Bubbles, bubbles, my bubbles!

The title of course comes from Bubbles, the lovable and high-strung yellow tang in Disney’s “Finding Nemo”. I was inspired to write this because one of the most common questions I get regarding the reef aquarium is – somewhat surprisingly to me – about the bubble algae, rather than about the animals. Bubble algae are considered to be single-celled algae in the genera Valonia, Ventricaria, Boergesenia or Dictyospheria. Whether or not they are is apparently in question because of some unusual features described by Shepherd et al. (2004). In fact, there has been a considerable body of work on the ultrastructure and function of the cell wall of some species because of this. There is less information available on how to control this invasive alga, although the topic is frequently discussed online.

Valonia species are marble-shaped, whereas Ventricaria spp. look like small balloons. Boergesenia spp. Are elongated, and look somewhat like green hot dogs. Dictyospheria spp. are smallish and often grow in clusters. They have in common that once in a reef aquarium they are virtually impossible to get rid of. The species in the UNBC reef tank is most likely Ventricaria (formerly Valonia) ventricosa (Olsen and West 1998). It is dark green, often with a metallic shimmer caused by refraction. Bubbles start off small, but eventually reach a size of about 3-4 cm long and perhaps ¾ of the length in diameter. They attach firmly to any hard substrate, including coral skeletons. This sometimes causes corals to be dislodged or overgrown. When mature, the bubble will burst (no pun intended) and release spores, leading to the establishment of new bubble algae if the spores end up on suitable substrates.

One of the most common recommendations for combatting bubble algae is through the introduction of emerald crabs, Mithraculus sculptus. While these crabs consume some

Female emerald crab, Mithraculus sculptus. Photo by Mark Loch. Used under the Creative Commons Attribution-Share Alike 2.0 Generic license.

small bubble algae, they are omnivores, and the effect will largely depend on what alternative food sources are available to them (Figueiredo et al. 2008). Another frequent suggestion is the lettuce “nudibranch”, Elysia crispata. This sacoglossan sea slug feeds on a number of algae species, and has been reported to use kleptoplasty (acquisition of functioning chloroplasts for photosynthesis) as a means of producing energy in the absence of food, although this has been questioned in recent papers (Christa et al. 2014a,b). I have added both emerald crabs and lettuce sea slugs to the UNBC reef tank on numerous occasions, but I can’t say that I have seen any improvement in the bubble algae density as a result. Many sea slugs are quite specialized in terms of their food, and there is at least one species that that appears to specialize on bubble algae. This fascinating example is Ercolania kencolesi, a species that manages to get inside the bubble of Boergeseniaspp. without bursting it (Grzymbowski et al. 2007, Händeler et al. 2009).

Ercolania kencolesi feeding inside bubble algae Boergesenia. From Händeler et al. 2009. Figure 2C. Used under Creative Commons BY 2.0 via Wikimedia Commons

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A related sea slug, Ercolania endophytophaga feeds inside the basal cells of Struvea plumosa in the wild, but also on Valonia spp. in the laboratory (Jensen 1999). According to a post in the Sea Slug Forum, it has also been found inside Valonia on the Great Barrier Reef (http://www.seaslugforum.net/showall/ercoendo).

Since emerald crabs are rather inefficient for the most part, and the sea slugs are difficult to get hold of and keep alive, bubble algae will likely be a feature of the UNBC reef tank for the foreseeable future.

References
Christa, G. J. de Vries, P. Jahns, and S.B. Gould. 2014a. Switching off photosynthesis. The dark side of sacoglossan slugs. Commun. Integr. Biol. 7: e28029, 3 pp.

Christa, G., V. Zimorski, C. Woehle, A. G. M. Tielens, H. Wägele, W. F. Martin and S. B. Gould. 2014b. Plastid-bearing sea slugs fix CO2 in the light but do not require photosynthesis to survive. Proc. R. Soc. B. 281: 20132493

Figueiredo, J., L. Narciso, R. Turingan, and J. Lin. 2008. Efficiency of using emerald crabs Mithraculus sculptus to control bubble alga Ventricaria ventricosa (syn. Valonia ventricosa) in aquaria habitats. J. Marine Biol. Assoc. U.K. 88: 95-101.

Grzymbowski, Y., K. Stemmer, and H. Wagele, H. 2007. On a new Ercolania Trinchese, 1872 (Opisthobranchia, Sacoglossa, Limapontiidae) living within Boergesenia Feldmann, 1950 (Cladophorales), with notes on anatomy, histology and biology. Zootaxa. 1577: 3-16

Händeler K., Y.P. Grzymbowski, P.J. Krug, and H. Wägele H. 2009. Functional chloroplasts in metazoan cells – a unique evolutionary strategy in animal life. Frontiers in Zoology 6: 28, 18 pp.

Jensen, K.R. 1999. A new species of Sacoglossa (Mollusca, Opisthobranchia) from Rottnest Island, Western Australia. Pp. 377-383 in D.J.Walker and F.E.Wells (Eds). The Seagrass Flora and Fauna of Rottnest Island, Western Australia. Western Australian Museum, Perth .

Olsen, J.L., and J.A. West. 1988. Ventricaria (Siphonocladales-Cladophorales complex, Chlorophyta), a new genus for Valonia ventricosa. Phycologia 27: 103-108.

