Porcelain Anemone Crab – Detailed Guide: Care, Diet, and Breeding

Porcelain Anemone crab (Neopetrolisthes maculatus) logo

Porcelain Anemone crab (Neopetrolisthes maculatus) is one of the saltwater crabs common in Indo-Pacific region. They are well known for their remarkable spot patterns and for being symbiotically associated with sea anemones. So, if you are looking to add some variety to your marine tank, or maybe you just want a change of pace in your community tank, these anemone crabs will be a great choice.

This guide will teach you more about keeping Porcelain Anemone crab plus better ways to take good care of them, including their compatibility with other types of species, breeding, and appearance. I will show you the results of the experiments, provide useful information, give some tips, and that is all in one place.

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Quick Notes about Porcelain Anemone Crab

Name Porcelain Anemone Crab
Other Names
Spotted porcelain crab, Porcelain Crab, Anemone crab 
Scientific Name Neopetrolisthes maculatus (Synonymised names: Neopetrolisthes ohshimai, Petrolisthes ohshimai, Porcellana maculata)
Tank size (minimum) 5 gallons (~20 liters)
Keeping Easy
Breeding Difficult 
Size (carapace) up to 2.5 cm (~1 inch)
Optimal Temperature 24 – 27°C  (~75°F – 80°F)
Water type SG = 1.020 – 1.025
Optimal PH 8.1 – 8.4
Optimal KH 7 – 12
Nitrate Less than 20 ppm
Diet Mostly Carnivore / Omnivore   
Temperament Peaceful
Life span up to 5 years
Color Form Creamy white coloration with number of small red/purple spots and/or blotches

Interesting fact about Porcelain Anemone Crab

Porcellanidae, commonly known as porcelain crabs, is a family of decapods belonging to the infraorder Anomura. Therefore, Porcelain Anemone crabs are not true crabs. They superficially resemble true crabs and have flattened bodies adapted to living in crevices and under rocks. However, they are more related to hermit crabs than crabs.

In addition, unlike the true crabs, the abdomens of Neopetrolisthes maculatus still retain a tail fan similar to that of lobsters or shrimp. 

Taxonomy problem of Porcelain Anemone Crab

There is a lot of confusion regarding taxonomy of these crabs and scientific names provided by aquarium stores are often wrong. A lot of aquarists believe that Neopetrolisthes maculatus and Neopetrolisthes ohshimai are two different species of the crabs. Well, they are not!

According to the study, a different spot pattern on the body is not enough to become a separate species.

The Indian and Pacific Ocean populations have different spot patterns. However, both species could not be distinguished using other morphological characters. There­fore, biologists consider it preferable to treat Neopetrolisthes ohshimai under the name Neopetrolisthes maculatus.

Natural Habitat of the Porcelain Anemone Crab

In nature, Porcelain Anemone crabs are commonly found in rocky and coral reefs of temperate and tropical coasts. These crabs are one of the common crustaceans in tropical and subtropical shallow subtidal waters. The Neopetrolisthes maculatus species are often found to live as on sea anemone and are collected from depths ranging from 5 to 12 meters.

They are widely distributed in the Indo-West Pacific and can be found from the east coast of Africa (Zanzibar, Mozambique. Madagascar) to Christmas Island and Western Australia, Bismarck Archipelago, Queensland, Moluccas, Palau, Taiwan, Southern Japan (Ryukyu Islands), New Caledonia, Marshall and Fiji Islands.

Description of the Porcelain Anemone Crab

Porcelain Anemone crab (Neopetrolisthes maculatus) front viewPorcelain Anemone crab is a spotted crab with two different color forms:

  • In one form, carapace, claws, and legs are white, with an uneven pattern of irregular sizes of red blotches.
  • In the other form, the carapace, claws, and legs have a uniform pattern of numerous small, reddish-purple spots.

The red/purple color sometimes takes the form of large, irregularly-shaped blotches, and sometimes of very regularly and evenly distributed small spots.

This is a relatively small crab. Fully grown Porcelain Anemone crab is on the smaller end and can reach a maximum size of 6 – 8 cm (~2.4 – 3 inches) across the leg span. Carapace length of crabs usually ranges from 2.5 – 3 cm (~1 inch).

The body shape is compressed which is an advantage for staying in a stable position in turbulent water.

Porcelain Anemone crabs have huge and flattened front claws. At first glance, these claws look frightening, in reality, there is nothing to worry about. They only use these scary appendages during territorial fights with their own species, and not for hunting. In most cases, they simply shove other crabs away and never actually pinch anything.

Their long transparent antennas are directed to the sides all the time, they never lift them high.

Another interesting feature of this crab is its legs. First of all, they are rather short. Second, unlike most crab species, Porcelain Anemone crab uses only three pairs of legs (the fourth pair is hidden under the carapace), while other types of crabs move on four.

