The Colorful Life of Costa Rica’s Nudibranch

by Tristan Paylado · Published November 28, 2016 · Updated July 6, 2018

Photo courtesy from National Geographic

Diving in Costa Rica is known not just for the big stuff like manta rays and bull sharks but also for small creatures like the nudibranch which is known for their extraordinary colors and forms. Comprising about 2,300 known species worldwide, this marine gastropod thrives virtually in all water column ranging from the shallow intertidal zone up to depths of 700 meters (2,300 feet).

Body Parts of a Nudibranch. Photo courtesy from seaslug.org

Considered as a benthic organism, you can see nudibranch crawling slowly in the substrate except for a few species that are known to possess some swimming capabilities. Also called as sea slugs, nudibranch vary in sizes ranging from the smallest 4 millimeter to the largest 60 centimeters. Although they are classified as gastropods, their outer shells have disintegrated during larval development where adults only have a soft-mantled body. The name nudibranch was derived from the way they extract oxygen in the water breathing in the so called naked and exposed gills. Cephalic tentacles called rhinophores can be found on its head serving as a sensory arm.

Why are Nudibranch so brightly colored?

Despite being a slow-moving crawler, have you ever wondered why nudibranch have stunning colors that easily attracts predator? While the bright color characteristics may be true in some marine creatures like fishes, it may not be the case for nudibranch. Instead, the color signals its predator that the animal to be preyed upon has a toxin that may become distasteful when eaten.

nudibranch-costa-rica All nudibranch are carnivore feasting primarily on sponges and hydroids that may contain a stinging cell called nematocysts. As the nudibranch feeds, the toxin is accumulated in its body until it reaches a potent level. In the case of nudibranch, the potency of the toxin is not lethal but is primarily focused as a chemical defense to predator giving them an undesirable taste when the nudibranch is eaten.

How and Where to Find Nudibranch in Costa Rica?

Your first consideration in looking for nudibranch is their relative small size. With this, you need to take a closer look at the reef’s substrate, where in some instances, are covered in algae. You also have to talk and plan with your Divemaster or Instructor if you wish to observe nudibranch as a typical dive usually employs continuous finning and motion. You need to stop in order to observe nudibranch in close range. But it does not mean that you are allowed to touch the bottom as you may disturb or destroy nearby reef colonies. Always maintain neutral buoyancy. Eventually, gaining experience allows you to easily spot and observe nudibranch. If you wish to explore a dive site with a good population and diversity of nudibranch, then we recommend the small and tranquil island if Tortuga, the Cabo Blanco Marine Reserve in Nicoya Peninsula, Catalina Island, the rocky isles near the Gulf of Papagayo and Cocos Island.

Nudibranch in Costa Rica: A Macro-Photographers Dream

While Asia and other tropical countries are a haven for macro-photography due to its huge variety of nudibranch, Costa Rica has its fair share of nudibranch diversity. If you are lucky, you may encounter over 10 species of nudibranch in just a single dive which will keep your camera lenses on the move. Here are some nudibranch species you may find in Costa Rica.

Lettuce Sea Slug (Elysia crispata)

Common Name: Lettuce Sea Slug
Scientific Name: Elysia crispata
Max. Length: 15 centimeters
Ave. Length: 10 centimeters
Diet: Sponges and Hydroids
Frequency: Abundant but threatened due to Live Aquarium Species Trading
Range: Eastern Pacific Waters

Photo courtesy from imgur.com

Found in algal beds to shallow reef areas of up to 15 meters (50 feet) deep, you can easily identify this sea slug due to the lettuce-like appearance of its upper mantle. This is one of the nudibranch species that shows poecilogonomy which a conditional larval development triggered by environmental cues.

Diomede’s Sapsucker (Elysia diomedea)

Common Name: Diomede’s Sapsucker
Scientific Name: Elysia diomedea
Max. Length: 10 centimeters
Ave. Length: 6 centimeters
Diet: Sponges and Hydroids
Frequency: Abundant but threatened due to Live Aquarium Species Trading
Range: Eastern Central Pacific Waters

Photo courtesy from baue.org

Also called as the Sap Sucking Slug, Diomede’s Sapsucker feeds primarily on the floral saps of algae particularly Padina (Peacock’s Tail algae) and Codium (Dead Man’s Finger Algae). They are usually found in shallow algal beds to rocky crevice’s up to 30 meters (100 feet) deep.

Ornate Flabellina (Flabellina bicolor)

Common Name: Ornate Flabellina
Scientific Name: Flabellina bicolor
Max. Length: 2 centimeters
Ave. Length: 1 centimeter
Diet: Sponges and Hydroids
Frequency: Abundant but threatened due to Live Aquarium Species Trading
Range: Western and Eastern Pacific Waters

Photo courtesy from The Sea Slug Forum

The Ornate Flabellina is one of the smaller nudibranch that can be found crawling in encrusting turf algae. One of their sources of foods comes from hydroids particularly Eudendrium or commonly called as the White Sticky Hydroid.

