Zoogeography of marine parasites

Latitudinal gradients in species numbers of marine parasites, differences between the Atlantic and Indo-Pacific Oceans, latitudinal gradients in frequency and intensity of infection, in host range and specificity, and in fluctuations of infection are discussed, as well as differences between shallow and deep water, parasite endemicity at remote oceanic islands, and importance of temperature for parasite distribution. Examples are given to demonstrate the usefulness of marine parasites as biological tags and as indicators of the geographical origin of hosts.     

Ecology of tropical marine fungi

Lignicolous material was collected from 5 marine locations in Brunei: a rocky headland, a sandy beach, a man-made brackish lake, a healthy mangrove and an oil polluted mangrove. Higher marine fungi present were identified and their percentage occurrence noted. The common marine fungi varied from habitat to habitat. Antennospora quadricornuta was most common at the rocky headland, Corollospora pulchella at the sandy beach and Halosarpheia marina at the brackish lake. In the mangroves the most common species were Halocyphina villosa (healthy) and Cirrenalia pygmea and Lulworthia grandispora (oil polluted). Differences in species composition from one habitat to the next were observed, although some fungi occurred throughout. There were significantly less diversity and numbers of fungi in the oil polluted mangrove when compared to the healthy mangrove. Observations concerning the ecology of tropical marine fungi are made.     

Increased viviparity of marine parasites at high latitudes

For the first time, Thorson's rule, that non-pelagic development increases with latitude, is shown to apply to a group of marine parasites. Relative and absolute numbers of species of viviparous Monogenea, gill parasites of fish, increase with increasing latitude. The gradient can be explained by the inability, in cold waters, of (a) free larvae to locate suitable habitats (hosts) and/ or (b) small invertebrates to produce pelagic larvae in sufficient numbers. Viviparous Monogenea are also more common in cold than in warm freshwater, but have not been fund in the deep sea.     

Ecology of hatching size for marine snails

Summary Chances for survival increase as a snail grows, and the resulting size-specific survival curve dictates hatching size. Related species tend to hatch at the same size, reflecting similarities in ecological roles. Hatching size depends upon macrohabitat and microhabitat among the Muricidae. Thais emarginata hatches large enough to escape from a major predator (the hermit crab) of newly hatched T. lamellosa. However, Thais hatching sizes reflect a general trend for upper shore muricids to hatch larger than lower shore ones, rather than a response to predators. A given volume of yolk will yield the same volume of hatchlings (regardless of hatching type or number of hatchlings) for all prosobranchs, including those whose embryos feed on nurse eggs. Therefore, no hatchlings are inflated more than others to make them less attractive to predators.     

Ecology of antarctic marine sponges: an overview

Sponges are important components of marine benthic communitiesof Antarctica. Numbers of species are high, within the lowerrange for tropical latitudes, similar to those in the Arctic,and comparable or higher than those of temperate marine environments.Many have circumpolar distributions and in some habitats hexactinellidsdominate benthic biomass. Antarctic sponge assemblages contributeconsiderable structural heterogeneity for colonizing epibionts.They also represent a significant source of nutrients to prospectivepredators, including a suite of spongivorous sea stars whoseselective foraging behaviors have important ramifications uponcommunity structure. The highly seasonal plankton blooms thattypify the Antarctic continental shelf are paradoxical whenconsidering the planktivorous diets of sponges. Throughout muchof the year Antarctic sponges must either exploit alternatesources of nutrition such as dissolved organic carbon or bephysiologically adapted to withstand resource constraints. Incontrast to predictions that global patterns of predation shouldselect for an inverse correlation between latitude and chemicaldefenses in marine sponges, such defenses are not uncommon inAntarctic sponges. Some species sequester their defensive metabolitesin the outermost layers where they are optimally effective againstsea star predation. Secondary metabolites have also been shownto short-circuit molting in sponge-feeding amphipods and preventfouling by diatoms. Coloration in Antarctic sponges may be theresult of relict pigments originally selected for aposematismor UV screens yet conserved because of their defensive properties.This hypothesis is supported by the bioactive properties ofpigments examined to date in a suite of common Antarctic sponges.     

Ecology of type II secretion in marine gammaproteobacteria

Compelling findings on the direct association of the type II secretion (T2S) system with different ecological functions in marine bacteria have challenged the traditional view of the T2S pathway, the function of which has been mostly studied in pathogenic bacteria. The availability of a number of whole-genome sequence data sets enabled the analysis of the genetic composition of the T2S system across a number of Vibrios and Alteromonads. The widespread Gammaproteobacteria , in particular the Alteromonadales and the Vibrionales group, are recognized to play significant roles in the cycling of nutrients in coastal and pelagic marine ecosystems and are also found associated with marine eukaryotes. The combined analysis of the role and the genetic composition of the T2S system in Gammaproteobacteria provides important evidence for the significance of the T2S pathway in the ecology of environmental bacteria.     

