Identical digeneans in coral reef fishes from French Polynesia and the Great Barrier Reef (Australia) demonstrated by morphology and molecules

Three coral reef fish species, Zanclus cornutus, Chaetodon vagabundus and Naso lituratus, were collected in French Polynesia and on the Great Barrier Reef, Queensland. These fish species were each infected by one morphologically similar digenean species in both localities; Schistorchis Zancli Hanson, 1953 was found in Zanclus cornutus. Preptetos laguncula Bray and Cribb, 1996 in Naso lituratus and Neohypocreadium dorsoporum Machida and Uchida, 1987 in Chaetodon vagabundus. In addition, on the Great Barrier Reef P. laguncula was also found in Naso unicornis and N. dorsoporum in Chaetodon ephippium and Chaetodon flavirostris. Morphometric differences between the species from the two sites were only slight. Sequences from the second internal transcribed spacer of the ribosomal DNA of each worm revealed total homology or negligible divergence between samples from hosts caught in French Polynesia and on the Great Barrier Reef. These results show that across more than 6000 km these digeneans are similar in morphology and genotype. Some species of fishes and molluscs a-re considered to have distributions that encompass the entire tropical Indo-West Pacific. These findings suggest that at least some of their parasites have similarly broad distributions. (C) 2001 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.

Gill pathology caused by infestations of adult and preadult Dissonus manteri Kabata (Copepoda : Dissonidae) on coral trout, Plectropomus leopardus (Lacepede), (Serranidae)

Adult and preadult Dissonus manteri attached to the gills of Plectropomus leopardus cause significant pathology in the form of large hyperplastic nodules on the afferent (leading), edges of gill filaments. Nodules result from the dual actions of parasite attachment and feeding. The host response is characterized by severe epithelial hyperplasia, supplemented by fibroplasia and inflammation. Parasites attach close to the gill arch near the base of filaments. They have little effect on gill vasculature as the maxillipeds penetrate the filament superficial to the efferent filament artery and do not interfere with the blood vessels of the secondary lamellae. Tissue proliferation is limited to the wide portion of filament 'edge' epithelium in the proximal third and also does not extend to the secondary lamellae. Nodules are most numerous towards the ends of hemibranchs and are generally absent from the central regions. Leading hemibranchs bear significantly more nodules than their trailing counterparts. Of the total number of nodules, 20.5% are located on the pseudobranchs. Distribution patterns are considered to be primarily the result of D. manteri avoiding strong water currents, although this cannot explain the difference between numbers on leading and trailing hemibranchs.

Latitudinal variability in symbiont specificity within the widespread scleractinian coral Plesiastrea versipora

We examined the genetic diversity of symbiotic dinoflagellates (Symbiodinium sp.) in the widespread hermatypic coral Plesiastrea versipora from tropical/subtropical (north-eastern Australia) and temperate waters (south-eastern Australia) using restriction fragment length polymorphisms of partial 18S ribosomal DNA (rDNA), together with sequence analysis of partial 28S rDNA. This study revealed that P. versipora associates with at least two distinct genotypes of symbiotic dinoflagellates and that the presence of these genotypes varies with latitude. P. versipora colonies from subtropical and tropical waters contained symbionts belonging to Symbiodinium clade C, while P. versipora colonies at high-latitude sites contained clade B. Variability within the two groups of symbionts (clades H and C) was minimal, suggesting possible host fidelity. The geographically distinct varieties of symbionts within the tissue of this hermatypic coral are likely to be associated with algal physiological differences, which in turn may relate to changing selective pressures as a function of latitude along the eastern Australian seaboard.

Genetic variability of the symbiotic dinoflagellates from the wide ranging coral species Seriatopora hystrix and Acropora longicyathus in the Indo-West Pacific

