Natural hybridization between Vanilla claviculata (W.Wright) Sw. and V. barbellata Rchb.f. (Orchidaceae): genetic, morphological, and pollination experimental data

Vanilla claviculata (W.Wright) Sw. and K barbellata Rchb.f. grow sympatrically in the southwestern part of herto Rico. At three localities in the range of the two species, individuals with flowers that appeared Merent from previously known species were found. To test whether these were hybrids between V. claviculata and V. barbellata , 11 morphological floral characters were recorded at seven populations and allozyme profiles of the three taxa compared. Principal component analysis on the morphological characters gave three distinct groups with minor overlaps. The first component axis reflects variation in overall size of the flowers, while the second component reflects variation in the size of the distal aperture of the labellum. Allozyme data revealed that the putative hybrids have a significant surplus of heterozygotes ( F _IS = - 0.65) as expected in a F ₁ generation. Both data sets support the hypothesis that the individuals are hybrids, which is further augmented by interspecific pollination experiments between the putative parental species. This is the first case of natural hybridization reported in the genus Vanilla .     

The influence of leaf litter on zooplankton in floodplain wetlands: changes resulting from river regulation

1. The loss of input of leaf litter through clearing of riparian vegetation may result in significant changes to aquatic ecosystems. River red gums (Eucalyptus camaldulensis) surrounding floodplain wetlands in the Murray–Darling Basin, Australia, contribute large quantities of leaf litter, but the quality of this resource may change depending on the timing of inundation. 2. We used experimental mesocosms to test the hypotheses that zooplankton would have a greater abundance with an input of leaf litter and that fewer zooplankton would emerge from egg banks in cleared than forested wetlands. The experiment was carried out in summer/autumn and in spring to test a third hypothesis that zooplankton would respond to changes in the timing of wetland inundation as a result of river regulation. 3. In summer/autumn, leaf litter reduced zooplankton abundance by 89% at the beginning of the experiment through its influence on water quality. Only a few taxa (Polyarthra spp., Colurella spp. and the cladoceran Family Moinidae) responded positively to leaf litter when water quality improved later in the experiment, indicating a switch in the role of leaf litter from a non‐trophic to a trophic pathway. 4. In spring, microcrustaceans emerged in smaller numbers from sediment sourced from cleared compared to forested wetlands, reflecting different communities in these two wetland types and/or disturbances to the sediment that interfere with emergence. 5. Although leaf litter appears not to be an important resource for zooplankton in floodplain wetlands, riparian clearing may have lasting effects on future emerging zooplankton communities. Additionally, river regulation may have considerable impacts on the influence of leaf litter on zooplankton, which has implications for the management of floodplain river systems.     

Similar hypotensive responses to resistance exercise with and without blood flow restriction

Low intensity resistance exercise (RE) with blood flow restriction (BFR) has gained attention in the literature due to the beneficial effects on functional and morphological variables, similar to those observed during traditional RE without BFR, while the effects of BFR on post-exercise hypotension remain unclear. The aim of the present study was to compare the blood pressure (BP) response of trained normotensive individuals to RE with and without BFR. In this cross-over randomized trial, eight male subjects (23.8 ± 4 years, 74 ± 3 kg, 174 ± 4 cm) completed two exercise protocols: traditional RE (3 x 10 repetitions at 70% one-repetition maximum [1-RM]) and low intensity RE (3 x 15 repetitions at 20% 1-RM) with BFR. Blood pressure measurements were performed after 15 min of seated rest (0), immediately after and 10 min, 20 min, 30 min, 40 min, 50 min and 60 min after the experimental sessions. Similar hypotensive effects for systolic BP (SBP) were observed for both protocols (P < 0.05) after exercise, with no differences between groups (P > 0.05) and no statistically significant difference for diastolic BP (P > 0.05). These results suggest that in normotensive trained individuals, both traditional RE and RE with BFR induce hypotension for SBP, which is important to prevent cardiovascular disturbances.     

Biochemical Basis of Different Sensitivity to Methotrexate in Daucus carota and Oryza sativa Cell Cultures

The biochemical basis of the different sensitivity to methotrexateof Daucus carota and Oryza sativa cell cultures has been investigated.Carrot cells have a dihydrofolate reductase activity about tentimes higher than rice cells. In addition, they show a loweruptake rate of the inhibitor. No relevant differences have beenfound in the K_m value for the dihydrofolate of the two enzymesand in the degree of inhibition of their activity by methotrexate. Key words: Dihydrofolate reductase, Methotrexate resistance, Plant cell suspension cultures, Oryza sativa, Daucus carota     