Influences of parasites and thermoregulation on grouping tendencies in marine iguanas

I determined whether grouping behavior influences parasite loadand bodytemperature of Galápagos marine iguanas,reptilesthat rest gregariously. Mobile (or predatory) Ornithodorosticks(4.7 mm average body length) approached at a ground speed of65 cm/minand parasitized sleeping marine iguanas for 3.7 hper night, drawing about 0.1ml blood. Contagiously transmittedAmblyomma ticks hang on to iguanahosts for days or weeks. Marineiguanas sleeping alone had 2.0 mobile ticksper night, whileindividuals sleeping in groups had 0.1 to 1.1 mobile tickspernight. Single iguanas decreased their mobile parasite load to0.2 ticksper night by sleeping on bushes. Experimental nightlytranslocation of iguanasto areas without other sleeping iguanassignificantly increased their mobileparasite burden above levelsencountered by naturally single individuals(n = 4.6 ticks pernight). Creating an experimental group of twoanimals reducedinfestation with mobile ticks by 59% compared to levelson singleanimals. Over the course of weeks, mobile ectoparasite loadsatgrouping sites increased to levels found at single sites,at which pointmarine iguanas changed sleeping sites. Groupinghad no effect on theprevalence of contagious ticks. Furthermore,grouping did not help to conservebody temperature in Genovesaiguanas, as measured by radiotelemetry. Iconclude that marineiguanas group during daytime at microhabitats favored forthermoregulation(predation is absent in this population). Thermoregulationwasnot of prime importance for nightly aggregations, which insteadserved toreduce mobile ectoparasite load. As a minimum costof infestation, I estimatethat individuals sleeping alone wouldhave a 5.4% lower annual energybudget due to tissue removal,not including potential internal infections.     

Ecology of the parasites of a predatory bug, Blepharidopterus angulatus (Fall.)

Abstract. 1. On lime, Blepharidopterus angulatus is parasitized by a braconid, Peristenus sp., which is attacked by an ichneumonid hyperparasite, Mesochorus sp. The emergence and oviposition behaviour of the adult parasites and the growth of the larvae are described.
2. Parasitized B. angulatus are considerably heavier at maturity than normal, and nymphs parasitized by Peristenus consume, during their fifth instar, 2.1 times more in dry weight of prey (lime aphids). The growth efficiency of Peristenus is 30–37%.
3. An inverse relationship between percentage parasitism and host density on different trees may have been due to differences in synchronization.     

A bibliography of parasites and diseases of marine and freshwater fishes of India

A total of 531 references on the parasites and diseases of marine and freshwater fishes of India which appeared in 90 scientific journals have been documented.     

Fish introduction and parasites in marine ecosystems: a need for information

Invasive species provide unique and useful systems by which to examine various ecological and evolutionary issues, both in terms of the effects on native environments and the subsequent evolutionary impacts. While biological invasions are an increasing agent of change in aquatic systems, alien species also act as vectors for new parasites and diseases. To date, colonizations by hosts and parasites have not been treated and reviewed together, although both are usually interwoven in various ways and may have unpredictable negative consequences. Fish are widely introduced worldwide and are convenient organisms to study parasites and diseases. We report a global overview of fish invasions with associated parasitological data. Data available on marine and freshwater are in sharp contrast. While parasites and diseases of inland freshwater fish, ornamental, reared and anadromous fish species are well documented, leading to the emergence of several evolutionary hypotheses in freshwater ecosystems during the last decade, the transfer of such organisms are virtually unexplored in marine ecosystems. The paucity of information available on the parasites of introduced marine fish reflects the paucity of information currently available on parasites of non-indigenous species in marine ecosystems. However, such information is crucial as it can allow estimations of the extent to which freshwater epidemiology/evolution can be directly transferred to marine systems, providing guidelines for adapting freshwater control to the marine environment.     

Allee effects may slow the spread of parasites in a coastal marine ecosystem

Allee effects are thought to mediate the dynamics of population colonization, particularly for invasive species. However, Allee effects acting on parasites have rarely been considered in the analogous process of infectious disease establishment and spread. We studied the colonization of uninfected wild juvenile Pacific salmon populations by ectoparasitic salmon lice (Lepeophtheirus salmonis) over a 4-year period. In a data set of 68,376 fish, we observed 85 occurrences of precopular pair formation among 1,259 preadult female and 613 adult male lice. The probability of pair formation was dependent on the local abundance of lice, but this mate limitation is likely offset somewhat by mate-searching dispersal of males among host fish. A mathematical model of macroparasite population dynamics that incorporates the empirical results suggests a high likelihood of a demographic Allee effect, which can cause the colonizing parasite populations to die out. These results may provide the first empirical evidence for Allee effects in a macroparasite. Furthermore, the data give a rare detailed view of Allee effects in colonization dynamics and suggest that Allee effects may dampen the spread of parasites in a coastal marine ecosystem.     

