61 research outputs found

    Subtidal Hydroids (Cnidaria) of Northumberland Strait, Atlantic Canada, with Observations on Their Life Cycles and Distributions

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    Hydroids were examined in collections from a biological survey of Northumberland Strait undertaken by Fisheries and Oceans Canada from June to August 1975. No investigations have been undertaken previously on hydroids of the study area. Forty-eight species referable to 12 families were present in the samples, with Sertulariidae dominating in both numbers of species (12) and frequency. Gonophores were found in 30 of the species. As usual in hydroids of higher latitudes, a majority of those represented do not have a medusa stage in their life cycle. Gonophores in 42 of the 48 species are known to be fixed sporosacs while free medusae or medusoids occur in only six. Two major species groups were distinguished in a numerical analysis of hydroid species/station data. One of these groups included the three most ubiquitous species (Calycella syringa, Hydrallmania falcata, Sertularia latiuscula) together with 15 others most prevalent in samples from shallower (<20 m) and warmer stations. The second group included species occurring primarily in samples from stations in deeper (>20 m) and mostly colder waters. Two species (Lafoeina tenuis, Halecium lankesteri) are new to the Atlantic coast of North America. Eight others (Bougainvillia sp., Eudendrium dispar, Eudendrium ramosum, Cuspidella humilis, Opercularella pumila, Halecium scutum, Halecium sessile, Diphasia fallax) are reported in the southwestern Gulf of St. Lawrence for the first time. The subtidal hydroid fauna in open waters of Northumberland Strait is a cold-water assemblage typical of the boreal zone in the western North Atlantic, and no relict warm-temperate species were found

    Hydrozoa of Southern Chesapeake Bay

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    Hydrozoans of southern Chesapeake Bay and its tributaries were studied from April 1965 until March 1968 to determine faunal diversity, seasonality and reproductive periodicities. Laboratory culture techniques were used in describing unknown or inadequately known stages in the life history of several species and as an aid in identification. A total of 55 species was identified, including 43 hydroids and 32 medusae. Of these, 22 hydroids and 15 medusae are reported in Chesapeake Bay for the first time. Two species earlier reported from the bay, Eudendrium carneum and Blackfordia virginica, were not found. Clytia paulensis and the hydroid of Proboscidactyla ornata are previously unreported in North America, and the hydroid of Amphinema dinema is recorded for the first time from the North American Atlantic coast. The southern range of Hybocodon prolifer, Obelia longissima and Opercularella pumila is extended, as is the northward range of Podocoryne minima, Clytia kincaidi and Phialucium carolinae. Both hydroids and hydromedusae show an affinity with the Carolinian Zoogeographic Province; 76% of the hydroids and 77% of the hydromedusae occur south of Cape Hatteras, while 59% of the hydroids and 35% of the hydromedusae occur north of Cape Cod. The hydroid of Dipurena strangulata and the older medusae of Bougainvillia rugosa and Lovenella gracilis are described for the first time. Partial life histories are described for four other species. The genus Calyptospadix Clarke, 1882 is placed in synonymy with Bimeria Wright, 1859. Hydroids are shown to be characteristically seasonal in occurrence due to the annual water temperature range, which varies from approximately 2 C to 28 C. During seasons of inactivity, laboratory-tested species, Ectopleura dumortieri, Bougainvillia rugosa and Eudendrium ramosum, remained in a dormant state in the stems, stolons, or both, until favorable temperatures returned. Field observations on other hydroid species indicated a similar phenomenon. Dormant stages are resistant to unfavorable temperatures and may have important implications on hydrozoan zoogeography. In nature, the temperature at which renewed growth commenced in spring for winter-dormant species was higher than that at which regression occurred in autumn, and the converse was true for summer-dormant species. This may be an adaptive mechanism insuring favorable conditions for growth once development has begun. Of 23 hydroids whose seasonality was studied in detail, 16 were ’’summer” species and 7 were ’’winter” species. Among the hydromedusae, seasonality was typically less prolonged, with a maximum diversity in late summer and early autumn and a minimum diversity in winter. Although undescribed species or endemics to the bay were not found, two unidentified hydroids, ’’Campanulina” sp. and coast and should not be ruled out as being new species, endemics or both, until more is known about their biology

