Limited ecological population connectivity suggests low demands on self-recruitment in a tropical inshore marine fish (Eleutheronema tetradactylum: Polynemidae)

The diversity of geographic scales at which marine organisms display genetic variation mirrors the biophysical and ecological complexity of dispersal by pelagic larvae. Yet little is known about the effect of larval ecology on genetic population patterns, partly because detailed data of larval ecology do not yet exist for most taxa. One species for which this data is available is Eleutheronema tetradactylum, a tropical Indo-West Pacific shorefish. Here, we use a partial sequence mitochondrial cytochrome oxidase subunit 1 (COI) marker and five microsatellite loci to survey the genetic structure of E. tetradactylum across northern Australia. Structure was found throughout the range and isolation by distance was strong, explaining approximately 87 and 64% of the genetic variation in microsatellites and mtDNA, respectively. Populations separated by as little as 15 km also showed significant genetic structure, implying that local populations are mainly insular and self-seeding on an ecological time frame. Because the larvae of E. tetradactylum have lower swimming performance and poor orientation compared with other tropical fishes, even modest larval abilities may permit self-recruitment rather than passive dispersal.     

Mitochondrial and nuclear DNA analyses reveal fine scale geographic structure in bottlenose dolphins (<Emphasis Type="Italic">Tursiops truncatus</Emphasis>) in the Gulf of Mexico

There is a need for biological information to support current stock designations of bottlenose dolphins (Tursiops truncatus) in the Gulf of Mexico. The existence of many inshore, resident “communities” raises questions as to the relationship these dolphins may hold with dolphins inhabiting neighboring inshore and coastal areas. In this study, population subdivision was examined among four resident, inshore bottlenose dolphin stocks (Sarasota Bay, FL, Tampa Bay, FL, Charlotte Harbor, FL and Matagorda Bay, TX) and one coastal stock (1–12 km offshore) in the Gulf of Mexico. Evidence of significant population structure among all areas was found on the basis of both mitochondrial DNA (mtDNA) control region sequence data and nine nuclear microsatellite loci. Estimates of relatedness showed no population contained a significantly high number of related individuals, while separate AMOVAs for males and females indicated that both sexes exhibit a significant level of site philopatry. Results presented here provide the first genetic evidence of population subdivision between the coastal Gulf of Mexico and adjacent inshore areas along the central west coast of Florida. Such strong genetic subdivision is surprising given the short geographical distance between many of these areas and the lack of obvious geographic barriers to prevent gene flow. These findings support the current, separate identification of stocks for bottlenose dolphins inhabiting the eastern coastal and inshore areas of the Gulf of Mexico.     

Stock structure of blue threadfin Eleutheronema tetradactylum across northern Australia, as indicated by parasites

The parasite fauna of the blue threadfin Eleutheronema tetradactylum, collected from 14 sites across northern Australia, was examined to evaluate the degree of movement and subsequent stock structure of the fish. Univariate and multivariate analysis of nine 'permanent' parasite species [the nematodes Anisakis (type I) and Terranova (type II), the cestodes Otobothrium australe, Pterobothrium pearsoni, Pterobothrium sp. A, Callitetrarhynchus gracilis, Parotobothrium balli and Nybelinia sp., and the acanthocephalan Pomphorhynchus sp.] demonstrated little similarity between sites, indicating limited mixing and therefore long-term separation of post-juvenile fish. As such, the effects of fishing are likely to be localized within the current administrative boundaries, implying little need for interstate co-operative management. Within each jurisdiction, management of E. tetradactylum populations, including the establishment of harvest strategies and fishery regulations, should be conducted in a way that recognizes the resident nature of the fish.     

Parasites as biological tags in population studies of demersal and pelagic fish species

Among the different techniques applied in a holistic approach for fish stock identification, the use of parasites as "biological tags" is becoming increasingly important. In this presentation, our recent studies on the use of some parasite species, identified by genetic markers, and the parasite/fauna composition, in stock identification of demersal (Merluccius merluccius), small pelagic (Trachurus trachurus), and large pelagic fish species (Xiphias gladius) are reviewed. Different species of Anisakis and Hysterothylacium were genetically identified by the application of genetic (allozyme) markers. Statistically significant differences in the spatial distribution of distinct species of Anisakis were found in the fish considered. As to the species of Hysterothylacium genetically detected, different relative proportions were detected in several Mediterranean and Atlantic samples of swordfish (X. gladius). This study demonstrates the potential value of these anisakid nematodes, at both larval and adult stages, as "biological tags" for these fish species in European waters.     

