Sea lice escape predation on their host

Parasites seldom have predators but often fall victim to those of their hosts. How parasites respond to host predation can have important consequences for both hosts and parasites, though empirical investigations are rare. The exposure of wild juvenile salmon to sea lice (Lepeophtheirus salmonis) from salmon farms allowed us to study a novel ecological interaction: the response of sea lice to predation on their juvenile pink and chum salmon hosts by two salmonid predators-coho smolts and cut-throat trout. In approximately 70% of trials in which a predator consumed a parasitized prey, lice escaped predation by swimming or moving directly onto the predator. This trophic transmission is strongly male biased, probably because behaviour and morphology constrain female movement and transmission. These findings highlight the potential for sea lice to be transmitted up marine food webs in areas of intensive salmon aquaculture, with implications for louse population dynamics and predatory salmonid health.     

Invasive slugs as under-appreciated obstacles to rare plant restoration: evidence from the Hawaiian Islands

Introduced slugs have invaded many parts of the world where they were recognized as important pests of gardens and agriculture, but we know little about the effects of introduced slugs on rare plants in natural areas. The Hawaiian Islands have no native slugs, but over a dozen introduced slug species are now established. We reviewed Rare Plant Recovery Plans produced by the U.S. Fish and Wildlife Service for Hawaii and found that introduced slugs were specifically mentioned as threats or potential threats to 59 rare plant species (22% of all endangered and threatened plants), based mainly on anecdotal observations by field biologists. We then initiated an experimental field study to assess the impact of slug herbivory on the growth and survival of two endangered plant species (Cyanea superba, and Schidea obovata), one non-endangered native species (Nestegis sandwicensis) and two co-occurring invasive plant species (Psidium cattleianum and Clidemia hirta). In mesic forest on the Island of Oahu, we tracked the fate of outplanted seedlings in replicated 1 m² plots, with and without slug control. Slugs decreased seedling survival of the endangered species by 51%, on average. Slugs did not significantly affect survival of the non-endangered or invasive plant species. Introduced slugs seem to be under-appreciated as a direct cause of plant endangerment. Invasive slugs may also facilitate the success of some invasive plant species by reducing competition with more palatable, native plant competitors. Slug control measures are relatively inexpensive and could facilitate rare plant establishment and population recovery.     

Giants invading the tropics: the oriental vessel fern, Angiopteris evecta (Marattiaceae)

The Oriental vessel fern, Angiopteris evecta (G.Forst.) Hoffm. (Marattiaceae), has its native range in the South Pacific. This species has been introduced into other localities since the 18th century and is now listed as an invasive species in several regions (Jamaica, Hawaii and Costa Rica). The purpose of our study is (1) to trace the distributional history of the species, and (2) to model its potential future range based on climatic conditions. The native range and the history of introduction are based on the existing literature and on 158 specimens from 15 herbaria, together with field observations. As there are taxonomic problems surrounding A. evecta, we limited our analysis to samples from the Pacific, most closely resembling the type from Tahiti. We modelled the potential range using GARP species distribution modelling with basic climatic variables, elevation, and location in relation to the coast. Analysis of past records shows that the species is able to colonise new ecosystems with relative ease. The modelling reveals that the species could be cultivated over a much wider range than where it currently is grown. The escape of cultivated plants into nature is probably due to distance from natural areas and is limited by local ecological factors, such as soil conditions or competitors. The predicted distribution in Asia and Madagascar is similar to the native distribution of the entire genus Angiopteris. It can therefore be assumed that most Angiopteris species have similar climatic preferences, and the absence of A. evecta in this predicted region may be due to dispersal limitation. In the Americas there is no native Angiopteris, but our climatic model predicts a vast potential habitat in tropical America; an invasion of A. evecta should be anticipated here in localities where the species is cultivated. Vessel ferns are known to alter the natural environment, which may reduce local biodiversity. Since A. evecta is not yet widely cultivated, it is advisable to restrict the trade and spread of the species and to discourage its cultivation as an ornamental. The global climate data available for modelling is however not detailed enough to predict the spread of A. evecta on a local or regional scale.     

Vertical distribution of bacterial and archaeal communities along discrete layers of a deep-sea cold sediment sample at the East Pacific Rise (∼13°N)

The community structure and vertical distribution of prokaryotes in a deep-sea (ca. 3,191 m) cold sediment sample (ca. 43 cm long) collected at the East Pacific Rise (EPR) approximately 13 degrees N were studied with 16SrDNA-based molecular analyses. Total community DNA was extracted from each of four discrete layers EPRDS-1, -2, -3 and -4 (from top to bottom) and 16S rDNA were amplified by PCR. Cluster analysis of DGGE profiles revealed that the bacterial communities shifted sharply between EPRDS-1 and EPRDS-2 in similarity coefficient at merely 49%. Twenty-three sequences retrieved from DGGE bands fell into 11 groups based on BLAST and bootstrap analysis. The dominant groups in the bacterial communities were Chloroflexi, Gamma proteobacteria, Actinobacterium and unidentified bacteria, with their corresponding percentages varying along discrete layers. Pairwise Fst (F-statistics) values between the archaeal clone libraries indicated that the archaeal communities changed distinctly between EPRDS-2 and EPRDS-3. Sequences from the archaeal libraries were divided to eight groups. Crenarchaea Marine Group I (MGI) was prevalent in EPRDS-1 at 83%, while Uncultured Crenarchaea group II B (UCII B) abounded in EPRDS-4 at 61%. Our results revealed that the vertically stratified distribution of prokaryotic communities might be in response to the geochemical settings and suggested that the sampling area was influenced by hydrothermalism. The copresence of members related to hydrothermalism and cold deep-sea environments in the microbial community indicated that the area might be a transitional region from hydrothermal vents to cold deep-sea sediments.     

