Laboratory culture of the lobate ctenophore Mnemiopsis mccradyi with notes on feeding and fecundity

Collection and culture of the large lobate ctenophore Mnemiopsis mccradyi Mayer is described, including the requirements for successful development of larvae. Particular attention must be given to the collection of these delicate animals, the handling and provision of live microzooplankton of suitable size for the larvae, and the provision of food densities for the adults which neither stimulate “wasteful” feeding nor limit their growth. Although these ctenophores will ingest detritus and algal cells in high concentration, they lost weight at the same rate as starved individuals unless provided with living zooplankton. Under optimum conditions, specimens would lay eggs within 13 days of their own birth. By the 17th day they laid eggs daily, and had produced an average of 8,000 eggs within 23 days after birth. The maximum number of eggs laid by a single wild individual within 24 h after being brought into the laboratory was 10,000. Their high fecundity, rapid generation time, and ability to self-fertilize help to explain their sudden appearance in bloom proportions at periods of high food concentration in the environment, often referred to in the literature.     

Carbohydrases of some marine invertebrates with notes on their food and on the natural occurrence of the carbohydrates studied

Extracts of 22 marine invertebrates were incubated with 29 different carbohydrates, and enzyme spectra estimated from chromatograms. Enzymatic activities were quantified as reducing sugar in 14 of these species. Significant hydrolysis of laminaran, glycogen, and amylose was found in nearly all species, while hydrolysis of oligosaccharides and structural polysaccharides in most cases was weak or absent. The strongest overall degradation of carbohydrates was found among crustaceans. Enzymatic degradation of laminaran shows some relation to food, but the spectra of carbohydrases are not directly predictable from knowledge of natural food sources. Some carbohydrases (sucrase, cellobiase, lactase) could not be explained by ecological considerations. The results indicate that structural polysaccharides are utilized only to a small extent.     

Hydrobiological notes on the high-salinity waters of the Sinai Peninsula

The Sinai Peninsula is surrounded by high-salinity seas and bordered by saline lagoons. The geologically long-lasting high-saline conditions have resulted in the formation of a metahaline marine fauna in the Red Sea. Metahaline marine elements also inhabit the saline lagoons with salinities up to 60 to 80 In open lagoons, beyond these values, a hyperhaline community of marine euryhaline organisms has established itself. Only beyond 100 S, or if the lagoon has no open connection with the sea, is this community replaced by hypersaline continental fresh-water elements. These observations are also discussed in the light of possible generalizations.     

Sound-producing mechanisms in carapid fishes,with notes on phylogenetic implications

The anatomy of otophysic structures associated with the swimbladders of Carapus bermudensis, Onuxodon parvibrachium, and O. margaritiferae is strikingly similar to that of certain ophidiids and indicates common origins and close affinities between carapids and ophidiids. The suggested function of these structures is the production of sound. The apparent inquiline habits, lack of sexual dimorphism in sound-producing mechanisms, and specialized larval structures of carapids support the nominal separation of these families.     

Consistent association of crenarchaeal Archaea with sponges of the genus Axinella

The association of sponges with microorganisms has been accepted to be a common feature of the phylum Porifera. Herein we describe the association between filamentous Archaea and three Mediterranean species of sponges from the family Axinellidae (Porifera: Demospongiae). Axinella damicornis, A. verrucosa and Axinella sp. harbor a high concentration of filamentous Archaea in the collagen that surrounds the siliceous spicules that form their skeleton. These Archaea have been found in every axinellid specimen studied, regardless of their environment and collection time. The morphology of the filaments has been studied using transmission electron microscopy, and they all show similar characteristics. Their nature has been determined by in situ hybridization experiments and by PCR amplification and sequencing of their 16S DNA. Each sponge species contains a single filamentous archaeal phylotype. The Archaea of the three sponges are closely related to each other and to the marine "group 1" crenarchaeotes. Our findings suggest that this newly described association could be defined as a symbiosis, where biochemical and/or metabolic relationships between the sponge hosts and their symbionts remain to be determined.     

The distribution of molluscs on littoral rocks in Ceylon,with notes on their ecology

Molluscs inhabiting littoral rocks were collected from 43 stations around Ceylon, and 57 species belonging to 20 families were identified. An account is given of the nature and distrbution of littoral rocks around the island, and the stations examined. On each shore, the distribution of the molluscs was studied in relation to the broad zonation of the shores themselves and observations were made on plant and animal associations of each speices. The limits of the broad zones of the shores were defined with reference to biological indicators. Analysis of the data collected led to a classification of the rocky shores into three groups, each characterized by particular combinations of mollusc species and distinct patterns of shore zonation. Some molluscs were found to be distributed over the whole island, others to be common to two groups of shores only, and still others to be confined to a single shore type. An attempt has been made to explain the presence or absence of species on various groups of shores, and to explain discontinuities in distribution on the basis of environmental factors such as the nature of the substratum, degree of wave exposure, and weed cover. A key, based primarily on external features, has been devised for the identification of the species listed.     

