The role of kleptoplasts in the survival rates of Elysia timida (Risso, 1818): (Sacoglossa: Opisthobranchia) during periods of food shortage

The importance of photosynthetic products derived from kleptoplasts in several sacoglossan species is being investigated in different fields, such as chemistry, biomolecular genetics and ecology. This study analyzes the effect of kleptoplasts on the survival rates of Elysia timida by evaluating the development of chlorophyll concentration, total length and survival rates of starved E. timida specimens kept in the light and in the dark. Although chlorophyll concentration values were similar in both cases, after 28 days specimens kept in the dark showed a greater size decrease and a lower survival rate (up to 30% lower) than those kept in the light. It is evident that kleptoplasts provide the mollusc with extra energy at the primary metabolism level to compensate for a shortage in food.     

Nitrate uptake and storage in the seaweed Ulva rigida C. Agardh in relation to nitrate availability and thallus nitrate content in a eutrophic coastal lagoon (Sacca di Goro, Po River Delta, Italy)

The seasonal cycle of biomass and tissue composition of Ulva rigida C. Agardh, in relation to nitrogen availability in the water column, was studied in 1991-1992 in the Sacca di Goro, a highly eutrophic lagoon in the Po River Delta (Italy). Nitrate uptake rates and storage capacity were also determined in laboratory experiments. The seasonal growth of U. rigida was related to the seasonal trend of nitrogen concentration in the water column. U. rigida biomass increased exponentially during spring and attained peaks of about 300-400 g dry mass (DM) m⁻² in June. As biomass increased, U. rigida depleted nitrate in the water column. Thallus nitrate reserves also declined from 100 μmol N (g DM)⁻¹ to almost undetectable levels, and total thallus nitrogen declined from 4% to 2.5% DM and 1.25% DM in 1991 and 1992, respectively. During summer, U. rigida decomposition increased, and organic nitrogen concentrations in the water column increased. The uptake experiments demonstrated an inverse relationship between thallus nitrate content and nitrate uptake rates. A modified Michaelis-Menten equation that accounts for thallus nitrate fit the uptake data well. U. rigida can accumulate up to about 400-500 μmol nitrate (g DM)⁻¹ in cellular reserves. U. rigida in the Sacca di Goro has higher K_m and lower V_max/K_m ratios for nitrate uptake than other chlorophycean species, indicating a low efficiency of uptake at low nitrate concentrations. This low uptake efficiency, and the ability to exploit N availability by storing cellular nitrate pools in excess of immediate growth needs, may represent a physiological response to an eutrophic environment where nitrate is in large supply for most of the year.     

Genetic structure of Phlebotomus (Larroussius) ariasi populations, the vector of Leishmania infantum in the western Mediterranean: Epidemiological implications

In recent years there has been growing interest in analyzing the geographical variations between populations of different Phlebotomus spp. by comparing the sequences of various genes. However, little is known about the genetic structure of Phlebotomus ariasi. In this study, we were able to sequence a fragment of the mitochondrial Cyt b gene in 133 sandflies morphologically identified as P. ariasi and proceeding from a wide geographical range covering 35 locations in 11 different regions from five countries. The intra-specific diversity of P. ariasi is high, with 45 haplotypes differing from each other by one to 26 bases and they are distributed in two mitochondrial lineages, one limited geographically to Algeria and the other widely dispersed across Mediterranean countries. The Algerian lineage is characterized by having 13 fixed polymorphisms and is made up of one sole haplotype. The European/Moroccan P. ariasi lineage is characterized by being made up of a great diversity of haplotypes (44) which display some geographical structuring. This could be one of the multiple factors involved in the epidemiological heterogeneity of the foci of leishmaniasis. Phlebotomus chadlii is the sister group of European/Moroccan P. ariasi. The separation of the Algerian haplotype, H45, from the rest of the specimens, European/Moroccan P. ariasi and P. chadlii, is well supported by the bootstrap analysis.     

