Postprandial acid–base balance and ion regulation in freshwater and seawater-acclimated European flounder, <Emphasis Type="Italic">Platichthys flesus</Emphasis>

The effects of feeding on both acid–base and ion exchange with the environment, and internal acid–base and ion balance, in freshwater and seawater-acclimated flounder were investigated. Following voluntary feeding on a meal of 2.5–5% body mass and subsequent gastric acid secretion, no systemic alkaline tide or respiratory compensation was observed in either group. Ammonia efflux rates more than doubled from 489 ± 35 and 555 ± 64 μmol kg⁻¹ h⁻¹ under control conditions to 1,228 ± 127 and 1,300 ± 154 μmol kg⁻¹ h⁻¹ post-feeding in freshwater and seawater-acclimated fish, respectively. Based on predictions of gastric acid secreted during digestion, we calculated net postprandial internal base gains (i.e., HCO₃⁻ secreted from gastric parietal cells into the blood) of 3.4 mmol kg⁻¹ in seawater and 9.1 mmol kg⁻¹ in freshwater-acclimated flounder. However, net fluxes of ammonia, titratable alkalinity, Na⁺ and Cl⁻ indicated that branchial Cl⁻/HCO₃⁻ and Na⁺/H⁺ exchange played minimal roles in counteracting these predicted base gains and cannot explain the absence of alkaline tide. Instead, intestinal Cl⁻/HCO₃⁻ exchange appears to be enhanced after feeding in both freshwater and seawater flounder. This implicates the intestine rather than the gills as a potential route of postprandial base excretion in fish, to compensate for gastric acid secretion.     

虎纹伯劳的巢生境选择与繁殖行为

2005年3~7月通过焦点动物取样法(focal animal sampling)和完全记录法(all-occur rencerecording)对四川南充地区虎纹伯劳的繁殖行为进行了研究。结果表明,虎纹伯劳喜在5~12m的高大阔叶乔木的冠部分叉处营巢。对15个巢址主成分分析表明,前5个主成分特征值均大于1,累积贡献率高达83.15%,说明前5个主成分已经基本包含了所有参数的总信息量。4月下旬开始陆续有虎纹伯劳迁到,初到时并未配对。5月上旬开始出现求偶行为,并伴有递食行为。5月中旬首次见到营巢,两性参与营巢,营巢期5~7d。营巢结束一两天后开始产卵,一天一枚,窝卵数4~6枚。营巢期和产卵期都有求偶和交配行为。产完最后1枚卵后即开始由雌鸟单独孵卵,孵卵期13~14d。两性育雏,育雏期13~15d。     

How long would it take to become a giant squid?

Laboratory and field studies suggest that cephalopod growth occurs rapidly and is linked to temperature throughout a short life span. For giant squid such as Architeuthis, a paucity of size-at-age data means that growth is only inferred from isolated field specimens, based on either statoliths or isotopic analyses of tissue. In this study we apply simple growth models to obtain projections of the life span required to achieve the Architeuthis average body mass in scenarios which include an energy balance between rates of food intake and expenditure on growth and metabolism. Although the analysis shows that a wide range for the estimated life span is possible, energy conservation suggests that achievement of a larger size would be assisted by slower exponential growth early on. The results are compared with a sparse set of size-at-age data obtained from male and female Architeuthis wild specimens and possibly hint at some behavioural differences between males and females.     

Feeding strategies for <Emphasis Type="Italic">E. coli</Emphasis> fermentations demanding an enriched environment

The addition of a carbon nutrient feed to a fed-batch cultivation is often not enough to obtain satisfactory growth and/or production. In some cases, an additional feed with for example supplementary amino acids or complex media is required. This work presents the development of feeding strategies where more than one feed is required and the knowledge of the growth requirements is low. Simulations and cultivations with E. coli are shown using the proposed feed controllers which are based on a probing control concept. The strategies work well and they can be used to shorten the process development phase considerably.     

Fatty acid composition of the amphipod Dikerogammarus villosus: feeding strategies and trophic links

Fatty acid (FA) compositions were determined for the invader amphipod Dikerogammarus villosus collected from July to September 2002, in an overheated, high-conductivity dammed reservoir in north-eastern France. Predominant fatty acids were the polyunsaturated fatty acids (PUFA): eicosapentaenoic acid (EPA), linoleic acid (LA), arachidonic acid (ARA), linolenic acid (LNA) together with the monounsaturated fatty acid 18:1omega9 and the saturated fatty acid 16:0. FA markers indicated that available food was constituted of incompletely degraded phytodetritus and terrestrial inputs, as well as animal remains. PUFA contents depended on the diet and the capacity of animals to desaturate and elongate LNA and LA in long chain PUFA as EPA and ARA respectively. Based on their FA compositions, we showed that gammarids represent naturally-occurring freshwater sources of essential PUFA, and could play a fundamental role in pelagic-benthic coupling and energy recycling in the ecosystem. The complexity of the feeding strategies of D. villosus--detritivorous, omnivorous, carnivorous--makes this species efficient at exploiting different components of the available food and may be a key factor in its high invasive success.     