Swimming Cynara (Flabellina cynara)

Common Name: Swimming Cynara
Scientific Name: Flabellina cynara
Max. Length: 5 centimeters
Ave. Length: 3 centimeters
Diet: Sponges and Hydroids
Frequency: Abundant but threatened due to Live Aquarium Species Trading
Range: Eastern Pacific Waters

Photo courtesy from The Sea Slug Forum

This is one of the small nudibranch that has the ability to swim. It uses its mantle to propel itself in the water. Usually, this nudibranch swims upward towards the surface and catch a ride courtesy of the water current where it is believed as a mechanism to escape predator or in search of a mate. Kidding aside, humans can relate to this, one way or another.

Blue Dragon (Glaucus atlanticus)

Common Name: Blue Dragon
Scientific Name: Glaucus atlanticus
Max. Length: 4 centimeters
Ave. Length: 2 centimeters
Diet: Sponges and hydroids
Frequency: Abundant but threatened due to Climate Change
Range: Pacific and Atlantic Coast

Glaucus Atlanticus - The Blue Dragon Nudibranch This is one of the nudibranch species that has the ability to swim and float at the surface. When you see a Blue Dragon swimming towards the surface, take a close observation where you can see that it will hang upside down at the surface water taking in air bubbles, thus allowing the animal to float. In some instances, they are washed up in the shore along with fluctuation of tides. So if you see a Blue Dragon trapped or stranded in the sand, take time and due diligence to save it by placing it back to the water.

Spanish Dancer (Hexabranchus sanguineus)

Common Name: Spanish Dancer
Scientific Name: Hexabranchus sanguineus
Max. Length: 60 centimeters
Ave. Length: 20 - 30 centimeters
Diet: Sponges, hydroids and Tunicates
Frequency: Abundant but threatened due to Climate Change
Range: Pacific and Atlantic Coast

Photo courtesy from National Geographic

The Spanish Dancer is the biggest among the nudibranch species that can grow up to 60 centimeters. This blood-colored slug is one of the swimming species of nudibranch that looks like a lady in red dancing to the tune of flamenco. For more information, you can read our related article on Spanish Dancer.

Agassiz’s Chromodorid (Hypselodoris agassizii)

Common Name: Agassiz’s Chromodorid
Scientific Name: Hypselodoris agassizii
Max. Length: 8 centimeters
Ave. Length: 5 centimeters
Diet: Sponges and Hydroids
Frequency: Abundant but threatened due to Live Aquarium Species Trading
Range: Eastern Pacific Waters

hypselodoris-agassizii-by-ryan-photographic If you are thinking that this nudibranch is named after a famous tennis player, then you are wrong. But on the lighter side, you can easily identify this nudibranch through its translucent white color with black or brown spots on its mantle and the gills and rhinophores (the body part that looks like an antenna) is colored orange or light red.

Common Marine Nudibranch (Glossodoris sedna)

Common Name: Common Marine Nudibranch
Scientific Name: Glossodoris sedna
Max. Length: 7.5 centimeters
Ave. Length: 5 centimeters
Diet: Sponges and Hydroids
Frequency: Abundant but threatened due to Live Aquarium Species Trading
Range: Western Atlantic and Eastern Pacific Waters

Photo courtesy from The Sea Slug Forum

The common marine nudibranch is one of the sea slug species that inhabits the shallow seas only ranging from 1 to 2 meters deep. Same with other nudibranch, the common marine nudibranch is a hermaphrodite where a single animal is both considered a male and a female. This unique characteristic becomes more evident during mating where you can see two sea slugs darting their penis’ out to each other inducing one of them to become the male and the other as the female. In this circumstance, the seaslug who successfully darted its reproductive organ to the body of another sea slug becomes the male. And definitely, this is not the case for us humans.

Tiger Dorid (Roboastra tigris)

Common Name: Tiger Dorid
Scientific Name: Roboastra tigris
Max. Length: 30 centimeters
Ave. Length: 20 centimeters
Diet: Sponges, Hydroids and Small Nudibranch
Frequency: Abundant but threatened due to Live Aquarium Species Trading
Range: Eastern Pacific Waters

The Tiger Dorid is one of the bigger species of nudibranch that has the capability to eat smaller nudibranch like Blue-striped Tambja (Tambja eliora) and Related Tambja (Tambja abdere). Aside from its relatively bigger size compared to other species of nudibranch, you can easily identify this seaslug due to its tiger-like patterns and color.

Related Tambja (Tambja affinis)

Common Name: Related Tambja
Scientific Name: Tambja affinis
Max. Length: 7 centimeters
Ave. Length: 5 centimeters
Diet: Sponges and Hydroids
Frequency: Abundant but threatened due to Live Aquarium Species Trading
Range: Western and Eastern Pacific Waters

Photo courtesy from nudibranch.org

The Related Tambja is one of the smaller species of nudibranch that has a yellow-colored lining found in the outer mantle of its body.

Blue-striped Tambja (Tambja eliora)

Common Name: Blue-striped Tambja
Scientific Name: Tambja eliora
Max. Length: 8 centimeters
Ave. Length: 5 centimeters
Diet: Sponges and Hydroids
Frequency: Abundant but threatened due to Live Aquarium Species Trading
Range: Western and Eastern Pacific Waters