Shepherd, V.A. , M.J. Beilby, and M.A. Bisson. 2004. When is a cell not a cell? A theory relating coenocytic structure to the unusual electrophysiology of Ventricaria ventricosa (Valonia ventricosa). Protoplasma 223: 79-91.

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“You are what you eat” and other defensive strategies of marine invertebrates, Part II

It has been a few months since I posted part one of this blog. It has been a busy spring. A number of events have come and gone. The Biology Club’s Annual “Save Nemo” event was again sold out, netting a respectable contribution to the maintenance of the reef tank. Additional pay cheque withdrawal donations have helped us maintain a healthy balance in the UNBC Reef Tank fund. A big thanks to everyone who kindly supports the tank – the animals appreciate it!

The 8th Prince George Reef Tank Tour gave reef tank enthusiasts the opportunity to view some excellent tanks and to discuss issues relevant to the hobby. Photos from the different tanks can be viewed in this series of posts on CanReef http://www.canreef.com/vbulletin/showthread.php?t=103966 (scroll down and you will get to them).

The UNBC Reef Tank has experienced some minor issues relating to water quality and I am continuing to address those by frequent water changes. The manifestation is that some corals are not expanding their polyps properly, and some algae growth indicates that there is a nutrient excess. It is a never-ending task to keep things on an even keel, so to speak.

“You are what you eat” and other defensive strategies of marine invertebrates, Part II
I have mentioned that corals and their relatives have unique cells, the cnidocytes (stinging cells) which contain a capsule, a nematocyst, which when touched releases a stinging thread, which sometimes can deliver a more-or-less potent venom. No other animals have these cells, hence corals, sea jellies, hydras and their relatives are classified together in the Phylum Cnidaria, the stinging animals. If you touch a tide pool anemone on the coast, you will notice that it feels like the tentacles are sticky. This is due to the stinging threads being fired into your skin. These anemones don’t deliver potent venom, however, so it doesn’t hurt. At the other end of the scale are some box jellyfish, which deliver such a potent venom that it may be lethal, and at best even minor stings can cause agonizing pain and muscle cramps that last for days or even weeks. You can get an idea of the potential problem in this video https://www.youtube.com/watch?v=9CHshkF8GDU. Heeding warnings of stingers is definitely a good idea!

Interestingly, some species of one other Phylum of animals, the molluscs, have figured out ways to a) get around the defense of the stinging animals, and b) to use it to their own advantage. Some version of this is found in several Classes, e.g., anemone fish and some crustaceans live among the tentacles of anemones without triggering the nematocysts (Mebs 2009), and males and immature females of the blanket octopus carries tentacles of its siphonophore (Portuguese Man-o’-War or blue bottle, Physalia sp.) prey for defense. Some Gastropods (snails and slugs), and more specifically in the marine aeolid nudibranchs, an Order of often unimaginably colourful sea slugs have taken this a step further, however. They will incorporate the unfired nematocysts, called kleptocnidae, into its own tissues. A few marine flatworms and at least one species of comb jelly also do this, but very little is known about them (Greenwood 2009).

Berghia coerulescens (Laurillard, 1830). Photo by Parent Géry. Licensed under Public domain via Wikimedia Commons – http://commons.wikimedia.org

Because these nudibranchs tend to be predators of Cnidaria (stinging animals) and other organisms, many are likely to feed on corals, and because they also tend to be a bit difficult to ship and keep, they are rarely seen in the reef tank trade. Some related organisms are available from time to time, however. and the UNBC tank has had two types, both unsuccessfully. One is the blue velvet nudibranch (Chelidonura varians Eliot) or head shield sea slug. In spite of its common name, this is not a nudibranch, but a member of the head shield slugs (Order Cephalaspidea). It is a predator of marine flatworms (Phylum Platyhelminthes), and is used in the reef tank hobby to bring these organisms under control. The specimen brought in for the UNBC tank was in poor condition when it arrived, and simply disappeared very quickly after being introduced into the tank. The second species brought in was a so-called lettuce nudibranch (Elysia crispata (Mörch)). This is not a nudibranch either, but a sacoglossan. There is a story related to the theme of this story with respect to this group, however. Sacoglossans are vegetarians, feeding on various algae. Some species will retain intact, live chloroplasts, a phenomenon called kleptoplasty (Cruz et al. 2013). For that reason, these some species of sacoglossans are able to use the chloroplasts to photosynthesize, and as such they would be unique in the animal kingdom. A recent study has cast some doubt on this, however (Christa et al. 2014), arguing that the kleptoplasts may represent a form of food storage because the genes necessary for the chloroplasts to function is not present. Wägele and Martin (2014) summarize knowledge on how photosynthesis is possible in the absence of a horizontal gene transfer from the algae into the slug genome.

But back to the kleptocnidae. Greenwood (2009) reviewed research on acquisition and functional significance of this stolen weaponry. As is always the case in biological systems, there is no simple and straightforward explanation. Acquisition is aided by physical protection in the nudibranch gut, whereby those nematocysts that do fire do not damage cells. Furthermore, mucus, either acquired from the prey or produced by the nudibranch may inhibit nematocyst firing. Interestingly, this is prey specific, so a nudibranch feeding on one species does not have protection from a different prey species. Some species of nudibranchs can switch prey, whereby the gain protection against the new prey species, but lose protection against the “old” prey species. Yet other nudibranchs acquire immature nematocysts which cannot fire, but mature in the cerrata (fleshy extensions lining the aeolid nudibranch body) where the kleptocnidae are housed (see below). Size also matters! Large nematocysts may prevent predation. Some nudibranchs prefer to feed on tunicates rather than cnidarians, but appear to feed on the latter solely to acquire nematocysts.

