In situ observation of coral recruitment using fluorescence census techniques

A novel method for the observation of recruitment of fluorescent taxa was developed combining fluorescence census techniques with conventional microscopic examination. The new technique was used to observe coral recruitment on natural limestone plates over a period of 4 months on Meras reef, North Sulawesi, Indonesia. During this period, fluorescence photos were taken of each plate on a weekly basis. This allowed for the detailed observation of fluorescent coral recruitment in-situ. After specific time periods, the plates were sampled and the detected recruits were categorized to family level using their skeletal structure. The fluorescence census technique detected 97.6% of all coral recruits bigger than one millimetre in diameter. The diameter measurements of the recruit's skeletons were used to estimate growth rates at family level. Using the photo series method, the time of settlement of fluorescent recruits on the plates was determined. The results showed roughly linear diameter growth of recruits in the first two months. Acroporidae-polyps were 1.14 mm in diameter when they settled and grew at rate of approximately 0.18 mm in diameter per week. Pocilloporidae-polyps settled at approximately 1.14 mm and showed a growth rate of approximately 0.23 mm in diameter per week. Recruits of three families were observed in detail over time on the artificial plates using this method. While recruitment was fairly continuous, an increase in pocilloporid recruits was observed during the month of September. Similar increases were observed for acroporid recruits during the middle of November and the second quarter of December. This method identifies the limits of detection for the fluorescence census technique used and represents a useful method for the temporal fine scale observation of recruitment in situ.     

Species abundance distribution and dynamics in two locally coupled communities

This study considered a model for species abundance dynamics in two local community (or islands) connected to a regional metacommunity. The model was analyzed using continuous probabilistic technique that employs Kolmogorov-Fokker-Planck forward equation to derive the probability density of the species abundance in the two local communities. Using this technique, we proposed a classification for the species abundance dynamics in the local communities. This classification was made based on such characteristics as immigration intensity, species representation in the metacommunity and the size of local communities. We further distinguished several different scenarios for species abundance dynamics using different ecological characteristics such as species persistence, extinction and monodominance in one or both local communities. The similarity of the species abundance distributions between the two local communities was studied using the correlation coefficient between species abundances in two local communities. The correlation is a function of migration rates between local communities and between local and metacommunity. Immigration between local communities drives the homogenization of the local communities, while immigration from the metacommunity will differentiate them. This community subdivision model provides useful insights for studying the effect of landscape fragmentation on species diversity.     

A new genus of monstrilloid copepods (Crustacea) with anteriorly pointing ovigerous spines and related adaptations for subthoracic brooding

Maemonstrilla gen. nov. , known exclusively from females, is proposed for Monstrilla longipes A. Scott, 1909, M. turgida A. Scott, 1909, and five new species from coral reef plankton in the Ryukyu Islands, Japan: Maemonstrilla hyottoko sp. nov. (type species), M. polka sp. nov. , M. spinicoxa sp. nov. , M. simplex sp. nov. and M. okame sp. nov. A syntype of M. turgida was examined, but the holotype of M. longipes is lost; the latter species, being similar to several of the new species, is regarded as unidentifiable, and the identity of specimens assigned to it by several authors is put in doubt. Until now, all known female monstrilloids have had posteriorly trailing ovigerous spines, but in Maemonstrilla gen. nov. these spines point anteriorly and hold the egg mass between the legs beneath the thorax. This is the first known instance of subthoracic brooding in a planktonic copepod; its functional significance is discussed, and brooding habits of non‐planktonic copepods are briefly reviewed. The intercoxal sclerites of legs 1–4 in Maemonstrilla gen. nov. are very wide, making room for the eggs. In all species except M. turgida comb. nov. , the inner seta of the proximal segment of each leg ramus is either absent or reduced to a nub; this may lessen interference of the egg mass with leg movement. All species have a uniramous leg 5 with two setae, except M. turgida comb. nov. (biramous with setae on both rami); M. turgida comb. nov. is evidently the sister‐group of its congeners, each sister‐group in the genus being defined by additional autapomorphies. Scanning electron micrographs of all the Ryukyuan species except M. simplex sp. nov. are provided; these constitute a preliminary survey of monstrilloid integumental organs and cuticular ornamentation. Among the unusual features are two lobes at the base of the coxa in legs 1–4 of M. polka sp. nov. and M. spinicoxa sp. nov. and two pairs of posterodorsal spine‐like scales on the first and second free pedigers of M. turgida comb. nov. Newly hatched nauplii of M. okame sp. nov. , examined by scanning electron microscopy, are generally similar to those of Monstrilla hamatapex Grygier & Ohtsuka, 1995, but with a different mandibular structure in which the distal hook and seta clearly represent the endopod, not enditic armament of the basis. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 152 , 459–506.     

