Figure 1: Top-down picture of my hitchhiking nudibranch; its length is approximately 1.5" (38 mm).

As virtually every live rock owner can attest, aquarists receive a mixture of desirable, undesirable and ugly hitchhikers. With my first shipment of live rock for my new tank, I received some rather ugly and undesirable hitchhikers: Cirolanid isopods. I later received a shipment of live rock from Tampa Bay Saltwater on July 24th, 2005.

On August 2nd, 2005 I was doing my nightly tank observation and discovered a "worm" crawling on my aquarium's glass. I retrieved it and moved it to my quarantine tank so I could attempt identification at a later date. Two days later I discovered another "worm" about half the size of the first. Fearing an outbreak of another undesireable hitchhiker, I intensified my search for an identification of this unknown animal, and soon discovered that I had a nudibranch of the sub-order Aeolidacea, animals more commonly referred to as aeolids.

Nudibranchs are marine snails that are often called "sea slugs." For more background information on nudibranchs I suggest reading Ron Shimek's articles Naked...Gills on Snails and Beautiful, But Unwelcome; Aeolid Nudibranchs in the Reef Aquarium, or visiting what I consider a great online resource: These resources were very helpful in my nudibranch research. Additional information and pictures of nudibranchs commonly seen in the hobby can be found in Marine Invertebrates (Shimek, 2004), Coral Reef Animals of the Indo-Pacific (Gosliner et al., 1996), 1001 Nudibranchs - Catalogue of Indo-Pacific Sea Slugs (Coleman, 2001), Invertebrates - A Quick Reference Guide (Sprung, 2001) and Nudibranchs and Sea Snails Indo Pacific Field Guide (Debelius, 1996). Keep in mind that many of these guides (with the exception of Dr. Gosliner's book, who is a nudibranch taxonomist) most likely contain identification errors.

Virtually all nudibranchs have specialized mouth parts and digestive tracts. This means that they consume only one or a few very closely-related foods, typically sponges or other sessile invertebrates that cannot be supplied adequately in aquariums. For this reason, then, most nudibranchs are doomed to slow starvation in our care.

Problematic Identification

Figure 2: A close-up of the head area showing the lack of zooxanthellae "veins."

The aeolids in my tank, however, were soon discovered to eat anemones. Arguably the most recognized aeolids in the aquarium hobby are Berghia verrucicornis (Costa, A., 1864) and Aeolidiella stephanieae (Valdes, 2005), famous for their ability to eat Aiptasia anemones and for not being fatally toxic to most tank inhabitants when expiring in captivity en masse. After consulting additional resources (Garcia-Gomez and Cervera, 1985; Gosliner, 1979; Marcus and Marcus, 1977), it appears that my nudibranchs could be Spurilla neapolitana. It should be noted that this is a tentative identification based on pictures, diet and egg mass similarities (see here for Spurilla neapolitana egg mass photos), and is in no way a definitive identification. Like most aquarists, I like knowing the scientific name of the creatures in my care. Nudibranch identification to species, however, is nearly impossible without dissection. This nudibranch, therefore, could easily be any of a number of closely related aeolids. Well-fed Spurilla neapolitana are often cited as having distinct "veins" of ingested zooxanthellae near their head (see here for pictures). As can be seen in Figure 2 below, my nudibranchs lacked these "veins," which further complicated identification attempts.

Diet, Care and Handling

What was more important to me than its scientific name was determining my nudibranchs' diet. I did not want to introduce them back into my tank to feast on my easily identified Acropora yongei, Acropora nobilis or Acropora aculeus (a little identification humor). I immediately put out a call to my fellow MARSH (Marine Aquarium and Reef Society of Houston, TX) club members for pest anemones as it appeared the nudibranchs were nearly starved (see Figure 3).

Figure 3: My nearly starved nudibranchs with a distinctive lack of color beginning their first meal of a "tulip" anemone.