The scleractinian coral species, Seriatopora hystrix and Acropora longicyathus, are widely distributed throughout the latitudinal range of the tropical west Pacific. These 2 coral species live in a mutually beneficial relation with symbiotic dinoflagellates (zooxanthellae), which are passed to their progeny by vertical transmission (zooxanthellate eggs or larvae) and horizontal transmission (eggs or larvae that acquire symbionts from the environment), respectively. For S. hystrix, vertical transmission might create biogeographically isolated and genetically differentiated symbiont populations because the extent of its larval migration is known to be limited. On the other hand, horizontal transmission in corals such as A. longicyathus may result in genetically connected symbiont populations, especially if its zooxanthellae taxa are widely distributed. To examine these hypotheses, symbionts were collected from colonies of S. hystrix and A. longicyathus living in the Great Barrier Reef (Australia), South China Sea (Malaysia) and East China Sea (Ryukyus Archipelago, Japan), and were examined using restriction fragment length polymorphism and sequence analysis of large and small subunit rRNA genes. Phylogenetic analysis assigned the symbionts to 1 of 3 taxonomically distinct groups, known as clades. Symbionts from Australian and Japanese S. hystrix were placed in Clade C, and Malaysian S. hystrix symbionts in the newly described Clade D. Seven of 11 Australian and all Japanese and Malaysian colonies of A. longicyathus had symbiotic dinoflagellates that also grouped with Clade C, but symbionts from the remaining Australian colonies of A. longicyathus grouped with Clade A. Analysis of molecular variance of Clade C symbionts found significant genetic variation in 1 or more geographic groups (69.8%) and to a lesser extent among populations within geographic regions (13.6%). All populations of Clade C symbionts from S. hystrix were genetically differentiated according to geographic region. Although Clade C symbionts of A. longicyathus from Japan resolved into a distinct geographic group, those from Australia and Malaysia did not and were genetically connected. We propose that these patterns of genetic connectivity correlate with differences in the dispersal range of the coral or symbiont propagules and are associated with their respective modes of symbiont transmission.

Response of a scleractinian coral, Stylophora pistillata, to iron and nitrate enrichment

The purpose of this study was to determine whether the addition of iron alone or in combination with nitrate affects growth and photosynthesis of the scleractinian coral, Stylophora pistillata, and its symbiotic dinoflagellates. For this purpose, we used three series of two tanks for a 3-week enrichment with iron (Fe), nitrate (N) and nitrate + iron (NFe). Two other tanks were kept as a control (C). Stock solutions of FeCl3 and NaNO3 were diluted to final concentrations of 6 nM Fe and 2 muM N and continuously pumped from batch tanks into the experimental tanks with a peristaltic pump. Results obtained showed that iron addition induced a significant increase in the areal density of zooxanthellae (ANOVA, p = 0.0013; change from 6.3 +/- 0.7 x 10(5) in the control to 8.5 +/- 0.6 x 10(5) with iron). Maximal gross photosynthetic rates normalized per surface area also significantly increased following iron enrichment (ANOVA, p = 0.02; change from 1.23 +/- 0.08 for the control colonies to 1.81 +/- 0.24 mu mol O-2 cm(-2) h(-1) for the iron-enriched colonies). There was, however, no significant difference in the photosynthesis normalized on a per cell basis. Nitrate enrichment alone (2 muM) did not significantly change the zooxanthellae density or the rates of photosynthesis. Nutrient addition (both iron and nitrogen) increased the cell-specific density of the algae (CSD) compared to the control (G-test, p = 0.3 x 10(-9)), with an increase in the number of doublets and triplets. CSD was equal to 1.70 +/- 0.04 in the Fe-enriched colonies, 1.54 +/- 0.12 in the N- and NFe-enriched colonies and 1.37 +/- 0.02 in the control. Growth rates measured after 3 weeks in colonies enriched with Fe, N and NFe were 23%, 34% and 40% lower than those obtained in control colonies (ANOVA. p = 0.011). (C) 2001 Elsevier Science B.V. All rights reserved.

Diurnal changes in the photochemical efficiency of the symbiotic dinoflagellates (Dinophyceae) of corals: photoprotection, photoinactivation and the relationship to coral bleaching

The photochemical efficiency of symbiotic dinoflagellates within the tissues of two reef-building corals in response to normal and excess irradiance at wafer temperatures < 30 C were investigated using pulse amplitude modulated (PAM) chlorophyll fluorescence techniques, Dark-adapted F-v/F-m showed clear diurnal changes, decreasing to a low at solar noon and increasing in the afternoon. However, F-v/F-m also drifted downwards at night or in prolonged darkness, and increased rapidly during the early morning twilight. This parameter also increased when the oxygen concentration of the wafer holding the corals was increased. Such changes have not been described previously, and most probably reflect state transition's associated with PQ pool reduction via chlororespiration. These unusual characteristics may be a feature of an endosymbiotic environment, reflective of the well-documented night-time tissue hypoxia that occurs in corals. F-v/F-m decreased to 0.25 in response to full sunlight in shade-acclimated (shade) colonies of Stylophora pistillata, which is considerably lower than in light-acclimated (sun) colonies. In sun colonies, the reversible decrease in F-v/F-m was caused by a lowering of F-m and F-o suggesting photoprotection and no lasting damage. The decrease in F-v/F-m, however, was caused by a decrease in F-m and an increase in F-o in shade colonies suggesting photoinactivation and long-term cumulative photoinhibition. Shade colonies rapidly lost their symbiotic algae (bleached) during exposure to full sunlight. This study is consistent with the hypothesis that excess light leads to chronic damage of symbiotic dinoflagellates and their eventual removal from reef-building corals. It is significant that this can occur with high light conditions alone.