Microbial communities of ancient seeds derived from permanently frozen Pleistocene deposits

Microbial communities from the surface of ancient seeds of higher plants and embedding frozen material dated to the late Pleistocene (formed about 30 thousand years ago) were studied by various methods: scanning electron microscopy, epifluorescence microscopy, and inoculation of nutrient media, followed by identification of isolated cultures. Both prokaryotic and eukaryotic microorganisms were found on the surface of ancient seeds. The total quantity of bacterial cells determined by direct counting and dilution plating (CFU) for the samples of ancient seeds exceeded the value in the embedding frozen material by one to two orders of magnitude. This pattern was not maintained for mycelial fungi; their quantity in the embedding material was also rather high. A significant difference was revealed between the microbial communities of ancient seeds and embedding frozen material. These findings suggest that ancient plant seeds are a particular ecological niche for microorganisms existing in permafrost and require individual detailed study.     

Role of gestation delay in a plankton-fish model under stochastic fluctuations

The present paper studies a minimal prey-predator model in the context of marine plankton interaction together with predation by planktivorous fish. The time lag required for gestation of the predator is incorporated and the resulting delayed model is analyzed for stability and bifurcation phenomena. A stochastic extension of the model is considered by perturbing the growth process of phytoplankton using colored noise process known to be more appropriate for the marine environment. The stochastic models with and without gestation delay are analyzed for stability aspects and a threshold value of gestation delay is obtained; this threshold is then compared with that of the deterministic model.     

River hydrological seasonality influences life history strategies of tropical riverine fishes

Under a particular set of selective forces, specific combinations of traits (strategies) will be favored in a given population, within the particular constraints of the considered species. For fishes, three demographic strategies have been suggested to result from adaptive responses to environmental predictability (i.e., seasonality): periodic, opportunistic and equilibrium [Winemiller KO, Rose KA (1992) Patterns of life-history diversification in North American fishes: implications for population regulation. Can J Fish Aquat Sci 49:2196–2218]. These strategies optimize fitness within predictable, unpredictable and stable systems, respectively. We tested these predictions of life history trait distribution along a gradient of hydrologic seasonality in West African tropical rivers at the drainage basin scale. We used logistic regression of species presence–absence data to test whether dominant life history traits of species caused community compositional change in response to a gradient of seasonality in hydrologic regime across basins. After accounting for taxonomic relatedness, species body size and statistical redundancy inherent to related traits, we found a higher proportion of species producing a great number of small oocytes, reproducing within a short period of time and presenting a low degree of parental care (the periodic strategy) in highly seasonal drainage basins (e.g., rivers with a short and predictable favorable season). Conversely, in more stable drainage basins (e.g., rivers with a wet season of several months), we observed a greater proportion of species producing small numbers of large oocytes, reproducing within a long period of time and providing parental care to their offspring (the equilibrium strategy). Our results suggest that distributions of tropical freshwater fishes at the drainage basin scale can be partly explained by the match between life history strategies and seasonality gradients in hydrological conditions. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Contrasting ectomycorrhizal fungal communities on the roots of co-occurring oaks (Quercus spp.) in a California woodland

Plant host species is considered an important factor influencing ectomycorrhizal (EM) communities. To gain insights into the role of host species in structuring EM communities, EM communities on sympatric oak (Quercus) species were compared in the Sierra Nevada foothills of California. Using molecular methods (polymerase chain reaction, cloning, restriction fragment length polymorphism and DNA sequencing), EM fungi on roots of deciduous Quercus douglasii and evergreen Quercus wislizeni trees were identified from 64 soil cores. The total EM species richness was 140, of which 40 taxa were detected on both oak hosts. Greater diversity and frequency of EM fungi with epigeous fruiting habit were found on Q. wislizeni, while taxa in the Ascomycota were more frequent and diverse on Q. douglasii. Using ordination, it was determined that both soil extractable phosphorus and oak host species explained a significant proportion of the variation in EM species distribution. These results indicate that plant host species can be an important factor influencing EM fungal community composition, even within congeneric trees.     

