Live coral repels a common reef fish ectoparasite

Coral reefs are undergoing rapid changes as living corals give way to dead coral on which other benthic organisms grow. This decline in live coral could influence habitat availability for fish parasites with benthic life stages. Gnathiid isopod larvae live in the substratum and are common blood-feeding parasites of reef fishes. We examined substrate associations and preferences of a common Caribbean gnathiid, Gnathia marleyi. Emergence traps set over predominantly live coral substrata captured significantly fewer gnathiids than traps set over dead coral substrata. In laboratory experiments, gnathiids preferred dead coral and sponge and tended to avoid contact with live coral. When live gnathiids were added to containers with dead or live coral, significantly fewer were recovered from the latter after 24 h. Our data therefore suggest that live coral is not suitable microhabitat for parasitic gnathiid isopods and that a decrease in live coral cover increases available habitat for gnathiids.     

Fish mucous cocoons: the 'mosquito nets' of the sea

Mucus performs numerous protective functions in vertebrates, and in fishes may defend them against harmful organisms, although often the evidence is contradictory. The function of the mucous cocoons that many parrotfishes and wrasses sleep in, while long used as a classical example of antipredator behaviour, remains unresolved. Ectoparasitic gnathiid isopods (Gnathiidae), which feed on the blood of fish, are removed by cleaner fish during the day; however, it is unclear how parrotfish and wrasse avoid gnathiid attacks at night. To test the novel hypothesis that mucous cocoons protect against gnathiids, we exposed the coral reef parrotfish Chlorurus sordidus (Scaridae) with and without cocoons to gnathiids overnight and measured the energetic content of cocoons. Fish without mucous cocoons were attacked more by gnathiids than fish with cocoons. The energetic content of mucous cocoons was estimated as 2.5 per cent of the fish's daily energy budget fish. Therefore, mucous cocoons protected against attacks by gnathiids, acting like mosquito nets in humans, a function of cocoons and an efficient physiological adaptation for preventing parasite infestation that is not used by any other animal.     

Hematozoa of teleosts from Lizard Island, Australia, with some comments on their possible mode of transmission and the description of a new hemogregarine species

Little is known of the blood parasites of coral reef fishes and nothing of how they are transmitted. We examined 497 fishes from 22 families, 47 genera, and 78 species captured at Lizard Island, Australia, between May 1997 and April 2003 for hematozoa and ectoparasites. We also investigated whether gnathiid isopods might serve as potential vectors of fish hemogregarines. Fifty-eight of 124 fishes caught in March 2002 had larval gnathiid isopods, up to 80 per host fish, and these were identified experimentally to be of 2 types, Gnathia sp. A and Gnathia sp. B. Caligid copepods were also recorded but no leeches. Hematozoa, found in 68 teleosts, were broadly hemogregarines of 4 types and an infection resembling Haemohormidium. Mixed infections (hemogregarine with Haemohormidium) were also observed, but no trypanosomes were detected in blood films. The hemogregarines were identified as Haemogregarina balistapi n. sp., Haemogregarina tetraodontis, possibly Haemogregarina bigemina, and an intraleukocytic hemogregarine of uncertain status. Laboratory-reared Gnathia sp. A larvae, fed experimentally on brushtail tangs, the latter heavily infected with the H. bigemina-like hemogregarine, contained hemogregarine gamonts and possibly young oocysts up to 3 days postfeeding, but no firm evidence that gnathiids transmit hemogregarines at Lizard Island was obtained.     

Parasite-mediated enemy release and low biotic resistance may facilitate invasion of Atlantic coral reefs by Pacific red lionfish (<Emphasis Type="Italic">Pterois volitans</Emphasis>)

Successful invasions are largely explained by some combination of enemy release, where the invader escapes its natural enemies from its native range, and low biotic resistance, where native species in the introduced range fail to control the invader. We examined the extent to which parasites may mediate both release and resistance in the introduction of Pacific red lionfish (Pterois volitans) to Atlantic coral reefs. We found that fewer lionfish were parasitized at two regions in their introduced Atlantic range (The Bahamas and the Cayman Islands) than at two regions in their native Pacific range (the Northern Marianas Islands and the Philippines). This pattern was largely driven by relatively high infection rates of lionfish by didymozoan fluke worms and parasitic copepods (which may be host-specific to Pterois lionfishes) in the Marianas and the Philippines, respectively. When compared with sympatric, native fishes in the Atlantic, invasive lionfish were at least 18 times less likely to host a parasite in The Bahamas and at least 40 times less likely to host a parasite in the Cayman Islands. We found no indication that lionfish introduced Pacific parasites into the Atlantic. In conjunction with demographic signs of enemy release such as increased density, fish size, and growth of invasive lionfish, it is possible that escape from parasites may have contributed to the success of lionfish. This is especially true if future studies reveal that such a loss of parasites has led to more energy available for lionfish growth, reproduction, and/or immunity.     

