Historical Zoogeography of the Eusuchian Crocodilians: A Physiological Perspective

The historical zoogeography of eusuchian crocodilians has rarelybeen reviewed in any detail and yet is of increasing interestto students of crocodilian biology as large amounts of comparativeinformation on a wide range of species come to hand. Previousinterpretations of crocodilian zoogeography have been basedon one or another of two assumptions–that the major continentalland masses have remained more or less fixed in position, andthat the eusuchians have had only very limited powers of dispersalacross marine barriers. Both of these assumptions are inappropriatein light of our present knowledge of continental drift and crocodilianphysiology. In this paper we attempt a reinterpretation of eusuchian zoogeographybased on new information on their systematic relationships,physiological capacity for marine dispersal, and fossil history.We postulate that anatomical and physiological adaptations toa marine existence have played an important role in eusuchianhistory. We propose that Gavialis and Tomistoma, now restrictedto fresh waters, may have been derived secondarily from ancestorsadapted to salt water. In the case of Tomistoma, similaritiesin lingual gland and buccal cavity anatomy to the true crocodiles(Crocodylus and Osteolaemus) suggest that marine adaptationspredated the divergence of tomistomine and crocodyline stocks.The buccal morphology of Gavialis suggests it also has a marineancestry. Its systematic affinities are uncertain, lying perhapswith Tomistoma or, on other interpretations, with the Mesosuchia.In both cases, the fossil record is not inconsistent with thispossibility. Palaeontological information now available is inadequate toreconstruct the evolutionary history of the Eusuchia in detail.However, saltwater adapted eusuchians are more common in thefossil record than is widely recognized and the likelihood ofdispersal across marine "barriers" by non-alligatorid crocodilianscannot be ignored.     

脊尾白虾生理性体温调节的初步观察

爬行类动物在升温和降温时不同的心率变化(心率滞后)是其进行生理性体温调节的重要机制.在与爬行类系统进化关系较远的甲壳类动物脊尾白虾 Exopalaemon carinicauda 的研究中发现,在升温和降温时也出现心率滞后现象,这对温度敏感的甲壳类动物的体温调节十分有利,同时对其体温调节的可能生理机制进行了讨论.     

Osmoregulation in Crocodilians

Recent crocodilians live primarily in freshwater habitats. Howevertwo species (Crocodylus acutus and C. porosus) are estuarinespecialists; two others (C. niloticus and C. johnstoni) thatare primarily found in fresh water, have estuarine populations.Routes of uptake of water and sodium include drinking, feedingand associated incidental drinking, and integumental and buccaldiffusion. Routes of loss include faeces-cloacal fluid, lingualsalt glands, integumental and buccal diffusion, and respiratoryloss. The least understood route of salt and water exchangeis that of the oral and buccal epithelia, which are much morepermeable to water and sodium than the general integument. Thefreshwater alligator (Alligator mississippiensis) osmoregulatesin a manner typical for an amphibious reptile. Body sodium turnoveris low and the general integument is quite low in permeabilityto sodium. Water turnover is more rapid (in terms of molar exchange)but still relatively low for an aquatic reptile. Most waterexchange occurs across the integument and buccal epithelia.The presence of lingual salt glands in freshwater crocodiliansremains enigmatic, as does the failure of these exocrine glandsin estuarine species to respond to saline loading. Secretiondoes occur after injection of the parasympathetic stimulantmethacholine chloride. The "salt water crocodile" (C. porosus)possesses a suite of osmoregulatory adaptations similar to thosefound in other estuarine reptiles. Water and sodium balanceare maintained primarily by an extremely low general permeabilityto sodium, by economies in water loss, and by excretion of excesssodium by the lingual salt glands. Further work is needed toexamine newly hatched C. porosus, and the possibility of ontogeneticchange in lingual gland function in C. acutus. The importanceof incidental drinking of sea water during feeding (recentlydiscovered in turtles) needs to be evaluated in crocodilians.The use of osmoregulatory data in interpretation of the evolutionaryhistory of the genus Crocodylus needs to be viewed with caution.The hypothesis that all species of Crocodylus originated fromthe transoceanic migration of a saline-tolerant form may notbe the most parsimonious explanation.     

