Stilt Root Structure in the Neotropical Palms Iriartea deltoidea and Socratea exorrhiza1

Many arborescent palms develop a stilt root cone that provides increased mechanical support on steep hillsides, better root aeration under waterlogged conditions, resprouting after mechanical damage, and rapid stem elongation. However, for most species the role of stilt roots is not well understood. We determined how palm size and slope inclination affected the structure of stilt roots in the neotropical palms Iriartea deltoidea and Socratea exorrhiza. We expected palm height to be lower on steep slopes because the effectiveness of root support could decrease as slope inclination increases, and thus, the structure of the root cone would vary mostly with slope. Alternatively, if stilt root development is determined by palm size, their production should match stem height, with taller palms having larger cones. We measured the stilt root cone of 31 Iriartea and 36 Socratea palms in San Ramón Biological Reserve and Golfito Wildlife Refuge, Costa Rica. We divided the cone into five variables (horizontal projections of the cone base and stilt root height up and down the slope, and width of the cone base), from which we extracted the first two principal components and used them to measure the effects of slope and palm size on stilt root structure. We found stilt roots to be determined by palm size, not by slope conditions. Stilt roots matched palm size, with larger palms having taller and larger cones, maintaining stability under diverse slope conditions.     

A Standard Protocol for Liana Censuses1

A recent increase in published studies of lianas has been paralleled by a proliferation of protocols for censusing lianas. This article seeks to increase uniformity in liana inventories by providing specific recommendations for the determination of which taxa to include, the location of diameter measurement points on individual stems, the setting of minimum stem diameter cutoffs, the treatment of multiple‐stemmed and rooted clonal groups, and the measurement of noncylindrical stems. Use of more uniform liana censusing protocols may facilitate comparison of independently collected data sets and further our understanding of global patterns in liana abundance, diversity, biomass, and dynamics.     

Early ontogeny of the commercially valuable fish red-bellied pacu Piaractus brachypomus (Characiformes,Serrasalmidae) from the Amazon,Brazil

The initial development of the red-bellied pacu Piaractus brachypomus is described using morphological, meristic and morphometric characteristics. A total of 127 individuals were analysed (47 in the yolk-sac, 35 in pre-flexion, five in flexion, 20 in post-flexion and 20 in juvenile) with standard length varying between 2.92 and 48.61 mm. The larvae are born poorly developed and have a discoidal yolk at ~6.33 mm standard length. During early ontogeny, the mouth passes from terminal to subterminal and the anal opening reaches the vertical line over the midline region of the body. There are changes in body shape from long and moderate to deep, head length from small to large, and eye diameter from moderate to large. Dendritic chromatophores were present in the ventral, dorsal and upper part of the swim bladder in the early larval stages. Rounded spots are evident all over the body in juveniles. The total number of myomeres ranges from 39 to 41 (20–23 pre-anal, 17–20 post-anal). Through the morphometric relationships, it was evidenced that the greatest changes during the initial ontogeny of P. brachypomus occur in the transition from the post-flexion stage to the juvenile period, indicating changes in behaviour, foraging and physiology.     

Fermentative production of l-lactic acid by Lactobacillus casei DSM 20011 and product recovery using ion exchange resins

In order to produce l(+)-lactic acid to be employed in poly-l-lactic acid polymer production, for biomedical applications, the strain Lactobacillus casei subsp. casei DSM 20011 was studied in a conventional batch mode using different initial concentrations of glucose. The results obtained showed that the initial glucose concentration exerts an influence on the fermentation pattern, modifying the different fermentation parameters. Nevertheless, the product yield remained at a constant value of 0.86 g·g^–1. The proposed novel system of product recovery, based on the use of ion-exchange resins, gave high yields of pure lactic acid. Correspondence to: D. Matteuzzi     

Fruit abundance may fine-tune timing of reproduction of the Chilean Elaenia (Elaenia chilensis), a long-distance migratory bird in South America