Impact of micropredatory gnathiid isopods on young coral reef fishes

The ecological role of parasites in the early life-history stages of coral reef fish, and whether this varies between fish with and without a pelagic phase, was investigated. The susceptibility to, and effect of reef-based micropredatory gnathiid isopods on larval, recently settled, and juvenile fishes was tested using two damselfishes (Pomacentridae): Neopomacentrus azysron, which has pelagic larvae, and Acanthochromis polyacanthus, which does not. When larval and recently settled stages of N. azysron and very young A. polyacanthus juveniles (smaller than larval N. azysron) were exposed to one or three gnathiids, the proportion of infections did not vary significantly among the three host types or between the number of gnathiids to which the fish were exposed. The overall infection was 35%. Mortality, however, differed among the three gnathiid-exposed host types with most deaths occurring in larval N. azysron; no mortalities occurred for recently settled N. azysron exposed to one or three gnathiids, and A. polyacanthus exposed to one gnathiid. Mortality did not differ significantly between larval N. azysron and A. polyacanthus juveniles, failing to provide support for the hypothesis that reef-based A. polyacanthus juveniles are better adapted to gnathiid attack than fish with a pelagic phase. The study suggests that settling on the reef exposes young fish to potentially deadly micropredators. This supports the idea that the pelagic phase may allow young fish to avoid reef-based parasites.     

A simple molecular technique for identifying marine host fish by sequencing blood-feeding parasites

Gnathiid isopods are common ectoparasites of fish on the Great Barrier Reef, Australia. While screening for appropriate markers for phylogenetic studies of gnathiids, we found that primers for 12S and 16S rDNA preferentially amplified the host fish DNA instead of gnathiid DNA. This amplification occurred even when using gnathiids that were not engorged with host blood and adult gnathiids that do not feed on fish blood. This method could be used in host-parasite studies to identify hosts without having to sample parasites directly from the host (which can be costly and requires considerable skill in a marine environment). Target ribosomal DNA sequences can be amplified from total DNA extracted from parasites that are captured in funnel traps or plankton tows. Sequence data from these can be used to identify the hosts that gnathiids were feeding on before capture.     

Predation on parasitic gnathiid isopods on coral reefs: a comparison of Caribbean cleaning gobies with non-cleaning microcarnivores

Coral Reefs - On coral reefs, gnathiid isopods are a common blood-feeding ectoparasite of reef fishes that can have significant impacts on reef-fish health and fitness. Cleaner fishes and shrimps...     

Indo-Pacific lionfish are larger and more abundant on invaded reefs: a comparison of Kenyan and Bahamian lionfish populations

The invasion by Indo-Pacific lionfish (Pterois volitans and P. miles) of the western Atlantic, Caribbean and Gulf of Mexico is emerging as a major threat to coral reef communities across the region. Comparing native and introduced populations of invasive species can reveal shifts in ecology and behaviour that can accompany successful invasions. Using standardized field surveys replicated at multiple sites in Kenya and the Bahamas, we present the first direct comparisons of lionfish density, body size, biomass and behaviour between native and invaded coral reefs. We found that lionfish occur at higher densities with larger body sizes and total biomass on invaded Bahamian coral reefs than the ecologically equivalent species (P. miles) does on native Kenyan reefs. However, the combined average density of the five lionfish species (Pterois miles, P. antennata, P. radiata, Dendrochirus brachypterus and D. zebra) on Kenyan reefs was similar to the density of invasive lionfish in the Bahamas. Understanding the ecological processes that drive these differences can help inform the management and control of invasive lionfish.     

Habitat-related differences in the abundance of parasites from a coral reef fish: an indication of the movement patterns of Hemigymnus melapterus

The prevalence and number of an undescribed Benedenia sp. on Hemigymnus melapterus were significantly greater on fish from the reef flat than from the slope at Heron Island, Great Barrier Reef. In contrast, the abundance of gnathiid isopods on the fish did not differ significantly between habitats. As monogeneans do not leave their hosts, the differences in parasite abundance between the habitats suggest that H. melapterus does not move between the reef flat and reef slope, habitats separated by only a few hundreds of metres. Benedenia may thus be a useful biological tag for following the small-scale movement patterns of coral reef fish.     

