Effects of the environment on developmental rates of sporelings of two Hypnea species (Rhodophyta: Gigartinales)

Growth of sporelings of Hypnea cervicornis J. Agardh and H. chordacea Kuetzing in response to gradients of selected environmental factors has been investigated. The sporelings of H. cervicornis tolerated higher levels of the tested parameters (e.g. salinity and temperature) than those of H. chordacea. In all the treatments, the sporelings of H. cervicornis grew significantly faster than those of H. chordacea. The ecological and agronomic implications of these findings are discussed.Extracted from a Ph. D. dissertation submitted to the Graduate Division of the University of Hawaii in Fall, 1974.     

Effects of solar UV radiation on germination of conchospores and morphogenesis of sporelings in <Emphasis Type="Italic">Porphyra haitanensis</Emphasis> (Rhodophyta)

The effects of ultraviolet radiation (UVR 280–400 nm) on the germination of Porphyra haitanensis conchospores and on the growth and morphogenesis of the subsequent sporelings were investigated by culturing the released conchospores under natural sunlight from 29 September to 6 October 2005. Germination increased with time and was faster when UV-B was excluded using cut-off filters. There were significant negative effects of UV-B radiation on growth and cell division of sporelings, with decreases up to 18% for thallus length, between 6 and 18% for thallus width, up to 29% for thallus area, and between 6 and 14% for cell size as compared to PAR-controls. UV-A had a significant positive effect on morphogenesis, enhancing the formation of sporelings with cells dividing transversely; on the other hand, UV-B delayed the formation of such sporelings. We also tested the effects of solar UVR on the growth of P. haitanensis juveniles and found no significant effects. Our results indicate that UV-A has an important role in the germination and morphogenesis of the species, but on the other hand, sporelings of P. haitanensis are more sensitive to UV-B radiation than juveniles.     

Relationships between species richness, evenness, and abundance in a southwestern savanna

Species richness and evenness are components of biological diversity that may or may not be correlated with one another and with patterns of species abundance. We compared these attributes among flowering plants, grasshoppers, butterflies, lizards, summer birds, winter birds, and rodents across 48 plots in the grasslands and mesquite-oak savannas of southeastern Arizona. Species richness and evenness were uncorrelated or weakly negatively correlated for each taxonomic group, supporting the conclusion that richness alone is an incomplete measure of diversity. In each case, richness was positively correlated with one or more measures of abundance. By contrast, evenness usually was negatively correlated with the abundance variables, reflecting the fact that plots with high evenness generally were those where all species present were about equally uncommon. Therefore richness, but not evenness, usually was a positive predictor of places of conservation value, if these are defined as places where species of interest are especially abundant. Species diversity was more positively correlated with evenness than with richness among grasshoppers and flowering plants, in contrast to the other taxonomic groups, and the positive correlations between richness and abundance were comparatively weak for grasshoppers and plants as well. Both of these differences can be attributed to the fact that assemblages of plants and grasshoppers were numerically dominated by small subsets of common species (grasses and certain spur-throated grasshoppers) whose abundances differed greatly among plots in ways unrelated to species richness of the groups as a whole.     

Interactions between environment, species traits, and human uses describe patterns of plant invasions

Although invasive alien species (IAS) are a major threat to biodiversity, human health, and economy, our understanding of the factors controlling their distribution and abundance is limited. Here, we determine how environmental factors, land use, life-history traits of the invaders, residence time, origin, and human usage interact to shape the spatial pattern of invasive alien plant species in South Africa. Relationships between the environmental factors and the extrinsic and intrinsic attributes of species were investigated using RLQ analysis, a multivariate method for relating a species-attribute table to an environmental table by way of a species presence/absence table. We then clustered species according to their position on the RLQ axes, and tested these groups for phylogenetic independence. The first three axes of the RLQ explained 99% of the variation and were strongly related to the species attributes. The clustering showed that, after accounting for environmental factors, the spatial pattern of IAS in South Africa was driven by human uses, life forms, and reproductive traits. The seven clusters of species strongly reflected geographical distribution, but also intrinsic species attributes and patterns of human use. Two of the clusters, centered on the genera Acacia and Opuntia, were phylogenetically non-independent. The remaining clusters comprised species of diverse taxonomic affinities, but sharing traits facilitating invasion in particular habitats. This information is useful for assessing the extent to which the potential spread of recent introductions can be predicted by considering the interaction of their biological attributes, region of origin, and human use.     