Patterns of larval release in the Florida stone crab, Menippe mercenaria

Larval release patterns in brachyuran crabs are often synchronized with environmental cycles. While previous studies have focused extensively on supratidal and intertidal taxa, there have been relatively few investigations of subtidal species. This study examined patterns of larval release by the Florida stone crab, Menippe mercenaria, from three different tidal regimes. Ovigerous stone crabs were collected from Sebastian Inlet on the east coast of Florida, Tampa Bay on the west coast of Florida, and the Florida Keys. Patterns of larval release were monitored in the laboratory in relation to local tidal and diel cycles. Results showed a significant diel pattern in initiation of hatching by crabs from each of three study areas. Larval release consistently occurred during the diurnal phase despite the maintenance of females in constant laboratory conditions for up to 96 h prior to hatching. This implies that release may be controlled by a circadian clock. Patterns of release by stone crabs in relation to tidal cycle were more variable. Larval release by females from populations near Tampa Bay and Sebastian Inlet were not synchronized with the tides, whereas females collected from the Florida Keys exhibited a pattern that was strongly related to tidal cycle. These results may be explained by differences in tidal amplitude at the three sampling locations.     

Movements and migrations of yellowfin bream, Acanthopagrus australis (Günther), in Moreton Bay, Queensland as determined by tag recoveries

Yellowfin bream were tagged and released in three non-spawning areas and two spawning areas in Moreton Bay, a large estuarine system on the east coast of Australia. A total of 194 fish were recaptured. Juvenile fish made only small-scale movements (less than 6 km) from the release site. Small-scale movements were also recorded for adult fish, although large-scale movements from 10 to 90 km were also recorded. The large-scale movements appear to be associated with the migration of adult fish to or from surf bar spawning areas. Some adult fish remained in feeding areas during the spawning season (May-August). There was no indication from tag recoveries of any movements of yellowfin bream outside Moreton Bay and the results indicate that adult yellowfin bream in Moreton Bay may be regarded as a unit stock for the purpose of fisheries management.     

Three new species of Polyclithrum Rogers, 1967 (Gyrodactylidae: Monogenea) from mugilid fishes from Australia and Brazil, with a redescription of P. mugilini Rogers, 1967

Polyclithrum mugilini Rogers, 1967, a parasite of Mugil cephalus Linnaeus, is redescribed from type-material from Lake Seminole, Georgia, USA. Three new species of Polyclithrum Rogers, 1967 are also described: P. alberti n. sp. from M. cephalus from the Albert River, Queensland, Australia; P. boegeri n. sp. from M. platanus Günther from Rio da Guarda, State of Rio de Janeiro, Brazil; and P. corallense n. sp. from M. cephalus from Heron Island, Great Barrier Reef, Australia. The four species can be distinguished by the size and shape of haptoral sclerites, but in particular by accessory bar number 3, the dorsal bar, the marginal hooks and the hamulus point to shaft angle. The validity of Micropolyclithrum parvum Skinner, 1975, a parasite of M. cephalus in Biscayne Bay, Florida, is discussed, and a key to the species of Polyclithrum is presented.     

Parasitology of the English Sole, Parophrys vetulus Girard in Oregon, U.S.A.

A total of 877 juvenile English sole ( Parophrys vetulus Girard) from the Yaquina Bay estuary and742 juvenileandadultsole from the Pacific Ocean off Oregon were examined forparasites. Fifteen species of parasites were found in juvenile English sole on the estuarine nursery ground. Differences in the prevalence and intensity of parasite infection between size classes of juvenile sole and between sole occupying the upper and lower estuary were determined. An additional 14 parasite species were found in offshore English sole, bringing the total observed in all fish to 29 species. Parasites acquired only in the estuary included the microsporidan Glugea stephani , the acanthocephalan Echinorhynchus lageniformis , and the nematode Philometra americana . Those acquired only in offshore areas included the trematodes Otodistomum veliporum and Zoogonus dextrocirrus , the leech Oceanobdella sp. and three species of copepods. An attempt to use parasite data to indicate the presence of distinct English sole stocks along the Oregon coast was inconclusive.     