Host preference and specialization in Gnathia sp., a common parasitic isopod of coral reef fishes

A gnathiid species (Crustacea: Isopoda; one of the most common ectoparasites of coral reef fishes) from the Great Barrier Reef, Australia, was allowed to choose among fishes from three different families to feed on (using two species of fishes per family). Gnathiids showed a strong preference for labrids, rarely feeding on pomacentrids or apogonids. In a separate experiment, gnathiid host preference did not vary among three labrid fish species. Gnathiids that fed on labrids had higher survival than those that fed on apogonids. Male gnathiids that fed on labrids also moulted to the adult stage more quickly. This suggests that host specialization and local adaptation might be occurring between these ectoparasites and their host fishes at the host fish family level.     

Habitat degradation drives increased gnathiid isopod ectoparasite infection rate on juvenile but not adult fish

Widespread coral mortality is leading to coral reef degradation worldwide. Many juvenile reef fishes settle on live coral, and their predator-avoidance behaviour is disrupted in seawater exposed to dead corals, ultimately increasing predation risk. Gnathiid isopods are micropredatory fish ectoparasites that occur in higher abundances in dead coral. However, the effect of seawater associated with dead coral on the susceptibility of fish to micropredators has never been investigated. We tested whether the infection rate of cultured gnathiid ectoparasites on individual damselfish, Pomacentrus amboinensis Bleeker 1868, from two different ontogenetic stages (juveniles and adults) was influenced by seawater exposed to three different treatments: dead coral, live coral, or no coral. Seawater treatments were presumed to contain different chemical properties and are meant to represent environmental changes associated with habitat degradation on coral reefs. Gnathiid infection of juvenile fish in seawater exposed to dead coral was twice as high as that of fish in live coral or no coral. Infection rates did not significantly differ between live coral and no coral treatments. In contrast to juveniles, the susceptibility of adults to gnathiids was not affected by seawater treatment. During experiments, juvenile fish mortality was relatively low, but was higher for infected fish (9.7%), compared to fish held without exposure to gnathiids (1.7%). No mortality occurred in adult fish that became infected with gnathiids. Our results suggest that chemical cues released from dead corals and/or dead coral colonisers affect the ability of juvenile, but not adult fish to avoid parasite infection. Considering increased habitat degradation on coral reefs and that gnathiids are more abundant in dead coral substrate, it is possible that wild juvenile fish may experience increased susceptibility to parasitic infection and reduced survival rate. This highlights the importance of including parasitism in ecological studies of global environmental change.

     

Invasive lionfish harbor a different external bacterial community than native Bahamian fishes

The introduction and subsequent spread of lionfish into the Atlantic Ocean and Caribbean Sea has become a worldwide conservation issue. These highly successful invaders may also be capable of introducing non-native microorganisms to the invaded regions. This study compared the bacterial communities associated with lionfish external tissue to those of native Bahamian fishes and ambient water. Terminal restriction fragment length polymorphism analyses demonstrated that lionfish bacterial communities were significantly different than those associated with three native Bahamian fishes. Additionally, all fishes harbored distinct bacterial communities from the ambient bacterioplankton. Analysis of bacterial clone libraries from invasive lionfish and native squirrelfish indicated that lionfish communities were more diverse than those associated with squirrelfish, yet did not contain known fish pathogens. Using microscopy and molecular genetic approaches, lionfish eggs were examined for the presence of bacteria to evaluate the capacity for vertical transmission. Eggs removed from the ovaries of gravid females were free of bacteria, suggesting that lionfish likely acquire bacteria from the environment. This study was the first examination of bacterial communities associated with the invasive lionfish and indicated that they support different communities of environmentally derived bacteria than Caribbean reef fishes.     

Regional Variation in Parasite Species Richness and Abundance in the Introduced Range of the Invasive Lionfish,Pterois volitans