Somatic condition of the fish, Notopterus notopterus (Pallas) during different phases of the reproductive cycle

The study on the mathematical relationship between length and weight of fishes has considerable importance in fishery research especially for the study of fish population dynamics and patterns of growth in fish stocks. This aspect is useful in rationally managing the population of fishes, and is an index of relative robustness of the fish). Variations from expected weight or length of an individual fish or group of fish indicate the general well being and state of gonadal development. The condition of fish can be influenced by the onset of maturity. The results indicate that the overall condition of the female and male fish seems to get improved towards the approach of maturing and mature stages of the gonads during pre-spawning phases. The reduction in the condition factor (K) and somatic condition factor (Ks) during spawning phase may be because of the fish becoming exhausted due to spawning activity. Although improvement in the condition of the fish was observed on the approach of breeding period, the overall condition seems to be better in the aquatic body from which the fish was collected.     

Critical swimming speeds of late-stage coral reef fish larvae: variation within species,among species and between locations

The swimming abilities of larval fishes are important for their survival, potentially affecting their ability to avoid predators, obtain food and control dispersal patterns. Near settlement swimming abilities may also influence spatial and temporal patterns of recruitment. We examined Critical speed (U-crit) swimming ability in late stage larvae of 89 species of coral reef fishes from the Great Barrier Reef and the Caribbean. Coefficients of variation in U-crit calculated at the individual level were high (28.4%), and this was not explained by differences in size or condition factor of these same larvae. Among species U-crit ranged from 5.5 cm s⁻¹ to 100.8 cm s⁻¹ (mean=37.3 cm s⁻¹), with 95% of species able to swim faster than the average current speed around Lizard Island, suggesting that most species should be capable of influencing their spatial and temporal patterns of settlement. Inter-specific differences in swimming ability (at both the family and species levels) were significantly correlated with size and larval morphology. Correlations were found between swimming performance and propulsive area, fineness ratio and aspect ratio, and these morphological parameters may prove useful for predicting swimming ability in other taxa. Overall, the swimming speeds of larvae from the same families at the two locations were relatively similar, although the Lutjanidae and Acanthuridae from the Caribbean were significantly slower than those from the great barrier reef. Differences in swimming speed and body form among late stage larvae suggests that they will respond differently to factors influencing survival and transport during their pelagic phase, as well as habitat use following settlement.     

Climate, habitat, and species interactions at different scales determine the structure of a Neotropical bat community

Climate, habitat, and species interactions are factors that control community properties (e.g., species richness, abundance) across various spatial scales. Usually, researchers study how a few properties are affected by one factor in isolation and at one scale. Hence, there are few multi-scale studies testing how multiple controlling factors simultaneously affect community properties at different scales. We ask whether climate, habitat structure, or insect resources at each of three spatial scales explains most of the variation in six community properties and which theory best explains the distribution of selected community properties across a rainfall gradient. We studied a Neotropical insectivorous bat ensemble in the Isthmus of Panama with acoustic monitoring techniques. Using climatological data, habitat surveys, and insect captures in a hierarchical sampling design we determined how much variation of the community properties was explained by the three factors employing two approaches for variance partitioning. Our results revealed that most of the variation in species richness, total abundance, and feeding activity occurred at the smallest spatial scale and was explained by habitat structure. In contrast, climate at large scales explained most of the variation in individual species' abundances. Although each species had an idiosyncratic response to the gradient, species richness peaked at intermediate levels of precipitation, whereas total abundance was very similar across sites, suggesting density compensation. All community properties responded in a different manner to the factor and scale under consideration.     