Infection of Gymnodinium sanguineum by the dinoflagellate Amoebophrya sp.: effect of nutrient environment on parasite generation time, reproduction, and infectivity

Preliminary attempts to culture Amoebophrya sp., a parasite of Gymnodinium sanguineum from Chesapeake Bay, indicated that success may be influenced by water quality. To explore that possibility, we determined development time, reproductive output, and infectivity of progeny (i.e. dinospores) for Amoebophyra sp. maintained on G. sanguineum grown in four different culture media. The duration of the parasite's intracellular growth phase showed no significant difference among treatments; however, the time required for completion of multiple parasite generations did, with elapsed time to the middle of the third generation being shorter in nutrient-replete media. Parasites of hosts grown in nutrient-replete medium also produced three to four times more dinospores than those infecting hosts under low-nutrient conditions, with mean values of 380 and 130 dinospores/host, respectively. Dinospore production relative to host biovolume also differed, with peak values of 7.4 per 1,000 microm3 host for nutrient-replete medium and 4.8 per 1,000 microm3 host for nutrient-limited medium. Furthermore, dinospores produced by "high-nutrient" parasites had a higher success rate than those formed by "low-nutrient" parasites. Results suggest that Amoebophrya sp. is well adapted to exploit G. sanguineum populations in nutrient-enriched environments.     

Local variability in metazoan parasites of the pelagic fish species, Engraulis ringens: implications for fish stock assessment using parasites as biological tags

Parasites have been used successfully as biological tags in population studies, mainly in marine fishes, but also in marine mammals, crustaceans and molluscs. Almost all published information dealing with parasites as biological tags evaluates differences between localities. However, local variability in the component community has not been assessed. In this work, we examined whether local variation of the metazoan parasite fauna of Engraulis ringens, extracted from five independent samples from two nearby localities in northern Chile, can be a factor causing bias in stock identification. Our results show that local variability, as estimated by a single sample, may suffice to represent component community variability with no need for replicated data.     

Multiple SNP Markers Reveal Fine-Scale Population and Deep Phylogeographic Structure in European Anchovy (Engraulis encrasicolus L.)

Geographic surveys of allozymes, microsatellites, nuclear DNA (nDNA) and mitochondrial DNA (mtDNA) have detected several genetic subdivisions among European anchovy populations. However, these studies have been limited in their power to detect some aspects of population structure by the use of a single or a few molecular markers, or by limited geographic sampling. We use a multi-marker approach, 47 nDNA and 15 mtDNA single nucleotide polymorphisms (SNPs), to analyze 626 European anchovies from the whole range of the species to resolve shallow and deep levels of population structure. Nuclear SNPs define 10 genetic entities within two larger genetically distinctive groups associated with oceanic variables and different life-history traits. MtDNA SNPs define two deep phylogroups that reflect ancient dispersals and colonizations. These markers define two ecological groups. One major group of Iberian-Atlantic populations is associated with upwelling areas on narrow continental shelves and includes populations spawning and overwintering in coastal areas. A second major group includes northern populations in the North East (NE) Atlantic (including the Bay of Biscay) and the Mediterranean and is associated with wide continental shelves with local larval retention currents. This group tends to spawn and overwinter in oceanic areas. These two groups encompass ten populations that differ from previously defined management stocks in the Alboran Sea, Iberian-Atlantic and Bay of Biscay regions. In addition, a new North Sea-English Channel stock is defined. SNPs indicate that some populations in the Bay of Biscay are genetically closer to North Western (NW) Mediterranean populations than to other populations in the NE Atlantic, likely due to colonizations of the Bay of Biscay and NW Mediterranean by migrants from a common ancestral population. Northern NE Atlantic populations were subsequently established by migrants from the Bay of Biscay. Populations along the Iberian-Atlantic coast appear to have been founded by secondary waves of migrants from a southern refuge.     

Parasitism in the bathypelagic fish, Melanostigma pammelas

Three hundred and thirty-seven specimens of the zoarcid fish, Melanostigma pammelas, collected between December, 1950 and December, 1969 from bathypelagic waters off southern California, were examined for their parasites. Incidences of infection were: digentic Trematoda 61%, Myxosporida 39%, larval Nematoda 9%. Two adult trematodes are described: Fellodistomum melanostigmum nov. sp. from the intestine, and Aponurus pacificus nov. sp. from the stomach. This parasite record is markedly unlike the typical record reported for eastern Pacific mesopelagic fishes in which many larval nematodes and few, if any, adult trematodes were found. Our long-term objective is to explain parasite pattern differences in the deep ocean in terms of their biological and physical environments. Our initial purpose is to determine the numbers and kinds of parasites in M. pammelas.     