In the cerrata, the nematocysts are engulfed by cnidophage cells, and over time they are actually digested (Greenwood 2009). The cnidophages are found in the tips of the cerrata in a cnidosac, which is an extension of the basal digestive diverticulum (See Figure 2 in Greenwood 2009). The kleptocnidae appear to be important for defense in most species, but in some their value may be marginal. Nevertheless, fish and crustaceans generally would eat nudibranchs when the cerrata were removed, whereas most would not eat intact specimens. Nudibranchs do have chemical defenses as well, however, so it is unclear what the relative role of the kleptocnidae may be (Greenwood 2009). In any case, the acquisition and use of nematocysts by aeolid nudibranch sea slugs is unique among metazoans, and exemplifies well that for every evolutionary invention to defend against predation, there will likely be an invention to get around that defense.

References
Christa, G., V. Zimorski, C. Woehle, A. G. M. Tielens, H. Wägele, W. F. Martin and S. B. Gould. 2014. Plastid-bearing sea slugs fix CO2 in the light but do not require photosynthesis to survive. Proc. R. Soc. B 281: 20132493

Cruz, S. R. Calado, J. Serôdio, and P. Cartaxana. 2013. Crawling leaves: photosynthesis in sacoglossan sea slugs. J. Exp. Bot. 64: 3999-4009.

Greenwood, P.G. 2009. Acquisition and use of nematocysts by cnidarian predators. Toxicon 54: 1065–1070.

Jones, E.C. 1963.Tremoctopus violaceus uses Physalia tentacles as weapons. Science 139: 764-766.

Mebs, D. 2009. Chemical biology of the mutualistic relationships of sea anemones with fish and crustaceans. Toxicon 54: 1071-1074.

Wägele, H., and W.F. Martin. 2014. Endosymbioses in sacoglossan seaslugs: plastid-bearing animals that keep photosynthetic organelles without borrowing genes. Pp. 291-324 in Endosymbiosis (W. Löffelhardt, ed.). Springer-Verlag, Vienna.

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“You are what you eat” and other defensive strategies of marine invertebrates, Part I

Upcoming events

Before delving into this post’s subject, a reminder that the biology club’s “Saving Nemo” event is on tonight (February 14) at 8:30 pm in the Thirsty Moose Pub. Furthermore, the third installment in this year’s Prince George Reef Tank Tour will be held on Sunday, February 16, noon to 4 pm. Contact Russell Vander Ende (whatcaneyedo@hotmail.com for directions if you are interested.

Portable homes

For all but a small number of very large animals, one of the main challenges in life is to simply avoid becoming somebody else’s dinner. For every organism, something tends to be around that wants to eat you. The ways in which some marine organisms ensure that this is less likely to occur is the topic of this and the next blog. It doesn’t fall clearly under the umbrella of symbiosis, because one of the participant organisms is frequently the dinner of the other. To add insult to injury, some of these organisms actually use some part of their meal ticket to defend themselves against their own predators. Such tactics aren’t necessarily unique to marine animals in that many terrestrial organisms may acquire toxic chemicals from their meal as a means of avoiding predation. Examples include butterflies that sequester defensive compounds from plants (Nishida 2002), and poison dart (Dendrobatidae) and Mantella species poison frogs (Mantellidae) of Madagascar that acquire toxins from the ants they feed on (Clark et al. 2005). In the case of the marine organisms I will describe below, however, we are discussing the use of parts of another organism.
In this post I will discuss an example that is represented in the reef tank, and where predation is only indirectly involved, i.e., the subject of the post is not the predator. These are the hermit crabs (Crustacea: Decapoda: Paguroidea), a group that includes both terrestrial and marine members. Most species have a very soft and vulnerable abdomen, and many are quite small, necessitating some form of protection against predation. They have solved this dilemma by utilizing the shells of suitably sized snails (Mollusca: Gastropoda) to get the protection they need. Hermit crabs cannot make their own shells, so the availability of suitably sized empty shells is frequently a limiting resource that influences behaviours and population dynamics of the crabs. Thus, acquiring a new shell as the old one is out-grown or becomes damaged becomes a very important task. The method that appears to be predominantly employed among marine hermit crabs is described by McLean (1974), and involves taking advantage of predation on suitably sized

An “electric blue hermit crab”, Calcinus elegans (H. Milne-Edwards) in the UNBC reef tank. This attractive hermit crab is native to the Marshall Islands.

snails by predators. Large numbers of hermit crabs accumulate around a predation event, a dominance hierarchy is established among the waiting crabs, and once the newly empty shell has been dropped by the predator, it is investigated and if suitable acquired. Similarly, Small and Thacker (1994) reported that terrestrial hermit crabs were strongly attracted to the the odour of dead conspecifics. Eviction of a smaller crab from a desired shell is also a possibility, as seen in this video http://www.arkive.org/common-hermit-crab/pagurus-bernhardus/video-03.html. When a hermit crab acquires a new shell, the old shell obviously becomes available, leading to a chain reaction, a “shell vacancy chain” (Chase et al. 1988), where smaller crabs move up to a larger size. Some hermit crabs may prey directly on gastropods to acquire shells, a behavior sometimes observed in reef tank environments, but this behavior appears to be rare, if it occurs at all. In fact, Laidre (2011) found that neither a marine nor a terrestrial species of hermit crab could readily access shells unless they were empty and on the surface of the substrate. Even a dead snail in the shell prevented access.