Low genetic differentiation among widely separated populations of the pearl oyster Pinctada fucata as revealed by AFLP

Genetic variation within and among five populations of the pearl oyster Pinctada fucata, from China (Daya Bay, Sanya Bay and Beibu Bay), Japan (Mie Prefecture) and Australia (Port Stephens) was studied using AFLP. Three primer pairs generated 184 loci among which 91.8-97.3% is polymorphic. An overall genetic diversity of 0.38 among populations and an average of 0.37 within populations (ranging from 0.35 in Japanese population to 0.39 in Beibu Bay population) were observed. Genetic differentiation among the five populations is low but significant as indicated by pairwise G_ST (0.0079-0.0404). AMOVA further shows that differentiation is significant among the five populations but is not significant at a broader geographical scale, among the three groups of Chinese, Japanese and Australian populations or among the two groups of Australian and north Pacific populations. The low level of genetic differentiation indicated that P. fucata populations in the west Pacific are genetically linked. Among the five populations, the Australian one is more differentiated from the others, based on both pairwise AMOVA and G_ST analyses, and is genetically isolated by distance as indicated by Mantel test. However, genetic differences among the three Chinese populations are not correlated with the geographic distances, suggesting that Hainan Island and Leizhou Peninsula may act as barriers blocking gene flow.     

Microsatellite diversity and population genetic structure of yellowcheek, Elopichthys bambusa (Cyprinidae) in the Yangtze River

Yellowcheek carp (Elopichthys bambusa) is the only species of genus Elopichthys. It is widely distributed in Chinese freshwaters but currently its populations have declined to threatening level. We examined the genetic diversity and population structure of E. bambusa in the Yangtze River basin. A total of nine polymorphic microsatellite markers were employed to study five populations occurring in middle and lower reaches of the river. The results revealed low-to-moderate genetic diversity. The number of alleles per locus varied between 3 and 8 with an average of 4.8. Observed heterozygosity ranged from 0.15 to a maximum of 1.00. Significant deviations (P < 0.01) from Hardy–Weinberg equilibrium were observed for all the tested locus-population combinations with clear heterozygosity deficits. AMOVA indicated that majority of the variance lies within populations (93.81%) than among the populations (7.05%). Pairwise F_ST and unbiased genetic distance pointed out significant differentiation among the samples from populations with different connections to the Yangtze River. In the UPGMA dendrogram, clustering pattern of populations indicated that most of the populations are reproductively isolated due to anthropogenic interventions. Clustering of PYL and DTL populations shows ongoing gene flow through the mainstream. The recent hydrological alterations and overfishing are major factors shaping the current genetic structure. These results can be helpful for effective management and sustainable conservation of E. bambusa populations.     

Genetic diversity within and among populations of the endangered species Taxus fuana (Taxaceae) from Pakistan and implications for its conservation

The West Himalayan yew, Taxus fuana Nan Li & R.R. Mill (Taxaceae), is an endangered species endemic to the Western Himalayas. An investigation of the genetic diversity of wild populations of T. fuana in Pakistan was undertaken. The genetic diversity and genetic structure was quantified using random amplified polymorphic DNA (RAPD) variation in 219 individuals of the 10 populations. Of the 32 universal primers screened 16 produced highly reproducible, clear RAPD bands. Using these primers, 193 discernible DNA fragments were generated, of which 164 (84.97%) were polymorphic. The statistical results indicated that there was a relatively low genetic diversity within populations (with percentages of polymorphic bands, PPB, ranging from 29.53 to 50.26%, with an average of 38.34% and a Nei's genetic diversity index (H_E) of 0.1165), and a high genetic differentiation among populations (G_ST = 0.5842, Φ_ST = 0.5685) within these populations. The gene flow (N_m) was low with only 0.3558.     

Age and growth of the sand smelt, Atherina boyeri (Risso 1810), in the Mar Menor coastal lagoon (SE Iberian Peninsula)

The age and growth of sand smelt, Atherina boyeri (Risso 1810), in the Mar Menor (SE Iberian Peninsula) were studied in samples taken from catches of local fishermen obtained between November 1997 and September 1998. The maximum lengths were 94 mm (FL, fork length) in females and 87 mm (FL) in males. Age determination based on scale readings and validated by length frequency analysis shows that the population has a 3‐year life cycle. Females were significantly longer than males in each of the age classes. Both sexes of the sand smelt grow allometrically (b = 3.113 males; b = 3.043 females) and attain approximately 56.2% of their maximum fork length in their immature first year, after which the annual growth rate drops quickly. The highest growth rate was observed from winter to spring (G_L = 16.01 males 1+; G_L = 11.25 males 2+; G_L = 17.18 females 1+; G_L = 9.62 females 2+). The condition cycles were similar for both sexes, with a minimum in June–July and two maximums in April and November.     