Holocene vegetation and climate evolution of Corpus Christi and Trinity bays: Implications on coastal Texas source-to-sink deposition

The Texas coastline stretches 595 km across almost 4° of latitude and is home to diverse coastal vegetation assemblages, yet only a handful of studies have documented the climate and vegetative change of this region through the Holocene. We provide a detailed palynological record of Holocene climate for coastal Texas, based upon three subaqueous sediment cores from Corpus Christi Bay and Trinity Bay. Cluster analysis and correspondence analysis were used to investigate changes in palynological assemblages through time within each core. Common to both bays are nonarboreal taxa including Asteraceae (mainly Ambrosia and Helianthus), Chenopodium, Poaceae, and arboreal taxa such as Carya, Pinus, and Quercus. Our record shows that the coastal environments of central Texas began a transition from herbaceous (nonarboreal) dominated vegetation to arboreal vegetation as early as 8.4 ka within Corpus Christi Bay, and 3.8 ka within Trinity Bay. We note flooding events at 8.2, 5.4, and 3.6 ka in Corpus Christi Bay, and at 1.7, 1.2, and 0.8 ka in Trinity Bay. These events were caused by storms, sea level changes including flooding of relict river terraces, and changes in sediment delivery to the bays. The pollen record also shows evidence for changes in fluvial discharge to Corpus Christi Bay at 4.1 and 2.2 ka, and at 1.8 ka in Trinity Bay. We also see Zea mays in Trinity Bay, indicating local Native American agriculture. We observe no significant changes during the middle Holocene Climatic Optimum, and subtle but not statistically significant evidence of more variable climate oscillations than other records from more interior sites in Texas available for the late Holocene. This indicates that coastal Texas’ climate has operated semi-independently from central Texas regions, and was primarily driven by a coast-wise gradient of precipitation and evapotranspiration.     

Stock discrimination and movements of narrow‐barred Spanish mackerel across northern Australia as indicated by parasites

The parasite fauna of Spanish mackerel Scomberomorus commerson from 10 sites across northern Australia and one site in Indonesia, was examined to evaluate the degree of movement and subsequent stock structure of the fish. Kupang fish (Indonesia) had very few Terranova spp., Grillotia branchi , Otobothrium cysticum or Pterobothrium sp. compared to Australian fish, indicating that no Australian fish enter the Kupang fishery. Univariate and discriminant function analysis of four 'temporary' parasite species, the copepod Pseudocycnoides armatus and the monogeneans Gotocotyla bivaginalis , Pricea multae and Pseudothoracocotyla ovalis , demonstrated little similarity between areas of northern Australia, indicating minimal short‐term exchange between neighbouring groups of S. commerson . Analyses of five 'permanent' parasite species, the larval helminths G. branchi , O. cysticum , Pterobothrium sp., Callitetrarhynchus gracilis and Paranybelinia balli , also revealed large differences between areas thus indicating long‐term separation. There are at least six parasitological stocks across northern Australia: Fog Bay/Bathurst Island, Cape Wessel, Groote/Sir Edward Pellew, Mornington Island, Weipa, and the Torres Strait. The occurrence of a few irregular fish in the samples suggested that up to 5% of fish moved between stocks during their lifetime. The similarity of within‐school variability to that between schools showed that the fish do not form long‐term school associations.     

Assessment of juvenile coho salmon movement and behavior in relation to rehabilitation efforts in the Trinity River, California, using PIT tags and radiotelemetry

Coho salmon (Oncorhynchus kisutch) of the Southern Oregon/Northern California Coast (SONCC) Evolutionarily Significant Unit (ESU) is federally listed as a threatened species. The Trinity River Restoration Program (TRRP) is rehabilitating the Trinity River to restore coho salmon (coho) and other salmonid populations. In order to evaluate the program’s actions, several studies of movements and behavior of coho in the Trinity River were conducted from 2006 to 2009, including snorkel surveys and mark-recapture techniques based on Passive Integrated Transponder (PIT) tags, elastomer tags, and radio transmitters. Catch, recapture, and condition of natural sub-yearlings, along with site fidelity and emigration of hatchery-reared yearlings in rehabilitated and reference habitats, were studied. Location was important because coho were absent from the lower controlled and rehabilitated sites most of the time. However, rehabilitation did not have a significant effect on natural coho salmon at the site level. Apparent survival of radio-tagged, hatchery-reared yearling coho released downstream from Lewiston Dam was much lower in the first 10 km downstream from the release site than in other areas between Lewiston Dam and the Klamath River estuary. Estimated survival of yearling hatchery coho salmon per 100 km down to Blake’s Riffle was estimated at 64 % over the distance of the 239 km study area. Migration primarily occurred at night in the upper Trinity River; however, as yearlings moved through the lower Trinity River towards the Klamath River, estuary nocturnal migration became less. Apparent survival was generally lowest in areas upstream from the North Fork of the Trinity River.     

