Species and Types of Nudibranchs: Beautiful, Strange and Toxic Ones | Sea Life, Islands and Oceania

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NUDIBRANCH SPECIES

Clown nudibranch

There are more than known 3,000 species of nudibranch (many scientists believe only about half of all nudibranch species have been found). Some species of sea slug and nudibanch float in the water and consume jellyfish. When they eat jellyfish they take the stinging cells into their gut unmolested. The toxin eventually migrates through the seas slug's tissue into its back and provided protection against predators. Glaucus atlanticus, which is camouflaged in blue and silver, prey on toxic Portuguese men-of-war, appropriating their stinging cells of its own defense in their finger-like cerata (spikes found externally on nudibranchs) (See Below). Other species like the Pyjama slug Chromodoris quadricolor may use their striking colors to alert potential predators of their nasty chemical taste.

Phyllodesmium Magnum are a type of aeolid nudibranch that uses their cerata for of breathing, digesting and defence. They are also regarded as solar-powered slugs because they feed on algae from within sea anemones and corals and store this algae which continues to photosynthesise within their cerata, providing them with a continuous source of food and sugars. About 13 centimeters (5 inches) in length, they are found in the western Pacific Ocean and have described in New Caledonia, northwest Australia, the Marshall Islands, Hong Kong, North Kermadec and Guam. [Source: Sophie Adams, Citrus Reef, March 9, 2023 **]

Spanish Shawls (scientific name: Flabellinopsis Iodinea) are very colorful aeolid nudibranchs. Native to the west coast of North America from British Columbia to Baja California Sur, and also found in the Gulf of California and the Galapagos Islands, they have a purple body, orange cerata and scarlet red rhinophores, The neon orange appendages on their back are oxygen-extracting cerata that also serve as extensions of their digestive system. They are also used to store the stinging cells of the anemones and fan-like hydroids that Spanish shawls eat. The purple, red, and orange colors are derived from a single carotenoid pigment, astaxanthin. Scientists think the animals’ gills are orange so they can camouflage with their prey while they are eating. The orange gills on their backs are warnings to potential predators. The color tells their predators that they are either poisonous or distasteful. [Source: Wikipedia]

Janoluses make ups a genus of small to large nudibranchs in the family Janolidae.The name Janolus is derived from the two-headed god Janus, of ancient Roman mythology. Adult individuals of Janolus species are between 2.5 and 8 centimeters (one to three inches) long, depending on the species. They are semi-translucent and the body is covered in short cerata and feed on Bryozoa, moss animals. Janolus sp. is a species Janolus nudibranch known for its brightly-colored, body-covering, stubby cerata. Their main predators are large sea slugs known as Navanaxes, which track the slime trails of Janolus using chemoreceptors. When Janolus sp. are about to be attacked, they roll themselves into balls like hedgehog, displaying their spiky cerata. Janolus are found worldwide, but mostly in warm, shallow waters in Europe, Africa, Australia and Japan. [Source: Wikipedia, Sophie Adams, Citrus Reef, March 9, 2023]

The four-centimeter-long “Phyliodesmium iriomotense” feed exclusively on corals. It’s translucent body houses a branching digestive gland with tentacle-like certa-outgrowths the creature can shed if attacked. The “bornella angilla”, a swimming nudibranch, flees dangers by folding its appendages and swimming like an eel.

Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se; Encyclopedia of Life eol.org; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; Monterey Bay Aquarium montereybayaquarium.org ; MarineBio marinebio.org/oceans/creatures; Websites and Resources on Coral Reefs: Coral Reef Information System (NOAA) coris.noaa.gov ; International Coral Reef Initiative icriforum.org ; Coral Reef Alliance coral.org ; Global Coral reef Alliance globalcoral.org ; Global Coral Reef Monitoring Network gcrmn.net

Types of Nudibranchs: Dorid and Aeolid

Nudibranchs are commonly divided into two main kinds: 1) dorid and 2) aeolid (also spelled eolid) nudibranchs. Dorids (clade Anthobranchia, Doridacea, or Doridoidea) have having an intact digestive gland and the feather-like branchial (gill) plume, which forms a cluster on the outside part of the body, around the anus. Fringes on the mantle do not contain any intestines. Additionally, dorid nudibranchs commonly have distinct pockets, bumps, and/or mantle dermal formations, which are distortions on their skin, used to store bioactive defense chemicals. [Source: Wikipedia]

Spanish shawl

Aeolids (clade Cladobranchia) have cerata (anatomical structures on on the backs of these nudibranch) instead of the branchial plume. The cerata (singular cera) serve in place of gills and facilitate gas exchange through the epidermis (skin). Additionally, aeolids possess a branched digestive gland, which may extend into the cerate and often has tips that contain cnidosacs (stinging cells absorbed from prey species and then used by the nudibranch).They lack a mantle. Some are hosts to zooxanthellae.