I quickly received some "tulip" anemones that look remarkably similar to Majano anemones. This was an acceptable first food as both specimens began to feed immediately (see Figure 3). I later acquired two different morphs of Aiptasia spp. anemones that were also readily consumed (see Figures 4 and 5). It is interesting to note that I had several rock anemones from my first live rock shipment that appeared to be healthy and growing before I added my second shipment of live rock. They all disappeared within a number of days of each other after the second shipment of live rock was added. While it is only speculation, it is possible that the nudibranchs consumed these as well before I removed them from the tank.

Figure 4: Aiptasia morph #1 being ingested.
Figure 5: Aiptasia morph #2 with first egg mass above it.

Care of these nudibranchs was relatively easy. My specimens tolerated a specific gravity ranging from 1.023 - 1.030 and temperatures of 74-82°F (23-28°C), but I usually kept their containers at 79°F (26°C) and 1.026 SG. The holding containers were bare buckets and cups that were un-aerated and contained no filtration; one 19-watt 6500K power compact bulb provided illumination. Regular 30-90% water changes were performed using filtered and aged tank water every two to five days. The water changes were important as the nudibranchs frequently sloughed off waste when eating or moving (see Figure 6). I first mistook this for an egg mass, but as you will see later, the eggs look very different from their waste.

Figure 6: Nudibranch waste/mucous accumulation.

Handling and transfer of nudibranchs is best performed by blowing water with a turkey baster gently near their foot until they release their hold on the substrate. They can then be scooped up using a small bowl to transfer them without breaking their fragile cerata that are easily snagged on nets or intentionally released by the animal when threatened.

Feeding Behavior

Most nudibranchs lack eyes and I did not detect any on my specimens. They hunt their prey by using a combination of their rhinophores and oral tentacles (see Figure 7). In my situation I noticed some interesting behavior. I typically kept my specimens in a container without anemones to keep the water quality more stable. If they were well-fed, the nudibranchs would typically move only at night. After the addition of an anemone, however, they would go into hunting mode within 10-60 seconds.

Figure 7: Rhinophores, oral tentacles and ceras of a nudibranch, seen here in hunting mode.

Hunting begins by moving the rhinophores into various positions. It is speculated this is done to smell the anemone and determine its general direction (see here). The nudibranch then begins to move forward with some side-to-side sweeps in an ever-widening cone shape. During this entire time its rhinophores are in constant motion, and its oral tentacles are held in front and slightly to the sides of its head (see Figure 7).

Once the oral tentacles make contact with the anemone, they determine the prey's orientation, as this nudibranch always ate beginning with the anemone's foot and consuming its tentacles last. The anemones would sting the nudibranchs, but they would only briefly recoil and then resume their feeding (see Figures 8 & 9 for feeding pictures). The nudibranchs would consume even a very large anemone in one feeding, with their mouth constantly attached to the food.

Figure 8: Beginning to feed, the nudibranch would slowly detach the anemone's foot from the substrate.

Figure 9: Here the anemone is roughly 50% consumed; smaller anemones such as this one were often overturned during feeding.

Feeding would typically take over two hours to consume a large tulip anemone and around 45-60 minutes for a similarly-sized Aiptasia. After feeding, the nudibranchs would rest and excrete waste. They have substantial appetites, however, and when supplied with a constant food source they ate 30 anemones in 10 days.

Reproductive Observations

Nudibranchs are sexually hermaphroditic. This means that one individual contains both male and female sexual organs. They are rarely self-fertilizing, though, and usually require two specimens to reproduce. I observed a mating "dance" that was essentially identical to the one described for Berghia by Anthony Calfo (2004). When provided with enough food an adult laid an egg mass in my system on average every one to three days. As shown in Figure 10, egg masses are typically laid in a loose spiral, but not always.

Figure 10: Egg masses.

It is interesting to note that when I first started feeding the nudibranchs on August 2nd, 2005, one specimen was 1.5" (38mm) in length while the other was barely 0.5" (13mm). While the larger specimen began laying eggs on August 5th, the smaller one did not begin to lay eggs until August 27th when it was 1" (25mm) long. Its first egg masses were very small and contained only a few hundred eggs.