Genetic diversity and local population structure in Ambrosina bassii (Araceae,Ambrosineae), a Mediterranean relict species

The effects of habitat fragmentation on the genetic structure of Ambrosina bassii are analyzed. The species, whose reproductive biology is mostly unknown, is the only representative of its genus and tribe and it is endemic to the central Mediterranean area. The selected study area was the island of Sicily, in which wild populations show a wide morphological variability and ecological amplitude. Patterns of within- and among-population genetic diversity in eleven Sicilian populations, occurring in six disjunct areas, were examined by means of allozyme electrophoresis. High levels of genetic diversity were found as shown by the mean expected heterozygosity (H_e = 0.263), the percentage of polymorphic loci (P₉₅ = 65.3), the mean number of alleles per locus (A = 2.0). Genetic differentiation between populations was relatively low (mean F_ST = 0.091 and Nm = 1.98). A very weak correlation exists between genetic distances and geographic distances between populations. Despite its restricted and fragmented geographical range, A. bassii showed (i) high levels of genetic diversity, mainly within populations; (ii) no genetic differentiation between populations and morphotypes.     

Length–weight relationships for 22 fish species of the Mar Menor coastal lagoon (western Mediterranean Sea)

Length–weight relationships were estimated for 22 species of the Mar Menor coastal lagoon (south‐eastern Spain): Lipophrys dalmatinus, Salaria pavo, Callionymus pusillus, Aphanius iberus, Engraulis encrasicolus, Gobius cobitis, G. niger, G. paganellus, Pomatoschistus marmoratus, Symphodus cinereus, Chelon labrosus, Liza aurata, L. ramado, L. saliens, Mugil cephalus, Diplodus puntazzo, D. sargus sargus, Lithognathus mormyrus, Sarpa salpa, Sparus aurata, Hippocampus guttulatus and Syngnathus abaster. The captures were made in shallow areas of the lagoon during 2002–2004. Significant length–weight relationships were found for all species.     

Multilocus population genetic analysis of the Southwest Pacific malaria vector Anopheles punctulatus

The population structure and history of the cryptic malaria vector species, Anopheles punctulatus (Doenitz), was investigated throughout Papua New Guinea and the Solomon Islands with the aim of detailing genetic subdivisions and the potential for movement through this biogeographically complex region. We obtained larval collections from over 80 sites and utilised a diverse array of molecular markers that evolve through different processes. Individuals were initially identified to species and genotyped using the ribosomal DNA second internal transcribed spacer. DNA sequencing of a single copy nuclear ribosomal protein S9 and the mitochondrial cytochrome oxidase I loci were then investigated and 12 nuclear microsatellite markers were developed and analysed. Our data revealed three genetically distinct populations – one in Papua New Guinea, the second on Buka Island (Bougainville Province, Papua New Guinea), and the third on Guadalcanal Island (Solomon Islands). Genetic differentiation within Papua New Guinea was much lower than that found in studies of other closely related species in the region. The data does suggest that A. punctulatus has undergone a population bottleneck followed by a recent population and range expansion in Papua New Guinea. Humans and regional economic growth may be facilitating this population expansion, as A. punctulatus is able to rapidly occupy human modified landscapes and traverse unsealed roads. We therefore anticipate extensive movement of this species through New Guinea – particularly into the highlands, with a potential increase in malaria frequency in a warming climate – as well as relatively unrestricted gene flow of advantageous alleles that may confound vector control efforts.     