Timing of reproduction has a great impact on the breeding success of birds because a mismatch with the moment when environmental conditions are warm or when food is most plentiful can reduce nestling survival and increase the energetic cost of parental care. Consequently, birds synchronize gonadal maturation with the most favourable environmental conditions, using photoperiod changes throughout the year as an initial proximal cue. Additionally, non-photic cues, such as temperature and food abundance, may be necessary to fine-tune reproductive timing. However, the influence of non-photic cues on finely tuning reproductive timing is not yet fully understood for migratory birds. Here, we evaluate how much non-photic cues influence the reproductive timing of the Chilean Elaenia Elaenia chilensis, a long-distance migrant that reproduces in the Andean–Patagonian Forest. We assessed associations of mean temperature, ripe fruit and arthropod abundances with the number of nests in the laying period, and also with the number of nests with hatchlings. In both analyses we used cross-correlations and partial least squares path modelling. Mean temperature was not consistently associated with the breeding phenology of Chilean Elaenias. The increase in number of nests in the laying period was preceded by the increase in caterpillar abundance and coincided with the increase in ripe fruit abundance. The timing of nests with hatchlings matched with the timing of highest ripe fruit abundance. Both types of food could contribute to the beginning of reproduction of birds and be used as proximal cues by Chilean Elaenias. Ripe fruits would also be beneficial for nestling growth because parents feed them with fruits, and might potentially play an ultimate role in reproduction. Because ripe fruit abundance was related to the egg-laying and hatching stages, it may be the main cue used by Chilean Elaenias to fine-tune reproductive timing. These findings allow advances in our understanding of the importance of non-photic cues in the reproductive phenology of migratory birds and also generalize our knowledge among regions and taxa, as most studies on this topic focus on the Northern Hemisphere.     

Second messenger signaling in olfactory transduction

Olfactory receptor neurons respond to odorants with G-protein mediated increases in the concentration of cyclic adenosine 3′,5′-monophosphate (cAMP) and/or inositol 1,4,5-triphosphate (InsP₃). These two second messengers directly regulate opening of cAMP- and InsP₃-regulated conductances localized to the apical transduction compartments of the cell (cilia and olfactory knob). In the presence of physiological concentrations of extracellular Ca²⁺, these second messenger regulated conductances mediate influx of Ca²⁺ into the olfactory neuron resulting in large, localized increases in intracellular Ca²⁺ ([Ca²⁺]_i). A significant advance in our understanding of the molecular mechanisms of olfaction is the recent realization that this increase in [Ca²⁺]_i plays an important role as a “third messenger” in olfactory transduction. Second messenger dependent increases in [Ca²⁺]_i cause opening of ciliary Ca²⁺-activated Cl⁻, cation and/or K⁺ channels that can carry a large percentage of the generator current, thus amplifying the signal substantially. As a result of this sequence of events, the generator potential in olfactory neurons can be depolarizing, leading to excitation of the neuron, or hyperpolarizing, leading to suppression of basal action potential firing rate. This dual effect of odorants on olfactory neurons may play an important role in quality coding and in the ability to detect low concentrations of odorants, particularly in complex mixtures. © 1996 John Wiley & Sons, Inc.     

HLA genetic profile of Mapuche (Araucanian) Amerindians from Chile

Amerindian Mapuche (Araucanians) are now living in Chile and Argentina at both sides of Andean Mountains. They are anthropologically and genetically different from southernmost South America Patagonian Amerindians. Most of the HLA alleles found in our Mapuche sample are frequent or very frequent in North and South America Amerindians: (1) Class I: A*02:01, A*03:01, A*68:01, B*39:09, B*51:01, (2) Class II: DRB1*03:01, DRB1*04:03, DRB1*07:01, DRB1*08:02, DRB1*14:02, DRB1*16:02. One of the nine most frequent extended haplotypes seems to be from European origin, suggesting the existence of a degree of admixture with Europeans in our Mapuche sample. It has been calculated of about 11 % admixture. Three of the extended haplotypes are also found in other Amerindians and five of them are newly found in Mapuche Amerindians: A*68:01-B*39:09-DRB1*08:02-DQB1*04:02; A*68:01-B*51:01-DRB1*04:03-DQB1*03:02; A*29:01-B*08:01-DRB1*03:01-DQB1*02:01; A*02:01-B*15:01-DRB1*04:03-DQB1*03:02; A*33:01-B*14:02-DRB1*07:01-DQB1*03:03. The medical importance of calculating HLA profile is discussed on the diagnostic (HLA and disease) and therapeutical bases of HLA pharmacogenomics and on the construction of a virtual transplantation HLA list profile. Also, anthropological conclusions are drawn.