The leaf-tying moth Hypocosmia pyrochroma (Lep., Pyralidae), a host-specific biological control agent for cat's claw creeper Macfadyena unguis-cati (Bignoniaceae) in Australia

Abstract:  Cat's claw creeper, Macfadyena unguis-cati , a major environmental weed in coastal and sub-coastal areas of Queensland and New South Wales, Australia is a target for classical biological control. Host specificity of Hypocosmia pyrochroma Jones (Lep., Pyralidae), as a potential biological control agent was evaluated on the basis of no-choice and choice larval feeding and survival, and adult oviposition preference tests, involving 38 plant species in 10 families. In no-choice tests, larval feeding and development occurred only on cat's claw creeper. In choice tests, oviposition and larval development was evident only on cat's claw creeper. The results support the host-specificity tests conducted in South Africa, and suggest that H. pyrochroma is a highly specific biological control agent that does not pose any risk to non-target plants tested in Australia. This agent has been approved for field release by relevant regulatory authorities in Australia.     

Biology and host specificity ofPlatphalonidia mystica (Lep.: Cochylidae) introduced into queensland to biologically controlParthenium hysterophorus (Asteraceae)

Platphalonidia mystica (Razowski &; Becker) has been studied as a potential biological control agent against parthenium weed (Parthenium hysterophorus L.). During host specificity testing, larval feeding damage occurred on sunflower (Helianthus annuus L.) and to a lesser extent onDahlia sp., but risk of damage to sunflower crops under field conditions is considered negligible. In view of the very great problem thatP. hysterophorus is causing, and the threat of its continued southward spread into Southern Queensland, New South Wales and Victoria, field release ofP. mystica was authorised and commenced in Queensland in late 1992.     

Population structure and dispersal of the saltmarsh mosquito Aedes vigilax in Queensland, Australia

Population genetics of the mosquito Aedes vigilax (Skuse) (Diptera: Culicidae), a major vector of arboviruses (e.g. Barmah Forest, Ross River), were investigated to obtain an indirect estimate of mosquito dispersal characteristics in typical habitats of Aedes vigilax in south-east Queensland: on the off-shore islands of Moreton Bay and on the mainland where disjunct breeding populations of Ae. vigilax are distributed along intertidal marsh. Six allozyme loci were assessed for genetic differentiation between samples from 11 localities. Significant larval variation between some breeding sites was attributed to site-specific selection. Nonsignificant genetic differentiation was found among collections of adult mosquitoes caught in light traps throughout the study area (exceeding 60x27 km), indicating widespread dispersal. As distances of < or = 9 km over water did not appear to act as effective barriers to Ae. vigilax dispersal, localized control activities applied to Ae. vigilax breeding sites are unlikely to be effective against the vagile adult population. Therefore, the contiguous shires programme of broad acre control is endorsed to prevent the spread of arboviruses carried by Ae. vigilax     

The metazoan parasites of Stellifer minor (Tschudi, 1844): an ecological approach

A quantitative and qualitative analysis of the parasite fauna of the sciaenid Stellifer minor (Tschudi) from Chorrillos, Perú, was made. Some characteristics of the infectious processes, in terms of intensity and prevalence of infection, as a function of host sex and size, are given. Moreover, comments on the characteristics of the parasite fauna, related with host role in the marine food webs are included. The parasite fauna of Stellifer minor taken off Chorrillos, Perú, include the monogeneans Pedocotyle annakohni, Pedocotyle bravoi, Rhamnocercus sp. and Cynoscionicola sp., the digenean Helicometra fasciata, the adult acantocephalan Rhadinorhynchus sp. and the larval Corynosoma sp., the nematode Procamallanus sp., the copepods Caligus quadratus, Clavellotis dilatata and Bomolochus peruensis and one unidentified isopod of the family Cymothoidae. A distinctive characteristic of the parasite fauna (Metazoa) of S. minor is the almost absence of larval forms.     

Nosema takapauensis n.sp., a microsporidan parasite of larvae of Costelytra zealandica (Coleoptera: Scarabaeidae) in New Zealand

Morphological and biological features of a microsporidan protozoan parasite of larvae of Costelytra zealandica collected at Takapau, southern Hawkes Bay, are described and evaluated taxonomically. The parasite multiplies in the fat body of all larval instars, causing massive tissue disintegration in advanced infection resulting in the retardation of development and ultimately death before pupation. The microsporidan forms one spore per sporont, and therefore belongs to genus Nosema’, it is considered to be specifically distinct from its nearest congener, N. melolonthae.