How tetrapods feed in water: a functional analysis by paradigm

Mechanical theory is used to erect a paradigm predicting the manipulations used by carnivorous aquatic amphibians, reptiles, birds and mammals to catch, subdue, process and swallow their prey. These predictions are confirmed by observational evidence. Most aquatic predatory tetrapods use long, prehensile tooth-armed jaws as pincer jaws to snap shut onto the prey and catch and kill it, although some use the flexibility of long necks in spear fishing and some odontocetes may stun prey with sonar. Most do not have cutting or nipping dentitions as these cannot be used on prey which is freely floating. They use caniniform dentition to hold and kill prey, or in some cases crushing dentition to break open hard-shelled prey. They dismember prey by dynamic loading, snatching bites so quickly that the prey tears. They use shake feeding, shaking the prey apart from side to side above the water. If the prey is too large to lift above the water they use twist feeding, twisting pieces off. Small pieces are easily swallowed but larger pieces are held above the water and swallowed by tilting the head back in gravity feeding, or by jerking the head back and forth in incrtial feeding. Some animals use mobile jaws to pull prey back into the mouth in ratchet feeding. Filter feeding evades these problems by feeding on very small prey. The use of paradigms in functional analysis is discussed with special reference to this work. The paradigm method is shown to be the most suitable one. There has been repeated convergent and parallel evolution of adaptations to feed in water.     

Effects of insect herbivory on early plant succession: comparison of an English site and an American site

We examined the survival, size, and agonistic behaviour of faster and slower developing rainbow trout ( Salmo gairdneri ) in an artificial stream channel with a simulated redd. The analysis was performed at two levels: between three full-sib families genetically marked at a hexosaminidase locus, and within families segregating for a regulatory allele Pgml-t(b) that is associated with faster developmental rate. The families differed significantly in their hatching times but showed little variation in emergence times. Fishes with the Pgml-t(b) allele hatched and emerged significantly earlier than their full-sibs without the allele. Despite the mortality of at least 50% of emerged fishes in the selection experiment, there was no significant difference in survival between either the three families or fishes with different genotypes at the Pgml-t locus. However, fishes from the faster developing family and those with the Pgml-t(b) allele had significantly higher levels of agonistic behaviour and had a tendency to be larger than slower developing individuals.     

Immediate effects of Ore on ants in the semi-arid mallee region of north-western Victoria

The immediate effects of a high intensity wildfire on the ant communities of a heath and a mallee site in semi-arid north-western Victoria are reported. Following fire the number of species trapped on the ground doubled (to ca. 80 each site), total ant abundance decreased by half (due to the demise of previously dominant species), surface activity of reproductive castes increased, and dramatic changes in species relative abundance (including shifts toward greater equitability) occurred. These changes are interpreted in terms of fire-induced simplification of the habitat and release from competition with dominant species. The results appear to illustrate the importance of interspecific competition in structuring foraging activity in mallee ant communities. Observations are also reported on seed-harvesting by ants, including changes in harvester ant abundance, germination from within-nest seed storage, and the first record of Heteroponera removing seeds.     

Forecasting the incidence of virus yellows in sugar beet in England

A new forecasting system for virus yellows incidence in sugar beet in the UK has been devised using multiple regression analyses. The forecast equations include data on (1) the previous year's virus incidence, (2) temperature in January and February and (3) the timing of the spring migration of Mytus persicae. Forecasts using the first two of these variables account for 63% of the variance in virus incidence in the main beet growing area of Eastern England and give growers information in time to decide on whether to apply aphicidal granules at drilling to control the vectors of the disease. Forecasts using all three variables account for 87% of the variance in virus incidence and can forewarn growers and the sugar industry of the likelihood of an epidemic. Forecasts for the northern and western regions of the beet growing area are derived from the forecast for the eastern region.     

The Gastropod, Siphonaria pectinata: a Factor in Destruction of Beach Rock

The marine gastropod, Siphonaria pectinata, has an active partin the complex formation of secondary solution features characteristicof outcroppings of beach rock in south Florida. Analyses weremade of the distribution, anatomy, and feeding activity ofthissnail. The results show that these molluscs are concentratedin areas of maximum algal growth. While grazing they rasp substratapresoftened by algae so that new rock surfaces are continuallyexposed to biochemical erosion.     

The Occurrence of Biogenic Calcian Struvite, (Mg, Ca)NH4PO4.6H2O, as Intracellular Crystals in Paramecium

ABSTRACT. Intracellular crystals are conspicuous refractile "inclusion bodies" commonly found in many protozoans, but very few have been identified mineralogically. We have isolated crystals from axenically grown mass cultures of Paramecium tetraurelia , and purified them using differential centrifugation. The crystals' structure and chemistry were analyzed using x-ray powder diffraction and energy-dispersive electron microprobe techniques. The morphology was studied by means of scanning electron microscopy. The crystals were identified as the orthorhombic mineral, calcian struvite, (Mg, Ca)NH₄PO₄.6H₂O. Struvite from P. tetraurelia exhibited a variety of crystal habits, including hemimorphic forms, epitactic overgrowths and several types of twins. A linear correlation between computed hydration number and Mg content suggests that the crystal composition may reflect the range of conditions under which struvite nucleation and growth occur. The mineral struvite also occurs in association with guano and other rich organic products, and can be biologically induced to precipitate extracellularly. Extracellular struvite has been well characterized in pathogenic calculi (kidney stones) of humans and cats, where precipitation is enhanced by bacterial urease activity that produces ammonia in the urinary tract. This is the first study demonstrating that struvite is also biologically controlled to form as an intracellular mineral. These crystals may have formed within lipid-rich, membrane-bound vesicles in Paramecium .     

Callitriche Stem Elongation is controlled by Ethylene and Gibberellin

Callitriche platycarpa is a freshwater plant characterized by floating rosettes of leaves connected to the water-bed by threadlike (diameter < 1 mm) stems. The internodes within the rosettes are immature and short (< 2 mm). If they mature at the water surface, they become 10 to 30 mm long, but if the rosette is submerged the internodes elongate faster and to a greater extent (25–60 mm). This method of growth rate control is of interest.