Under optimal conditions, Porcelain Anemone crab can live up to 3 – 5 years!

The Behavior of the Porcelain Anemone Crab

In general, Porcelain Anemone crabs have a very peaceful temperament. The only reason they can choose to fight when someone decides to bully them out of their anemone.

This species occurred as a male/female pair (the male is smaller than the female) on the sea anemone. The pair will not tolerate their own species on the same host.

It spends most of the daylight hours sitting in the anemone and putting out its fans to filter the food in the surrounding water.

Interesting fact: Porcelain Anemone crabs are small and maybe less well able to defend themselves by fighting back. Therefore, these crabs have the ability to voluntarily shed a limb or body part (autotomy) to limit damage to wounded body parts and escape from predation.

Therefore, a combination of extremely fragile body parts and the color gave this crab its name – Porcelain Anemone crabs.

Porcelain Anemone Crab and Anemone Partnership

Porcelain Anemone crab (Neopetrolisthes maculatus)
Photo by Walt Stearns

Porcelain Anemone crabs and Anemones are found in a symbiotic relationship in nature, they help each other. While anemones protect the crabs from its predators by providing shelter, crabs clean the host anemone by eating the food scraps and mucus off the anemone’s body surface.

A combination of being resistant to the toxins and the production of mucus that prevents the Anemones from stinging them, allows them to live together.

Because of the symbiotic relationship with Anemones, Anemone crabs almost never found lower than 12 meters (~40 feet). These crabs are relatively slow-moving, without Anemone’s protection they cannot survive in the ocean.

According to the studies, Neopetrolisthes maculatus has been encountered in association with several different genera of sea anemones, for example:

  • Stichodactyla spp.,
  • Cryptodendrum adhaesivum,
  • Gyrostoma
  • Telmatactis cricoides,
  • Cryptodendrum adhaesivum,
  • Macrodactyla doreensis,
  • Phymanthus sp.,
  • Heteractis spp.,
  • Actinodendron plumosum,
  • Anemonia sulcate,
  • Zoanthus sp.,
  • Lebrunia danae,
  • Entacmaea Quadricolor,

Porcelain Anemone crabs spend most of their time in the immediate vicinity of the tentacles of the anemone, on the column of the anemone and occasionally even on the tentacles and on the oral disk of the anemone. Contact between the Anemone crab and the tentacles do not stimulate feeding reactions of the anemone. The tentacles do not cling to the crab and the crab showed no signs of being stung.

Read also my article “Proper Care for Carpet Anemones”.

Can Porcelain Anemone Crabs Live in Aquarium without Anemone?

Some aquarists keep these crabs without anemones and believe that it is OK for them to live on Live Rock or on corals. Well, it is not!
Porcelain Anemone crabs evolved (over a period of million years) to be successful only when they live with anemones.

They feel vulnerable and get stressed without an anemone. As a result of constant stress, they die way faster, even if their aquarium has good water parameters.

I would like to remind these people that every Porcelain Anemone crabs sold in a pet store have been captured in the wild. So, if you are buying one, take responsibility to create at least a natural environment for them! DO NOT keep them without anemone! If you cannot do that, in this case, do not buy them at all.

Are the Porcelain Anemone Crab Reef Safe?

Yes, they are reef safe. Porcelain Anemone crabs will not damage anything in a reef tank.

Feeding Porcelain Anemone Crab

Porcelain Anemone crab (Neopetrolisthes maculatus) fanningThe most important thing that you need to know about Neopetrolisthes maculatus species is that they are active filter feeders. It is quite interesting to watch them feed. They use their fans on their mouth parts (plume-like bristles or filter appendages (third maxillipeds) to feed on particles (plankton, etc.) suspended in the water column.

In nature, the symbiotic lifestyle offers access to exposed sites in the intertidal and subtidal environments that are favorable for passive suspension-feeding activities.

The intertidal and shallow subtidal zones are characterized by continuously changing water flows. These variations are critical for suspension feeders like Anemone crabs, which feed from a stationary position, because water movements deliver food and oxygen, simultaneously removing waste products.

However, unlike freshwater filter-feeding shrimp (like Bamboo shrimp or Vampire shrimp), Porcelain Anemone crabs also can use their claws when it comes to feeding. So, the feeding habits of these crabs include scavenging (algae, detritus) too. They also eat mucus from the anemone.

In aquariums, Porcelain Anemone crabs will get their share when you feed corals. Spraying a little over top of the crab will make it happy. They fan all the time and do just fine on leftover food. They are omnivores.

Diet of the Porcelain Anemone crabs includes:

  • mysis,
  • brine shrimp,
  • rotifers,
  • bloodworms,
  • phytoplankton,
  • zooplankton,
  • marine snow,
  • flakes,
  • spirulina,
  • piece of meaty food,
  • fish or shrimp food,
  • meat-based pellets,
  • whatever they can catch in the fans.