鳜鱼口咽腔味蕾和行为反应特性及其对捕食习性的适应

用扫描电镜观察和行为学实验研究鳜鱼口咽腔味蕾形态和分布及吞食行为反应特性，结果表明，鳜鱼口咽腔味蕾丰富，几乎都是Ｉ型和Ⅱ型味蕾，着生于表皮乳突上，主要分布于上颌骨齿周围及内侧，下颌齿周围及外侧，舌前中区，下鳃骨细齿内侧等部位，其它区域分布较少，鳜鱼口咽腔味蕾对食物味道和软硬均非常敏感，鳜鱼仅吞食同时具有一定味道和软硬度的食物，本文探讨了鳜鱼口咽腔味蕾的结构功能关系及其对捕食习性的适应意义。     

EMG Reactivity and Oral Habits Among Facial Pain Patients in a Scheduled-Waiting Competitive Task

For individuals with temporomandibular disorder (TMD) it has been theorized that stressful events trigger oral habits (e.g., teeth grinding), thereby increasing masticatory muscle tension and subsequent pain. Recent research involving adjunctive behaviors found an increase in masseter surface EMG (sEMG) and oral habits when students with TMD symptomatology were placed on a fixed-time reinforcement schedule. The current study used a treatment-seeking community sample with TMD symptomatology in a competitive task designed to be a more naturalistic Fixed Time task. The experiment consisted of Adaptation, Free-Play, Scheduled-Play, and Recovery phases. During the Scheduled-Play phase participants played, and waited to play, an electronic poker game. Results indicated that masseter muscle tension in the Scheduled-Play phase was significantly higher (p<.001) than in any other phase. Moreover, during the Scheduled-Play phase masseter sEMG was higher (p#60;.001) when participants waited to play. Self-reported oral habits and overall affect were significantly higher (p's<.05) in the Free-Play and Scheduled-Play phases relative to Adaptation and Recovery. The observation that masseter sEMG was elevated during the Scheduled-Play phase relative to all other phases, and within the Scheduled-Play phase sEMG was highest while waiting, suggests that adjunctive oral habits may lead to TMD symptomatology.     

Multilevel inhibition of feeding by a peptidergic pleural interneuron in the mollusc<Emphasis Type="Italic"> Lymnaea stagnalis</Emphasis>

The pleural interneuron PlB is a white neuron in the pleural ganglion of the snail Lymnaea. We test the hypothesis that it inhibits neurons at all levels of the feeding system, using a combination of anatomy, physiology and pharmacology. There is just one PlB in each pleural ganglion. Its axon traverses the pedal and cerebral ganglia, running into the buccal ganglia. It has neuropilar branches in the regions of the cerebral and buccal ganglia where neurons that are active during feeding also branch. Activation of the PlB blocks fictive feeding, whether the feeding rhythm occurs spontaneously or is driven by a modulatory interneuron. The PlB inhibits all the neurons in the feeding network, including protraction and retraction motoneurons, central pattern generator interneurons, buccal modulatory interneurons (SO, OC), and cerebral modulatory interneurons (CV1, CGC). Only the CV1 interneuron shows discrete 1:1 IPSPs; all other effects are slow, smooth hyperpolarizations. All connections persist in Ca²⁺/Mg²⁺-rich saline, which reduces polysynaptic effects. The inhibitory effects are mimicked by 0.5 to 100 mol l^–1 FMRFamide, which the PlB soma contains. We conclude that the PlB inhibits neurons in the feeding system at all levels, probably acting though the peptide transmitter FMRFamide.Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00359-004-0503-x     

Passive hinge forces in the feeding apparatus of<Emphasis Type="Italic"> Aplysia</Emphasis> aid retraction during biting but not during swallowing

Swallowing and biting responses in the marine mollusk Aplysia are both mediated by a cyclical alternation of protraction and retraction movements of the grasping structure, the radula and underlying odontophore, within the feeding apparatus of the animal, the buccal mass. In vivo observations demonstrate that Aplysia biting is associated with strong protractions and rapid initial retractions, whereas Aplysia swallowing is associated with weaker protractions and slower initial retractions. During biting, the musculature joining the radula/odontophore to the buccal mass (termed the hinge) is stretched more than in swallowing. To test the hypothesis that stretch of the hinge might contribute to rapid retractions observed in biting, we analyzed the hinges passive properties. During biting, the hinge is stretched sufficiently to assist retraction. In contrast, during swallowing, the hinge is not stretched sufficiently for its passive forces to assist retraction, because the odontophores anterior movement is smaller than during biting. A quantitative model demonstrated that steady-state passive forces were sufficient to generate the retraction movements observed during biting. Experimental measures of the relative magnitude of the hinges active and passive forces at the protraction displacements of biting suggest that passive forces are at least a third of the total force.Abbreviations I1/I3 intrinsic buccal muscles 1 and 3 - I2 intrinsic buccal muscle 2 (nomenclature from Howells 1942)     

Effects of jaw adductor hypertrophy on buccal expansions during feeding of air breathing catfishes (Teleostei,Clariidae)

Some species of Clariidae (air breathing catfishes) have extremely well developed (hypertrophied) jaw closing muscles that increase the maximal biting force of these species. As these enlarged jaw muscles tightly cover the suspensoria, which are firmly connected to the neurocranium, we expect diminished lateral expansions during suction for species with hypertrophied jaw muscles. In turn, this could imply a reduced suction performance for these species. Compared to Clarias gariepinus, which has relatively small jaw closers, Clariallabes longicauda shows a clear hypertrophy of the jaw adductors. A kinematic analysis of prey capture in these two species is presented here. As predicted, Clariallabes longicauda shows less lateral expansion (average abduction of the hyoids of 19.0°) than Clarias gariepinus (abduction of 31.1°). However, our data indicate that the decrease in lateral expansion capacity in the species with excessive adductor development is compensated for by a larger and faster ventral expansion of the buccal cavity by depression of the hyoid.