1. Tried to get an ID of the bug. The number of researchers working in the field of tropical amphipods and copepods is about....one or two. I sent specimens to Dr. Ed Hendrycks in Canada and Dr. Sara LeCroy at USM. Neither were specialists in coral reef amphipods or copepods, and both sugggested I contact Jim Thomas at Nova. I also contacted Stephen Cairns at the Smithsonian who also suggested Jim Thomas. I was constantly attempting to contact Jim, with no response and getting pretty frustrated. As it turned out, his email server was rejecting my emails and I finally got in touch with him through Peter Glynn whom I am working on with another project (they were both advisors of the same grad student). So, Both Ed and Sara confirmed it was a copepod, and though I included the description of Tegastes acroporanus with the samples, Sara said the fifth maxillipeds were different, and that it was probably related to T. acroporanus and undescribed. This species is known only from the original description by the later Arthur Humes, who gave no notations about the ecology or biology, only the taxonomy and that it was a harpacticoid copepod associated with Acropora florida at Enewetak atoll. Most of Humes work also dealt with copepods that were elongate and dwelled in the coelenteron, and there is no mention of where on the coral this one was found, and no other records since then (paper published in 1981). Finally, I had Sara send the samples to Jim, and he was fascinated by the behavior. He also confirmed the ID as T. acroporanus despite Sara's mention of the maxilliped difference. So, based on the expertise of Jim Thomas, I will assume barring other examinations, that this is the proper ID of the copepod.
2. T. acroporanus is found to host on many species of Acropora, preferentially those with widely spaced corallites where they have room to move on the coenosarc. Species with large or "hairy" polyps - eg. A. millepora - seem to be quite resistant, although I have received two reports of them hosting on these types. I suspect that the coral consumes the bugs with nematocysts in these species before they can establish and colonize. I have no proof of this, but it seems plausible.
3. T. acroporanus appears to be an obligate symbiont of Acropora. I have removed copepods and offered them five other species of coral to host upon, including Pocillopora damicornis, Pocillopora verrucosa, Pavona cactus, Montipora digitata, and Montipora capricornis. They will not naturally move onto these corals, even when in small water volumes, or even when intentionally pushed onto the surface with a probe. In fact, they continue to swim about a glass dish until they die. Although I have not attempted any further surrogate hosts, there are no reports I am aware of that suggest they have been found on any genus other than Acropora.
4. T. acroporanus requires Acropora for its survival, thus its symbiosis appears to be parasitic as colonization of Acropora results in decreased growth, abnormal polyp extension, loss of color, and potentially death. Copepods placed into a shallow dish of seawater, loosely covered to prevent evaporation, die within 3-5 days in the absence of a host. Most are dead in three days, a few retain minimal swimming motion or slight twitching. All were dead at day 5 with no response. the ability of the copepod to recover from a "day 3" weakness if offered a host has not been examined.
5. T. acroporanus has a number of behavioral traits on its host coral. I have documented these through video microscopy. They are mostly stationary on an area of coral for periods of time where they appear to be digging into the coral tissue. At some points, they are almopst buried head first into the tissue like a tick but still actively digging. Upon moving the host, the majority use the hairs on their appendages to strongly latch onto pores and protrubances on the skeleton where they are very difficult to dislodge, even with suction or strong jets of water. A smaller number immediately bail off the coral and swim away...and they swim very quickly and well and they typically find another Acropora within seconds to minutes. They do not spend any time "hanging out" in the tank.
6. If a colonized Acropora has been weakened significantly and a healthy host is placed into a tank with the weakened host, the copepods will abandon the weaker host and move to the new host. This potentially allows recovery of the previous host, but I have not checked to ensure or record the time of recovery before recolonization, or if all copepods leave the weakened host - but I doubt there is 100% that abandon the original host. This trait, though, is a classic example of an effective parasite. However, there is also the possibility that in small volumes with large resources (such as aquariums), that all host may be simultaneously parasitized.