Hybridization and introgression between Indo-Pacific species of Diadema

We present the first case of hybridization between echinoid species evaluated through genetic markers and morphology. We examined the three tropical Indo-Pacific species of the genus Diadema: D. paucispinum A. Agassiz, D. savignyi (Audouin) Michelin and D. setosum (Leske). Specimens morphologically intermediate between two of these species, D. savignyi and D. setosumhave previously been noted. Fertile hybrids have also been produced in the laboratory. To determine extent of hybridization, we first assayed the allozyme products of 22 loci in individuals which, on the basis of morphology and collection locality, could be unambiguously assigned to one of the three species. We found four loci that were either diagnostic or semi-diagnostic between D. setosum and the other two species, and one locus semi-diagnostic between D. savignyi and D. paucispinum.We then assayed individuals of intermediate morphology to find out whether they had hybrid genotypes. In the Ryukyu Islands, where D. setosum and D. savignyi coexist, we found one specimen which on the basis of all four diagnostic loci was an F₁ hybrid, and several individuals that could be either F₂ (or later-generation) hybrids or progeny of backcrosses.We also found one individual that on both genetic and morphological grounds appeared to belong to D. paucispinum (even though this spcies has only been reported from Hawaii and Kiribati) and three other individuals that carried alleles characteristic of D. paucispinum. Thus, previous reports of hybridization between D. setosum and D. savignyi were correct; it is also possible that larvae of D. paucispinum occasionally arrive at localities outside Hawaii, reach sexual maturity, and hybridize with the other two species. Counts of pure and hybrid morphotypes in other populations across the western tropical Pacific revealed a low but widespread incidence of apparent F₁ hybrids and backcrosses of D.savignyi and D. setosum. However, the existence of diagnostic or semi-diagnostic loci, low interspecific gene-flow estimates based on F _st statistics, and the lack of Hardy-Weinberg or linkage disequilibria among individuals of pure morphology all suggest that gene introgression between the three species is limited.     

北京西山地区不同林分健康状况比较研究

以不同树种林分健康状况比较研究为切入点,以北京西山地区同一时期的油松×侧柏混交林、油松（Pinus tabulaeformis）林、侧柏（Platycladus orientalis）林和栓皮栎（Quercus variabis）林为研究对象。通过构建林分健康评价指标体系,计算林分综合健康指数,分别对不同林分的健康状况进行了分析和比较,探讨不同林分开展森林健康经营的关键环节,同时也从森林健康的角度说明造林树种选择的重要性。研究结果表明：各林分综合健康指数都为正值但数值都不高,这表明目前各林分都处于健康状态,但对外界扰动反应较为敏感,按健康状况排序：油松×侧柏林0．234〉栓皮栎林0．186〉油松林0．145〉侧柏林0．128;从单个指标看,各林分中都有负值指标出现,由此揭示,对负值指标的调整和增加正向指标的指标值是森林健康经营的关键。     

Spore germination and early stages of development in Hypnea musciformis (Rhodophyta,Gigartinales)

The early stages of development of the carpospores and tetraspores of Hypnea muscilormis (Wulfen) Lamouroux have been investigated. Both types of spores germinated immediately after liberation. The spores segmented repeatedly into, 2, 3, 4 cells, etc. until a multicellular ball of cells was produced. The germination pattern was thus of the discal type, i.e., Typus discalis mediatus (Inoh, 1947) or the Dumontia-type in the terminology of Chemin (1937). Subsequently, a relatively expansive attachment holdfast was produced from each sporeling. This was followed by the development of up to 4 or more shoot axes arising from the basal disc. These findings are discussed with reference to an earlier study by the senior author on the developmental biology of other species of Hypnea Lamouroux.     

Sequential extraction of cadmium in different soil phases and plant parts from a former industrialized area

Cd concentrations in mobile phases of soil are more representative than total Cd concentration for estimating Cd bioavailability, physicochemical reactivity and mobility. In this study, selective sequential extraction procedures were used to determine Cd in different soil phases. Soil samples and plants grown in these soils were collected from a serpentine and copper-mining area in Maden-Elazig-Turkey. The extracted fractions were exchangeable/carbonate, reducible-iron/manganese oxides, oxidizable-organic matter and sulfides, and residual phases except silicates. Concentrations of Cd in soils and plant samples were determined by flame atomic absorption spectrometry and inductively coupled plasma-mass spectrometry. We found that Cd concentrations in the EDTA and NH₂OH·HCl extracts are higher in most soil samples compared to the other extracts. We conclude that Cd levels in mobile phases are unexpectedly high. The observed Cd concentrations are in ranges of 0.03–3.4 mg kg⁻¹ for soil and 0.02–2.5 mg kg⁻¹ for plant parts. The percentages of cadmium up to 56% in exchangeable and carbonates fractions were observed to be significantly higher than in those values less than 2% reported in literature. This study has shown that the modified extraction method can be usefully applied to determine Cd concentrations in potentially mobile phase of soil. Furthermore, it was concluded that Brassicasea and Rumex leaves can be used as hyperaccumulator plants because their translocation factor and/or enrichment coefficient values were found to be higher than 1.0.     

