Macro
Nudibranchs
Nudibranchia · Marine gastropod mollusks, order Nudibranchia; order-level overview of more than 3,000 described species
Nudibranchs are the reason macro divers stop covering distance. More than three thousand described species of these shell-less snails crawl the world's seafloors wearing colors that work as warnings, advertisements, and camouflage all at once, and more are named every year, with muck hotspots regularly producing animals new to science. The order splits broadly in two: dorids, carrying a rosette of gills on the back, many recycling sponge toxins into chemical defense; and aeolids, fringed in tentacle-like cerata that store working stinging cells stolen from the hydroids they eat. Rhinophores, the paired head antennae, smell the water for prey and mates. Most species live weeks to a year, so casts turn over fast and no two months on the same site produce the same list. Slow to a crawl and the sand starts producing.
Where and when to see one
"Resident" means most dives at that destination encounter them; "seasonal" means reliably present in the listed months; anything else is a bonus, not a plan.
| Destination | Reliability | Months | Notes |
|---|---|---|---|
| AnilaoPhilippines | Resident: seen on most dives | Year-round | |
| Lembeh StraitIndonesia | Resident: seen on most dives | Year-round | |
| Dumaguete, Dauin & Apo IslandPhilippines | Resident: seen on most dives | Year-round | |
| Poor Knights IslandsNew Zealand | Resident: seen on most dives | Year-round | |
| British ColumbiaCanada | Resident: seen on most dives | Year-round | |
| Milne BayPapua New Guinea | Resident: seen on most dives | Year-round |
Best month, at a glance
Understanding them
Habitat: Every bottom type divers visit (reef, rubble, sand, kelp, jetty piles, mud), wherever each species' prey grows; the order as a whole ranges from tide pools to the deep sea.
Range: All oceans, polar to tropical; the Coral Triangle holds the richest shallow-water diversity known.
Behavior: Slow, chemically defended browsers; hermaphrodites that mate side by side and lay coiled egg ribbons. Aeolid species store working stinging cells from the hydroids they eat.
Diet: Specialists almost to a species: sponges, hydroids, bryozoans, tunicates, anemones, eggs, or other sea slugs.
Size: typically around 0.03 m; documented up to 0.6 m (order-wide range; most diver-found species are 1–6 cm, while the Spanish dancer reaches about 60 cm).
How to behave around one
Shoot without touching or relocating: posed slugs on borrowed backgrounds are the macro world's staged wildlife problem. Keep strobe sessions short per animal.
Conservation
Almost none have been evaluated for the IUCN Red List; their fortunes track the sponges, hydroids, and other prey they depend on.
Charted sites known for them
Highlighted sites were charted for this species by our editors; numbers are GBIF occurrence records logged within about 5 km of a site since 1990.
Watch
From the official channels
Wildlife of Monterey | New film in our auditorium
Live Aviary Cam | Monterey Bay Aquarium
Live Aviary Cam | Monterey Bay Aquarium
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