Relatedness and microgeographic genetic variation in Rhytidoponera mayri,an Australian arid-zone ant

Summary We use a multiallelic regression and jack-knife technique to estimate relatedness and its confidence limits in a sample of 117 nests of the Australian arid zone ant Rhytidoponera mayri, using the genotypes at a prolifically-polymorphic amylase locus. Relatedness between workers from the same nest is low, whether calculated with respect to the complete sample of nests (b=0.121<0.158<0.195), or by restricting the analysis to those nests bordering a cell in a Gabriel-connectedness graph (b=0.101<0.126<0.151). Relatedness between workers of neighboring nests was determined for nearest-neighbors (b=0.021<0.054<0.087), and for nests connected in the Gabriel network (b=0.018<0.036<0.054). Relatedness is thus low but significant at both within- and between-nest levels, as is consistent with a life history involving multiple egg-layers and colony foundation via fission. Estimating relatedness for the different alleles separately yields some significant differences between alleles. We also tested for geographic substructuring using autocorrelation analysis of nine alleles separately and the factor scores for the first two principal components of all the allele frequencies: six of the eleven patterns tested differed significantly from randomness at the 95% level.     

Measurement of photosynthetic production of a marine phytoplankton population using a stable 13C isotope

The use of stable isotope of carbon, ¹³C, for the determination of the photosynthetic rate of a marine phytoplankton population was examined. Particular concern was paid to the effects of non-phytoplanktonic organic carbon and the enrichment of inorganic carbon on the estimation of the photosynthetic rate. Photosynthetic rates determined by the ¹³C method showed a remarkable agreement with those determined by the ¹⁴C method. Insitu determinations of photosynthetic rate were made in three different water types: open ocean, coastal and neritic waters, which included oligo- and mesotrophic waters, by using the ¹³C method established.     

Growth and production of the inshore marine copepod Pseudodiaptomus marinus in the central part of the Inland Sea of Japan

The growth and production of the inshore marine copepod Pseudodiaptomus marinus was studied in the central part of the Inland Sea of Japan. The stage-specific growth rate was determined under controlled laboratory conditions by examining the length-weight relationship and development rates at various temperatures. The stage duration was short and constant from NII to CII, beyond which development was retarded. Males developed faster than females in CIV and CV. The specific growth rate was highest in copepodite stages followed by the nauplii and adult females (=egg production rate). The daily production of P. marinus was estimated from the stage-specific growth rate and stage-specific abundance in nature as the sum of the individual stages. The production changed seasonally with water temperature and population biomass. Daily production and biomass (P/B) ratios increased linearly with temperature. Total annual production was 20.7 mg C m^-3 yr^-1.     

Decomposition of urea associated with photosynthesis of phytoplankton in coastal waters

Decomposition of urea in seawater was studied in Mikawa Bay, a shallow eutrophic bay on the southern coast of central Japan. The urea concentration in seawater ranged from 1.3 to 5.9 μg-at. N/1 and comprised 12 to 40% of the dissolved organic nitrogen. Using ¹⁴C labelled urea, the rate of CO₂ liberation from urea and the incorporation rate of urea carbon into the particulate organic matter were determined. For the surface samples, high rates of CO₂ liberation from urea as well as the incorporation of urea carbon into the particulate organic matter were observed in the light, while much lower rates were obtained in the dark. Incubation experiments with exposure to different light intensities revealed that the rate of CO₂ liberation from urea and the incorporation of urea carbon into particulate organic matter changed with light intensity, showing a pattern similar to that of photosynthesis. The highest liberation and incorporation rates were observed at 12,000 lux. Incubation in light and in dark produced marked decreases and increases, respectively, in urea and ammonia, while no appreciable changes were observed for nitrate and nitrite. It is suggested that urea decomposition associated with photosynthetic activity of phytoplankton is one of the major processes of urea decomposition, and that it plays a significant role in the nitrogen supply for phytoplankton in coastal waters.     