Size and structure of echinoderm populations associated with different coexisting coral species at Aldabra Atoll,Seychelles

The associated echinoderm fauna of 125 living heads of massive microatolls of Porites spp., branched heads of Porites nigrescens Dana and small, densely packed heads of the hydrocoral Millepora exacea Forskål of a shallow sublittoral lagoon flat at Aldabra Atoll, Seychelles was examined. The weight and number of echinoderms increased with coral size in all cases. The microatolls were the largest coral heads and sheltered the most diverse, underlying echinoderm cryptofauna comprising the largest bodied species, regardless of class or family. The infauna in heads of P. nigrescens was less diverse and smaller bodied than the echinoderms under microatolls. Only with P. nigrescens did species number increase with increasing coral size. Heads of M. exacea were the smallest and provided a habitat of compact interstitial spaces for the most depauperate, smallest bodied infauna which included juveniles of larger species. Ophiuroids dominated the coral-associated echinoderm faunas whereas larger bodied classes, such as echinoids and holothuroids, were less well represented. Large bodied ophiuroids such as certain ophiodermatids occurred only under microatolls, whereas the usually small bodied ophiotrichids dominated in the heads of M. exacea. The generally ubiquitous ophiocomids were well represented in, or under all corals. Heads of M. exacea could be nursery areas for recently metamorphosed juvenile ophiuroids and echinoids which, as they grow, seek shelter in corals with larger interstitial spaces such as P. nigrescens. Significant interspecific ophiuroid associations were related to space availability for larger species under microatolls and in heads of P. nigrescens. The possibility of microhabitat partitioning in corals among some ophiuroids is suggested.     

The effect of oxytetracycline on physiological and enzymatic defense responses in aquatic plant species Egeria densa,Azolla caroliniana,and Taxiphyllum barbieri

Oxytetracycline is an antibiotic widely employed in aquaculture to control and treat bacterial diseases of fish. Due to ineffective wastewater treatment, antibiotic residues from fish ponds are directly released into surface and groundwater affecting the environment. The Green Liver System® is a sustainable and cost-effective water treatment based on the ability of aquatic plants to biotransformation xenobiotics. To expand the application range of this system, Egeria densa, Azolla caroliniana, and Taxiphyllum barbieri were tested in response to oxytetracycline exposure. The aquatic plants were exposed to 0.5, 2.0, 5.0, and 25 μg/L oxytetracycline (n = 4) for 24 h in order to analyze the physiological responses (photosynthetic pigment contents and hydrogen peroxide formation -- H₂O₂), the biotransformation process (activity of glutathione S-transferase), and the antioxidant defense (glutathione reductase; peroxidase; and catalase) responses. There were no statistical differences in the photosynthetic pigment contents and H₂O₂ level between the treatment and control groups in the three aquatic plant species. It can be concluded that oxytetracycline does not provoke physiological damage to the tested species within 24 h of exposure. Nevertheless, the antioxidant defense mechanism was activated. Peroxidase and catalase were the most prominent antioxidant enzymes in the three plant species, whereas glutathione S-transferase activity was significantly increased in A. caroliniana and T. barbieri.     

The relationship between diversity profiles,evenness and species richness based on partial ordering

Problems with the notion of evenness, such as ambiguity, proliferation of indices, choice of indices, etc. can be overcome by a more fundamental, mathematical approach. We show that the Lorenz curve is an adequate representation of evenness. The corresponding Lorenz order induces a partial order in the set of equivalent abundance vectors. Also diversity can adequately be studied through a partial order and represented by a curve derived from the classical Lorenz curve. This curve is known as the intrinsic diversity profile (or k-dominance curve) and was introduced by Patil and Taillie (1979) and Lambshead et al. (1981).     

Antioxidant defense properties of Arctic amphipods: comparison between deep-, sublittoral and surface-water species

The toxic reactive oxygen species (ROS), produced naturally in an oxygenated environment, led to the development of antioxidant defenses by aerobic organisms to prevent tissue damage. Polar marine waters are regarded as a strongly prooxidant ecosystem, due to the high dissolved oxygen level and intense UV radiation during summer, while the deep waters are considered refuges against oxidative stress. In order to further elucidate the prooxidant and antioxidant forces associated with cold-water ecosystems and the implications of UV radiation, we sampled three amphipod species living at three different depths in the same water mass of the Arctic Ocean, characterized by low temperature (ca. 0°C), high oxygen level, and high ROS concentration in the surface water. The three species were the deep-sea amphipod Eurythenes gryllus, the benthic sublittoral amphipod Anonyx nugax and the surface-water species Gammarus wilkitzkii inhabiting the ice pack. The total oxyradical scavenging capacity (TOSC) was measured in the cytosolic fraction of the digestive gland and in the cell-free hemolymph of the three amphipod species. A significantly low TOSC toward peroxyl and peroxynitrite radicals (P<0.05) in E. gryllus compared with the shallow-water species (A. nugax) can be explained by the low metabolism of the deep-sea species. In the cell-free hemolymph, TOSC values are similar between E. gryllus and A. nugax, while in G. wilkitzkii a lower and higher TOSC toward hydroxyl and peroxynitrite, respectively, indicate specific adaptation to oxidative stress. Experimental exposure of A. nugax and G. wilkitzkii to H₂O₂ resulted in a significant change in TOSC (P<0.05) measured in the digestive gland and in the cell-free hemolymph of A. nugax, while no change (P>0.05) was noted in G. wilkitzkii. These data suggest that A. nugax is highly susceptible to oxidative stress and that G. wilkitzkii is characterized by a mechanism that prevents the diffusion of exogenous ROS through the gills or allows excretion of internal H₂O₂ through the gills to the environment.Communicated by M. Kühl, Helsingør     