Animal phylogeny in the light of the trochaea theory

Ultrastructural similarities unite Choanoflagellata and Metazoa as the Kingdom Animalia. Mctazoa (Porifera + Placozoa + Gastraeozoa) are characterized by the presence of collagen, septate/tight junctions and spermatozoa. Porifera and Placozoa lack basal lamina, nerve cells and synapses, which characterize Gastraeozoa (Cnidaria + Trochaeozoa). Gnidaria have cnidoblasts and lack the multiciliate cells found in almost all Trochaeozoa (Gastroneuralia + Protornaeozoa). Gastroneuralia (Spiralia + Aschelminthes) have an apical brain and a pair of ventral nerves, a blastopore which becomes mouth and anus, a mouth surrounded by a downstream collecting system of compound cilia, and a mesoderm formed from the blastopore lips. Spiralia (Articulata + Parenchymia + Bryozoa) have spiral cleavage and 4d-cell mesoderm, whereas these characters are lacking in Aschelminthes, which all lack primary larvae. Protornaeozoa (Ctenophora + Notoneuralia) have mesoderm from vegetal cells. Ctenophores have colloblasts. Notoneuralia have a dorsal nervous system behind the apical area and form a new mouth surrounded by an upstream collecting system of single cilia on monociliate cells; the blastopore becomes the anus surrounded by a ring of compound cilia.
These features fit the trochaea theory, which proposes that Gastroneuralia and Notoneuralia evolved independently from the trochaea, a blastaea with the blastopore surrounded by a ring of compound cilia, which were both locomotory and particle collecting.     

Growth of macrophytes and ecosystem consequences in a lowland Danish stream

SUMMARY. 1. The River Suså is a small, nutrient-rich stream situated in an open landscape with clayish subsoil under intensive cultivation. Discharge was variable daily and seasonally due to low groundwater input. Above-ground development of submerged macrophytes was restricted to late May to November, when water velocity and depth were low. Dominant macrophytes were rooted Potamogeton pectinatus and Sparganium emersum and unrooted Cladophora . Biomass development was closet) related to light availability.
2. Growth rates of macrophytes were linearly related to light availability when self-shading was accounted for. Potamogeton pectinatus grew rapidly m May-June, concentrated the biomass at the water-surface during July-August, and then declined exponentially when the shoots became basally senescent. Sparganium emersum had linear, flexible leaves that were continuously replaced from a basal meristem. Sparganium emersum was less susceptible to high water velocities than Potamogeton pectinatus and the biomass declined later and at lower rates during autumn. Sparganium emersum also regrew after culling that left its meristem intact in the sediment. Unrooted Cladophora developed a high biomass during sunny periods and subsequently disappeared at high discharges. The summer biomass of rooted macrophytes was greater in years with high summer discharge, whereas the biomass of Cladophora and of the epiphytic microbial community was lower due to scouring.
3. Submerged macrophytes played a key role in structure and functioning of the ecosystem. They reduced water velocities two to four fold during summer and promoted extensive organic sedimentation. The biomass of benthic diatoms declined parallel to increased macrophyte shading and sedimentation. In addition, submerged macrophytes formed a large substratum for macroinvertebrates and for a microbial community.     

Transfer of Photosynthetically Produced Carbohydrate from Endosymbiotic Chlorellae to Paramecium bursaria*

Paramecium bursaria (Ehrenberg) and an endozoic zoochlorella Chlorella conductrix (Brandt) live in a symbiotic relationship. Uptake of NaH¹⁴CO₃ was studied to determine if carbohydrate products of photosynthesis are transferred to the host paramecium. Paramecium bursaria containing the algal symbionts took up NaH¹⁴CO₃ but those without the algal symbionts did not. Radioactive maltose, glucose, fructose and malate were identified from the ethanolic extract of paramecia. Transfer of materials from Paramecium to Chlorella and the transfer of other materials from Chlorella to Paramecium, led to the conclusion that this is a mutualistic relationship, both organisms benefiting from the relationship.     

Food resource partition in the beech leaf-feeding guild

Abstract. 1. The position and zonation of mines and galls along beech leaves were recorded and analysed by means of an R X C test of independence using the G-test; in a few cases analysis of variance was applied.
2. Ten arthropod species, of which a few were congeneric, were studied. All species were recorded from all leaf sections; however, in all species except one, significant preferences for certain zones were demonstrated. High frequencies of leaf mines and galls were recorded from the middle and basal leaf sections. Apparently, the leaf apex is an unimportant microhabitat for stationary beech phyllophages, except the eriophyid Aceric stenaspis stenaspis and final leaf mining stages of the beech weevil Rhynchaenus fagi; intra-leaf differences are discussed in relation to leaf grazing by mobile, chewing phyllophagous insects.
3. The position of some abundant phyllophages in space and time is discussed. In old beech stands feeding activity is largely concentrated in the low canopy. Presumably, differences in feeding technique and position of feeding tracks of beech phyllophages on the leaf contribute to food resource partition in this canopy layer. In three congeneric eriophyid species niche diversification occurred. Further, in two cecidomyiid species phenologjcal differentiation may contribute to subdivision of food resources.     

The Relationships of Entoprocta, Ectoprocta and Phoronida

Comparisons of life-cycles of entoprocts, ectoprocts and phoronidsindicate that the ectoprocts probably have evolved from entoproct-likeancestors, whereas the phoronids are of a quite different type.A review of our knowledge of structure and development of thethree groups lends support to this idea. The Entoprocta andEctoprocta should accordingly be united into the phylum Bryozoa,which is related to the Annelida and Mollusca. The Phoronidaare probably more related to the deuterostomes.