Dorid nudibranchs (Scientific name: Hypselodoris) are members of a genus of colourful sea slugs or, marine gastropod mollusks in the family Chromodorididae. They are pproximately 70 described species, which are commonly divided into two major clades. 1) Eastern Pacific and Atlantic and 2) Indo-Pacific. It is thought that these two groups were separated by the Pacific Ocean and the division predates the formation of the Panama isthmus, which is why the Eastern Pacific and Atlantic species are group together.

Thick-Horned Nudibranch

Thick-horned nudibranch (Scientific name: Hermissenda crassicornis) are commonly found in coastal areas — around tidepools, and on rocks, pier pilings, and mudflats — from low-tide water line to depths of 35 meters (110 feet) along the West Coast of North America from Kodiak Island, Alaska to Baja California, Mexico. They are benthic (bottom-dwelling) organisms that can be found crawling on rocks, seaweed, and various other substrates on the ocean floor. [Source: Gena McKinley, Animal Diversity Web (ADW) /=]

Thick-horned nudibranchs are popular with scientists studying neurology on the cellular level and psychological properties, such as learning and memory. They have also been used as lead toxicity studies. In these studies, lead significantly reduced the ability of these nudibranch to experience and acquire associative conditioning.The behavioral studies can be related to identifiable cells in the ganglia of the head. /=\

Thick-horned nudibranchs feed on a wide variety of sea life, such as sponges, hydroids, corals, and many other types of invertebrates. In some cases, they are cannibalistic, eating other nudibranchs, and fighting each other, during which they bite chunks of tissue off of each other. Studies indicate that Thick-horned nudibranchs locate food by chemotaxis (movement of an organism or entity in response to a chemical stimulus). These studies also showed that a diet of turbularia ( "whirlpools" of microscopic particles created close to the skins of aquatic species) resulted in a very high growth rate in the Thick-horned nudibranchs.

Thick-Horned Nudibranch Characteristics

20110307-NOAA nudibranch hermisseda_100.jpg
thick-horned nudibranch
Thick-horned nudibranchs are beautiful invertebrates. They are 8 centimeters (3.25 inches) long, and one centimeter (0.4 inches) wide on average. They are bluish-white with an orange line down the middle of its back. The margins have pale electric blue lines. These colors are mainly carotenoids ( yellow, orange, or red fat-soluble pigments) and carotenoproteins (proteins with a covalently-bound carotenoids).

Thick-horned nudibranchs have two pair of tentacles (rhinophores) located on the top of the head. According to Animal Diversity Web: The first pair has blue lines, and the second pair is bluish with raised rings. In the middle, there are numerous finger-like projections, called cerata, in two clusters on each side of the back. These projections are brilliantly colored in bright orange with a white tip on each ceratum.

Thick-horned nudibranchs protect themselves with different types of defense. One means is warning coloration. The orange color of Thick-horned nudibranch indicates to predators that it is distasteful and is poisonous. Another means of defense is contained in the cerata found on the back of the animal. The cerata contain stinging cells to keep predators away. These stinging cells developed from the nematocysts of sea anemones and hydroids that the thick-horned nudibranch feeds on. These nematocysts are undigestible, causing them to be stored in the cerata. During digestion, the nematocysts of prey remain undischarged and travel through interconnecting tubules from the diverticula into the cerata.