    Ecology of Marine Invertebrate Fouling Organisms in Hampton Roads, Virginia

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    Investigations were conducted from 15 May 1964 to 3 January 1966 to determine the incidence, distribution, and abundance of marine invertebrate fouling organisms in Hampton Roads, Virginia. Dredging carried out at seven stations revealed that benthic organisms most likely to be involved in fouling were Thuiaria argentea, Alcyonidium verrilli, Microciona prolifera, Amathia vidovici, and Aeverrillia armata. All of these species occur in the Pier 12 berthing area of the Norfolk Naval Base, with. !· argentea and~- verrilli being most abundant. Detailed studies of the organisms attaching to asbestos fiber test panels were made at Pier 12 of the Naval Base. Attachment occurred throughout the year, but was heaviest from May to November, and lightest from January to March. Preliminary results indicate· that the intensity of fouling differs from station to station in the harbor as well as from year to year at the same station. A regular cyclic pattern of dominance occurred on the panels as a result of the reproductive periods of the organisms. Barnacles (Balanus improvisus) dominated in spring and autumn, while tunicates (Molgula manhattensis, Botryllus schlosseri) and serpulids (Hydroides hexagona) dominated in summer. Maximum accumulated dry weight of fouling on test panels occurred in May, August, and November

    Strobilation Of The Sea Nettle, Chrysaora Quinquecirrha, Under Field Conditions

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    The sea nettle, Chrysaora quinquecirrlza (Desor, 1848) , is locally abundant during summer along the east coast of the United States from southern New England to Florida. The venomous medusa stage of this species is a significant pest and a negative economic factor, particularly in the Chesapeake Bay region. In common with many other cnidarians, C. quinquecirrha undergoes an alternation between polyp and medusa stages in its life history. While the medusa population dies off annually, the sessile polyp or scyphistoma stage may remain active all year and is potentially perennial (Truitt, 1939). The scyphistoma is capable of asexual reproduction, most commonly through podocyst formation. These cysts are also resistant to adverse environmental conditions. Given favorable conditions the scyphistomae undergo strobilation, a process leading to the production of free swimming ephyrae. The proximal portion of the polyp remaining after strobilation undergoes renewed growth, returning the scyphistoma to normal size and morphology. It is then capable of continued asexual reproduction and perhaps repeated strobilation. The ephyrae develop rapidly into medusae, which are dioecious. Fertilization results in a free-swimming planula larva, which settles on a firm substrate and develops into the scyphistoma, thereby completing the life cycle. While the morphological details of strobilation in C. quinquecirrha have been described (Littleford, 1939; Cones, 1969), little is known about the ecology and seasonal dynamics of the process. The only relevant field data available to date on strobilation in this species were based on collections of ephyrae by Cargo and Schultz (1966, 1967). The present study was undertaken to determine (1) when strobilation begins and ends in nature; (2) the percentage of polyps strobilating at a given time; (3) the number of ephyrae produced per strobila, as observed throughout the season; (4) whether a given polyp will strobilate more than once a season under field conditions