Behavioral Thermoregulation and the "Final Preferendum" Paradigm

Wider attention to Fry's (1947) "final preferendum" paradigmwould facilitate comparative studies of temperature preference(behavioral thermoregulation) among different animal groups.According to Fry's bipartite definition, the final preferendumis that temperature at which preference and acclimation areequal, and to which an animal in a thermal gradient will finallygravitate regardless of its prior thermal experience (acclimation).This paradigm is helpful in distinguishing between acute thermalpreferenda (measured within 2 hr or less after placing an animalin a thermal gradient), which are influenced by acclimationtemperature, and the species-specific final preferendum (measured24–96 hr after placement in the gradient), which is essentiallyindependent of prior acclimation because reacclimation occursduring the gravitation process. The paradigm does not take intoaccount non-thermal acclimatization influences (e.g., season,photoperiod, age, light intensity, salinity, disease, nutrition,pollutants, biotic interactions) which can also affect temperaturepreference. However, a graph of acutely preferred temperaturesversus acclimation temperatures can be employed to determinean equivalent acclimation temperature for any given acclimatizationstate, as a simple means of quantifying acclimatization statesresulting from interactions of many influences. This paradigm,developed for use with fishes, can also be applied to otherectothermic taxa, although it is most easily employed with aquaticorganisms because of the simplicity of specifying aquatic thermalenvironments in terms of water temperature alone. Methodologiesused in studies of behavioral thermoregulation should take theparadigm into account (especially with respect to length oftests) to enhance the comparative value of data across taxa.     

Crocodilians in Perspective!

The prediction of the 1960s that crocodilians would soon beextinct has happily proven to be unduly pessimistic. The survivaland recovery of substantial stocks provides us with the unexpectedopportunity to learn about their adaptations, important notonly because of their place as relicts of a major reptilianradiation, but also as giant animals, reptiles substantiallylarger than all but marine turtles.     

Behavioral Thermoregulation by Juvenile Spring and Fall Chinook Salmon, Oncorhynchus Tshawytscha, during Smoltification

Fall chinook salmon evolved to emigrate during the summer months. The shift in the temperature preference we observed in smolting fall chinook but not spring chinook salmon may reflect a phylogenetic adaptation to summer emigration by (1) providing directional orientation as fall chinook salmon move into the marine environment, (2) maintaining optimal gill function during emigration and seawater entry, and/or (3) resetting thermoregulatory set-points to support physiological homeostasis once smolted fish enter the marine environment. Phylogenetically determined temperature adaptations and responses to thermal stress may not protect fall chinook salmon from the recent higher summer water temperatures, altered annual thermal regimes, and degraded cold water refugia that result from hydropower regulation of the Columbia and Snake rivers. The long-term survival of fall chinook salmon will likely require restoration of normal annual thermographs and rigorous changes in land use practices to protect critical thermal refugia and control maximum summer water temperatures in reservoirs.     

Behavioral and Physiological Characteristics of the Antarctic Krill, Euphausia superba

The antarctic krill, Euphausia superba, is considered a successin the intensely seasonal environment of the Southern Oceanbecause of its abundance and central role as an important fooditem for many of the larger carnivores in the ecosystem. Thebehavioral and physiological characteristics that foster thissuccess are: (1) the ability to find concentrations of foodin several types of habitat and efficiently exploit whateverfood is available; (2) the close correspondence of the lifecycle with seasonal cycles of food availability; and (3) a combinationof physiological mechanisms that enable krill to survive thelong winter period of low food availability. We evaluated therelative importance of the following four major winter-overmechanisms that have been proposed for adult krill west of theAntarctic Peninsula. The three-fold reduction in metabolic rateis the most important winter-over mechanism for these adults,although lipid utilization and shrinkage also help satisfy energyrequirements in the winter. Alternate food sources did not appearto contribute significantly as a winter energy source. However,the extent, predictability and complexity of the ice cover ina region during winter may have a great influence on the relativeimportance of these winter-over mechanisms for different populations.Ice cover in the waters west of the Antarctic Peninsula is unpredictableand smooth surfaced when it occurs, providing the krill withlittle refuge from predation. In multi-year pack ice of theWeddell Sea, however, ice cover is predictable and extensive,and there is a complex undersurface that provides hiding places.In this multi-year ice, adult krill have been observed underthe ice feeding, whereas west of the Antarctic Peninsula mostadult krill are in the water column in the winter and are notfeeding. The balance between acquiring energy and avoiding predationmay be different in these two regions in the winter becauseof differences in predictability and complexity of the ice cover.     

Intrinsic Behavioral and Physiological Differences Among Laboratory Populations of Prairie Deermice

The emphasis of this presentation is that social behavior isbasically involved in the curtailment of growth of laboratorypopulations of prairie deermice through inhibiting influenceson the reproductive development and function of population animals.Reproductive inhibition is not directly related to the numbersof animals present per se since physiological characteristicsare similar between animals from populations differing widelyin density under identical conditions of the physical environment.Thus, density should be interpreted relative to social or otherbehavioral factors and we should think of animals in a populationin a qualitative as well as a quantitative sense. Populationgrowth is controlled either by cessation of reproduction orby mortality of young and while 95% of the young remain reproductivelyimmature and fail to reproduce, the weights and characteristicsof their reproductive organs differ dependent upon the mechanismby which population growth is curtailed. Mechanisms of growthcurtailment thus develop intrinsically to each population andinvolve communication through one or more of the senses of touch,smell, sight, hearing or taste. My data suggest that tactilecues from population animals (not necessarily overt aggression)may be of major importance in producing the reproductive retardationobserved although chemosignals or other stimuli such as visualor auditory cues may act to slow reproductive recovery of inhibitedanimals. Data presented support the contention of a behavioral-physiologicalrelationship distinct for each population.     

