Marine invertebrates of Ocean City & Assateague

Field-guide profiles for jellyfish, comb jellies, sea stars, sand dollars, sponges, and other invertebrates around Ocean City, Maryland, including Assateague Island National Seashore and Assateague Island State Park. Crabs and shellfish have their own directories; this page covers the rest of the wash-line menagerie.

Where to see wildlife Mollusks Crustaceans Nature Guide overview

12 starter species curated for visitors—not every bay invertebrate. Likelihood stars rate how often a typical visitor might notice the species around OC / Assateague MD (1 rare · 5 common). Treat all stinging jellies with respect, even when stranded.

Showing 12 of 12 species

Atlantic Sea Nettle (Chrysaora chesapeakei) — Ocean City, Maryland Atlantic Sea Nettle Chrysaora chesapeakei · Jellyfish / siphonophore · ★★★★★ Maryland’s infamous summer stinger. White or milky bells with long trailing tentacles in the coastal bays and sometimes the ocean. Moon Jelly (Aurelia aurita) — Ocean City, Maryland Moon Jelly Aurelia aurita · Jellyfish / siphonophore · ★★★★★ The classic translucent “saucer” jelly of Ocean City beaches. Mild sting, four horseshoe gonads, and frequent wash-ups after warm spells. Cannonball Jellyfish (Stomolophus meleagris) — Ocean City, Maryland Cannonball Jellyfish Stomolophus meleagris · Jellyfish / siphonophore · ★★★★☆ Firm, dome-shaped ocean jellies that wash onto Mid-Atlantic beaches. Short tentacles and a mild sting compared with sea nettles. Clam Worm (Alitta succinea) — Ocean City, Maryland Clam Worm Alitta succinea · Marine worm · ★★★★☆ Segmented bait worm of Mid-Atlantic mud and sand, wriggling in wrack, under rocks, and on clam flats around Ocean City. Five-holed Sand Dollar (Mellita quinquiesperforata) — Ocean City, Maryland Five-holed Sand Dollar Mellita quinquiesperforata · Echinoderm · ★★★★☆ Flat, round echinoderm of Mid-Atlantic sands. Live animals are purple-brown; bleached white “dollars” are classic beach souvenirs. Sea Walnut (Mnemiopsis leidyi) — Ocean City, Maryland Sea Walnut Mnemiopsis leidyi · Comb jelly · ★★★★☆ Gelatinous comb jelly of Mid-Atlantic bays. Not a true jellyfish, and it doesn’t sting. Night lights can show its rainbow comb rows. Atlantic Purple Sea Urchin (Arbacia punctulata) — Ocean City, Maryland Atlantic Purple Sea Urchin Arbacia punctulata · Echinoderm · ★★★☆☆ Spiny purple urchin of Mid-Atlantic hard bottoms and jetties. Occasional beach find and a relative of sand dollars. Forbes' Sea Star (Asterias forbesi) — Ocean City, Maryland Forbes' Sea Star Asterias forbesi · Echinoderm · ★★★☆☆ Five-armed Mid-Atlantic sea star of jetties, bay bottoms, and occasional beach wrack. The “starfish” visitors hope to find. Orange-striped Anemone (Diadumene lineata) — Ocean City, Maryland Orange-striped Anemone Diadumene lineata · Anemone · ★★★☆☆ Small striped sea anemone of docks, jetties, and oyster shell. Tiny tentacle crowns on Mid-Atlantic hard structure. Red Beard Sponge (Clathria prolifera) — Ocean City, Maryland Red Beard Sponge Clathria prolifera · Sponge · ★★★☆☆ Bright orange-red encrusting sponge of Mid-Atlantic pilings, shells, and jetties, often mistaken for coral or algae. Sea Pansy (Renilla reniformis) — Ocean City, Maryland Sea Pansy Renilla reniformis · Other · ★★★☆☆ Leaf-shaped soft coral of sandy Mid-Atlantic bottoms. Purple “petals” bioluminesce and wash ashore after rough seas. Portuguese Man o' War (Physalia physalis) — Ocean City, Maryland Portuguese Man o' War Physalia physalis · Jellyfish / siphonophore · ★★☆☆☆ Occasional Ocean City / Assateague wash-up: purple-blue float with long, potent tentacles. Not a true jellyfish, and a serious sting risk.

Beach Blog on Marine invertebrates

Trip reads written for this hub—pacing and advice, not a second directory.

All posts about Marine invertebrates
Sea nettle booties for bay wades — Beach Blog photo, Ocean City, Maryland

Sea nettle booties for bay wades

Casey Nguyen Marine invertebrates

Bioluminescence hope vs hype: bay night magic you cannot schedule — Beach Blog photo, Ocean City, Maryland

Bioluminescence hope vs hype: bay night magic you cannot schedule

Grace Okonkwo Marine invertebrates

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