Like other nudibranchs, Thick-horned nudibranchs are hermaphrodites, possessing both male and female organs. They lay eggs in strands that can range in number from a few hundred to a million. The development of eggs is very much influenced by water temperature and can take as little as five days or as long as 50 days. The development of the egg is most favorable in warm temperatures. The egg develops into a larval stage called a veliger that floats around on the ocean floor until environmental conditions cause the veliger to settle on the ocean floor and develop into adult form. /=\

Blue Dragon Nudibranch

Blue dragon nudibranchs (Scientific name: Glaucus Atlanticus) look like living starships. Among the world’s strangest and rarest types of nudibranchs, these tiny creatures generally only grow to a maximum length of about 2.5 centimeters (one inch) and swims in the open water unlike most types of nudibranch, which stay close to the ocean floor. Blue dragon nudibranchs spend much of their time suspended upside down on the surface of the water at the mercy of waves and currents. They feed on jellyfish, including the Portuguese man o' war, ingesting and storing the toxic cells of stinging jellyfish to protect themselves from predators. Humans handling these nudibranchs may receive a very painful and potentially dangerous sting.[Source: Sophie Adams, Citrus Reef, March 9, 2023]

Blue dragon nudibranchs (Glaucus Atlanticus)

Blue dragon nudibranchs are also known as blue sea dragons, sea swallows, blue angels, blue glaucus, dragon slugs, blue dragosn, blue sea slugs and blue ocean slugs. Thought to reside in all the world’s oceans, they are pelagic (open-ocean) aeolid nudibranch, a shell-less gastropod mollusk in the family Glaucidae. When they float upside down they use the surface tension of the water to stay up. They employ countershading — the blue side of their bodies faces upwards, blending in with the blue of the water and their silvery gray side faces downwards, blending in with the sunlight reflecting on the ocean's surface when viewed look upwards underwater. [Source: Wikipedia]

Blue dragon nudibranchs are usually found in tropical and subtropical areas, floating on ocean surfaces thanks to stored gulped-down air stored inside their stomachs. The sometimes make noises when air escapes out of their stomach as they feed. Blue dragon nudibranchs look similar to and are closely related to,G. marginatus, which looks fatter and is now understood to be several species that live in the Indian and Pacific Oceans. All these species are called "blue dragons". They can live up to a year under the right conditions.

Blue Dragon Nudibranch Characteristics and Feeding of Portuguese Man O’Wars

Blue dragon nudibranchs have a silvery grey back side, and dark and pale blue underside. ventrally and dark blue stripes on their head. They have flat, tapering bodies and six appendages that branch out into rayed, finger-like cerata. Cerata, also known as papillae, extend laterally from three different pairs of peduncles. The papillae are placed in a single row (uniseriate) and may be up to 84 inches total. [Source: Wikipedia]

Blue dragon nudibranchs’ radula have serrated teeth and strong jaws and denticles which allow them to grasp prey and "chip down" parts of it. The position of these slugs’ gas-filled sac is what causes them to float upside down. The upper surface of the blue dragon is actually the foot, which is the underside in other nudibranchs, slugs and snails.

Blue dragon nudibranchs preys on larger pelagic organisms. They move toward prey or mates by using their cerata to make slow swimming movements. Among their prey are dangerously venomous Portuguese man o' war, (Physalia physalis), by-the-wind-sailors (Velella velella), blue buttons (Porpita porpita), and the violet snail, Janthina janthina. In captivity, occasionally, individuals attack and cannibalize other blue dragon nudibranchs .They able to feed on Portuguese man o' war due to their immunity to the jellyfish’s venomous nematocysts. The slug consumes chunks of the organism and appears to select and store the most venomous nematocysts for its own use against future prey. The nematocysts are collected in specialized sacs (cnidosacs) at the tip of the animal's cerata, the thin feather-like "fingers" on its body. Because these nudibranchs concentrates the venom, they can produce a more powerful and deadly sting than Portuguese man o' wars.

Like almost all heterobranchs, blue dragons are hermaphrodites and their male reproductive organs have evolved to be especially large and hooked to avoid their partner's venomous cerata. Unlike most nudibranchs, which mate with their right sides facing each other, blue dragons mate with face to face. After mating, both individuals are able to lay eggs and can release up to 20 on an egg string, often laying them in wood pieces or carcasses. On average, these nudibranchs can lay 55 egg strings per hour.

Black-Margined Nudibranch— a Dorid Nudibranch

Black-margined nudibranchs (scientific name: Doriprismatica atromarginata) are dorid nudibranchs. Native to the Pacific and Indian Oceans, they are a common nudibranch species n. typically found in marine habitats such as reefs and inter-tidal areas at depths from zero to 28 meters (92 feet). They are generally found in shallow water. Most live near the ocean surface. They have a life expectancy of one year in the wild but some have lived up to six years in captivity. [Source: Melanie Kuehl; Joanne Sountis; Christy Young; Craig Zagata, Animal Diversity Web (ADW) /=]

Black-margined nudibranchs are enjoyed by snorkelers and divers, and are beautiful creatures that add to the diversity of marine life. However beyond this they little impact on humans. They not considered threatened or endangered. They have not been evaluated for the International Union for Conservation of Nature (IUCN) Red List. They have no special status according to the Convention on the International Trade in Endangered Species (CITES).