Evidence for genetic differentiation of Octopus vulgaris (Mollusca, Cephalopoda) fishery populations from the southern coast of Brazil as revealed by microsatellites

Octopus vulgaris is a cephalopod species in several oceans and commonly caught by artisanal and industrial fisheries. In Brazil, O. vulgaris populations are mainly distributed along the southern coast and have been subjected to intensive fishing during recent years. Despite the importance of this marine resource, no genetic study has been carried out to examine genetic differences among populations along the coast of Brazil. In this study, 343 individuals collected by commercial vessels were genotyped at six microsatellite loci to investigate the genetic differences in O. vulgaris populations along the southern coast of Brazil. Genetic structure and levels of differentiation among sampling sites were estimated via a genotype assignment test and F-statistics. Our results indicate that the O. vulgaris stock consists of four genetic populations with an overall significant analogous F_ST (Φ_CT = 0.10710, P < 0.05) value. The genetic diversity was high with an observed heterozygosity of Ho = 0.987. The negative values of F_IS found for most of the loci examined suggested a possible bottleneck process. These findings are important for further steps toward more sustainable octopus fisheries, so that this marine resource can be preserved for long-term utilization.     

Evidence of a planktonic food web response to changes in nutrient input dynamics in the Mar Menor coastal lagoon,Spain

Nutrient input dynamics in the Mar Menor coastal lagoon has recently changed as a consequence of changes in agricultural practises. An interannual comparison of the environmental variables and the planktonic biomass size-spectra was performed between 1988 and 1997. While nitrate concentration was low in 1988, the values in 1997 increased considerably. Since 1995, two alloctonous jellyfish species (Rhyzostoma pulmo and Cotylorhiza tuberculata) occurred in large numbers in summer time and reached peak abundance in summer of 1997. The size-spectra analysis comparison revealed that, in spite of changes in nutrient input that stimulated the growth of larger phytoplankton cells, there were no significant differences in the spectra slope which followed a similar seasonal trend in both years. However, the plankton biovolume considered under the size range compared (between 2 and 1000 m diameter) was, paradoxically, always lower in 1997. Given that there were higher nutrient levels in 1997, this finding suggest a strong top-down control mechanism of size structure. Gut contents of jellyfishes showed their preference for large diatoms, tintinnids, veliger larvae and copepods, corroborating that size structure in these assemblages can be subject to top-down control. The implication of these results is that the feeding activities of large gelatinous zooplankton (jellyfishes) may play an important role controlling the consequences of eutrophication within the Mar Menor coastal lagoon.     

A Mediterranean Holocene restricted coastal lagoon under arid climate: Case of the sedimentary record of Sabkha Boujmel (SE Tunisia)

The Holocene sedimentary record of Sabkha Boujmel (SE Tunisia) is expressed by a shallowing-upward carbonate lagoon-tidal flat cycle (2.3 m thick) unconformably overlying continental silt-sandy sediment, Late Würmian in age. The sedimentary package of this cycle starts with transgressive marginal shallow marine (intertidal to subtidal) bioclastic sands grading upwards to black mudstone, rich in organic matter (T.O.C. up to 1.3%) deposited within a lagoon protected from the sea by Upper Pleistocene lithified sand spits.The uppermost part of the cycle is represented by oobioclastic carbonate sands covered with dead biodegraded microbial mats and/or reddish sands of aeolian origin deposited in intertidal to supratidal environments. The facies arrangement, particularly the spatial distribution of the ancient and the more recent microbial mats, records the progressive infilling of the lagoon as well as the progradation of the shoreline during the last 2000 years. The organic-rich facies which provide an age varying between 4130 and 6800 yr B.P. were deposited when the Boujmel lagoon started to be progressively separated from the Mediterranean Sea.The main factors controlling the facies and the thickness variation are the local topographic sea-floor irregularities most likely controlled by the inheritance morphology resulting from an important fluviatile digging that occurred during the last glacial maximum, the relative sea-level fluctuations, the hydro-isostatic rebound and the climate.     

Genetic diversity of the endangered species Kirengeshoma palmata (Saxifragaceae) in China

In order to investigate the levels of genetic diversity of the endangered species Kirengeshoma palmata (Saxifragaceae), four extant populations were sampled and analyzed using inter-simple sequence repeats (ISSR) markers. We expected a low genetic diversity level, but our results revealed a high level of intraspecific genetic diversity, probably resulting from this species being in a refuge during the last glaciation (at population level: P = 63.25%, A_e = 1.47, H_E = 0.26 and H_O = 0.37; at species level: P = 79.00%, A = 1.5538, H_T = 0.2586 and H_sp = 0.3104). A low level of genetic differentiation among populations was detected based on Nei's genetic diversity analysis (16.69%) and AMOVA (19.36%). Populations shared high levels of genetic identity. Insect pollination and seed dispersal by wind may have facilitated extensive gene flow and are likely responsible for this present structure of genetic variation.     

