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Life Among Tentacles

Life Among Tentacles


The symbiosis between clownfishes and sea anemones is a fascinating subject of study. The sea anemones are mostly fixed to the substrate and rarely move. Each anemone thus form the territory of its associate fish, which therefore seldom venture far from it, retreating into its tentacles when feeling threatened. Dr. Cuthbert Collingwood first made a written account of the association of sea anemone and anemonefish in 1868 though the phenomenon may be know prior to this.


Sea anemones live throughout the world's oceans and up to 40mts of depth in clear waters where sunlight can reach. Many types of marine creatures live in symbiosis with sea anemones such as anemone fishes, damsel fishes, various trpes of shrimp (Periclimenes brevicarpalis and Thor amboinensis) and Porcelain Anemone Crab.



Fishes, crabs and shrimps keep the body of sea anemone clean of parasites and instead get protection from sea anemone’s stinging tentacles.


10 Legged Reef Cleaners

The decapods or Decapoda (literally "ten-footed") are an order of crustaceans which includes many known groups, such as shrimps, crabs, lobsters and prawns. Decapods estimated to contain nearly 15,000 species, nearly half of these species are crabs (appx 8000 species) and shrimps (appx 3000 species). Hermit crabs, porcelain crabs, squat lobsters accounts for appx  2500 species. 10 legs are in the form of five pairs of thoracic (chest region) appendages on the last five thoracic segments. The front three pairs function as mouth parts.

Shrimps as Cleaning Symbionts

Shrimps are known to have symbiotic association (a relationship in which both parties benefit) with many marine animals such as starfishes, sea urchins, fishes, sea turtles etc. For example, in symbiotic relation between fish and shrimp, fish benefit by having parasites removed from them, and the shrimp gain the nutritional value of the parasites.

Cleaner shrimp is a common name for any swimming 10 legged crustacean that cleans other organisms of parasites. In coral reefs, cleaner shrimp congregate at cleaning stations (example Stenopus hispidus).

Cleaner shrimps usually belong to any of three families, Palaemonidae (e.g. Periclimenes brevicarpalis), Hippolytidae (e.g. the Pacific Cleaner Shrimp, Lysmata amboinensis) and Stenopodidae (e.g. the Banded Coral Shrimp, Stenopus hispidus).

Periclimenes brevicarpalis

 Periclimenes brevicarpalis

Northern Cleaner Shrimp Lysmata amboinensis

 Lysmata amboinensis

Stenopus hispidus

 Stenopus hispidus

Some common examples of symbiotic shrimps from Indian coral reefs

Starfish and Shrimp: Many species of starfishes particularly Pincushion Stars have their symbiotic shrimps. The tiny shrimps Periclimenes soror stay on the lower side of the starfish. Several individuals can be seen on a single starfish. Shrimps keep the starfish free of parasites and instead get protection from its spiny armour.

Periclimenes sororPericlimenes soror  Closeup

Anemone and Shrimp: Like sea urchins, sea anemones are also host for many species of shrimps. The stinging tentacles of an anemone provide ideal refuge for shrimp which in turn keep sea anemone clean of debris and parasites. Ex. Periclimenes brevicarpalis.

Periclimenes brevicarpalis

Cave Cleaner Shrimp: Like cleaner wrasse, cleaner shrimp also performs the same role. These small shrimps (Palaemon serratus) occur in large numbers inside prominent caves or crevices. Fishes and other animals frequent these places to get serviced from these shrimps.

Palaemon serratus

Sea Urchin and Shrimps: Sea urchins have spiny armour on its body. The long, pointed spines provide a perfect refuge to shrimps (Athanas cf marshallensis) which spend their entire life among these spines. Each species of sea urchin has its specific host shrimp. Shrimps help sea urchins to become free of parasites.

Heterocentrotus mammillatus Slate-pencil Urchin1 copy


Butterflies Underwater ….

You may call them sea slugs or nudibranchs or sea butterflies, there are very few parallels to these remarkable creatures, for their beauty, for their adaptations and for their survival strategies. From the great depths to pelagic, from tiny to over 60cm gigantic, from sap sucking herbivorous to most ferocious hunters, from nocturnal to diurnal, from slow moving to incredibly fast swimmers, from tropical to temperate distribution, from reefs to mud flats, from palatable to highly toxic, these remarkable creatures have occupied every niche of oceans and seas across the world. Yet we know so little about them.

Sea slugs are nothing but relatives of seashells. There are not more than 5000 species known worldwide. Yet they have most remarkable evolutionary history, as few freaks among seashells thought of giving away its armored defense like shells, an evolutionary gamble they seems to have won handsomely. However, most of them have shell in larval stage called ‘valiger’.

The primitive opisthobranchs such as bubble shells have a shell into which animal can withdraw entirely. However, in most of the species, the shell has lost completely. There are few species that resembles to sea slugs such as Onchidium. Earlier they were considered as opisthobranchs are now placed under pulmonates and are not from the classical sea slugs group. Lamellariids also in many ways resemble sea slugs. However, they are infact prosobranch snails. The three illustrations shown here can help amateur to distinguish the difference between pulmonates, opisthobranchs and lamellariids. 