Parasites can play an important role in biological invasions. While introduced species often lose parasites from their native range, they can also accumulate novel parasites in their new range. The accumulation of parasites by introduced species likely varies spatially, and more parasites may shift to new hosts where parasite diversity is high. Considering that parasitism and disease are generally more prevalent at lower latitudes, the accumulation of parasites by introduced hosts may be greater in tropical regions. The Indo-Pacific lionfish (Pterois volitans) has become widely distributed across the Western Atlantic. In this study, we compared parasitism across thirteen locations in four regions, spanning seventeen degrees of latitude in the lionfish''s introduced range to examine potential spatial variation in parasitism. In addition, as an initial step to explore how indirect effects of parasitism might influence interactions between lionfish and ecologically similar native hosts, we also compared parasitism in lionfish and two co-occurring native fish species, the graysby grouper, Cephalopholis cruentata, and the lizardfish, Synodus intermedius, in the southernmost region, Panama. Our results show that accumulation of native parasites on lionfish varies across broad spatial scales, and that colonization by ectoparasites was highest in Panama, relative to the other study sites. Endoparasite richness and abundance, on the other hand, were highest in Belize where lionfish were infected by twice as many endoparasite species as lionfish in other regions. The prevalence of all but two parasite species infecting lionfish was below 25%, and we did not detect an association between parasite abundance and host condition, suggesting a limited direct effect of parasites on lionfish, even where parasitism was highest. Further, parasite species richness and abundance were significantly higher in both native fishes compared to lionfish, and parasite abundance was negatively associated with the condition index of the native grouper but not that of the lionfish or lizardfish. While two co-occurring native fishes were more heavily parasitized compared to lionfish in Panama any indirect benefits of differential parasitism requires further investigation. Future parasitological surveys of lionfish across the eastern coast of North America and the Lesser Antilles would further resolve geographic patterns of parasitism in invasive lionfish.     

In situ evidence for ectoparasites as a proximate cause of cleaning interactions in reef fish

Although cleaning interactions are deemed a textbook example of mutualism, there is limited evidence that clients benefit from cleaning in terms of reduced ectoparasite loads. The proximate causes of cleaning behaviour are also contentious. We examined the effect of ectoparasite load (i.e. the number of larval gnathiid isopods) on client behaviour under natural conditions. Diel variation in gnathiid loads of longfin damselfish, Stegastes diencaeus, a common coral reef fish client of cleaning gobies (Elacatinus spp.), was correlated with variation in gnathiid emergence from the substratum at sites in both Puerto Rico and St John, northeastern Caribbean. Both benthic emergence of gnathiids and their infestation on damselfish peaked in the morning. Concomitantly, clients spent significantly more time posing for and being inspected by cleaners in the morning than at other times of day. Our results corroborate recent experimental results on captive clients and are consistent with the mutualistic interpretation of cleaning symbioses.     

Invasive lionfish drive Atlantic coral reef fish declines

Indo-Pacific lionfish (Pterois volitans and P. miles) have spread swiftly across the Western Atlantic, producing a marine predator invasion of unparalleled speed and magnitude. There is growing concern that lionfish will affect the structure and function of invaded marine ecosystems, however detrimental impacts on natural communities have yet to be measured. Here we document the response of native fish communities to predation by lionfish populations on nine coral reefs off New Providence Island, Bahamas. We assessed lionfish diet through stomach contents analysis, and quantified changes in fish biomass through visual surveys of lionfish and native fishes at the sites over time. Lionfish abundance increased rapidly between 2004 and 2010, by which time lionfish comprised nearly 40% of the total predator biomass in the system. The increase in lionfish abundance coincided with a 65% decline in the biomass of the lionfish's 42 Atlantic prey fishes in just two years. Without prompt action to control increasing lionfish populations, similar effects across the region may have long-term negative implications for the structure of Atlantic marine communities, as well as the societies and economies that depend on them.     

Effects of invasive Pacific red lionfish Pterois volitans versus a native predator on Bahamian coral-reef fish communities

The recent irruption of Pacific red lionfish (Pterois volitans) on Caribbean and Atlantic coral reefs could prove to be one of the most damaging marine invasions to date. Invasive lionfish are reaching densities much higher than those reported from their native range, and they have a strong negative effect on the recruitment and abundance of a broad diversity of native coral-reef fishes. Otherwise, little is known about how lionfish affect native coral-reef communities, especially compared to ecologically similar native predators. A controlled field experiment conducted on small patch-reefs in the Bahamas over an 8-week-period demonstrated that (1) lionfish caused a reduction in the abundance of small native coral-reef fishes that was 2.5?±?0.5 times (mean?±?SEM) greater than that caused by a similarly sized native piscivore, the coney grouper Cephalopholis fulva (93.7 vs. 36.3?% reduction); (2) lionfish caused a reduction in the species richness of small coral-reef fishes (loss of 4.6?±?1.6 species), whereas the native piscivore did not have a significant effect on prey richness; (3) the greatest effects on the reef-fish community, in terms of both abundance and richness, occurred when both native and invasive predators were present; and (4) lionfish grew significantly faster (>6 times) than the native predator under the same field conditions. These results suggest that invasive lionfish have stronger ecological effects than similarly sized native piscivores, and may pose a substantial threat to native coral-reef fish communities.     