Morphology and field behavior of pteropod molluscs: feeding methods in the families Cavoliniidae,Limacinidae and Peraclididae (Gastropoda: Thecosomata)

From 1983 to 1985 we studied the in-situ feeding behavior of fourteen species belonging to nine genera of thecosomatous pteropods, one in the family Limacinidae, seven in the family Cavoliniidae, and one in the family Peraclididae. All the euthecosomes we examined fed with a large spherical mucous web. Peraclis reticulata (D'Orbigny), however, uses a funnel-shaped mucous sheet, resembling that of other pseudothecosomes. Although the feeding mechanisms are similar in all the animals we examined closely, we found great differences in the size and morphology of the external part of the mantle. In species of Diacria and Cavolinia the external mantle attains its greatest complexity, and appears to be used for the sorting or rejection of food and for flotation. Species of the other five cavoliniid genera we studied have greatly reduced external mantles and sink slowly while feeding. Species of Limacina have no external mantle but appear to arrest sinking by setting their mucous webs. P. reticulata, which also appears to be neutrally buoyant, has an extensive external mantle that completely covers the shell. We conclude that feeding with a large mucous web explains the presence of fragments of large, fast moving prey in the stomach contents of both pseudothecosomes and euthecosomes. At present, it is impossible to decide whether thecosomes should be regarded as carnivorous trappers of prey or as suspension feeders. The use of an external mucous web for feeding is probably common to all thecosome pteropods and is the fundamental andaptation that enables them to live holoplanktonically.     

Ecology of the metahaline pool of Di Zahav,Gulf of Elat,with notes on the siphonocladacea and the typology of near-shore marine pools

The hydrobiology of a metahaline near-shore pool, at Di Zahav on the Sinai coast of the Red Sea, has been studied. Salinity of the pool fluctuates between 45 and 60, and winter temperatures are as low as 10°C. The shore consists partly of beach rock, some of it still in statu nascendi. Serpulid reef-boulders also occur, covered with typical marine species. Three siphonocladacean green algae (Siphonocladus rigidus, Dictyosphaeria cavernosa, and Valonia utricularis), form abundant crusts on the boulders. Several peculiar faunal elements are discussed. Traits in common with the Suez Canal biota are discerned. A typology for the nearshore pools of Sinai is proposed.     

文化差异与跨文化营销的研究进展

围绕文化差异与跨文化营销的主要研究成果,分析文化差异与跨文化营销研究的兴起情况以及国内外学者对文化差异和跨文化营销的研究的现状.     

Morphology and orientation of tube extensions on aggregations of the polychaete annelid Phragmatopoma californica

The morphology of organisms can influence fluid flow near their surfaces which, in turn, can influence the rates of mass exchange as well as the ability of the animals to capture and retain particles. In this paper, the morphologies and orientations of extensions on the tubes of aggregated individuals of the sabellariid polychaete Phragmatopoma californica from different habitats are described. The effects of these structures on fluid exchange and feeding-tentacle deflection are also assessed. The tube shape of aggregated P. californica varies among habitats. In exposed habitats, extensions on tubes (flares) encircle the entire circumference of the worms' apertures. In more protected habitats, extensions (hoods) partially encircle the circumference of apertures and are oriented so that the opening of the hood faces into the predominant direction of water flow over the aggregation. After the surface structures are damaged, hoods are repaired more quickly than flares. In this study, all damaged hodds were repaired within 24 h while flares were fully repaired only after 240 h. The repaired hoods are oriented in the same direction as the original structures Both hoods and flares decrease the rate of fluid exchange between the aggregation surface and the mainstream water flow. These structures also decrease the deflection of the feeding tentacles by the water flow. The orientation of the hoods relative to the direction of water flow affects both the rates of fluid exchange and the deflection of the tentacles. Present address: Hawaii Institute of Marine Biology, P.O. Box 1346, Kaneohe, Hawaii 96744, USA     

Effect of the receding ice-edge on the condition of mid-water fishes in the northwestern Weddell Sea: results from biochemical assays with notes on diet

