Fish identification archive / Mangrove upside-down jellyfish

Mangrove upside-down jellyfish

Cassiopea xamachana

Fun facts for your next surface interval

The oral arms face upward while the bell rests on the bottom. [source]
Its mucus can contain tiny stinging structures called cassiosomes. [source]
Algal partners help trigger the transition from polyp to medusa. [source]

Florida and local context

Florent Charpin’s species gallery identifies the photographed animal as Cassiopea xamachana and explicitly captions the photograph Blue Heron Bridge, Florida. This is a source-labeled photograph, not an independently reidentified voucher or a current sighting guarantee.

A documented past record does not establish present abundance or guarantee an encounter.

Sources: Named-site photograph: source identification, not independently reidentified

How to recognize this animal

The bell rests against the bottom while the branching oral arms face upward. That inverted posture suggests Cassiopea, but color and posture alone are insufficient to separate every species in the genus.

Sources: Ames and colleagues 2020: Cassiopea cassiosomes and stinging mucus

Size and life stages

The local photographic guide lists 15–18 cm. Because the entry does not specify a measured local specimen or establish a maximum, this profile leaves the directory length filter unassigned.

Sources: Named-site photograph: source identification, not independently reidentified

Habitat and where to look

The 2020 researchers observed animals in Florida Keys mangrove waters, including Key Largo. Shallow sheltered bottoms provide the setting; the separate Blue Heron Bridge photograph establishes that named locality.

Sources: Ames and colleagues 2020: Cassiopea cassiosomes and stinging mucus

Range and local context

This guide uses two specific Florida contexts: the primary Key Largo study and the source-labeled Blue Heron Bridge photo. Neither proves presence at every site between them.

Sources: Ames and colleagues 2020: Cassiopea cassiosomes and stinging mucus; Named-site photograph: source identification, not independently reidentified

What is on the menu?

Photosynthetic dinoflagellates contribute food, and the jellyfish also captures animal prey. The 2020 study showed that released stinging-cell structures could kill prey in laboratory trials.

Sources: Ames and colleagues 2020: Cassiopea cassiosomes and stinging mucus

Daily habits and behavior

Even without direct contact, mucus containing stinging structures can enter surrounding water. Remaining on the bottom does not make the jellyfish harmless.

Sources: Ames and colleagues 2020: Cassiopea cassiosomes and stinging mucus

Mating and the next generation

A polyp stage precedes the familiar medusa. Research links the transition to acquisition of algal partners; no local spawning calendar or growth rate is inferred here.

Sources: Montesanto and colleagues 2026: algal partnerships and strobilation

Look-alikes and identification traps

Other upside-down jellyfish can look similar, and color forms are not separate species. Keep the local record attributed to its source identification rather than claiming an independent diagnostic examination.

Sources: Named-site photograph: source identification, not independently reidentified

Observe without disturbing

Give the jellyfish and surrounding water space. Do not touch it, fan its arms or stir up the bottom for a picture. Avoid directing fins or camera equipment into a patch of animals.

Sources: Ames and colleagues 2020: Cassiopea cassiosomes and stinging mucus

Harvest, protection and eating safety

Live-only collection; closed sites override

Verified listed-group live collection, not recreational food harvest and not a blanket protected-species designation.

This color is a qualified summary, not permission to collect or a guarantee that a particular animal is safe to eat.

Can it be hunted or harvested?

Cassiopea: explicitly listed genus. Where lawful, land and maintain alive with adequate life support; five per species within 20 organisms daily, and ten within 40 in two-day possession. License requirements apply; recreational sale is prohibited.

Florida seasons and areas

No affirmative year-round season clearance is assigned. State marine-life requirements also apply in federal waters. Check the mapped site before any take. Blue Heron Bridge closes listed marine-life collection, not all county fishing. Biscayne prohibits ornamental collection without a superintendent permit and has a mapped March 1–May 31 fishing/possession closure effective in 2026, with a stowed continuous-transit exception. Pennekamp disallows tropical-fish collection and spearfishing. Key Largo Management Area prohibits tropical-fish take, marine-invertebrate take except specified lobster/stone-crab activities, and spearfishing. Sanctuary Preservation Areas prohibit fishing/collection except expressly stated exceptions. These are site rules, not whole-corridor bans.

Can it be speared?

Do not spear a live-only collection species. FWC allows specified nonlethal methods; no quinaldine. FWC restricts spearfishing near public swimming beaches, fishing piers/bridges, jetties and in state parks. The Long Key-north Monroe restriction concerns state waters; Key Largo Management Area has a separate prohibition. Federal location alone is not clearance.

Is it safe to eat?

Live-only collection is not recreational food harvest. No food-safety clearance, recipe or meal frequency is established. Consult current Florida Health guidance for the animal, capture site and consumer. A legal allowance does not establish that a catch is safe to eat. No dated species-matched local menu evidence was verified.

Cassiopea: explicitly listed genus.

This review covers the Vero Beach–Key Largo Atlantic corridor: Indian River, St. Lucie, Martin, Palm Beach, Broward, Miami-Dade and Monroe counties. Florida Atlantic state waters and South Atlantic federal waters are distinct jurisdictions. Do not extend a state-water season tag to federal waters or transfer Atlantic rules to Gulf-side Keys waters. Park and sanctuary boundaries can override a species allowance.

Before you act: Confirm the species, date, exact management area, state or federal waters, gear, licenses and current local closures. A local occurrence record never grants permission to take an animal.

Official rules and health guidance

Reviewed 2026-11-11. Rules and advisories can change; check the linked authorities before acting.

Identification and source cautions

Use this species-labeled site photograph only. Generic upside-down jellyfish references do not prove additional Cassiopea species.
Do not count color forms as separate taxa.
The local identification is the cited photographer or publisher’s identification; it has not been independently reidentified from a specimen.
Broad range or non-Florida research does not establish abundance, spawning dates or encounter probability at this Florida site.
Unverified species-specific details are identified in the relevant section rather than inferred from related animals.

Sources and review

Biology and taxonomy reviewed 2026-11-11. Photographs on cited sites are reference material and are not reproduced here.

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