Invasive Predator, <Emphasis Type="Italic">Bythotrephes</Emphasis>, has Varied Effects on Ecosystem Function in Freshwater Lakes

Bythotrephes longimanus is an invertebrate predator that has invaded the North American Great Lakes and a number of inland lakes, where it preys on crustacean zooplankton. We examined the effect of Bythotrephes on two measures of ecosystem function during a four-month observational study of freshwater lakes on the boreal shield. Bythotrephes-invaded lakes had significantly lower epilimnetic zooplankton abundance and production compared to reference lakes. On average, Bythotrephes consumed 34% of zooplankton production when it was present in lakes. There was some evidence of changes in the timing of zooplankton production, as well as shifts to cooler, less productive habitats, which may lessen the overall effect of the invader on the transfer of energy to higher trophic levels. We experimentally demonstrated a weak trophic cascade where invader predation reduced zooplankton biomass, and subsequently increased phytoplankton growth. However, the response was small in magnitude and not biologically relevant at the whole lake-scale. The most conspicuous effect of Bythotrephes that we measured was a diversion of energy away from native predators at higher trophic levels. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

[3H]Choline Uptake and Metabolism in Nonsynaptic Regions of a Crustacean Sensory Nerve

Abstract: The posterior stomach nerve (PSN) is a crustacean sensory nerve containing about 60 cholinergic neurons, which are devoid of synaptic interactions. Kinetic analysis shows that the PSN takes up [³H]choline by both low-affinity ( K _m= 163 μM) and high-affinity (Na⁺-dependent) ( K _m= 1 μM) processes. The capacity of the high-affinity system is only about 1% that of the low-affinity system. The high-affinity system is not tightly coupled to acetylcholine (ACh) synthesis, and it appears that both ACh and phosphorylcholine are formed from an intracellular pool of choline, which is fed by both uptake systems. There are differences in the rates of [³H]choline uptake and ³H metabolite accumulation between regions of the PSN that contain neuronal cell bodies and those that do not. These differences may arise from differences in the relative proportion of neuronal to nonneuronal tissue in each nerve region.     

Flight or fight: flexible antipredatory strategies in porcelain crabs

Autotomy, the voluntary shedding of limbs or other body partsin the face of predation, is a highly effective escape mechanismthat has evolved independently in a variety of taxa. Crabs areunusual in that the limb that is typically sacrificed duringautotomy, the anterior clawed cheliped, can also be used toward off attack. During an encounter with a predator, an individualmust thus decide between two mutually exclusive strategies:flight or fight. We used experimental predation encounters withtwo species of porcelain crabs (genus Petrolisthes) to examinethe factors that influence the decision to flee versus fightand to determine the degree to which this decision is context-dependent.We found that autotomy was highly conditional. The characteristicsthat best predicted autotomy—smaller body size or femalegender—also correlated with a lower escape rate by thealternative escape tactic, struggling and pinching the predator.Variation among individuals in the benefit of autotomy (relativeto alternative tactics) appears to drive variation in propensityto autotomize. Porcelain crabs thus demonstrate adaptive flexibility,employing the costly strategy of autotomizing a limb as a lastresort, only when their chance at success by struggling is low.     

Recent trends in biological extraction of chitin from marine shell wastes: a review

The natural biopolymer chitin and its deacetylated product chitosan are widely used in innumerable applications ranging from biomedicine, pharmaceuticals, food, agriculture and personal care products to environmental sector. The abundant and renewable marine processing wastes are commercially exploited for the extraction of chitin. However, the traditional chitin extraction processes employ harsh chemicals at elevated temperatures for a prolonged time which can harm its physico-chemical properties and are also held responsible for the deterioration of environmental health. In view of this, green extraction methods are increasingly gaining popularity due to their environmentally friendly nature. The bioextraction of chitin from crustacean shell wastes has been increasingly researched at the laboratory scale. However, the bioextraction of chitin is not currently exploited to its maximum potential on the commercial level. Bioextraction of chitin is emerging as a green, cleaner, eco-friendly and economical process. Specifically in the chitin extraction, microorganisms-mediated fermentation processes are highly desirable due to easy handling, simplicity, rapidity, controllability through optimization of process parameters, ambient temperature and negligible solvent consumption, thus reducing environmental impact and costs. Although, chitin production from crustacean shell waste through biological means is still at its early stage of development, it is undergoing rapid progress in recent years and showing a promising prospect. Driven by reduced energy, wastewater or solvent, advances in biological extraction of chitin along with valuable by-products will have high economic and environmental impact.     

Measures of Heart and Ventilatory Rates in Freely Moving Crayfish

The fear, flight or fight response serves as the fundamental physiological basis for examining an organism''s awareness of its environment under an impending predator attack. Although it is not known whether invertebrates posses an autonomic nervous system identical to that of vertebrates, evidence shows invertebrates have a sympathetic-like response to regulate the internal environment and ready the organism to act behaviorally to a given stimuli. Furthermore, this physiological response can be feasibly measured and it acts as a biological index for the animal''s internal state. Measurements of the physiological response can be directly related to internal and external stressors through changes in the central nervous system controlled coordination of the cardio-vascular and respiratory systems. More specifically, monitoring heart and ventilation rates provide quantifiable measures of the stress response not always behaviorally observed. Crayfish are good model organisms for heart and ventilatory rate measurements due to the feasibility of recording, as well as the rich history known of the morphology of the crayfish, dating back to Huxley in 1888, and the well-studied typical behaviors.