As I have already said, unlike some true filter feeders they are not completely dependent on using only their setae to feed.  Porcelain Anemone crabs can be a part of the clean up crew.

Keeping Porcelain Anemone Crab

As aquarium residents, Porcelain Anemone crabs are hardy, undemanding and easy to care for. That is why they have become pretty popular in our hobby. However, before obtaining your crabs, it is important to prepare for their arrival so you can meet their needs.

Tank Size

Depending on your livestock, the small tanks (5-gallon or 20-liter) can be good enough for a pair Porcelain Anemone crabs. Ideally, you need a 10-gallon (40-liter) tank. Bigger tank will also help to reduce fluctuations in water quality.

Water Parameters

Although Anemone crabs are fairly adaptable to a wide range of water parameters they still have some preferences.

Porcelain Anemone crabs thrive in the warm parts of the Pacific and Indian Ocean. Therefore, the temperature should stay in the range of about 72 to 88 F (22 to 31 C) with around 75 to 80 (24 – 27C) being optimal. Therefore, it is advisable to install a heater and thermometer to control that the water is kept at a constant.

The pH should be kept around 8.1 to 8.4 and alkalinity should be kept in the range of 7 to 12 dKH, although these often go a little higher or lower. Porcelain Anemone crabs need a specific gravity that is between 1.021 and 1.026.

Water Flow

As filter feeders, they like to be in strong water flow. They will clean your water so whenever you see fine particles floating around that is what these crabs eat. 

Anemones

This part is a little bit difficult. On the one hand, beginners are advised to avoid keeping an anemone until they are a little more experienced. On the other hand, Porcelain Anemone crabs need anemones, this is crucial for their well-being.

Anemones are harder to keep than Anemone crabs, so if you are trying to pair the two, your tank must be designed around the Anemones first. After purchasing, follow proper acclimation steps before introducing it into the tank.

Lighting

Lighting should be adapted to the needs of symbiotic sea anemones. Anemones usually house photosynthetic microorganisms that provide the anemone with energy. So, light improves overall health and color.

Notes: Filtration should be robust for these crabs. Ammonia is the biggest rick in any hard-water aquarium.

Important: In a reef tank, lots of fishes, shrimp, and crabs die young,  because most people are not able to keep water parameters stable and constant beyond a couple of months. Eventually, it affects animals and slowly weakens them.  You need to check water conditions often, as the faster a problem is found, the easier it will be to put right again.

Do not forget that Porcelain Anemone crabs need careful acclimation (read more about it here) as all invertebrates. Do it very slowly. In general, 2 – 3 hours will be good enough.

Basic Tank Equipment (links to check the price on Amazon)

Molting Porcelain Anemone Crab

Like other crustaceans, Porcelain Anemone crabs shed their exoskeleton (molt) as they grow. This is a key stage in the life cycle of any crustaceans. The frequency of molting depends on the age of the crab. Do not touch the crab as they are very vulnerable at this point and may die if disturbed.

During pre-molt period, they will display signs of decreased activity and feeding. During molting, Porcelain Anemone crabs absorb a lot of water until their carapace opens up in a breaking point. After that, they use this opening to wriggle out of its old shell. It takes at least a few hours for the new bigger exoskeleton to harden.

Note: In some cases, Porcelain Anemone crabs can even leave their anemone and hide somewhere in the rocks. So, do not worry too much if you cannot find the crab.

Sexing Porcelain Anemone Crab

Sexing Porcelain Anemone crabs can be somewhat tricky. Some aquarists believe that males and females have slightly different coloration. They think that the color of the spots of the female specimen is red, whereas that of the male is purple. The spots on the carapace are sparser, larger, and more irregular in the female than the male.

Unfortunately, biologists reported that differences in coloration are not related to each sex and a male/female pair of similar coloration has been found in the same host.

So, is there any way to differentiate the gender of Porcelain Anemone crabs? Well, yes. However, unless you are a biologist, it will be very difficult.

According to the studies, there are several indicators that give away the sex of the animal. 

Males with pair of developed pleopods on second abdominal somite. Pleopods on third to fifth abdominal somites each reduced to small, rounded, inconspicuous rudiment with small pore. Females with pairs of developed pleopods on third to fifth abdominal somites, those on fourth and fifth somites large.

Breeding Porcelain Anemone Crab

I have to start off by saying that due to many different factors, the breeding process presents various difficulties. So far, there have been no reports of successful breeding Porcelain Anemone crabs in captivity.

Even biologists in their experiments have not done it yet. The most successful attempt let them reach the second Zoae stage.