Partial sequencing of sodA gene and its application to identification of Streptococcus dysgalactiae subsp. dysgalactiae isolated from farmed fish

AIMS: To investigate the difference between Lancefield group C Streptococcus dysgalactiae (GCSD) strains isolated from diseased fish and animals by sequencing and phylogenetic analysis of the sodA gene. METHODS AND RESULTS: The sodA gene of Strep. dysgalactiae strains isolated from fish and animals were amplified and its nucleotide sequences were determined. Although 100% sequence identity was observed among fish GCSD strains, the determined sequences from animal isolates showed variations against fish isolate sequences. Thus, all fish GCSD strains were clearly separated from the GCSD strains of other origin by using phylogenetic tree analysis. In addition, the original primer set was designed based on the determined sequences for specifically amplify the sodA gene of fish GCSD strains. The primer set yield amplification products from only fish GCSD strains. CONCLUSIONS: By sequencing analysis of the sodA gene, the genetic divergence between Strep. dysgalactiae strains isolated from fish and mammals was demonstrated. Moreover, an original oligonucletide primer set, which could simply detect the genotype of fish GCSD strains was designed. SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows that Strep. dysgalactiae isolated from diseased fish could be distinguished from conventional GCSD strains by the difference in the sequence of the sodA gene.     

Novel ecological niche of Cetobacterium somerae, an anaerobic bacterium in the intestinal tracts of freshwater fish

AIMS: This study was conducted to clarify the taxonomic status of Bacteroides type A strains with high vitamin B(12)-producing ability that is widely distributed in the intestinal tracts of freshwater fish. METHODS AND RESULTS: Seventeen strains of Bacteroides type A isolated from five fish species were all rod-shaped and gram-negative. The strains were positive for esculin hydrolysis, nitrate reduction, resistance to bile, acid phosphatase, and negative for the production of catalase and urease and the susceptibility to vancomycin. The G+C content of DNA from the 17 strains was 29 x 1-31 x 9 mol%, and 16S rDNA sequence analysis revealed a close phylogenetic relationship between Bacteroides type A strains and Cetobacterium somerae sharing 99 x 7-100% sequence similarity. In addition, strains were capable of producing vitamin B(12) at a rate of 1 x 82-13 x 98 ng ml(-1) in 48 h. CONCLUSION: Phenotypic and phylogenetic characteristics indicated that all isolates previously classified as Bacteroides type A strains belong to C. someare. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provided the important finding of novel niche of vancomycin-resistant bacteria such as C. somerae in the intestinal tract of freshwater fish.     

Indirect effects of the algivorous fish Plecoglossus altivelis altivelis on the growth of two insectivorous benthic fish

1. Animals exploiting different resources may nevertheless interact if one species indirectly alters the abundance and distribution of the food of the other. To analyse this indirect effect, we conducted experiments in artificial pools and in the field to investigate the influence of the algivorous fish Plecoglossus altivelis altivelis (known as the ayu) on two species of insectivorous benthic fish, Pseudogobio esocinus esocinus and the goby Gymnogobius petschiliensis .
2. In the pool experiments, algal biomass was not correlated with the number of ayu, but the percentage of blue-green bacteria rose as the number increased. The number of aquatic macroinvertebrates on the upper surface of ceramic tiles placed in the pool bed decreased as the number of ayu increased.
3. Although ayu and the benthic species did not interact directly, the reduction in invertebrate abundance on the upper surface of tiles in the pool reduced the growth rate of the benthic insectivores.
4. In field experiments, the introduction of ayu into habitats with P. esocinus esocinus or G. petschiliensis reduced the growth rate of these benthic fish. In the field experiment that was carried out over 5 years in the G. petschiliensis habitat, the population density of the goby decreased when ayu were stocked.
5. The ayu is a strong interactor or bioengineer in streams, affecting not only benthic algae but also aquatic invertebrates and fishes. We conclude that to predict the outcome of interspecific interactions amongst fishes in streams with high algal production, possible indirect effects must be considered alongside better known direct effects.