Black-margined nudibranchs live on a sponge or coral its whole life. They eat corals, sponges and Hyatella (a genus of bivalves). They are preyed upon by crabs, lobsters, sea spiders, and other sea slugs such as Navanax inermis. Black-margined nudibranch are simultaneous hermaphrodites in which individuals have sex organs of both sexes and can produce both sperm and eggs even in the same breeding season. Females and males sexual maturity at two to four months. Eggs are typically deposited on sponges. Gestation occurs over five to 50 days and in warmer waters, egg maturation occurs sooner.

Black-Margined Nudibranch Characteristics

Black-margined nudibranchs are elongated nudibranchs with white to creamish background color and dark bands running down the dorsal midline. They reach lengths of six centimeters (2.36 inches), with their average length of 4 to 4.5 centimeters (1.4 to 1.8 inches). According to Animal Diversity Web: The mantle edge is very sinuous and has a dark brown to black margin. This sea slug has dark rhinophore clubs on the dorsal surface. Gills range in number from 14-22. The simple gills are also long, cream colored and have a dark margin. [Source: Melanie Kuehl; Joanne Sountis; Christy Young; Craig Zagata, Animal Diversity Web (ADW) /=]

Black-margined nudibranchs are mostly active during the day. They "craws" along the surface of rocks and sponges, moving their body in a wave-like pattern as they go. When not moving, they are known to coil up their body.

Black-margined nudibranchs sense using ultraviolet light, touch and chemicals usually detected with smelling or smelling-like senses. They communicate with vision and chemicals usually detected by smelling. They also use mimicry. Black-margined nudibranch has cephalic tentacles on its head. These tentacles are sensitive to touch, taste, and smell. It has aposematic coloring to warn predators that it is poisonous.

Phestilla Sibogae— an Aeolid Nudibranch

Phestilla sibogae

Phestilla sibogae are aeolid nudibranchs. Native to the western Pacific Ocean and Indian Ocean, they live in tropical waters among coral reefs. Because of its total dependence on its prey, specific kinds of porites corals, it is always found on or near colonies of these corals. Phestilla sibogaes’ primitive brain and nervous system with easy to identify neurons make them useful in neural research. [Source: Terri Nelson, Animal Diversity Web (ADW) /=]

There are no accurate counts of P. sibogae populations. They have no special status on the International Union for Conservation of Nature (IUCN) Red List or the Convention on the International Trade in Endangered Species (CITES). However, things that have a negative impact on coral reefs they live in — such as chemical pollution, silt, or human disturbance — could affect the health of P. sibogae populations.

Phestilla sibogaes are corallivores — specialized predators that feeds only on corals and feeds feeds only on the genus Porites. These nudibranch are ravenous eater, and were it not for predatory control they could quickly eat their way through an entire reef. An adult P. sibogae can eat up to 6.4 square centimeters of coral each day. Various species of reef-dwelling crustaceans and fish eat P. sibogae. The nudibranch avoids some predators by hiding during daylight and only moving around at night. Research on P. sibogae indicates that if it had no natural predators, it would continue to reproduce and eat Porites coral until the coral was gone. /=\

Phestilla Sibogae Characteristics

Phestilla sibogae reaches lengths of three to four centimeters (1.2 to 1.6 inches) and weigh between 0.8 and 1.7 grams (0.03 and 0.06 ounces) They very well camouflaged on Porites coral they live among and are difficult to see there. These nudibranch exhibit external bilateral symmetry (both sides of the animal are the same), although some internal organs are slanted to the right (called detorsion). Phestilla sibogae eat by scraping their radula, a flexible tongue-like membrane with two or three rows of teeth, across the coral surface to draw food into its mouth. [Source: Terri Nelson, Animal Diversity Web (ADW) /=]

Like many other nudibranchs, P. sibogae has two sets of tentacles. One of the sets of tentacles, called rhinophores, are located on the dorsal side and are about five millimeters long and are used to sense prey, predators, and members of the same species. The other set of tentacles, the slightly flattened looking oral tentacles, extend from the mouth area and are 5-7 millimeters long. The nerves of these structures both connect to the cerebral ganglia. The brain of this species consists of three pairs of fused sections; the cerebral ganglia, the pleural ganglia, and the pedal ganglia. The neurons are large and easily identifiable. Also found on the head are slender extensions called cerata, which aid in gas exchange. Unlike other nudibranchs, P. sibogae does not store the nematocysts (stinging organelles) of its prey in its cerata.