Grouper as a natural biocontrol of invasive lionfish

Lionfish (Pterois volitans/miles) have invaded the majority of the Caribbean region within five years. As voracious predators of native fishes with a broad habitat distribution, lionfish are poised to cause an unprecedented disruption to coral reef diversity and function. Controls of lionfish densities within its native range are poorly understood, but they have been recorded in the stomachs of large-bodied Caribbean groupers. Whether grouper predation of lionfish is sufficient to act as a biocontrol of the invasive species is unknown, but pest biocontrol by predatory fishes has been reported in other ecosystems. Groupers were surveyed along a chain of Bahamian reefs, including one of the region's most successful marine reserves which supports the top one percentile of Caribbean grouper biomass. Lionfish biomass exhibited a 7-fold and non-linear reduction in relation to the biomass of grouper. While Caribbean grouper appear to be a biocontrol of invasive lionfish, the overexploitation of their populations by fishers, means that their median biomass on Caribbean reefs is an order of magnitude less than in our study. Thus, chronic overfishing will probably prevent natural biocontrol of lionfishes in the Caribbean.     

Estimates of species diversity of free-living marine isopod crustaceans on coral reefs

 A core group of isopod crustacean genera appears to be present at many coral reef sites. Within these genera, however, species show high local endemicity. Based on the estimated percentage of endemism for the Atlantic (19% for individual sites, 90% for the tropical western Atlantic as a unit), the Indian Ocean (50%), the eastern-central Pacific (80%), and the western Pacific (40%), it is estimated that there are some 5,000 to 13,000 isopod species in the world’s coral reefs, and that some 2,000 to 6,000 of these are endemics. (At present, approximately 4,400 species of marine and 560 species of freshwater isopods have been described.) Based on the crudely estimated relative abundances of other peracaridan crustaceans in coral reefs (compared to isopods), the total diversity of reef amphipods, tanaidaceans, cumaceans, and mysidaceans is approximately 54,500 species. Accepted: 29 August 1997     

Do early life history characteristics determine species ranges and dispersal of coral reef fishes in the Indo‐Pacific?

The Indo‐Pacific consists of extensive continuous coastlines and many island groups of varying sizes and isolation. The species ranges of coral reef fishes vary enormously from Indo‐Pacific wide to highly endemic. There is also great variation in the early life history characteristics of coral reef fishes ( e.g . pelagic larval durations, spawning strategies and swimming abilities). We use individual‐based models (IBMs) to simulate the dispersal of coral reef fishes in the Indo‐Pacific. The development of dispersal strategies is explored based on ecological and geographical constraints. Simulations are presented for climatic and anthropogenically‐induced events.     

An annotated list of fish parasites (Isopoda, Copepoda, Monogenea, Digenea, Cestoda, Nematoda) collected from Snappers and Bream (Lutjanidae, Nemipteridae, Caesionidae) in New Caledonia confirms high parasite biodiversity on coral reef fish

ABSTRACT: BACKGROUND: Coral reefs are areas of maximum biodiversity, but the parasites of coral reef fishes, and especially their species richness, are not well known. Over an 8-year period, parasites were collected from 24 species of Lutjanidae, Nemipteridae and Caesionidae off New Caledonia, South Pacific. RESULTS: Host-parasite and parasite-host lists are provided, with a total of 207 host-parasite combinations and 58 parasite species identified at the species level, with 27 new host records. Results are presented for isopods, copepods, monogeneans, digeneans, cestodes and nematodes. When results are restricted to well-sampled reef fish species (sample size[THIN SPACE]>[THIN SPACE]30), the number of host-parasite combinations is 20[EN DASH]25 per fish species, and the number of parasites identified at the species level is 9[EN DASH]13 per fish species. Lutjanids include reef-associated fish and deeper sea fish from the outer slopes of the coral reef: fish from both milieus were compared. Surprisingly, parasite biodiversity was higher in deeper sea fish than in reef fish (host-parasite combinations: 12.50 vs 10.13, number of species per fish 3.75 vs 3.00); however, we identified four biases which diminish the validity of this comparison. Finally, these results and previously published results allow us to propose a generalization of parasite biodiversity for four major families of reef-associated fishes (Lutjanidae, Nemipteridae, Serranidae and Lethrinidae): well-sampled fish have a mean of 20 host-parasite combinations per fish species, and the number of parasites identified at the species level is 10 per fish species. CONCLUSIONS: Since all precautions have been taken to minimize taxon numbers, it is safe to affirm than the number of fish parasites is at least ten times the number of fish species in coral reefs, for species of similar size or larger than the species in the four families studied; this is a major improvement to our estimate of biodiversity in coral reefs. Our results suggest that extinction of a coral reef fish species would eventually result in the coextinction of at least ten species of parasites.