In their experiment of rearing breeding Neopetrolisthes maculatus:

  • Filtered seawater from the collection site was used for rearing.
  • Water temperature and salinity were kept at 29.0-29.5°C and 34.0-35.0%,
  • Each day, zoeas were fed with newly hatched nauplii of Artemia
  • The excrement of the larvae was removed with a pipette.
  • The water in each rearing vessel was maintained at a constant level by the addition of seawa­ter.

Although the larvae of Porcelain Anemone crabs passed through two zoeal stages, they died before molting to the following phase (megalop). The duration of the stage was 5 – 7 days.

First zoea size – 2.1-2.3 mm
Second zoea size – 2.8-3.1 mm
The importance of knowing the complete larval development of a species goes be­yond allowing the identification of larval specimens collected in the plankton.

Information about breeding Porcelain Anemone crabs

  1. The eggs are usually reddish-brown in color.
  2. Females can carry around 600 eggs
  3. The eggs hatch as free-swimming zoae that feed on plankton.
  4. The larval development of porcellanids usually consists of two zoeal stages and one megalopal stage.

Porcelain Anemone Crab and Suitable Tankmates

Porcelain Anemone crab (Neopetrolisthes maculatus) in communityPorcelain Anemone crabs go about their business without bothering any other fishes and are harmless to other community tank members.

However, they will fight over anemone. If you add more than two (males and females) in the same tank, you will need to have several anemones to occupy and defend (they often squabble over them if they are in short supply).

Although ‘Sexy’ Shrimp also need anemones, anemone crabs often do not chase them away. 

Do not keep it with bullies in the tank – especially Clownfish. These fishes will try to get anemone for themselves. Clownfish usually win the competition.

Shrimps (such as Peppermint shrimpRed Fire shrimpSkunk Cleaner Shrimp)  can make interesting additions, they are peaceful and helpful by breaking down waste food. Harlequin Shrimps is another option.

Boxer crabs, snails (Cerith SnailsBumble Bee SnailsConch snailsNassarius snails, etc.), porcelain crabs, Emerald crabs, hermit crabs (Halloween hermit crabs, Blue Leg Hermit Crabs, etc.) usually do not mess with Porcelain Anemone crabs.

Do not keep Porcelain Anemone crabs with aggressive fish such as Groupers, Lionfish, Eels and Triggerfish as they will prey on them.

In Conclusion

Porcelain Anemone Crabs are some of the coolest looking crabs you could ever find. They are a peaceful species that make a wonderful addition to any reef aquarium. The only thing that you need to remember – they prefer to live in anemones.

This species does not require special care or feeding. Therefore, beginners will be able to keep these crabs with few problems since they are hardy and undemanding. They are really special crabs and are unlike any other crab you can put in your tank!

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References:

  1. Zoeal development of two spot-pattern morphs of Neopetrolisthes maculatus and N. spinatus (Crustacea: Decapoda: Anomura: Porcellanidae) reared under laboratory conditions. Yoshihisa Fujita, Masayuki Osawa. February. DOI: 10.12782/specdiv.8.175
  2. Adeyeye Emmanuel Ilesanmi, et al. (2019). Lipid Composition of the Male and Female Innards of Neopetrolisthes maculatus: A Ready Source of Essential Fatty Acids. CPQ Nutrition, 3(2), 01-30.
  3. Amino Acid Profiles of the Flesh of the Heterosexual Pairs of Neopetrolisthes Maculatus. January 2017. DOI: 10.18052/www.scipress.com/ILNS.61.23.
  4. Journal of the Royal Society of Western Australia. Vol. 48 Part 4. The Porcellanidae (Crustacea, Anomura) of Western Australia with descriptions of four new Australian species by Janet Haig*. Manuscript received and accepted 16th February, 1965.
  5. Chemical composition (proximate, minerals,vitamins),mineral ratios and mineral satety index of the innards of male and female neopetrolisthes maculatus. J.Bio.Innov6 (3), pp: 479-498, 2017 |ISSN 2277-8330 (Electronic).
  6. Vela MJ, González-Gordillo JI (2016) Larval descriptions of the family Porcellanidae: A worldwide annotated compilation of the literature (Crustacea, Decapoda). ZooKeys 564: 47–70. doi: 10.3897/zookeys.564.7018
  7. First report on Neopetrolisthes maculatus (H. Milne Edwards, 1837) (associated with Stichodactyla haddoni (Saville-Kent, 1893) from Grub Island, Andaman Islands. Proceedings of the International Academy of Ecology and Environmental Sciences, 2017, 7(1): 20-24
  8. A new species of the genus Neopetrolisthes Miyake, 1937 (Crustacea: Decapoda: Porcellanidae) from the Ryukyu Islands, southwestern Japan. PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON. 114(1):162-17L 2001.
  9. Porcellanidae (Crustacea: Decapoda: Anomura) from Christmas and Cocos (Keeling) Islands. RAFFLES BULLETIN OF ZOOLOGY Supplement No. 30: 255–262. December 2014

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