Morphological, Behavioral, and Physiological Characterization of Bimodal Breathing Crustaceans

SYNOPSIS Bimodal breathing crustaceans, while representing astage in the transition from the aquatic to terrestrial habitat,also constitute a distinct group that can be characterized bymorphological, behavioral, and physiological traits. Morphologically,this group displays reduced gill surface area and enlarged branchialchambers. The lining of the branchial chambers, the branchiostegites,also has increased surface area and is highly vascularized.The branchiostegites can be smooth, cutaneous epithelia, orthey can have more complex evaginations or invaginations tofurther increase surface area. In addition, the thickness ofthe branchiostegal epithelium is greatly reduced, compared tothat in the gills, thus minimizing the diffusion distance betweenair and hemolymph. These animals maintain a store of water inthe branchial chamber that covers the gills and allows for simultaneousgas exchange with two media (air and water). There is also apartitioning of gas exchange, with oxygen uptake occurring preferentiallyfrom air across the branchiostegites, and carbon dioxide excretionoccurring across the gills into the branchial water. One criticalfactor that appears to separate bimodal breathing crustaceansfrom fully terrestrial, exclusively air-breathers is the abilityof the latter group to excrete CO₂directly into air across thegills and branchiostegites. It is suggested that the incorporationof the enzyme carbonic anhydrase into the membrane fractionof the branchiostegites may have been one of the key molecularevents which allowed for pulmonary CO₂ excretion into air.     

Crocodilians and Their Helminth Parasites: Macroevolutionary Considerations

Crocodilian relationships supported by the phylogenetic relationshipsof digenean and nematode parasites are compared with currentestimates of crocodilian phylogeny. The parasite data support(1) the placement of Gavialis as the sister-group of the alligatoridsand the crocodylids, (2) the monophyly of alligators and caimans,(3) the placement of Caiman (as a monophyletic group) as thesister-group of Melanosuchus plus Paleosuchus, and (4) ancientorigins of Crocodylus consistent with patterns of continentaldrift. The parasite data do not support the monophyly of Crocodylus,but the "misplaced" species (C. palustris and Osteolaemus) havehad few parasites reported from them. There is evidence of widespreadhost-switching, but most of the ambiguity appears to resultfrom uneven representation of parasite groups in host species.This is probably due both to uneven sampling by parasitologistsand to parasite extinctions associated with crocodilian extinctions.     

A Physiological and Behavioral Mechanism for Leaf Herbivore-Induced Systemic Root Resistance