7. The use of Interceptor as a drug against T. acroporanus. This drug was used in multiple trials at a local coral farm (Reef Savers) heavily infested with the copepods. Despite the presence of many species of corals at the time, only Acropora were colonized. Interceptor was obtained from my local veterinarian for trials. A 90 gallon tank was used to treat the many infested Acroporids and smaller tanks used to determine dosages. Dosages were initially followed according to Dortonââ"šÂ¬Ã¢"žÂ¢s protocol. Three doses were used, and it was determined that all copepods were eliminated after two doses in about forty specimens of Acropora. Verification was obtained by careful examination of each specimen under a dissecting scope. Although some copepods remained attached to the coral, they were dead showing no signs of movement or life. Even so, they were difficult to remove from the coral, even with a pipette. Dosages were increased to 10X and 100X the recommended dosage, and corals were grossly unaffected. However, it should be noted that virtually all over associated organisms died, including barnacles, polychaete worms, amphipods, copepods, and associated crustacean fauna (coral crabs) at all dose levels. Therefore, I would suggest that Interceptor appeared to be very safe for corals, but not for other organisms in tanks that may be present at a high bioload and also make the suggestion that ââ"šÂ¬Ã…"œin tankââ"šÂ¬Ã‚ treatment can result in an unacceptably and potentially dangerous loss of infauna biomass. It is my feeling that corals should be removed from tanks and treated alone in a treatment tank, regardless of the potential inconvenience of removing large, attached and established acroporids. There has been no study of the effects of the drug on corals or on other organisms that do not die outright, and there may be significant impacts that are not grossly visible.
In a separate experiment, acroporids colonized by T. acroporanus treated with a 5x dose of Interceptor resulted in the death of the corals, nor resulted in the death of all copepods, but it is unknown if the drug or other factors caused the mortality. There were also tapered elongate flatworms present at the skeleton tissue interface unaffected by Interceptor that may have played a role in the continued tissue loss, but again this is an unknown flatworm and effect of these symbionts. In any event, a second trial seemed to be relatively ineffective in killing T. acroporanus.
These conflicting studies demand the establishment of an LD50 for both parasite and corals. This aspect is currently being studied in subsequent trials in the Barse lab, Unfortunately, the associated flatworms did not survive the transport, and efforts are currently underway to provide another sample of flatworms.
It should also be noted that Inteceptor dissolves poorly in seawater, and it I suggest that the drug be dissolved in the smallest possible amount of DMSO in which it and all the filler ingredients dissolve readily, allowing a more precise dosing concentration, and DMSO does not seem to negatively impact the results on coral or parasite
8. Other treatments:
a) Rid: an over-the counter medication to treat external skin lice, the drug was effective in removing copepods. There appears to be a surfactant present indicated by a foaming action upon application that may collapse respiratory structure of the copepod. The effect on corals was moderate, with heavily colonized corals showing the most severe effects with some corals lost during treatment, although a small number. Furthermore, this treatment may be effective using more carefully controlled dosages.
b) Lugolââ"šÂ¬Ã¢"žÂ¢s solution: We used two high dose Lugolââ"šÂ¬Ã¢"žÂ¢s dips as a method of dipping to kill copepods. Within about 30 seconds, most copepods had bailed off the corals, and fallen to the bottom of the treatment vessel, rapidly dying and turning black. Several corals maintained attached to the coral but were dead. The dose level was 5m/L and up to ten minutes was tolerated by even highly colonized corals, although the effect on the coral was seriously stressful, resulting in partial bleaching, abnormally increased mucus production, and in a few cases, death. The majority of corals survived and recovered within a week and without any copepods present. The duration of treatment varied from 3-10 minutes, and examination under a dissecting scope was done every minute to assess the status of the parasites. At 10ml/L, copepods died generally within 30 seconds, with some lasting up to 2 minutes. The effects on the corals were more pronounced and resulted in significant mortality, especially at durations from 2-5 minutes. This may be a good ââ"šÂ¬Ã…"œdipââ"šÂ¬Ã‚ method for minimally colonized corals that can tolerate the high dosage of Lugolââ"šÂ¬Ã¢"žÂ¢s solution.
c) Heartguard: another veterinarian medicine comprised of a different ingredient, In general, the drug did not have a significant effect on corals or T. acroporanus.
d) Freshwater dips: these are inherently stressful to the corals, and although most tegastids abandon the host, it is not particularly effective in killing the copepods.
e) Doramectin: a saline injectible and soluble solution that is as effective as Interceptor in its minimal effects on coral and maximal effect on parasites. It is available as primarily bovine injectable and is soluble in seawater and thus provides a more controlled dose, It is, however, effective in much the same way in Inteceptor with a similar mode of action, it is harder to acquire and is expensive.