Phestilla sibogae sense using chemicals usually detected with smelling or smelling-like senses and communicate with chemicals usually detected by smelling. They senses their prey through distance chemoreception. Epithelial tissue on the rhinopores is sensitive to amino acids released by Porites corals, allowing recognition. These nudibranchs follow slime trails left by others to and from reproductive sites.

Once they have settled on Porites corals, adult P. sibogae tend to stay out of the way of trouble. During the day they hide among coral branches to avoid being seen by predators, venturing out only at night to feed on the coral branches. Many P. sibogae usually live in the same coral colonies.

Phestilla Sibogae Reproduction and Development

Thecacera-Pacifica

Phestilla sibogae are simultaneous hermaphrodites in which individuals have sex organs of both sexes and can produce both sperm and eggs even in the same breeding season. They employ sperm-storing (producing young from sperm that has been stored, allowing it be used for fertilization at some time after mating) and use delayed fertilization in which there is a period of time between copulation and actual use of sperm to fertilize eggs; due to sperm storage and/or delayed ovulation. There is no parental involvement in the raising of offspring. [Source: Terri Nelson, Animal Diversity Web (ADW) /=]

Individuals reach maturity when they are 15-25 millimeters long. Two individuals mate and cross-fertilize each other. Mating can occur before the individual is mature enough to lay eggs, so sperm may be stored until later. The eggs are then laid in one session of repeated spawning. They have an egg membrane and a covering of albumen. Masses of them are enclosed together in a cylinderical cord covered with a thick layer of mucus for protection. The long, gelatinous loops of eggs resemble ribbons. /=\

Phestilla sibogae grows and reproduces fairly quickly, with about forty days between generations. The free-swimming planktonic larvae are called veligers. They have transparent, caplike shells and operculums (bones that serves as a facial support structure and a protective covering for the gills) not found in adult individuals. They hatch and begin to feed on other plankton approximately five days after fertilization. The velum, which the larvae use to swim and feed, are bilobed and ciliated around their mouths. The velum is reabsorbed along with the shell during metamorphosis Seven to ten days after hatching, they are physically able to metamorphose. Porites releases a chemical which induces the larvae to settle on it and begin metamorphosis. /=\

Pikachu- and Rose-Like Nudibranchs

Pikachu (Scientific name: Thecacera-Pacifica) is a species of nudibranch in the genus Thecacera and family Polyceridae. that looks the famous Pokemon character it is nicknamed after. It is mainly yellow and black like Pikachu and has a jelly-like continence and translucence. This species is known sightings in Vanuatu, Mozambique on the east African coast of the Indian Ocean and the famous muck dive sites of Tulamben in Bali, Indonesia. It has also been reported in the Gulf of Mexico and Atlantic Ocean. [Source: Wikipedia. Sophie Adams, Citrus Reef, March 9, 2023]

Pikachu is polycerid nudibranch with black tips to its rhinophores and gills. The rhinophore sheaths are edged with black with a patch of blue at the widest part. This blue colour is also present at the tip of the tail and at the tip of the lateral papillae beside the gills, separated from the orange of the body by a black band. Some specimens have black linear marks on the body with blue centres.

Hopkin's rose nudibranchs (Scientific name: Okenia Hopkinsia) are dorid nudibranchs that live the east Pacific Ocean and have been from Oregon to Baja California. They are bright pink in color and are is covered in by pink papillae (tentacle-like appendages), which can grow up to 2.5 centimeters (one inch). Their hot pink spiral eggs are the perfect match to the creatures themselves. [Source: Sophie Adams, Citrus Reef, March 9, 2023]

Hopkin's rose nudibranch have characterized by numerous long papillae on their back, tapering into a round tip. These papillae are sometimes more or less white at their tips. Their pink color is most likely produced feeding on the cheilostomatous bryozoan, Integripelta bilabiata. Their mantle, foot and the head are merged into one entity with a flattened profile. They have no oral tentacles. Their 20 gills are situated around the anal papillae and are somewhat shorter. The shape of the radula is their family is unique as the middle tooth is large and elongated, ending in a hook-like tip. The lateral teeth are reduced to a rudimentary plate.