Indirect plant-mediated interactions between herbivores are important drivers of community composition in terrestrial ecosystems. Among the most striking examples are the strong indirect interactions between spatially separated leaf- and root-feeding insects sharing a host plant. Although leaf feeders generally reduce the performance of root herbivores, little is known about the underlying systemic changes in root physiology and the associated behavioral responses of the root feeders. We investigated the consequences of maize (Zea mays) leaf infestation by Spodoptera littoralis caterpillars for the root-feeding larvae of the beetle Diabrotica virgifera virgifera, a major pest of maize. D. virgifera strongly avoided leaf-infested plants by recognizing systemic changes in soluble root components. The avoidance response occurred within 12 h and was induced by real and mimicked herbivory, but not wounding alone. Roots of leaf-infested plants showed altered patterns in soluble free and soluble conjugated phenolic acids. Biochemical inhibition and genetic manipulation of phenolic acid biosynthesis led to a complete disappearance of the avoidance response of D. virgifera. Furthermore, bioactivity-guided fractionation revealed a direct link between the avoidance response of D. virgifera and changes in soluble conjugated phenolic acids in the roots of leaf-attacked plants. Our study provides a physiological mechanism for a behavioral pattern that explains the negative effect of leaf attack on a root-feeding insect. Furthermore, it opens up the possibility to control D. virgifera in the field by genetically mimicking leaf herbivore-induced changes in root phenylpropanoid patterns.Insect herbivores constantly compete for plants as a primary terrestrial source of organic carbon and nitrogen (Denno et al., 1995). Consequently, resource competition is thought to be a major determinant of the distribution and abundance of insects in natural and agricultural systems (Begon et al., 2006). Recent evidence suggests, however, that in many cases, insect herbivore competition may not follow the traditional theoretical assumptions of direct interference and/or resource exploitation, but may be determined by indirect plant-mediated effects (Kaplan and Denno, 2007; Poelman et al., 2008). Among the most striking examples of indirect plant-mediated interactions is the interplay between root- and leaf-feeding insects (Blossey and Hunt-Joshi, 2003). Despite their nonoverlapping feeding niches, leaf and root herbivores determine each other’s performance through shared host plants (Bezemer and van Dam, 2005). Although root feeders can have positive or negative effects on leaf feeders (van Dam and Heil, 2011), the effect of leaf herbivores on root consumers is predominantly negative (Johnson et al., 2012; Huang et al., 2014).Despite the increasing number of examples demonstrating negative effects of leaf attack on root herbivores (Tindall and Stout, 2001; Blossey and Hunt-Joshi, 2003; Soler et al., 2007; Gill et al., 2011), the mechanisms underlying this form of systemic induced resistance remain poorly understood (Erb et al., 2008; Rasmann and Agrawal, 2008). Pieris brassicae, for instance, was found to increase glucosinolate levels in the roots, which correlated with a reduced survival of the root feeder Delia radicum (Soler et al., 2007). Understanding why root feeders perform worse on leaf-infested plants would allow for more detailed investigations regarding the adaptive and evolutionary context of the phenomenon, and may allow for its exploitation in agriculture (for instance, by triggering root resistance through targeted leaf treatments).A promising system to study the mechanisms and agroecological consequences of plant-mediated interactions between herbivores is maize (Zea mays) and its associated pests. In the field, maize is attacked by a suite of herbivores, including leaf feeders, stem borers, and root feeders. The highly specialized root-feeding larvae of the western corn rootworm Diabrotica virgifera virgifera cause significant plant damage and yield loss in the United States and Eastern Europe. Earlier studies demonstrated that D. virgifera attack increases leaf resistance against Spodoptera spp. by triggering drought stress responses (Erb et al., 2009, 2011b). In the opposite direction, leaf feeding by Spodoptera spp. caterpillars reduces D. virgifera growth and development in a sequence-specific manner in the laboratory and the field (Erb et al., 2011c; Gill et al., 2011). D. virgifera was subsequently demonstrated to avoid leaf-infested plants by detecting and responding to a reduction in root ethylene emissions (Robert et al., 2012). However, it remains unclear whether nonvolatile chemical changes in the roots of leaf-infested maize plants affect D. virgifera foraging and performance. In this study, we explored the hypothesis that leaf infestation by Spodoptera spp. caterpillars triggers a short-range avoidance response in D. virgifera. Through a combination of bioactivity-guided fractionation of root extracts and biochemical and molecular manipulation, we show that systemic changes in soluble phenylpropanoid derivatives trigger a strong avoidance response in D. virgifera. We furthermore demonstrate that this avoidance response is mediated by systemic internal signals and is triggered specifically by herbivory, suggesting that D. virgifera actively and specifically recognizes and avoids leaf-infested plants.     

Thermoregulation im Hornissennest

Zusammenfassung Im Nest von Vespa crabro wird im Bereich der Puppen von den weiblichen Imagines (Arbeiterinnen und Königinnen) eine sehr konstante Temperatur von 30,0° C aufrecht erhalten. Zwischen Larvenzellen sind die Tagesschwankungen größer, die Durchschnittstemperatur um 0,4° C niedriger. Die Larven werden von den Imagines nicht gewärmt.In Nestern ohne Imagines läßt sich eine autonome Temperaturregulation durch die Larven nachweisen. Die thermoregulatorischen Bewegungen der Larven werden beschrieben und von den als Hungersignale zu wertenden Bettelbewegungen abgegrenzt.Weibliche Imagines wärmen ältere, pigmentierte Puppen auch außerhalb des Nestes. Dieses Verhalten wird vermutlich durch ein Pheromon ausgelöst. Es werden die Unterschiede in der Thermoregulation gegenüber den Honigbienen und V. orientalis diskutiert.

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Thermoregulation in the nests of hornets

Summary In the nest of Vespa crabro, a very constant temperature of 30° C is maintained by female adults (workers and queens) in the vicinity of pupae. Daily temperature variation between larval cells on the other hand is larger and the average temperature about 0,4° C lower. Larvae are not warmed by the adults.Larvae in nests without adults exhibit an autonomous temperature regulation. In this paper the thermoregulatory movements of larvae are described and distinguished from those normally described as hunger signals and begging movements.Female adults warm older pigmented pupa, even when outside the nest. This behavior is probably stimulated by a pheromone.Differences in thermoregulation are discussed and are contrasted with those of the honey bee and V. orientalis.

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