Concentration of lodine and bromine by plants in the seas of Japan and Okhotsk

Iodine and bromine content were measured in 24 species of red (Rhodophyta), brown (Phaeophyta) and green (Chlorophyta) seaweeds and 2 species of higher water plants (Embryophyta) from the Sea of Japan, as well as in 12 species of the abovecited taxa and 1 species of flowering plant from the Sea of Okhotsk. Iodine was determined by photometric extraction with brilliant green, and bromine by neutron activation of samples. Phaeophyta and Rhodophyta were richest in iodine and bromine content. Representatives of the order Ceramiales (Rhodophyta) had high iodine and bromine contents. Thus, iodine concentrations in Ptilota filicina, Campylaephora hypnaeoides and Myriogramme yezoensis, a new iodine concentrator discovered by us, amount to 0.42, 0.094 and 0.75%, respectively. Bromine content in representatives of the family Rhodomelaceae was 3.36 and 3.74% in Japan Sea and Okhotsk Sea Rhodomela larix, respectively. Polysiphonia japonica (Rhodomelaceae) is a newly discovered concentrator of bromine (3.20%). Many species of the order Laminariales (Phaeophyta) were characterized by high iodine contents: Laminaria japonica, L. cichoriodes, L. inclinatorhiza, Cymathaere japonica and Alaria marginata. The Br:I ratio for all the species except those that concentrated iodine, was more than 1. Seaweeds that grow at greater depths showed increased iodine and bromine contents. A tendency toward increased iodine content was observed in species growing further to the North. Iodine and bromine were accumulated selectively by various organs of Sargassum pallidum.     

Nutrients and biomass distribution in the Gulf of Aqaba (Elat), Red Sea

The distribution of phosphate, nitrate and silicate values obtained from 300 samples and of biomass determined by displacement volume in about 1,900 vertical plankton hauls (65, 200 and 330 m) collected from 8 oceanographic station during 1974–1975 in the Gulf of Aqaba (Elat) are summarized and illustrated by crosssections. Generally, the Gulf is poor in nutrients and the data indicate that it is filled with upper (150 m) Red Sea waters, flowing in over the sill of Tiran. Nutrient content of the upper and deep waters immediately outside the sill are well within the known range of those in the northern Red Sea. Biomass values are relatively low in the Gulf are generally similar to those reported from the northern Red Sea. Both nutrients and biomass values display seasonal and bathymetric variations in the Gulf and outside the sill.     

Possible strategy for the survival of marine bacteria under starvation conditions

A population of a psychrophilic marine vibrio (Ant-300) suspended at a low cell density in natural seawater (SW) or artificial seawater (ASW) showed an initial 200-fold increase in cell numbers. Ant-300 suspended in ASW at various densities showed a magnified initial increase in numbers as well as increased longevity as the population density decreased. The magnitude of the initial increase and the viability of the cells after 7 weeks continued incubation were the same whether the cells were suspended in SW, ASW amended with amino acids, or organic-free ASW. Continued incubation (long-term starvation) of a culture of Ant-300 at low cell densities in ASW showed that after 70 weeks over 15 times the orginal number of cells were still viable. When compared to the starvation survival of other bacceria, Ant-300 exceeds the longest reported starvation survival by at least 2.5 times. Our data indicate that Ant-300 is especially adapted for survival at low nutrient concentrations and low population densities due to a sustained increase in cell numbers that may represent a species survival mechanism for marine bacteria.Technical Paper No. 4493, Oregon Agricultural Experiment Station.     

Development of a new antifouling method for a marine cooling water system

Variations in meristic characters occur within and between samples of milkfish Chanos chanos (Forsskal) collected on June 1977 from five localities in Philippine waters. The unbranched anal and ventral fin rays are the most plastic, and vertebral number is the most stable of nine meristic characters examined. The number of ventral fin rays is the only meristic feature which differed consistently enough to suggest distinct population groups: South China Sea, comprising samples from Ilocos and Panay Island; Pacific Ocean from Bicol; and Celebes Sea, from Zamboanga and Davao. A discriminant analysis which incorporated generalized distance (Mahanalobis D²) and percent overlap of a reduced set of characters indicated several morphometric subgroups of milkfish in Philippine waters, although geographic subgroups were not clearly demonstrated.SEAFDEC Contribution No. 218     

Population genetic structures of the fissiparous seastar Coscinasterias acutispina in the Sea of Japan

The morphological characteristics and the population genetic structures of the fissiparous seastar Coscinasterias acutispina were investigated for eight sites in the Sea of Japan in order to clarify the presence of sexual and asexual reproduction. Morphological observation based on arm length showed that fission was common at all eight sites examined, indicating the likely production of clonal individuals. A random amplified polymorphic DNA (RAPD) marker was used to detect clones arising by fission and to assess gene flow among sites. A simulation approach using RAPD data revealed the presence of clonal individuals at almost all sites, suggesting the existence of asexual reproduction. The result of phylogenetic analysis according to RAPD genotype showed no relationship between genetic and geographic distances. Considering the limited movement ability of seastar species during the adult phase, these observations suggest the existence of marked gene flow among sites, due to dispersal of planktonic larvae produced by sexual reproduction. These observations suggest that multi-locus genotypic compositions depend on the relative amounts of recruitment from sexual and asexual reproduction in each population.