Once both adults were full-sized and laying eggs, each mass contained thousands or even tens of thousands of eggs. Each individual egg was well under 1mm in diameter, but I did not have a way to measure anything smaller than 1mm. It would take between five to eight days for an egg mass to hatch. Several images of egg masses in the process of hatching are seen below (Figures 11-14).

Figure 11: This egg mass is just beginning to hatch (4x magnification).
Figure 12: The egg mass is seen here disintegrating during hatch with larvae clearly visible in the lower center (4x magnification).

Figure 13: Each loop in an egg mass contains hundreds or thousands of eggs (60x magnification).
Figure 14: The larvae are seen here one hour after hatching (200x magnification).

Raising Efforts

Good documentation is available (Calfo, 2004; Borneman, 1998; Carroll & Kempf, 1990) on raising Berghia nudibranchs, but I could not find any information on raising Spurilla neapolitana. I set up a system similar to that described by Calfo (2004) and Carroll & Kempf (1990). However, after 45 days of attempts, I was unable to raise the babies successfully. Raising aeolids is a time intensive task, and I simply did not have enough time. If hobbyists acquire a breeding pair of these aeolids and want to attempt raising their young, they should be prepared to spend 7-20 hours per week to adequately care for the adults, eggs and babies, and to culture their anemone food supply.

Nudibranch larvae hatch in a wide variety of forms, but there are two extremes. On one end of the scale the nudibranchs hatch as miniature sea slugs and begin seeking a food source immediately. On the other end are eggs that hatch as free-swimming larvae that feed for a long time in their planktonic stage. Larvae that need to feed while in their planktonic stage make aquarium rearing very difficult. For a longer discussion of larval size, see "When Nudibranchs hatch, are they just smaller versions?" by Bill Rudman.

Berghia verrucicornis have been reported to be lecithotrophic, which means free-swimming at first, but they do not need to feed in the planktonic stage and quickly transform into small sea slugs and begin feeding. While my nudibranchs did hatch out as free-swimming larvae (see Figures 11 & 12 and these videos: video 1, video 2, video 3), they appear to be non-feeding and around 90% of them settle in eight hours if the appropriate Majano anemones are present (Rozsenich, pers. comm.).

Because I did not have enough time to dedicate to their raising, I arranged to have a dedicated Berghia breeder, Yvonne Rozsenich, take over the breeding efforts. While Yvonne has raised the larvae only to 30 days on her best attempt, it appears likely that she will succeed. I have combined my observations with hers to find several factors that could help others attempt to raise them, and these are detailed in the list below. It appears that the babies prefer to settle near Majano anemones, as settling near Aiptasia spp. has not yet been observed (Rozsenich, pers. comm.).

Tips to help increase success in raising the larvae:

1. The large number of eggs in each egg mass means that the hatched larvae will cause a lot of damage and kill large anemones before they can be consumed. This causes rapid fouling of the water and larval deaths. It is suggested that immediately after the egg mass is laid, a small portion of the egg mass should be severed and used to raise a smaller number of larvae.1
2. As with Berghia, very small anemones, or diced anemone flesh, should be present when the egg mass hatches in order to induce larval settlement.1
3. Egg masses should not be exposed to air as they were not observed to hatch after prolonged exposure to air. Instead, either the adults should be moved after laying an egg mass or the egg masses should be scraped from the surface using a credit card or razor blade and transferred using a cup or bowl.2
4. The egg masses are extremely sticky and nearly impossible to remove from live rock or other uneven surfaces. The egg laying adults should be kept in bare containers with flat surfaces.2
5. All of the animals' life stages should be kept in aged and filtered water (a coffee filter minimally, a 0.45 µm filter would be the preferred option) and with no live rock, as it is a potential source of predators for all stages.2
6. 6. Feeding each adult one medium-sized (15-25mm diameter, measured tentacle tip to tentacle tip) anemone every two to three days was enough to maintain egg mass production at one mass every two to three days. At this rate of feeding, egg masses hatched after five to eight days, and the larvae moved vigorously. However, it is unknown whether feeding the adults additional food would have led to better survival rates for the larvae.2
7. Heavily feeding the adults reduced the frequency of egg mass production to every three to five days and increased the difficulty in maintaining water quality.2
       1Tip provided by Yvonne Rozsenich (pers. comm.).
         2Tip provided by Brian Plankis.