Ten new microsatellite markers for the buttonwood mangrove (Conocarpus erectus L., Combretaceae)

We present 10 microsatellite markers for the buttonwood mangrove, Conocarpus erectus, a wide-range mangrove associate species. Polymorphism was assessed among individuals from six different populations along the Pacific Coast of Mexico and Costa Rica, as well as in two individuals from the Yucatan Peninsula in the Atlantic. The number of alleles detected in the Pacific ranged from two to five. All loci amplified in the Yucatan samples and seven loci revealed a unique Atlantic allele. These markers will be useful for studies in the conservation of the species and to study the basic biology of C. erectus.     

Maastrichtian Challengeriidae (phaeodarian radiolaria) from deep sea sediments of SW Pacific

The paper reports three species of fossil phaeodarian Radiolaria of the family Challengeriidae, of which two (Protocystis pacifica and Challengeron takahashii) are new and one is determined at generic level. They have been found in a Maastrichtian sample from Site 275 of the Deep Sea Drilling Project located on Campbell Plateau, near New Zealand. Together with the two species of the same family recently described by Bragina [Paleontol. J. 37 (2003) 8] from the upper Cenomanian of Sakhalin Island, and three other species found by Takahashi [Tenth Meeting of the International Association of Radiolarian Palaeontologists, Abstracts and Programme, Lausanne (2003) 107] from the upper Campanian to lower Maastrichtian of central Japan, they represent the only Cretaceous phaeodarian species so far known. The family Challengeriidae, to which most of these species belong, seems to contain the most resistant phaeodarians to fossilization. These species prove that the skeleton structure of Cretaceous Challengeriidae is similar to Recent ones and that the difference between them is only at species level.     

Tollip, a negative regulator of TLR-signalling, is encoded by twin genes in salmonid fish

The factor Tollip is known to dampen TLR2- and TLR4-mediated signalling in mammals. No negative regulator of the piscine TLR-signalling cascade has been described so far, albeit a sizable collection of factors contributing to this ancient pathogen-sensing system are known from fish to date. We identified two closely related Tollip-encoding genes in Atlantic salmon (Salmo salar) and the respective ortholog mRNA molecules in rainbow trout (Oncorhynchus mykiss). The salmonid Tollip genes are segmented into 6 exons, similar to the human orthologous gene. The protein-encoding sequences are homologous to >97% among the twin factors and also between the species. Both encoded proteins contain a C2 domain and an ubiquitin system component, which are also characteristic features of the mammalian Tollip factor. We analysed the expression of these genes in trout. Both Tollip-encoding genes are ubiquitously and also equally expressed, as indicated by similar mRNA concentrations of both factors in any one tissue. Tollip expression was found to be up-regulated by viral infection. Our data suggest that the Tollip genes were duplicated before salmon and trout were evolutionary separated. Moreover, pathways dampening the activity of the TLR-cascade may have been conserved from lower vertebrates to mammals since Tollip, as a respective key factor has been highly conserved from fish to human.     

The Role of Sharks and Longline Fisheries in a Pelagic Ecosystem of the Central Pacific

The increased exploitation of pelagic sharks by longline fisheries raised questions about changes in the food webs that include sharks as apex predators. We used a version of Ecopath/Ecosim models to evaluate changes in trophic interactions due to shark exploitation in the Central North Pacific. Fisheries targeted on blue sharks tend to produce compensatory responses that favor other shark species and billfishes, but they have only modest effects on the majority of food web components. Modest levels of intraguild predation (adult sharks that eat juvenile sharks) produce strong, nonlinear responses in shark populations. In general, analysis of the Central North Pacific model reveals that sharks are not keystone predators, but that increases in longline fisheries can have profound effects on the food webs that support sharks. Received 19 April 2001; accepted 2 October 2001.     

Have Native Coho Salmon (Oncorhynchus Kisutch) Persisted in the Nooksack and Samish rivers Despite Continuous Hatchery Production Throughout the Past Century?

For over a century, Washington State Department of Fish and Wildlife has implemented hatchery programs as a means to boost salmon abundance. Concerns have developed that native populations may be replaced by hatchery strains, decreasing the genetic diversity required to respond to environmental changes. We report a comparison of microsatellite DNA variation in wild-spawning and hatchery-strain coho salmon from the Nooksack and Samish rivers in northern Puget Sound. Significant heterogeneity in genotype frequencies was detected between wild-spawning coho salmon from the upper North Fork (NF) Nooksack River and hatchery-strain coho salmon from the Nooksack River (descendants of primarily Nooksack River broodstock). Little difference in genotype frequencies was detected between wild-spawning coho salmon from the Samish River and hatchery-strain coho salmon from the Nooksack River. The 13-locus suite provided high resolution: in assignment tests over 85% of wild-spawning coho salmon from the upper NF Nooksack River were assigned to source. Wild-spawning coho salmon collected below hatcheries in the Nooksack River and 50% of wild-spawning Samish River coho salmon were assigned to hatchery collections. The genetic divergence of wild-spawning coho salmon in the upper NF Nooksack River is remarkable given the extensive stocking history and proximity of a hatchery. We suggest that these upper river fish are native coho salmon and that wild spawners in the lower Nooksack and Samish River are descendants of hatchery productions. We attribute divergence to earlier run timing in upper NF Nooksack River wild spawners, availability of extensive spawning and rearing habitat upstream of a hatchery in the upper NF Nooksack River, and a longer stocking history in the Samish River.