Electrona antarctica and Bathylagus antarcticus are dominant fishes in the Southern Ocean pelagic ecosystem with disparate life histories, making them excellent subjects for comparative studies. Twenty-one indices of nutritional condition were compared in both species by observing changes in each index as it varied spatially and temporally in association with the marginal ice-zone bloom in the northwestern Weddell Sea. E. antarctica and B. antarcticus exhibited very different patterns of response to the bloom. Nutritional condition increased in 11 of 21 measures in E. antarctica, suggesting that it was in poorer condition at ice-covered stations and in greatly improved condition in post-bloom, open-water stations. The data, combined with a few observations of larvae, indicate that E. antarctica increases feeding before the spring bloom, rapidly building stores of lipid, which are probably used for spawning. In contrast, only three measures of condition were variable in B. antarcticus, and lipid actually decreased from ice-covered to open water. RNA:DNA values increased in open water, coinciding with an increase in food volume present in their guts. These observations, coupled with observations of larvae in ice-covered stations, suggest that B. antarcticus possesses sufficient energetic stores to spawn prior to the bloom, so that larvae are able to fully utilize available resources associated with the spring bloom. Increased somatic growth, as indicated by RNA:DNA, may not begin until later, when the bloom was beginning to decline. Earlier work, which suggested that the deeper living, non-migrating species, like B. antarcticus, would not be affected by the bloom until after shallower, migratory species, like E. antarctica, is supported. Of the assays tested, RNA:DNA appeared to be the most sensitive. The combined assessment of many measures including biochemical, compositional, dietary, and age estimates from single specimens is possible if the samples are treated with sufficient care. The reliance upon a single measure to help interpret the ecology of a species, especially in nekton-sized species, is not as effective as techniques used in combination. Received: 12 January 2000 / Accepted: 16 August 2000     

The effects of hyper-and hypo-chlorinities on members of the wood-boring genus Limnoria

Three species of the marine wood-boring genus Limnoria were subjected to hypo-and hyper-chlorinities under laboratory conditions for a 28-day period. L. lignorum was more tolerant to hypo-chlorinities and L. tripunctata more tolerant to hyper-chlorinities. L. quadripunctata was the most sensitive species. L. tripunctata had the highest burrowing rate at all chlorinities and L. quadripunctata the lowest rate.     

Halistaura bruuni sp. nov. (Leptomedusae,Mitrocomidae) with notes on its distribution and ecology

A new hydromedusa collected in 1963 in the Bay of Bengal during the International Indian Ocean Expedition by the RV Anton Bruun is here described as Halistaura bruuni sp. nov. Some environmental data are given. The new species is characterized by a number of open marginal vesicles approximately equal to that of the tentacles, oval gonads on the distal half of the radial canals, and by the presence of nematocyst depots in the tentacle bulbs.Publ. No. 273 of the Instituto Oceanográfico da U. S. P.     

Reproduction of meso- and bathypelagic chaetognaths in the genus Eukrohnia

Reproduction of meso- and bathypelagic chaetognaths, a major group of zooplankton and hermaphroditic animals, became clear after the microscopic examination of samples collected from the Pacific Subarctic Water. Species of the genus Eukrohnia carry their developing eggs in two marsupial sacs, one on each side, and the young are retained in these marsupia for at least some period after hatching. This is in line with a general trend for low fecundity, as care of the young increases. Almost all individuals are protandric, the testes maturing sooner than ovaries. These facts suggest that the reproduction of these species depends upon cross-fertilization.     

Nutrient regeneration by zooplankton during a red tide off Peru,with notes on biomass and species composition of zooplankton

During March and April 1976, a red tide, dominated by the dinoflagellate Gymnodinium splendens Lebour, developed in the vicinity of 15°06'S and 75°31'W off Peru. At the height of the bloom, the euphotic zone was 6 m deep and the chlorophyll a at the surface was 48 g l^-1. A daily collection of zooplankton at 09.00 hrs showed large fluctuations of biomass, from 0.2 to 3.84 g dry weight m^-2 in a water column of 120m. Copepodids and nauplii dominated the collections. During a period of reduced wind, the adult copepods were a mixture of the species characteristic of the coastal upwelling system and the neritic species associated with more northerly, tropical waters. Nitrogen regeneration by the zooplankton varied with the development of the bloom, the type of zooplankton dominating the experiment, and biomass fluctuations, but never accounted for more than 25% of the nitrogen uptake by phytoplankton.     

土壤pH对锰赋存形态的影响

以热带亚热带土壤为研究对象，用连续分级浸提法探讨了土壤中锰赋存形态与ｐＨ值的关系。结果表明：土壤中的锰处于一种动态平衡状态，各形态锰的含量及其占全锰的比例随ｐＨ的变化而变化，其中代换态锰和有机态锰随ｐＨ值升高而减少，氧化态锰、无定形铁结合态锰和晶形铁结合态锰则随ｐＨ值升高而增加，土壤中锰的生物有效性则随ｐＨ值升高而降低。     

