The Physiological Ecology of Planktonic Sarcodines with Applications to Paleoecology: Patterns in Space and Time1

ABSTRACT. Planktonic sarcodines, suspended in the water column, are conveniently grouped into three categories based on functional morphology: (1) gymnamoebae and their relatives, which lack major living or nonliving compartmentalizing barriers, (2) foraminifera, and testate amoebae enclosed by a test or shell with one or more major openings, but lacking extensive cytoplasmic compartmentalizing barriers, and (3) radiolaria, which exhibit distinct compartmentalization of the cytoplasm into functional zones. Differences in feeding strategies and trophic activity of members in the three groups reflect in part these differences in functional morphology. Members of all three groups form symbiotic associations with Monera and protists, including algae, thus partially offsetting interspecific trophic competition among species occupying the same water mass. Physiological and morphological adaptations supporting a symbiotic association are presented. C¹⁴-labeling studies of endosymbiotic radiolarian species show a substantial contribution of carbon to the host. Rates of calcification (planktonic foraminfera) and silica deposition (radiolaria) are reported, based on morphometric analyses and isotopic labeling studies. Major distributional patterns in space and time for each of the three groups, and some ecological principles explaining these regularities, are presented as related to population growth dynamics, niche differentiation, water-mass properties, and the role of symbionts in supporting highly diverse communities of species within the same locale in the water column.     

Divergence in cuticular hydrocarbons between parapatric subspecies of the meadow grasshopper, Chorthippus parallelus (Orthoptera, Acrididae)

Two subspecies of the grasshopper Chorthippus parallelus (Orthoptera; Acrididae) meet and form a hybrid zone in the Pyrenees. Here we investigate whether the subspecies differ in the blend of cuticular hydrocarbons. Such differences may function as chemical signals, being detected via contact chemoreception and used during mate choice as in other insects. Gas chromatography shows that the subspecies have diverged in the composition of their cuticular hydrocarbons. This difference between subspecies exists over and above variation in cuticular hydrocarbons among individual populations. The majority of the difference can be attributed to the relative amounts of a small group of compounds present in the cuticle. The possible consequences of this chemical divergence for mating encounters between the subspecies are discussed.     

The Effects on Temperature on Growth in vitro of Pseudomonas syringae and Xanthomonas pruni

Growth rates in vitro of Pseudomonas syringae and Xanthomonas pruni were measured over the temperature range 0–36 °C. The estimated temperature optimum for X. pruni was 31 °C, with a doubling time of 1.53 h. The estimated temperature optimum for P. syringae was 28 °C with a doubling time of 1.27 h, although analysis showed no significant difference in the doubling times over the range 23–33 °C, indicating an unusual plateau at the maximum rate of growth of this organism. P. syringae and related plant pathogenic Pseudomonas spp. grew well at low temperatures, but X. pruni did not. Cultures of P. syringae and X. pruni had a very short lag phase after their incubation temperature was changed from 4 °C to a temperature close to their optimum (29 °C). When the incubation temperature of these organisms was changed from 11.5–29 °C, X. pruni grew without a lag phase at the rate expected for the higher temperature. However, the initial growth rate of P. syringae at the higher temperature was significantly greater than that at which the organism subsequently developed. The ecological significance of these points is discussed. The usefulness of the Arrhenius coefficients as characteristics of these organisms is discussed.     

Fat, Energy and Mammalian Survival

Adipose tissue plays a critical role in mammalian life historystrategies, serving as an organ for the storage of food andenergy, as a source of heat and water and as thermal insulation.The food and energy storage roles are especially important inallowing the animals to survive food shortages and stressesassociated with competition for mates, territorial defense,gestation and lactation, and to accomplish migrations. The composition,cellularity and anatomical site of adipose depots in a mammalcan influence both the amount of fat stored and its availabilityand usefulness in any given situation. The fatty acids and complexlipids in adipose tissue, blood vessels, nerves and brain changein response to ambient temperature and the low body temperaturesduring hibernation. Early nutrition may influence the numberof fat cells developed by a mammal, and thus affect its abilityto survive adversity. Desert species develop localized depotswhich will not interfere with temperature regulation, whileanimals in cold environments use their extensive superficialfat layers as insulation.     

Activity Changes in Selected Enzymes from Soybean Leaves Following Ozone Exposure

Soybeans [Glycine max(L.) Merr.] were harvested at various time periods after a 2-h exposure to either 0 or 0.5 μ1/1 ozone to determine the effects of ozone on selected enzymes. Carbohydrate metabolism was modified by a depression of glyceraldehyde 3-phaosphate dehydrogenase and an activation of glucose 6-phosphate dehydrogenase. Ozone did not alter the levels of RNase, protease, acid phosphatase or esterase as might be expected if ozone enhanced leaf senescence. The activities of phenylalanine ammonia lyase, polyphenol oxidase and peroxidase were initially depressed and then stimulated following the ozone exposure. The reactions of soybeans to an acute ozone stress were more nearly akin to those elicited in response to other stresses than to the process of senescence.     

The effect of food availability, female culture-density and photoperiod on ephippia production in Daphnia magna Straus (Crustacea: Cladocera)

SUMMARY. A method is described whereby ephippia (sexual eggs plus protective membranes) are experimentally induced at low food levels (≤ 0.05 mg spinach D. magna ^-1), high female culture-densities (≤ 0.4 D. magna ml^-1) and in short-day photoperiods (L:D < 12:12, 12°C). The density-dependent ephippial response was related to an increased encounter rate between females at the higher densities. External metabolites had no significant effect on ephippia production. Ephippia were formed in the second generation after exposure to short day-lengths. Five clones from the same population exhibited genetic variation in their critical photoperiods for induction of sexual reproduction (≥= 10% ephippia). There was evidence of a genetic difference in photoresponse between two populations of D. magna. The evolution of timing mechanisms for ephippia production are discussed in relation to the predictability of environmental change.     

松梢蚧

松梢蚧又称松针蚧,是同翅目珠蚧科松蚧属专寄生在松树针叶上的害虫。由于它发生起始于松树梢头的新针叶,有些地区的群众称它为松梢蚧,表达了它发生的特点。松树受害严重的可使枝梢上的针叶大部脱落,影响松树生长。 在我国浙江早已发现中华松梢蚧(Matsucoccus sinensis Chen)。Ferris(1950)重新描述了在昆明云南松上采到的所谓中华松梢蚧。我们研究了从昆明采集的标本,发现它不是中华松梢蚧,而是一个新种。Ferris的鉴定和重新描述,很容易引起对中华松梢蚧的误解。     

On the taxonomy of Littorina africana (Mollusca: Gastropoda)

L. africana and L. knysnaensis are regarded as two morphs of a single species which exhibits a genetic cline along the south-eastern coast of southern Africa. The dark brown morph knysnaensis dominates the western, cooler end of the cline and is replaced by the pale blue morph africana at the warmer end of the cline. These conclusions are based on evidence from the latitudinal distributions, the complete range of intermediate forms regarding shell colour and shell morphology and the lack of differences in redular morphology, penial morphology or habitat.