Cleaner fish Labroides dimidiatus reduce 'temporary" parasitic corallanid isopods on the coral reef fish Hemigymnus melapterus

To determine if cleaners affect 'temporary' parasitic corallanid isopods (Argathona macronema) on fish, we used caged fish Hemigymnus meldpterus (Labridae) on 5 patch reefs on Lizard Island, Great Barrier Reef, and removed all cleaner fish Labroides dimidiatus (Labridae) from 3 of the reefs, In a short-term experiment, fish were sampled after 12 or 24 h, at dawn and sunset respectively, and in a long-term experiment they were sampled after 12 d at sunset. Isopod prevalence, abundance and size were measured. In the short-term experiment, on reefs without cleaners the prevalence of A. macronema was higher after 24 h than after 12 h while on reefs with cleaners, prevalence was low at all times, Although the abundance of A, macronema did not vary after 12 and 24 h, when combined over the 24 h, the effect of cleaners was significant with only 2 % of all the A. macronema found on reefs with cleaners. Cleaners had no effect on the size frequency distribution of A. macronema in the short-term experiment, most likely because fish had so few isopods on reef with cleaners. In the longer-term experiment, the effects of cleaners on isopod prevalence and abundance were less clear. Their effect on isopod size was, however, significant with smaller parasites on reefs without cleaners. The reduction of isopod prevalence and abundance by cleaner fish over a period of hours may explain why these A, macronema are rare on wild fish. Our findings support the idea that cleaning is beneficial to clients and has important implications for the control of parasites of fish farmed in cages,

Petrology and geochemistry of the Bandas del Sur Formation, Las Canadas Edifice, Tenerife (Canary Islands)

The Bandas del Sur Formation preserves a Quaternary extra-caldera record of central phonolitic explosive volcanism of the Las Canadas volcano at Tenerife. Volcanic rocks are bimodal in composition, being predominantly phonolitic pyroclastic deposits, several eruptions of which resulted in summit caldera collapse, alkali basaltic lavas erupted from many fissures around the flanks. For the pyroclastic deposits, there is a broad range of pumice glass compositions from phonotephrite to phonolite. The phonolite pyroclastic deposits are also characterized by a diverse, 7-8-phase phenocryst assemblage (alkali feldspar + biotite + sodian diopside + titanomagnetite + ilmenite + nosean-hauyne + titanite + apatite) with alkali feldspar dominant, in contrast to interbedded phonolite lavas that typically have lower phenocryst contents and lack hydrous phases. Petrological and geochemical data are consistent with fractional crystallization (involving the observed phenocryst assemblages) as the dominant process in the development of phonolite magmas. New stratigraphically constrained data indicate that petrological and geochemical differences exist between pyroclastic deposits of the last two explosive cycles of phonolitic volcanism. Cycle 2 (0.85-0.57 Ma) pyroclastic fall deposits commonly show a cryptic compositional zonation indicating that several eruptions tapped chemically, and probably thermally stratified magma systems. Evidence for magma mixing is most widespread in the pyroclastic deposits of Cycle 3 (0.37-0.17 Ma), which includes the presence of reversely and normally zoned phenocrysts, quenched mafic glass blebs in pumice, banded pumice, and bimodal to polymodal phenocryst compositional populations. Syn-eruptive mixing events involved mostly phonolite and tephriphonolite magmas, whereas a pre-eruptive mixing event involving basaltic magma is recorded in several banded pumice-bearing ignimbrites of Cycle 3. The periodic addition and mixing of basaltic magma ultimately may have triggered several eruptions. Recharge and underplating by basaltic magma is interpreted to have elevated sulphur contents (occurring as an exsolved gas phase) in the capping phonolitic magma reservoir. This promoted nosean-hauyne crystallization over nepheline, elevated SO3 contents in apatite, and possibly resulted in large, climatologically important SO2 emissions.