While the shell offers protection, it also is cumbersome, and often leads to awkward situations for the crabs. You can observe this in the reef tank as the crabs often fall off corals and end up upside down, a position where they are potentially vulnerable. It is somewhat comical to watch them trying to right themselves, nervously exiting only far enough to reach the bottom, and rapidly withdrawing at the slightest disturbance.

References
Chase, I.D., M. Weissburg and T.H. Dewitt, 1988. The vacancy chain process: a new mechanism of resource distribution in animals with application to hermit crabs. Animal Behaviour, 36: 1265-1274.
Clark, V.C., C. J. Raxworthy, V. Rakotomalala, P. Sierwald, and B.L. Fisher. 2005. Convergent evolution of chemical defense in poison frogs and arthropod prey between Madagascar and the Neotropics. PNAS 102: 11617–11622.
Laidre, M.E. 2011. Ecological relations between hermit crabs and their shell-supplying gastropods: Constrained consumers. Journal of Experimental Marine Biology and Ecology. 397: 65–70.
McLean, R.B. 1974. Direct shell acquisition by hermit crabs from gastropods. Experientia 30: 206-208
Nishida, R. 2002. Sequestration of defensive substances from plants by Lepidoptera. Annual Review of Entomology. 47: 57–92
Small, M.P. and R.W. Thacker. 1994. Land hermit crabs use odors of dead conspecifics to locate shells. Journal of Experimental Marine Biology and Ecology 182: 169-182.

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Upcoming events

Prince George Reef Tank Tour
The first of four stops on the 8th Annual Prince George Reef Tank Tour was held at UNBC on January 19. We enjoyed record attendance, with about 30 visitors over the course of the day, in part thanks to a timely article in the Free Press. A few photos are posted here : http://www.canreef.com/vbulletin/showthread.php?t=103966 (scroll down for photos). The next event will be this coming Sunday, 12 noon – 4 pm, when we visit Russell Vander Ende’s beautiful tank. Attendees will have the opportunity to talk to, and learn from, the most successful reef tank keepers in Prince George, e.g., Russell has been a key source of information and very generous with his time in times of crisis – there is little doubt that the tank would not be as successful without his advice. Russell is also the organizer of the tour, incidentally. If you are interested in attending, please contact Russell directly at whatcaneyedo@gmail.com or by telephone 250-964-7007 for directions.

UNBC Biology Club “Saving Nemo” Event
The Biology Club will have their annual “Saving Nemo” event in support of the reef tank fund at the Thirsty Moose Pub, Friday February 14. Over the past few years, the club has raised close to $1,000, which has been used for parts, metal halide light bulbs, livestock, salt etc. Please contact Kacie Young at bioclubunbc@gmail.com for additional information.

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A UNBC Reef Tank update

Shrimp goby news. In my last blog I wrote that the orange spotted goby that was partnered with the Randall’s pistol shrimp appeared to have passed on, and as a result I added a yellow watchman goby to the tank. A few days ago, the missing goby was back on its post in front of the burrow they share, which explains why the yellow watchman never managed to pair up with the shrimp. If you are at the tank at the right time, you may see the pair at the left end of the tank between two rocks right next to the Hawaiian feather duster tubeworm. This is an example of the ever changing scenarios in the tank. Organisms that seem to have disappeared suddenly reappear.

Major refurnishing. Over the Christmas break, I decided that the orange plate Montipora coral had gotten too large, as it was right up to the surface, and also shading many of the smaller corals. Consequently I removed about ¾ of it, which amounted to ¾ of a 5 gallon bucket full of coral pieces. Plate corals, because of their growth pattern, provide an incredible maze of chambers where small creatures can live in relative safety. Along with numerous small brittle stars of the genus Amphiura (more about them in a future blog) I found the porcelain crab, Petrolisthes sp., which promptly vanished after its introduction to the tank last fall. Right after the pruning, the corals looked a little worse for wear, but they now have recovered and are growing nicely again.

Photo of Reef Tank from 2013, showing the Montipora plate coral in the back. At the time of this photo it was about half the size it was when pruned in December.

Prince George Reef Tank Tour. The Annual Prince George Reef Tank Tour will kick off its 8th season at the UNBC reef tank on Sunday, January 19, 2014, 12 noon to 4 pm. This event is open to anyone interested in reef tank keeping. Meet experts and beginners, view the tank, ask questions and get advice on aquarium keeping. Usually we have “frag” sales, i.e., reef tank keepers will bring in pieces (frags) of coral for sale at extremely discounted prices for other reef tank keepers. The Tour continues with home visits to reef tank keepers on February 2, February 16, and hopefully March 2. For picture highlights from last year’s Tank Tour see: http://www.canreef.com/vbulletin/showthread.php?t=93326

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A Christmas story of the coral reef variety