种植密度对不同株型玉米生长及根系形态特征的影响

选取平展型(ND108)、紧凑型(ZD958)、小株小穗型(CF008)玉米品种,采用PVC管土柱法种植,密度为1株/盆、2株/盆和3株/盆,探讨种植密度对不同株型玉米的生长特性及根系形态的影响.结果表明:种植密度增加,不同株型玉米个体生长均受到抑制,各项根系形态指标显著降低(P<0.01),但较低幅度增密对平展型品种(ND108)根系各项形态指标无显著影响;种植密度对不同株型玉米品种比根长(SRL)与比根表面积(SRS)的影响程度有显著差异,对平展型品种(ND108)影响最大,对紧凑型品种(ZD958)影响最小;穗根比、根系生物量分配比例存在显著基因型差异,平展型品种(ND108)较其它两个品种具有较高的根系干物重分配比例,但其穗根比较低.综上,增密过程中平展型品种(ND108)倾向于通过形成庞大根系以提升单株竞争能力,但是个体间激烈的竞争将限制群体产量的提高;而紧凑型品种(ZD958)和小株小穗型品种(CF008)个体间竞争较弱,因而在群体压力增大时能够通过增强自身根系的吸收能力以保证对地上部水分、养分供应,有可能获得更高的群体产量.     

不同耕作制度对土壤中锰赋存形态及其有效性的影响

以花岗岩母质发育的旱地红壤和水稻土为研究对象，探讨了不同耕作制度下土壤中锰的赋存形态及其生物有效性。结果表明：在水旱轮作条件下，土壤中的锰更多地以代换态和晶形铁结合态存在；旱作土壤中的锰则较多地以有机态和无定形铁结合态存在．然而，单位有机质络合的锰量却是水稻土大于红壤。水旱轮作措施具有活化锰的作用，使得土壤中锰有效性更大并且主要以代换态存在。旱作土壤则不同，土壤活性锰除来自代换衣外，尚有大约４５％以有机态或无定形铁结合态存在。     

The reproductive biology of Hymenaster membranaceus from the Rockall Trough,North-East Atlantic Ocean,with notes on H. gennaeus

Samples of the deep-sea spinulosan asteroid Hymenaster membranaceus Wyville Thomson were collected in a timeseries of 19 bottom trawls spanning the period April 1978 to October 1981 from a 2200 m-deep station in the northern Rockall Trough. The reproductive biology of this species was studied from histological sections of the gonad, and compared with that of H. gennaeus H. L. Clark which was collected in the same hauls. At first sexual development, oogonia develop in nests surrounded by small accessory cells. Previtellogenic oocytes remain in the periphery but, at maturity, oocytes ranging up to 1 100 m fill the ovary. A variety of accessory cells pack the lumen and may be nutritive or degenerative. It appears that a small number of oocytes are spawned intermittently, but there is no evidence of overproduction and break-down of superfluous oocytes. A few large oocytes become senescent and undergo internal break-down, releasing periodic acid Schiff-positive material into the lumen. Size-frequencies of oocytes indicate that eggs may be spawned as a continuous slow release, and there is no evidence of reproductive synchrony between or within samples. On reaching maturity, males appear always to be ready to release spermatozoa. Spawning is probably stimulated by egg release during chance encounters with mature females. There is no evidence for brooding, and from the large size and yolky nature of the egg direct lecithotrophic development at or near the seabed is inferred. A limited histological study of H. gennaeus indicates that egg production is very similar, but the two species differ in the nature of the accessory cells and amorphous material filling the lumen.     

Evolution, radiation and chemotaxonomy of Lamellodysidea, a demosponge genus with anti-plasmodial metabolites

Sponges of the family Dysideidae (Dictyoceratida) are renowned for their diversity of secondary metabolites, and its genus Lamellodysidea, particularly Lamellodysidea herbacea, is the most studied taxon biochemically. Despite its importance, the taxonomic status of L. herbacea—whether it is a distinct species or a species complex—has never been assessed. Recent biochemical profiling revealed anti-plasmodial activity of brominated compounds in Lamellodysidea of the Pacific. Here, we present a comparative chemotaxonomic and molecular analysis of selected Dysideidae from the Pacific and the Indian Ocean (New Caledonia, Great Barrier Reef, Fiji, Mayotte, Guam, Palau). We investigated the phylogenetic relationships between the populations and assessed their bioactive (PBDE) compounds in order to unravel the taxonomic status of this commercially important group of sponges and assessed patterns of dispersal and biochemical variation. The molecular phylogeny was based on the internal transcribed ribosomal spacer and compared against a PBDE phylogeny for several specimens. Molecular data revealed a diversity of Indo-Pacific L. herbacea populations, also reflected by different PBDE compound profiles. Molecular and biochemical data also revealed a Lamellodysidea species new to science. Several specimens misidentified as Lamellodysidea were detected based on their position on different clades in the molecular phylogeny and their production of different halogenated compounds (brominated vs. chlorinated). The direct comparison of molecular and biochemical data also provided evidence for the occurrence of a host switch event and support for the theory that abiotic factors, such as sedimentation, affect the chemical constituents produced in L. herbacea.