Welding and rheomorphism of phonolitic fallout deposits from the Las Canadas caldera, Tenerife, Canary Islands

The Las Canadas caldera is a nested collapse caldera formed by the successive migration and collapse of shallow magmatic chambers. Among the pyroclastic products of this caldera are phonolitic fallout deposits that crop out in the caldera wall and on the extracaldera slopes. These deposits exhibit an uninterrupted facies gradation from nonwelded to lava-like and record continuous volcanic deposition. Densely welded and lava-like facies result from the extreme attenuation and complete homogenization of juvenile clasts that destroy original clast outlines and any evidence of fallout deposition. Agglutination contributes significantly to the final degree of flattening observed in the welded facies. After deposition, rheomorphic flowage occurs. Emplacement temperatures for one of the welding sequences are calculated from magmatic temperatures and a model of tephra cooling during fallout. Results are 486 degreesC for the nonwelded facies and 740 degreesC for the moderately welded facies. For the same welding sequence, a cooling time between 25 and 54 days is estimated from published experimental and computational data as the possible duration of welding and rheomorphism. Following deposition and agglutination, the lava-like pyroclastic facies had the rheological properties of viscous lavas and flowed down the outer slopes away from the caldera. Some lava-like masses detached from proximal areas to more distal regions. During deposition, the eruptive style evolved from Plinian fallout to fountain-fed spatter deposition. This evolution was accompanied by a decrease in explosive power and a lower height of the eruptive column, which produce higher emplacement temperatures and more effective heat retention of pyroclasts.

The influence of increased line-fishing mortality on the sex ratio and age of sex reversal of the venus tusk fish

The age of sex reversal of the venus tusk fish Choerodon venustus, caught by line fishing at various locations on the southern Great Barrier Reef, indicated that C. venustus is capable of modifying its life cycle in response to increased mortality. The evidence suggests Masthead Reef fish, which experience the highest mortality, underwent sex reversal at a smaller size and younger age than at the other sites. The largest female fish, sexually transitional fish and males were smaller at Masthead Reef than at the Swains Reefs or One Tree Reef at Masthead Reef. There was also considerable overlap in the size of males and females within the exploited populations indicating that sex reversal is not initiated at a particular length but may have a social cause. The sex ratio of fish was essentially the same for fish fully susceptible to line fishing in the Swains and Masthead samples. Circumstantial evidence suggested that the absence of large males in a population may initiate sex reversal, indicating the maintenance of a constant sex ratio may have a social basis. (C) 2002 The Fisheries Society of the British Isles.

The phylogeography and connectivity of the latitudinally widespread scleractinian coral Plesiastrea versipora in the Western Pacific

Whereas terrestrial animal populations might show genetic connectivity within a continent, marine species, such as hermatypic corals, may have connectivity stretching to all corners of the planet. We quantified the genetic variability within and among populations of the widespread scleractinian coral, Plesiastrea versipora along the eastern Australian seaboard (4145 km) and the Ryukyu Archipelago (Japan, 681 km) using sequences of internal transcribed spacers (ITS1-2) from ribosomal DNA. Geographic patterns in genetic variability were deduced from a nested clade analysis (NCA) performed on a parsimony network haplotype. This analysis allowed the establishment of geographical associations in the distribution of haplotypes within the network cladogram, therefore allowing us to deduce phylogeographical patterns based under models of restricted gene flow, fragmentation and range expansion. No significant structure was found among Ryukyu Archipelago populations. The lack of an association between the positions of haplotypes in the cladogram with geographical location of these populations may be accounted for by a high level of gene flow of P. versipora within this region, probably due to the strong Kuroshio Current. In contrast, strong geographical associations were apparent among populations of P. versipora along the south-east coast of Australia. This pattern of restricted genetic connectivity among populations of P. versipora on the eastern seaboard of Australia seems to be associated with the present surface ocean current (the East Australian Current) on this side of the south-western Pacific Ocean.

Malaria vectors on Buka and Bougainville islands, Papua New Guinea

Anophelines were sampled from 82 locations oil Buka and Bougainville islands in Papua New Guinea by larval collections, carbon dioxide-baited Mosquito traps, and human biting catches. Anopheles farauti s.s. was collected in larval Surveys but infrequently in mosquito traps on both islands; on Buka Island this species was readily collected in human biting catches. Anopheles faraunti 2 was commonly collected in larval surveys on both islands however. it was not collected in either mosquito traps or human biting catches. Anopheles punctulatus was found only on Buka Island, where it was commonly collected as larvae, but rarely in human biting catches and mosquito traps. Anopheles lungae was collected Lis larvae from only I site on Bougainville. Anopheles farauti s.s. led consistently throughout the night (1900-0600 h): small peaks at midnight and dawn were not statistically significant. Of 1,156 An. farauti s.s. specimens examined by enzyme-linked immunosorbent assay for malaria sporozoites. 20 were found to be positive: 12 were positive for Plasmodium falciparum and 8 were positive for P. vivax (247 variant = 5: 210 variant = 3). Anopheles farauti s.s. seems to be the major malaria vector on these islands, whereas An. punctulatus may play a minor role on Buka Island. Anophele farauti 2 is unlikely to be involved in malaria transmission on Buka or Bougainville islands.