It has been a while since I had a chance to write something about the reef tank. Given that it is Christmas, I thought I would pick a topic that related to the season, but before I get into that, I will introduce the latest addition to the tank. As I mentioned in the post An almost-blind killer and its watchman, the shrimp goby-pistol shrimp symbiosis was no longer visible. Unfortunately it was not because the pair had moved, but rather it appears that the goby passed away. The shrimp is still in roughly the same spot. Last week I finally managed to get a potential replacement, which is a yellow watchman goby, or yellow prawn goby, Cryptocentrus cinctus(Herre). This species was described in 1936, and

Yellow watchman goby, Cryptocentrus cinctus, with pistol shrimp, Alpheus djiboutensis. Photo: Nick Hobgood, licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

comes from the Indo-Pacific. The first week, the specimen in the reef tank was stationed by the far left wall of the tank, but at the time of writing this it has moved to under the rock with the anemones on the right hand side of the tank. It is currently only about 3 cm long, but may grow to 8 cm. I am hoping that it will eventually find the pistol shrimp and pair up, but there is of course no guarantee that this will happen.

The Christmas-associated part of this blog will still link to the general theme of symbiosis that I started a few blogs ago, but in this case it is a somewhat one-sided association between a worm (Phylum Annelida) and a coral (Phylum Cnidaria). While the reef tank had this pair many years ago, they no longer inhabit the tank. One of the reasons is that the coral in question (a fairly non-descript species in the family Poritidae, and specifically the genus Porites) is fairly difficult to maintain in a reef tank. These SPS (small polyp stony) corals are generally beige-brown in colour with very small polyps. They require very strong light and high water movement. Many species are so called finger corals, but some species are encrusting or make more or less round rocks, e.g., the boulder coral, P. solida.

On occasion, these corals are for sale as Christmas tree corals. This is a misnomer, because the Christmas tree reference is to a symbiotic polychaet (=many bristles) worm, the Christmas tree worm, Spirobranchus giganteus (Pallas), which lives embedded in the coral head as a commensal symbiont. These tube worms are obligate symbionts (although see Skinner et al. 2012) of a variety of coral species (Floros et al. 2005), but in the reef tank trade they are usually sold with Porites colonies. It is viewed as a commensal symbiosis because the coral does not normally benefit in any way from the presence of the worm, and it may in fact be damaged by the tubes constructed by the worms. DeVantier et al. (1986), suggested that polyps growing adjacent to the worms may be protected from predation by the crown-of-thorn sea star, Acanthaster planci(L.) (Phylum

Assorted Christmas tree worms, Spirobranchus giganteus on a porite coral. Photo Nick Hobgood, licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Echinodermata), thus ensuring that the coral colony survives, which is important as these corals persist for many years and can be dominant in shallow waters. Ben-Tzvi et al. (2006) observed similar protection from predation on corals. Potts et al. (1985) reported on one specimen on the Great Barrier Reef that was at least 677 years old, for example. Pratchett (2001) showed that coral symbionts do affect dietary preference by the crown-of-thorn sea star, although he did not specifically test Christmas tree worms. The worm on the other hand gains a very secure burrow in the calcareous skeleton of the coral, and an excellent perch for feeding.

Why Christmas tree worm? Well if you look at the photograph it becomes rather obvious. Each worm has two specialized palps, which make up a branchial or radiolar crown. Each tentacle has a feathery look to it, which gives it a large surface area. These appendages serve the dual purpose of food filtering and respiration. When the worm is feeding, the crown is extended from the tube, but when disturbed it can be quickly withdrawn and covered by a lid, or operculum. As the Latin generic name implies, the radiolar crowns are spiral, and they look like small trees. In addition, they are extremely colourful, reminiscent of the decorated Christmas trees. What determines the colour morphs is something I haven’t been able to establish, but suffice it to say that these animals are extremely attractive, and a favourite subject of underwater photographers.

A relative of the Christmas tree worm is present in the UNBC reef tank. This is a Hawaiian feather duster, Sabellastarte spectabilis (Grube), which is in the family Sabellidae. The crown differs considerably from those in the family Serpulidae, and in particular, the tube housing the worm is leathery rather than calcareous, and these worms lack an operculum. Nevertheless, they feed in a similar fashion and you can see the reaction to disturbance if a fish gets too close, for example.

Merry Christmas and a Happy New Year to you all.

 References
Ben‐Tzvi, O., S. Einbinder, and E. Brokovich. 2006. A beneficial association between a polychaete worm and a scleractinian coral? Coral Reefs 25:98.

DeVantier, M., R.E. Reichelt, and R.H. Bradbury. 1986. Does Spirobranchus giganteus protect host Porites from predation by Acanthaster planci: predator pressure as a mechanism of coevolution? Marine Ecology Progress Series 32: 307-310

Floros, C.D., M.J. Samways, and B. Armstrong. 2005. Polychaete (Spirobranchus giganteus) loading on South African corals. Aquatic Conservation: Marine and Freshwater Ecosystems 15: 289–298.

Potts, D.C., T.J. Done, P.J. Isdale, and D.A. Fisk. 1985. Dominance of a coral community by the genus Porites (Scleractinia). Marine Ecology Progress Series 23: 79-8.

Pratchett, M.S. 2001. Influence of coral symbionts on feeding preferences of crown-of-thorns starfish Acanthaster planci in the western Pacific. Marine Ecology Progress Series 214:111-119.