Genetic diversity and population genetic structure of saltmarsh Spartina alterniflora from four coastal Louisiana basins

Seventy-two Spartina alterniflora accessions originating from four coastal Louisiana basins (18 accessions per basin) were used to evaluate the genetic structure of this native perennial low-intertidal plant species. The objective of this study was to determine the population genetic structure and diversity of S. alterniflora accessions originating from these four basins using amplified fragment length polymorphism (AFLP) markers. A total of 250 unambiguous and highly repeatable AFLP markers, 186 of which (74.4%) were polymorphic, were obtained using four primer combinations. Overall, pairwise similarity estimates between accessions ranged from 0.70 to 0.93 (average = 0.80) with only a small portion of alleles (0.54–1.08%) unique to each basin. The average H_s (genetic diversity within coastal basins) was 0.20 with an H_s values of 0.19, 0.20, 0.20, and 0.21 for Mermentau, Terrebonne, Calcasieu, and Barataria-Breton basin, respectively. AMOVA analysis showed no genetic structure among basins, with the majority of genetic variation, 96.6%, residing within the basins. There was no indication of isolation by distance. Our results suggest that maintaining high levels of genetic diversity can be accomplished through the use of an adequate number of S. alterniflora samples collected within any large basin. Choosing parental lines from several Louisiana coastal basins for breeding purposes may not significantly increase genetic variability among the progeny lines.     

Allozymatic divergence between border populations of two cryptic species of the Drosophila buzzatii cluster species (Diptera: Drosophilidae)

Drosophila antonietae and Drosophila gouveai are allopatric, cactophilic, cryptic and endemic of South America species, which aedeagus morphology is considered the main diagnostic character. In this work, single close populations from the edge distributions of each species, located in an “introgressive corridor”, were analyzed regarding temporal isozenzymatic genetic variability. Isocitrate dehydrogenase (Idh) appeared as a diagnostic locus between D. antonieate and D. gouveai because each population was fixed for different alleles. Moreover, several polymorphic loci showed accentuated divergence in the allele frequency, as evidenced by Nei’s I (0.3188) and D (1.1432), and also by Reynolds’ genetic distance and identity (1.3207 and 0.7331, respectively). Our results showed that, in spite of the very similar external morphology, related evolutionary histories, close distributions, and events of introgression in the studied area, these cryptic species have high allozymatic differentiation, and this is discussed here.     

Systematics and evolution of the genus Torrubiella (Hypocreales, Ascomycota)

Torrubiella is a genus of arthropod-pathogenic fungi that primarily attacks spiders and scale insects. Based on the morphology of the perithecia, asci, and ascospores, it is classified in Clavicipitaceae s. lat. (Hypocreales), and is considered a close relative of Cordyceps s. 1., which was recently reclassified into three families (Clavicipitaceae s. str., Cordycipitaceae, Ophiocordycipitaceae) and four genera (Cordyceps s. str, Elaphocordyceps, Metacordyceps, and Ophiocordyceps). Torrubiella is distinguished morphologically from Cordyceps s. lat. mainly by the production of superficial perithecia and the absence of a well-developed stipitate stroma. To test and refine evolutionary hypotheses regarding the placement of Torrubiella and its relationship to Cordyceps s. lat., a multi-gene phylogeny was constructed by conducting ML and Bayesian analyses. The monophyly of Torrubiella was rejected by these analyses with species of the genus present in Clavicipitaceae, Cordycipitaceae, and Ophiocordycipitaceae, and often intermixed among species of Cordyceps s. lat. The morphological characters traditionally used to define the genus are, therefore, not phylogenetically informative, with the stipitate stromata being gained and/or lost several times among clavicipitaceous fungi. Two new genera (Conoideocrella, Orbiocrella) are proposed to accommodate two separate lineages of torrubielloid fungi in the Clavicipitaceae s. str. In addition, one species is reclassified in Cordyceps s. str. and three are reclassified in Ophiocordyceps. The phylogenetic importance of anamorphic genera, host affiliation, and stipitate stromata is discussed.