Coriocella sp1Onchidium verruculatumPhidiana militaris 1

Lamellarid                                    Onchidium                                   Sea slug


Sea slugs show remarkable and variety of adaptations of which many are similar to butterflies and thus they are also commonly called as ‘sea butterflies’. The only difference that they lake true wings as in butterflies. As butterflies, many species of sea slugs believe in camouflage (Aplysia dactylomela) as primary way of defense. However, many show various chemical defenses (Chromodoris fidelis stores neatocysts, Dendrodoris tuberculata secretes Hydrocynic Acid), few species believe in mimicry. Some make perfect disguises (Notodoris citrina.) resembling a piece of sponge. As butterflies, many are brilliantly coloured, few can swim fast (Euselenops luniceps) and can migrate to short distances. Most of the slugs have a short life not over one and half year.

A brief account of about 100 common sea slugs is given in the book Field Guide to marine Life of India and will help you explore your sea shores. Please remember that these are delicate animals thus handling is not advisable. It is best to capture them on camera. They look better in photographs than in jars.

Where to find sea slugs?

Sea slugs are found virtually in all habitats. For beginners it is best to search shallow tidal pools. Most of the species are nocturnal thus you will have to see them under rocks or dead coral slabs. However, make sure you keep the rock back to its original position, since life that grows under rock cannot survive direct sunlight exposure.

What they eat?

Most nudis are carnivorous and feed on variety of diet such as tunicates, hydroids, sea anemones and even coral polyps. Few from genus Elysia and Thuridiella are sap sucking and feed on green algae from genus Caulerpa. Some are cannibalistic.

How they communicate?

It is one of the most complex processes and there are several research studies on the way they communicate. They use chemical cues to find partner.

How they reproduce?

All sea slugs are hermaphrodite i.e. each animal having both sexes. Applysia and bubble shells however have interesting behaviour. They form long chain in which each animal except the first and last, acts as a male to the animal ahead and a female to the animal behind. All the sea slugs have a free-floating stage called veliger. In most of the species, veliger stage has a shell, which however, is lost during the development.

Common Sea slugs or Opisthobranchs

Bubble shells

These are the most primitive opisthobranchs. Most of the species are nocturnal and remain buried under sand during daytime. Breeding congregations are common in winter months. 

Haminoea cymbalum2Haminoea sp.Gujarat

 Haminoea cymbalum                                                       Haminoea sp.

Sea Hares

All the species form these families are herbivores and remain hidden under or among algal mass in shallow waters. They can grow to large size (up to 60cm). If noticed and attacked by predators, they release dark purple ink that makes surrounding murky thus the animal buys time to escape from predator. 

Aplysia oculiferaAplysia parvula Morch 1863

Aplysia oculifera                                                  Aplysia parvula

Side-gilled Sea Slugs

The gills of these animals are placed on the right side of the body thus the group is commonly called as pleurobranchs. The individuals from family Pleurobranchidae are known to secrete acid against predators. Few species are cannibalistic and others feed primarily on sponges, ascidians and sea anemones.

Pleurobanchus peroniPleurobranchus forskalii.2

Pleurobanchus peroni                                        Pleurobranchus forskalii

Sap-sucking Sea Slugs

Species from family Plakobranchidae (Elysiidae) are herbivorous and feed predominantly on Caulerpa, a green algae.

Elysia expansaElysia rufescens Pease 1871

Elysia expansa                                                    Elysia rufescens

Nudibranchs or true sea slugs

Nudibranchs or true sea slugs are by far the largest group of opisthobranchs. Nudibranchs are formed of two major groups, Dorids and Aeolids.

Atagema spongiosa1Dendrodoris tuberculosa 2Sakuraeolis gujaratica1

Dorid: Atagema spongiosa           Dorid: Dendrodoris tuberculosa   Aeolid: Sakuraeolis gujaratica

Sea slugs are presently unexplored frontiers of marine biodiversity. We know so little about them that we cannot even say how many species we have in India, let alone its conservation. Yet they have shown great promise for medical frontier in the form of active substances they posses.

For a naturalist, it is a sheer delight to see them, yet at times searching them is totally frustrating so tiny they are. They are little masters of ocean realm. They have million stories to tell and many lessons to teach. One undoubtedly is their shrude survival strategy that teaches us a great lesson, ‘Survival of Fittest’, Darwin’s yet undisputed theory of Evolution.

So next time when you are on a beach, do spend time to find one. Who knows that one experience will evoke you to be a totally ‘nudi’ fan.


Sea Cucumber

 Sea Cucumbers

Sea cucumbers are soft-bodied animals and belong to phylum Echinodermata. They typically comb the sea floor, feeding on organic sediment. Increase numbers of sea cucumber can be a sign of organic pollution. Sea cucumbers have an unusual method of respiration; they take in water through their anus to breathe. When disturbed or frightened some sea cucumbers pour out a mass of sticky white threads to repel or trap their enemies. Others are capable of releasing toxins which, in aquaria, have been known to kill all the animals, including the sea cucumbers themselves.