Skinner, L.F., A.A. Tenório, F.L. Penha, and D.C. Soares. 2012. First record of Spirobranchus giganteus (Pallas, 1766) (Polychaeta, Serpulidae) on Southeastern Brazillian coast: new biofouler and free to live without corals? Pan-American Journal of Aquatic Sciences 7: 117-124.

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Reef doctors and dentists

Parasitism is a form of symbiosis where the parasite benefits at the expense of the host organism. Most organisms have some kind of parasite associated with them, and reef animals are no different. When we have a problem, we go to the dentist or medical doctor (or some people prefer non-traditional healers), but what do reef animals do? For most of them, there is no real solution, but for fish there is. There is a group of organisms that have become specialized on cleaning parasites off fish, and this blog will introduce you to those present in the UNBC Reef Tank.

Cleaner shrimp showing prominent, contrasting colours and long white antennae used to advertise cleaning services.

There are two cleaner organisms in the UNBC Reef Tank, a cleaner shrimp, Lysmata amboinensis (De Man) (Decapoda: Hippolytidae), which has a number of common names (northern cleaner shrimp, scarlet cleaner shrimp, skunk cleaner shrimp, Pacific cleaner shrimp), but is usually simply referred to as cleaner shrimp in the reef tank trade. There are two specimens in the tank, and this is the result of an apparently hard-wired tendency that leads to only a monogamous pair of shrimp remaining at any one cleaning station (Wong and Michiels 2011). I purchased three, but the third shrimp vanished in short order after introduction. You can find them behind the anemones at the right hand side of the tank. Incidentally, this seems to be a dangerous place as the shrimp are not immune to the sting of the anemone. If their antennae touch an anemone tentacles, they have to pull to free it – watch if one comes out and you may be able to see this. At feeding time, they will venture out from behind the anemone rocks to catch whatever morsels they can find, because they are really scavengers, i.e., their cleaning habit is facultative. If you look carefully, you may see that each individual frequently carries 20 or so large, greenish eggs under her abdomen, so they must be females. Yes, but both of them are also male, because they are protandrous simultaneous hermaphrodites (Bauer 2000). This means that all are born male, but develop female reproductive organs as they mature, although some specimens apparently remain male only (Lin and Zhang 2001). To make matters even more complicated, they can serve as males at any time, even when brooding eggs, but can only serve as females shortly after a molt!

In nature, or in the presence of larger fish, they normally position themselves in a cave or under an overhang. They have bright, contrasting white and red colours, and long white antennae, which advertises their presence to passing fish. Fish will come in to these stations to get cleaned, i.e., parasites and food remnants removed from their mouth, and this is where it gets interesting. Even fish that eat other types of shrimp, will not eat the cleaner shrimp. Instead they will keep their mouth open, and the shrimp will enter and pick off the offending items. They will also pick items off the skin of the fish, gaining food whereas the fish will get rid of parasites or food remnants.

There are a number of species of so-called cleaner shrimps in several families. A previous occupant of the UNBC Reef Tank was the banded coral shrimp, Stenopus hispidus , (Decapoda: Stenopodidae), which is really a small lobster rather than a shrimp, and consequently armed with some fairly impressive pincers.

Sharknose cleaner goby at a station under a plate Montipora coral.

The second member of the cleaning crew in the UNBC Reef Tank is the sharknose cleaner goby, Elacatinus evelynae (Böhlke & Robins) (Family Gobiidae), also represented by two specimens. These small fish are from the Caribbean, where they live in pairs at cleaning stations. The relationship with their host fish appears to depend on the parasite load in the area, so that when load is low, the gobies cheat by feeding on host fish tissue (Cheney and Côté 2005). In the UNBC Reef Tank, the gobies take food when other fish are being fed, but they also appear to take advantage of the mayhem to clean the other fish at that point. Generally they seem to approach other fish from the side – I have never seen them at the business end( the mouth) of another fish. Their pectoral fins are modified so they function like suction cups, allowing these fish to hang upside down under a coral or on the glass of the aquarium.

There are a number of other species of cleaner gobies, and many are available in the reef aquarium trade. More familiar to the general public is the bluestreak cleaner wrasse, Labroides dimidiatus (Valenciennes) (Labridae), which also is available in the trade from time to time. This species has a reputation as being difficult to keep alive, however, but like the cleaner goby, it is a facultative cleaner that also cheats by feeding on host tissues, as well as taking other food items (Grutter 1997). Unlike the gobies, cleaner wrasses perform an elaborate dance in front of hosts, which then will remain still with their mouth and gill covers wide open if they accept the cleaner.

Cleaner stations are often occupied by several species of cleaners, working together on hosts arriving for service. But why are the diminutive cleaners not eaten by their often predatory guests? It appears that certain colour patterns and size signal to potential customers what is a cleaner and what isn’t (Stummer et al. 2004). There are several models, but certain stripes and colours appear to be convergent factors.

