explore its scale, then check the measurements and sources.
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Why this measurement?
Why we use 20 cm
We compare the body length of a sea hare. This is an illustrative comparison value, not a claim that every example is the same. The recorded range is 12 cm to 30 cm.
A defined 20 cm Aplysia sea hare measured along the relaxed body. Species, maturity and posture vary greatly; extended oral tentacles are excluded.
The marked horizontal span follows the measured feature, not the edges of the image. How calibrated comparisons work →
Recorded properties
Dimensions and measurements
| Property | Selected value | Recorded range | Basis |
|---|---|---|---|
| 20 cm | 12 cm to 30 cm | defined specimen |
Around this scale
Explore nearby values.
Compare examples with lower, similar and higher values. Each card names the measurement being compared.
Nearest lower valueLiving thingsGeoduck17 cmDefined shell lengthA geoduck is a large burrowing marine clam with a comparatively small shell and a very long siphon.
Around the same scaleLiving thingsBasket star20 cmDefined arm-tip spanA basket star is a marine echinoderm related to brittle stars, with repeatedly branching arms adapted for filter feeding.
Nearest higher valueLiving thingsBrown rat25 cmBody lengthA brown rat is a medium-sized rodent that adapts easily to urban and rural environments.Sources and method
Want to check the number?
The source records and measurement method remain available for inspection.
- Monterey Bay Aquarium — California sea hareSea-hare anatomy and broad size variation; the atlas uses a smaller defined Aplysia specimen.
There’s always another scale
Follow your curiosity.
Living thingsNudibranch10 cmA nudibranch is a soft-bodied marine mollusc, often brightly coloured, commonly known as a sea slug.
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