Spanish Dancers

Spanish dancers ((Scientific name: Hexabranchus Sanguineus) are dorid nudibranchs that undulates through the water looking like ray wings with no body. They are usually orange-red speckled multiple small white dots but can be uniformly bright red or yellow with red scattered spots or patterned. The fluttering movements they make have been compared with flamenco dancers unfurling their dresses. Their eggs are laid together in a delicate mass, resembling a chiffon scarf. Giants of the sea slug family, the can reach a length of 60 centimeters (two feet), making them the largest nudibranchs, and feed exclusively on sponges.

Out of 3,000 species of nudibranch, Spanish dancers are the only one that can swim. They drift gracefully through the water, twisting and turning their bodies as they go. Their displays are rarely seen as they generally take place at night. Dance-offs are a way of attracting a mate. Spanish dancers can also move along the bottom of a reef or ocean surface like other nudibranch. too. [Source: Sophie Adams, Citrus Reef, March 9, 2023]

Spanish dancers’ scientific name Hexabranchus sanguineus literally means "blood-colored six-gills. They are usually between 20 and 30 centimeters (8 inches and one foot) long. Their bodies are soft and flattened. The front part of the animal has a pair of retractable rhinophores (pair of chemosensory rod-shaped structures) and the rear part has six contractile gills inserted independently in the body. The large “wings” are a pair of oral tentacles with flexible fin-like membranes. Juveniles are rather whitish to yellowish with multiple purplish points and orange rhinophores and gills.[Source: Wikipedia]

Spanish dancers are widespread throughout the tropical and subtropical waters of the Pacific and Indian Oceans, ranging from as far west as the eastern coast of Africa and the Red Sea, as far east as Hawaii and as from Japan in the north to Australia in the south. They like rocky and coral reefs with many sponges and shelters from one to 50 meters (three to 165 feet) deep.In normal circumstances, Spanish dancers crawl on ocean substrates, with the edges of their mantle curled upwards creating a peripheral blister. When they are disturbed, they “unfold” their edges and swim by contracting and undulating their bodies to move away from the source of the disturbance.

During daytime, Spanish dancers hide in crevices. At night they come out and feed on various species of sponge. Like all nudibranchs, they hermaphrodites. They lay bright red to pink spiral-shaped egg ribbons. Spanish Dancers consumes sponges among the family Halichondria, which supply the nudibranchs with a potent chemical that they it can use in defense. Spanish dancers can pass these toxins into their egg ribbons via macrolides, giving the physically defenseless eggs ribbons a toxin defense. These egg ribbons in turn are coveted by some other species of nudibranch such as Favorinus tsuruganus or Favorinus japonicus, and other creatures like Emperor shrimp (Periclimenes imperator), a commensal shrimp is commonly found living on Spanish dancers.

Sargassum Nudibranch

Sargassum nudibranch (Scientific name: Scyllaea pelagic) is usually found in warmer waters of the Atlantic Ocean and is most common in the Gulf of Mexico. It is a pelagic (open ocean) species that spends almost all of its life grazing in patches of drifting sea weed, particularly Sargassum. Sargassum nudibranch mimics its environment — Sargassum seaweed — very accurately. The leaf-like lobes along its back, and their Sargassum-like color make it almost impossible to spot when floating in a patch of Sargassum. This is a form of camouflage that is very effective in eluding predators. [Source: Gabriel Vaughn, Animal Diversity Web (ADW)]

Sargassum nudibranchs are orange-brown and yellow in color, and is about seven to ten centimeters (three to four inches) in length. Like all nudibranchs, they are sea slugs that have no shell. Only secondary gills are present. They have two pairs of sensory organ tentacles near the head — an anterior pair of cephalic tentacles, and a posterior ring of tentacles. These tentacles don't aid in capturing prey, but are sensory organs that also aid in respiration. They resemble the leaf-like lobes found on Sargassum.

Sargassum nudibranchs usually feed on hydroids that are living in Sargassum seaweed. They don’t hunt for prey; they graze on prey of eat prey that floats by in the particular patch of sea weed they reside on. Sargassum nudibranchs are hermaphroditic. Fertilization is internal. As is true with most nudibranchs, the larva of Sargassum nudibranch passes through a planktonic trochophore-like stage.

Image Sources: Wikimedia Commons, NOAA

Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated May 2023