References

Bauer, RT. 2000. Simultaneous hermaphroditism in caridean shrimps: a unique and puzzling sexual system in the Decapoda. Journal of Crustacean Biology, 20(Special Number 2): 110-128

 
Cheney, KL, and IM Côté. 2005. Mutualism or parasitism? The variable outcome of cleaning symbioses. Biology Letters, 1: 162-165

 
Grutter, AS. 1997. Size-selective predation by the cleaner fish Labroides dimidiatus. Journal of Fish Biology 50: 1303–1308

 
Lin, J, and D Zhang. 2001. Reproduction in a simultaneous hermaphroditic shrimp, Lysmata wurdemanni: any two will do? Marine Biology, 139: 1155-1158

 
Stummer, LE, JA Weller, ML Johnson, and IM Côté. 2004. Size and stripes: how fish clients recognize cleaners. Animal Behaviour, 68: 145–150

 
Wong, JWY, and NK Michiels. 2011. Control of social monogamy through aggression in a hermaphroditic shrimp. Frontiers in Zoology, 8:30.

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An almost-blind killer and its watchman

Symbiosis (from Greek, meaning living together) is almost a rule rather than an exception among the inhabitants of coral reefs. I have previously discussed the relationship between anemones and anemone- or clownfish (https://blogs.unbc.ca/reeftank/2013/06/14/everybodys-favourite-nemo/), and this time I will describe a very odd couple, the pistol shrimp and the shrimp goby. Unfortunately they are not visible in the UNBC reef tank anymore, after having taken up residence close to the front for a long time, but the association is too interesting to ignore.

There are over 600 described species of pistol shrimp in 45 genera. The species in the reef tank is the Randall’s pistol shrimp, Alpheus randalli Banner and Banner (Family Alpheidae), and it has partnered with an orange spotted shrimp goby, Amblyeleotris guttata (Fowler) (Family Gobiidae). The genus Alpheus alone has more than 280 described species (Encyclopedia of Life http://eol.org/pages/4264098/overview) making it the most species rich genus of all Decapod shrimps. Approximately 20 of these species associate with over 100 species of goby in seven different genera. Some of these gobies will hunker down with any willing shrimp partner, while some are specialists and will only live with a particular species of shrimp. Given their rather cryptic lifestyle, and the fact that the association has only been known since the late 1950’s, and studied in more detail since the 1970’s, I think it is safe to assume that there is still much to learn about these fascinating crustaceans and their fish partners.

How do you get a pair for your a reef tank? Well, you can sometimes buy a shrimp-goby pair from the live fish store, but this is not necessary. In the case of the UNBC tank, the goby was added almost a year before the shrimp, which was simply let go into the tank without consideration for where the goby was. The shrimp disappeared from view for a long time, but when the goby showed up in front of a burrow eventually, it had paired up with the shrimp and they have been together ever since.
What roles do the two partners have, i.e., why do they live together? Well, the goby is the watchman, keeping an eye out for predators and food. This is of great benefit to the shrimp, as it is nearly blind. When you watch a pair, you will find that the shrimp almost always keeps an antenna in contact with the fish when it is outside of its burrow. The shrimp in turn serves to construct the burrow, and it takes its job extremely seriously. When outside, the shrimp is constantly moving rocks and sand, sometimes carefully placing them around the opening and sometimes moving it away from the burrow. The chores appear endless, because you rarely, if ever, see the shrimp idle. Thus, this association is an example of mutualism, where both partners benefit.

Randall’s pistol shrimp and its orange spotted shrimp goby partner outside their burrow in the UNBC reef tank.Photo: D. Parkes.

Why the name pistol shrimp though? Well, a close look at the claws of this little shrimp reveals that they are asymmetrical. One is shaped in a rather odd way. The shrimp can open this claw, and then snap it together with great speed, making a sharp sound, hence the name. In a reef tank containing pistol shrimp, you can sometimes hear the sound as a click. But the sound is not generated by the closing claw. The force created by the claw, produces a jet of water that is so fast that a cavitation bubble is formed Versluis et al. 2000). When that bubble collapses, it produces the loud sound, which can approach 200dB (Au and Banks 1998). Furthermore, the collapse of the bubble generates heat, reaching temperatures of several thousand degrees (Lohse et al. 2001). So what in the world is the purpose of this? Appropriately, the shrimp uses the claw to “shoot” prey. Directing the snap at a prey animal will stun it, allowing the shrimp to capture other crustaceans or fish for food (You can view the process at https://www.youtube.com/watch?v=XC6I8iPiHT8) . For that reason, you have to expect some losses if you chose to keep a pistol shrimp. To date the toll has been quite modest in the UNBC reef tank (perhaps a few hermit crabs), and given that the pair remained in full view for at least a year, I consider the risk worth it.

References

Au, W.W.L. and K. Banks. 1998. The acoustics of the snapping shrimp Synalpheus parneomeris in Kaneohe Bay. The Journal of the Acoustical Society of America 103: 41-47.

Lohse, D., B. Schmitz and M. Versluis. 2001. Snapping shrimp make flashing bubbles . Nature 413: 477-478

Versluis, M., B. Schmitz, A. von der Heydt and D. Lohse. 2000. How snapping shrimp snap: through cavitating bubbles. Science 289: 2114-2117

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Feeling stressed? Try some aquarium therapy!

A large number of people come by the reef tank on a regular basis to view the fish, corals and variety of invertebrates. Personally I go out there and view the tank at least a couple of times each day. I have kept aquaria off and on since I was about 8 years old, and I credit my freshwater tank for getting me past math in high school. I remeber getting stuck on math problems. I would get up, sit in front of my tank for 15 minutes and then go back. More often than not, that was enough to clear my head and allow me to progress.