Relationship between sediment texture,species richness and volume of sediment sampled by a grab

This paper discusses the problems involved in obtaining grab samples for direct comparison of the respective benthic fauna, using information from a survey conducted across the South African Continental Shelf below the Benguela Current. Many factors influence the depth of grab penetration into the sediment and, hence, the grab sample volume. One of the most important of these factors is sediment texture. While this fact has been long recognised, most workers have attached little significance to it. It is shown here that an exponential relationship exists between the grab sample volume and sediment texture, until the minimum percentage of silt plus clay that will give a maximum grab sample volume is reached. This relationship only extends to a certain depth, in this case to 280 m. There are more species per unit number of specimens (“species richness”) in association with sand or muddy-sand than with mud. A linear relationship is given between the grab sample volume and species richness between the depths of 280 and 440 m, inclusive.     

Reproductive,growth and life-history contrasts between two species of grapsid crabs,Sesarma cinereum and S. reticulatum

Two grapsid crabs, Sesarma cinereum (Bosc) and S. reticulatum (Say), were studied in the region of Beaufort, North Carolina, USA, during the summers of 1977, 1983, and 1984. The two grapsid species showed differences in social organization, habitat preferences, and number and size of first-stage larvae. We analyzed several other characters (growth rates, size at sexual maturity, reproductive effort per clutch) to determine if these differences could be related to a coherent pattern of life-history trends. While some relationships between characters were consistent with those found among other crab species, few seemed peculiarly matched to the ecological contrasts represented by our species. Our results suggest that other factors (phyletic predisposition; decoupling of selection between larval and adult stages; equally adaptive alternatives) may obscure the rules governing relationships between life-history characters and evolutionary trends.     

Prediction of germination rates of weed species: Relationships between germination speed parameters and species traits

In fields, the timing of weed emergence flushes is mostly related to the timing and rate of seed germination, which depend on seed dormancy level, soil temperature and water potential conditions as well as soil tillage and crop sowing date. Seed germination parameters are essential in weed dynamics models to account for the effects of soil conditions on weed demography. Since these parameters are difficult to measure, our objective was to test the possibility of estimating them from easily accessible information. Seed germination parameters (germination lag-time, time to mid-germination and mid-germination rate) were measured or collected from the literature for 25 weed species with contrasted seed characteristics. Correlations were then searched for between these parameters and morphological, chemical and physiological seed traits as well as seed dormancy level. The dormancy level was positively correlated with speed of germination parameters. Earliness of germination was positively correlated with seed lipid content and the seed area to mass ratio. Germination was also earlier and faster in species with a high base temperature for germination. These relationships explained about half the observed variability in germination speed parameters but should be further tested before being used to predict the germination behaviour of weed species in the field in different seasons.     

Studies on the content and nature of the phycocolloid from Corynomorpha prismatica (Rhodophyta,Cryptonemiales)

The phycocolloid from the red seaweed Corynomorpha prismatica J. Agardh (Cryptonemiales, Crateloupiaceae) has been investigated and found to show positive optical rotation ([] _D ²⁵ + 83^o), to be soluble in potassium chloride solution, to have a total sulphate content of 18.6±1.2% in unmodified gel and 15.0±0.9% in gel modified with lime. Total phycocolloid yields of 17.6±1.6% and 32.2±3.0% were obtained in gel extraction without lime and with lime added, respectively. The infrared spectra of the phycocolloid showed a broad absorption band at 860 to 800 cm^-1 and lacked single sharp peaks at 805 cm^-1. The phycocolloid was concluded to be a carrageenan akin to the lambda-type.