Excessive collection of these animals for food is a serious threat for otherwise common animals. In some areas like coastal Konkan they were exterminated two decades ago. Thankfully, reintroduction by local fishery institutes bring back some of the species. Collection of all sea cucumbers is now banned under the Wildlife (Protection) Act, 1972. Despite the ban, illegal trade of these animals continues unabaited in places like Andaman, Tamilnadu. In Lakshadweep however, local customs prevent people collecting these animals thus providing them safe heaven.

Sea cucumbers are nature best sand cleaners. They feed on dead and decaing mater and inturn clean sand of putrifing material.

Holothuria atra (Black Sea Cucumber): This is one of the most abundant sea cucumbers in coastal areas. It has a very soft body. This species is common on sand flats, and can be seen actively feeding on detritus.

Holothuria nobilis (White-teated Sea Cucumber): The White-teated Sea Cucumber is a large sea cucumber and has many projections at the base. It is black with white spots.

Holothuria hilla: A small and slender sea cucumber it grows up to 15 cm. The bright orange colour with yellow spiny processes makes identification easy.

Holothuria pervicax: It is a small sea cucumber growing up to 15 cm and uncommon species from reef flats. Body is tuberculated and each tubercle have pink tip. It mostly remains under coral boulders and is nocturnal species.

Thelenota ananas (Prickly Sea Cucumber): A large sea cucumber (70 cm), the Prickly Sea Cucumber has pointed and branched papillae. This reddish brown species is usually seen in shallow waters.

Synapta maculata (Worm Sea Cucumber): Among sea cucumbers, the Worm Sea Cucumber is unusual. It grows up to 2 m and has a very extensible body. This species prefers grassy or sandy areas. If touched, it can contract its body to less than 6-8 cm, and also break into several pieces.

Euapta godeffroyi (Banded Sea Cucumber): The Banded Sea Cucumber looks like the Worm Sea Cucumber, but with much brighter colours. This sea cucumber is sticky and when touched the tube-feet immediately grip the hand.

Pearsonothuria graeffei (Blackmouth Sea Cucumber): A large sea cucumber (45 cm), this species is common in deeper waters. The black tentacles help to identify the species.

Holothuria atra Black sea cucumber congregationHolothuria nobilis

Holothuria atra                                                                          Holothuria nobilis 

Holothuria hilla1Holothuria pervicax

Holothuria hilla                                                                          Holothuria pervicax

Thelenota ananas Prickly Cucumber 1Synapta maculata Worm cucumber

Thelenota ananas                                                                     Synapta maculata 

Euapta godeffroyi2Pearsonothuria graeffei Blackmouth Sea Cucumber

Euapta godeffroyi                                                                  Pearsonothuria graeffei

 Holothuria atra Black Sea Cucumber.spawning low

Black Sea Cucumber: This rare image of male sea cucumber releasing sperms captured on camera in Lakshadweep won me Sanctuary Image of the Year award in 2009

Know Our Marine Habitats


Rocky Shores


Marine life is abundant on rocky shores, which provide good refuge for numerous life forms such as frog shells, chitons, limpets, whelks and periwinkles, oysters, barnacles, cowries, crabs, starfishes, sea urchins, gorgonids, and a variety of algae and sea weeds. Low tide is a good opportunity to search for these creatures in shallow rock pools, since most of them come out for feeding during low tide. Distinct communities based on species interaction exist on rocky shores, e.g. barnacle & rock shells community, oyster & barnacle community, etc.


Rocks encrusted with Oysters                                               Rocks encrusted with Barnacles

Rock pools with an abundant algal growth of Caulerpa, Ulva, Codium, Sergassum, Hypnaea, Gracilaria and Dictyota are home to many life forms. Shallow rock pools are also home to some common winter migrants such as sea hares. Exposed rock pools provide good refuge to several species with terrestrial affinity such as periwinkle and nerita shells and crabs.

P2030122Aplysia dactylomela.ink4th stage

Aplysia or Sea Hare can be seen abundantly in the algae covered rock pools


 Periwinkle Echinilitorina malaccana seen abundantly on exposed rocks during low tides

Rocky shores covered by silt are preferred by murex shells at places like Okha in Gujarat. The rock pools dominated by green and red algae at Veraval and Chorwad are home to drupe shells and mussels. Oyster and barnacle infested rocks dominate Maharashtra coasts. Edible oysters also occur on rocky shores. Species composition on rocky shores varies significantly between high and low tide zones. Loose rocks are ideal places to search for shade loving, nocturnal and cryptic fauna. A number of Opisthobranchs can be found taking shelter on the bottom of loose rocks within inter-tidal areas.

Rock crevices are ideal shelter areas for nocurnal species like crabs, shrimps and sea anemones.


Sea anemones prefer sheltered areas of rock pools


Rock crevices are used by nocturna species like crabs and shrimps

Visit your nearest sea shore and explore the marine life of rocky shore!!

It's a fascinating experience!!

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