With their documented consumption of Aiptasia spp., tulip and Majano anemones, this is potentially a valuable aeolid species for the aquarium industry for pest anemone control. My tank contained several species of Zoanthus spp., mushroom polyps and soft corals that did not appear to suffer during the period when my nudibranchs were wandering undiscovered, nearly starved, in my tank. This species, however, appears to be a generalist feeder on cnidarians and more research will need to be completed to determine if it consumes other, more desirable, anemones or closely-related cnidarians in a reef aquarium.

This testing should be fairly easy to conduct once the juveniles are raised to sexual maturity, which should result in a corresponding increase in broodstock. I wish Yvonne the best of luck in successfully completing this task. In the meantime, aquarists receiving livestock from Florida or the Caribbean should keep their eyes out for this species in their shipments.

If you have the time and skill to dedicate, it is an interesting and beautiful species (although my wife would disagree on the last point) to attempt to care for and breed. If you do not have the time or desire to raise them, however, feel free to contact me or a local Berghia breeder to increase the knowledge base and broodstock on this poorly studied (in aquaria) species. Join me in my author forum if you have any questions or comments on this article.


I would like to thank my wife, Christine, for her patience during the time intensive care of these animals, and Dr. John Ramsey for lending me the microscope that allowed me to capture the magnified images and video included in this article. I would also like to thank several members of Reef Central and MARSH for their help in narrowing down the identification of these specimens and for supplying me with a steady supply of pest anemones. Finally, Yvonne Rozsenich and Bryan Green should be commended for their efforts to help me find a new home for these specimens and for their continuing efforts to study them.

All photographs are copyrighted by Brian Plankis and should not be used without his written permission.


Carroll, D.J. and S.C. Kempf. 1990. Laboratory culture of the aeolid nudibranch Berghia verrucicornis (Mollusca, Opisthobranchia): Some aspects of its development and life history. Biological Bulletin 179: 243-253.

Coleman, N. 2001. 1001 Nudibranchs - Catalogue of Indo-Pacific Sea Slugs. Neville Coleman's Underwater Geographic Pty Ltd, 144 pages.

Costa, A. (1867 for 1864). Sui molluschi eolididei del Golfo di Napoli. Ann. Mus. Zool. Napoli, 4(2): 26-37, pls. 1, 2.

Debelius, H. 1996. Nudibranchs and Sea Snails Indo Pacific Field Guide. IKAN - Unterwasserarchiv, Waldschulstrasse 166, 65933, Frankfurt, Germany, 321 pp.

Garcia-Gomez, J.C. and J.L. Cervera. 1985. Revision de Spurilla neapolitana Delle Chiaje, 1823 (Mollusca; Nudibranchiata). Journal of Molluscan Studies, 51: 138-156.

Gosliner, T.M. 1979. The systematics of the Aeolidacea (Nudibranchia: Mollusca) of the Hawaiian Islands, with descriptions of two new species. Pacific Science, 33(1), 37-78.

Marcus, E. and E. Marcus. 1977. An annotated checklist of the western Atlantic warm water opisthobranchs. Journal of Molluscan Studies, Supplement 4: 1-22.

Rozsenich, Y. 2006. Berghia breeder. Personal communications.

Shimek, R. L. 2004. A PocketExpert Guide: Marine Invertebrates: 500+ Essential-to-know aquarium species. Neptune City, NJ: TFH, 448 pp.

Valdés, A. 2005. A new species of Aeolidiella Bergh, 1867 (Mollusca, Nudibranchia: Aeolidiidae) from the Florida Keys, USA. The Veliger, 47: 218-223.

Internet Sources:

Borneman, E. 1998. The Berghia Training Program.

Calfo, A. 2004. Aquarium Culture of the Aeolid Nudibranch Berghia Predator on the Nuisance Anemone Aiptasia. Reefkeeping Magazine, 2(12).

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Observations on Anemone Predation and Reproduction by Hitchhiking Aeolid Nudibranchs by Brian Plankis -