    Seasonal Occurrence of Epifauna on Test Panels In Hampton Roads, Virginia

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    A two-year study was made on settling patterns of some marine epifaunal frmcrtebrales in the port of Hampton Roads, Virginia. Asbestos fiber test panels, submerged to a depth of 5 m from a pier at the Norfolk Navy Base, wf:re used as substrates. The fouling assemblage consisted of species characteristic of the temperate North American Atlantic coast. Over half of the 41 species identified were either coelenterates or arthropods, although sponges, tttrbellarians, ectoprocts, J\u3eolychaetes, mollusks, and ascidians were present as well. Four species, Aselomaris michaeli, Clytia edwardsi, Obelia bicuspidata and 0. commissuralis, all hydroids, represent new distributional records for Virginia. The large annual range of water temperature results in distinct seasonal patterns of settlement. Attachment was heaviest froni May to November and lightest fi·om January to March. Barnacles (Balanus improvisus) were prevalent during spring and autumn, while ascidians (Molgula manhattensis, Botryllus schlosseri) and serpulids (Hydroides hexagona) were predominant in summer. Only Balanus improvisus occurred on the panels throughout the year

    Bibliography on the Scyphozoa with selected references on Hydrozoa and Anthozoa

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    Our goal in assembling this bibliography has been to bring together literature references on all aspects of scyphozoan research. Compilation was begun in 1967 as a card file of references to publications on the Scyphozoa; selected references to hydrozoan and anthozoan studies that were considered relevant to the study of scyphozoans were included. In 1968, a major research program on the jellyfish of Chesapeake Bay was initiated at the Virginia Institute of Marine Science (VIMS) under Dr. E. B. Joseph, and work on the bibliography became an integral part of the program. In 1969 we began converting the bibliography into a form suitable for wider distribution, and in February 1970 a preliminary draft was completed. The present bibliography is an expanded and revised version of the preliminary draft

    Impacts of climate change on plant diseases – opinions and trends

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    There has been a remarkable scientific output on the topic of how climate change is likely to affect plant diseases in the coming decades. This review addresses the need for review of this burgeoning literature by summarizing opinions of previous reviews and trends in recent studies on the impacts of climate change on plant health. Sudden Oak Death is used as an introductory case study: Californian forests could become even more susceptible to this emerging plant disease, if spring precipitations will be accompanied by warmer temperatures, although climate shifts may also affect the current synchronicity between host cambium activity and pathogen colonization rate. A summary of observed and predicted climate changes, as well as of direct effects of climate change on pathosystems, is provided. Prediction and management of climate change effects on plant health are complicated by indirect effects and the interactions with global change drivers. Uncertainty in models of plant disease development under climate change calls for a diversity of management strategies, from more participatory approaches to interdisciplinary science. Involvement of stakeholders and scientists from outside plant pathology shows the importance of trade-offs, for example in the land-sharing vs. sparing debate. Further research is needed on climate change and plant health in mountain, boreal, Mediterranean and tropical regions, with multiple climate change factors and scenarios (including our responses to it, e.g. the assisted migration of plants), in relation to endophytes, viruses and mycorrhiza, using long-term and large-scale datasets and considering various plant disease control methods

    The comparative biology of New Zealand oystercatchers

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    Oystercatchers comprise a distinctive group of mollusc-eating shorebirds. They form an extremely uniform monogeneric family which has not undergone any major adaptive radiations into a diversity of ecological niches, but rather has dispersed from original centres of distribution to occupy identical niches in new geographical localities. The uniformity of structure and habit displayed within the group has been attributed by Larson (1957) to a high ecobiotic specialisation with centripetal selection involved. Throughout their range, oystercatchers exploit identical ecological niches which require specialised habits for successful utilisation. The specialised feeding habits of oystercatchers are well documented (Murphy, 1925; Dewar, 1940; Larson, 1957; Tinbergen and Norton-Griffiths, 1964; Dare, 1966), and a natural consequence of this specialisation is that it is restrictive to adaptive radiation

    <strong>Harry Beal Torrey (1873–1970) of California, USA, and his research on hydroids and other coelenterates</strong>

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    Calder, Dale R. (2013): Harry Beal Torrey (1873-1970) of California, USA, and his research on hydroids and other coelenterates. Zootaxa 3599 (6): 549-563, DOI: http://dx.doi.org/10.11646/zootaxa.3599.6.
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