Have you noticed that you feel better and more relaxed after visiting the reef tank? Well, it may not be just your imagination. In fact, watching aquatic life has been scientifically studied and may in fact have a calming effect on many people. Aquarium-watching ranked among the 6 most relaxing things to do according to an article today in Huffington Post (http://www.huffingtonpost.com/2013/08/15/national-relaxation-day-stress-tips_n_3758071.html?utm_hp_ref=tw) in honour of national relaxation day (there’s a good idea, USA!). Albeit non-significant at α=0.05, there was a trend (P=0.08) towards less pre-treatment stress in electroconvulsive therapy (ECT) patients  http://dx.doi.org/10.2752/089279303786992071. It should be noted that ECT is what you and I know as electroshock, so it is perhaps no wonder that it is hard to achieve anything highly significant in terms of stress reduction.

Either way, if you feel stressed, why not pop by the UNBC reef tank to have a look. What do you have to lose?

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Damsels by name – terrors by game.

In my last blog I wrote about clown fish, the lovable Nemo in most children’s mind. Clown or anemone fish belong to a large family of fish called the Pomacentridae, the damselfish. While I promised to write about symbioses, in this blog I will cover the other members of this family that inhabit the UNBC reef tank. Damselfish are relatively small, with the largest species reaching just over 35 cm in length. Many of them have stunning colours, while others may be relatively plain. A genus familiar to most people who have visited a tropical reef for some snorkeling is the sergeant majors, adorned with the delightful Latin genus name Abudefdaf . What damselfish lack in size, they often make up for in temperament becoming of much larger fish, however. One of the most commonly kept damsels, Chrysiptera cyanea, bears the telling common name “blue devil”, for example, even though it isn’t necessarily the worst offender. Even the most timid species generally come with a warning that they can take over and terrorize an aquarium.
The UNBC reef tank is home to two types of damselfish,neither of which fall in the terror category. One is the so called green chromis, Chromis viridis. The green (or blue green) chromis is relatively plain as damselfish go, but in certain light it displays a gorgeous blue-green sheen that gives the species its name. The colour is apparently produced by the

Green chromis, Chromis viridis

presence of chromatophores, allowing some colour change (Fujii et al. 1989). This species is as close to a schooling fish that you can come, and it is also readily available in the pet trade, relatively peaceful, completely reef safe (i.e., they do not feed on coral polyps) active and hardy, and therefore one of the most popular fish to keep.. The oldest member in UNBC reef tank is approximately 12 years old. The other two were added about 8 years ago, and it is only due to the size of the tank that they are still with us. Even the peaceful green chromis does not take kindly to newcomers in their territory it turns out. I added them because someone had traded them in to the LFS (=live fish store), they needed a new home, and the UNBC tank could use a few more. The minute the newcomers were released into the tank, however, the residents turned from peaceful bystanders to vicious bullies, attacking the new fish mercilessly. This went on for hours, but fortunately the victims managed to hide in the rock crevices and hence get some relief from their pursuers. Eventually they were accepted, and now live with the remaining elder. In agonistic encounters, green chromis apparently produce sounds (Amorim 1996), like many other fish so this may have been a noisy time in the tank! The lesson learned is that it is a bad idea to add fish of a species, or even one similar in appearance, to a tank with established residents of that or similar species.
The other species of damselfish is a relative newcomer to the UNBC reef tank. It is the yellowtail damselfish, Chrysiptera parasema. Considered one of the less aggressive damselfish, this species can still take over a tank under the right circumstances. In nature it lives in small groups over branching coral in protected waters, and you can see the natural behavior of hanging out above the coral, only to dive in among the coral branches and rocks when danger is perceived.

Yellowtail damselfish, Chrysiptera parasema

The yellowtail damsel is a jewel of a fish, with iridescent dark blue patterns over its blue body, and a yellow tail fin that gives it its common name. It is very hardy, and is sometimes used to help cycle a newly established tank. This is a practice that I (and most responsible reef tank keepers I should think) discourage, as it is cruel to subject fish to the often very high nitrate levels that build up before the microbial fauna has established itself in a new tank, even if the fish are capable of tolerating it and may survive. All it takes to cycle a tank properly is some patience. Nevertheless, both of these damselfish are quite hardy, so they are considered among the most suitable species for beginner reef tank enthusiasts. It helps that they are relatively inexpensive, fetching $4-8 depending on the retailer, and they accept most foods. In the wild, they forage on algae, thereby performing a valuable service on the coral reef, but they can occasionally nip coral polyps, and are therefore not completely reef safe. Different individuals may vary in their propensity to damage corals. Interestingly, some species of damselfish actively cultivate their preferred food source (Hata and Kato 2006) by defending a patch and pruning out unpalatable algae! The yellowtail damsel has interesting reproductive behavior, where males prepare a spawning nest where a female will lay eggs. The male will then aerate the eggs, and he aggressively defends the nest until the eggs hatch.
References
Amorim, M.C.P.D. (1996). Sound production in the blue-green damselfish, Chromis viridis (Cuvier, 1830) (Pomacentridae). Bioacoustics 6: 265–272.
Fujii, R., Kasukawa, H. and Miyaji, K. (1989). Mechanisms of skin coloration and its changes in the blue-green damselfish, Chromis viridis. Zool. Sci. 6: 477-486.
Hata H, and Kato M (2006). A novel obligate cultivation mutualism between damselfish and Polysiphonia algae. Biol Lett 2: 593–596.

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