Ecology of cutaneous leishmaniasis in Sinai: linking parasites,vectors and hosts

Cutaneous leishmaniasis (CL) is a neglected clinical form of public health importance that is quite prevalent in the northern and eastern parts of Egypt. A comprehensive study over seven years (January 2005-December 2011) was conducted to track CL transmission with respect to both sandfly vectors and animal reservoirs. The study identified six sandfly species collected from different districts in North Sinai: Phlebotomus papatasi, Phlebotomus kazeruni, Phlebotomus sergenti, Phlebotomus alexandri, Sergentomyia antennata and Sergentomyia clydei. Leishmania (-)-like flagellates were identified in 15 P. papatasi individuals (0.5% of 3,008 dissected females). Rodent populations were sampled in the same districts where sandflies were collected and eight species were identified: Rattus norvegicus (n = 39), Rattus rattus frugivorous (n = 13), Rattus rattus alexandrinus (n = 4), Gerbillus pyramidum floweri (n = 38), Gerbillus andersoni (n = 28), Mus musculus (n = 5), Meriones sacramenti (n = 22) and Meriones crassus (n = 10). Thirty-two rodents were found to be positive for Leishmania infection (20.12% of 159 examined rodents). Only Leishmania major was isolated and identified in 100% of the parasite samples. The diversity of both the vector and rodent populations was examined using diversity indices and clustering approaches.     

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.     

Ecology of marine algae on rocky shores and subtidal reefs in temperate Australia

Experiments in intertidal and subtidal rocky marine habitats in temperate Australia have identified the effects of various biological and physical factors on algal assemblages. In intertidal habitats, these involve micro- and macro-algae and grazing by gastropods. In subtidal habitats, interactions among micro- and macro-algae, echinoids, gastropods, micro-invertebrates and sessile invertebrates have been studied. Experimental studies on physical disturbances of algal assemblages have focussed on the effects of desiccation and storms. Most studies have not considered more than one spatial or temporal scale. Few have been concerned with seasonal influences and fewer have been concerned with variation from year to year. Most of the work lacks applicability to biogeographic comparisons. More experimental work across a variety of spatial and temporal scales is required to determine significant biological and physical processes affecting structure of algal assemblages across broad areas of temperate Australia.     

Trichodinid parasites (Ciliophora: Peritricha) from the gills of some Australian marine fishes

Three species of the genus Trichodina are reported from the gills of marine fishes in south-eastern Tasmania, Australia. Two of these species are new: T. australis n. sp. from five atherinid fish species, Atherinosoma microstoma, Leptatherina presbyteroides, Kestratherina brevirostris, K. esox and K. hepsetoides; and T. nesogobii n. sp. from Nesogobius sp. 1. One previously reported species, T. jadranica Raabe, 1958, was also found on Nesogobius sp. 1.     

Adaptive radiation within marine anisakid nematodes: a zoogeographical modeling of cosmopolitan, zoonotic parasites

Parasites of the nematode genus Anisakis are associated with aquatic organisms. They can be found in a variety of marine hosts including whales, crustaceans, fish and cephalopods and are known to be the cause of the zoonotic disease anisakiasis, a painful inflammation of the gastro-intestinal tract caused by the accidental consumptions of infectious larvae raw or semi-raw fishery products. Since the demand on fish as dietary protein source and the export rates of seafood products in general is rapidly increasing worldwide, the knowledge about the distribution of potential foodborne human pathogens in seafood is of major significance for human health. Studies have provided evidence that a few Anisakis species can cause clinical symptoms in humans. The aim of our study was to interpolate the species range for every described Anisakis species on the basis of the existing occurrence data. We used sequence data of 373 Anisakis larvae from 30 different hosts worldwide and previously published molecular data (n = 584) from 53 field-specific publications to model the species range of Anisakis spp., using a interpolation method that combines aspects of the alpha hull interpolation algorithm as well as the conditional interpolation approach. The results of our approach strongly indicate the existence of species-specific distribution patterns of Anisakis spp. within different climate zones and oceans that are in principle congruent with those of their respective final hosts. Our results support preceding studies that propose anisakid nematodes as useful biological indicators for their final host distribution and abundance as they closely follow the trophic relationships among their successive hosts. The modeling might although be helpful for predicting the likelihood of infection in order to reduce the risk of anisakiasis cases in a given area.