The fossil record of biodiversity: nutrients, productivity, habitat area and differential preservation

It is hypothesized that the Phanerozoic record of fossil diversity is a function of a secular increase in nutrient availability and productivity (food, energy), and cyclic changes in sea level and habitat area due to supercontinent assembly and rifting. Both variables may have affected biodiversity through the combined variable of {productivity  ×  area}. {Productivity  ×  area} remained relatively constant after the Cambro-Ordovician until the end of the Permian, as did the traditional curve for biodiversity. During assembly of Pangea, decreasing sea level and habitat area were counteracted by increasing nutrient inputs due to uplift and the spread of vascular plants and enhanced continental weathering. As Pangea underwent its final assembly, interior drainage increased, so that by the end of the Permian both habitat area and nutrient runoff decreased. Following the end-Permian extinctions, the traditional curve of diversity began to increase, habitat area, nutrient levels and productivity all increased. Despite the confounding factors of differential preservation and sampling bias toward the present, the fossil record reflects a real response by the marine biosphere to tectonism, sea level, paleoceanographic regime and climate, and the spread of terrestrial floras, and their influence on habitat area, nutrient inputs, and productivity through time.     

Concomitant diel vertical migration of a predatory leech and its amphipod prey

SUMMARY.

• 1 The concomitant diet vertical migrations of the predaceous leech Erpobdella montezuma and its pelagic amphipod prey (Hyalella montezuma) were monitored for 1 year in Montezuma Well, Arizona, U.S.A.
• 2 High densities of H. montezuma occurred in the subsurface strata of the water column during the day, but a substantial portion of the population migrated into the surface 1 m at sunset. E. montezuma remained in the lower water strata during the day, but migrated vertically after sunset to exploit the high densities of H. montezuma near the surface. Densities of E. montezuma progressively increased in the upper strata of the water column after sunset as light energy fell below 1 μEin m^?2 s^?1.
• 3 It is suggested that the synchronized nocturnal migrations of the predator E. montezuma in relation to its prey H. montezuma, increases the foraging efficiency of the leech in the highly predictable environment of Montezuma Well.

     

Abscisic Acid Effects on Growth and Metabolism in the Roots ofLemna minor

The effects of abscisic acid (ABA) on individual plants of Lemna minor L. were studied. The effects on growth and metabolism of the roots were the most noticeable and the most desirable to measure. Two mg/1 of ABA inhibited the root growth rate by 60% and this was accompanied by a 60% deceleration in the rate of uridine incorporation. The uptake of uridine and leucine and the incorporation of leucine were not affected by ABA. The latent period of root growth inhibition was 1 hour, whereas the inhibition of ribonucleic acid (RNA) synthesis occurred 2 to 4 hours after application. The growth inhibition caused an accumulation of starch in the peripheral, differentiated cell layer of the cortex. Apparently, the growth inhibition by ABA was not entirely due to an inhibition of RNA synthesis, and other plausible mechanisms of growth inhibition are discussed.     

Direct Action of Insulin on Plasma Membrane ATPase Activity in Human Lymphocytes

LITTLE is known about the effects of insulin on lymphocytes. Helmreich and Eisen¹ concluded that it has insignificant effects, but others^2–5 have made a case for a role in inflammatory and immunological responses. We^6,7 have demonstrated that noradrenaline enhances the uptake of both glucose and potassium by lymphocytes, as does insulin in several tissues. We have associated this action of noradrenaline with a direct effect on membrane adenosine triphosphatase (ATPase) activity⁷. The observation⁸ that insulin bound to ‘Sepharose’ polymers enhances glucose transport while in contact only with the plasma membrane indicated that insulin might have a direct action similar to that of noradrenaline on membrane ATPase. The observations reported here show that insulin stimulates ATPase activity and glucose uptake in the lymphocyte and suggest a relationship between membrane ATPase activity and glucose transport.     

Chemical Carcinogenesis in Mice inhibited by Interferon

SEVERAL experiments have demonstrated that the anti-viral substance, interferon, can inhibit the growth of spontaneous^1,2, transplanted³ and virus-induced neoplasms in mice^4–7. Lieberman et al.⁵ reported that interferon treatment partially suppressed X-radiation-induced leukaemia in C57B1/6 mice. As they pointed out, the inhibitory effect provided additional evidence for the theory that X-rays cause lymphoma through the activation of a leukaemogenic type C RNA viral intermediate. In this communication, we report studies with CF-1 mice (Carworth Farms, New York City) to determine the effects of interferon on SC tumour induction by 3-methylcholanthrene (3-MC). These mice were previously shown to harbour high levels of type C RNA gs antigen and.infectious virus in normal spleens and in induced tumours, while spontaneous tumours rarely develop until late in life^8–10.     

Ultrasonic Vocalizations in Rat Sexual Behavior

Ultrasonic vocalizations are very conspicuous during rat matingactivity. Two types of calls are produced by both sexes. Thefirst, brief complex calls with the main frequency centeredabout 50 kHz, occur primarily in conjunction with solicitationand mounting activity. The second type of call is the long,22 kHz whistle which is emitted mainly by the male during thepostejaculatory refractory period, but also by both male andfemale at other times during the copulatory sequence. The occurrenceof ultrasonic vocalizations is correlated with sexual motivationof rats. Males emit more 50 kHz calls before successful matingtests than before tests in which they fail to ejaculate. Furthermore,more vocalizations are emitted by the pair prior to intromissionsthan prior to mounts without intromission. Just before ejaculationthere is a large increase in the rate of calling and, at times,transition by the male to calling at 22 kHz. This latter eventmay represent physiological dearousal by the male. Followingejaculation, the male characteristically emits 22 kHz vocalizationsand exhibits a sleep-like EEG pattern. The function of the postejaculatoryvocalization may be to enforce separation between the matingpair, while at the same lime maintaining contact between thepartners. Fifty kHz calls, on the other hand, prime and facilitatesexual responsiveness of the female. Tape recorded vocalizationsof mating rats facilitate solicitation behavior of estrous femalesin the presence of castrated males, and such females also showa preference for these sounds in a "Y" maze. Deafening of femalesdoes not affect their normal pacing of copulatory contacts,but it drastically reduces their solicitation behavior. Thestudies summarized in this paper lead us to conclude that ultrasonicvocalizations play a major role in the integration of reproductiveactivity in the Norway rat, Rattus norvegicus.     

The Effect of Acetate on Euglena gracilis var. bacillaris as a Function of Environmental Conditions

SYNOPSIS. Acetate, a widely used substrate for the growth of Euglena gracilis var. bacillaris , becomes lethal to these organisms at pH's below 5.0. The kinetics, as well as the extent of acetate-induced death, depend upon both the hydrogen ion and acetate concentrations. Formic, propionic, butyric, and fluoroacetic acids also kill E. gracilis at low pH's, whereas fumaric, malic, succinic and pyruvic acids do not under these conditions.
It is suggested that death is caused by a lowering of the intra-cellular pH, due to the release of hydrogen ion brought into the cell by freely penetrating undissociated acetate molecules.     

Methane emission from Texas rice paddy soils. 1. Quantitative multi-year dependence of CH4 emission on soil, cultivar and grain yield

Methane emissions at different rice productivity levels were observed from Texas rice paddy soils during the years 1991–95. Analysis of field measurements showed that seasonal methane emission (E) was strongly dependent on soil, cultivar, and rice grain yield. The relationship can be quantitatively described by E (g m^–2) = 0.048 × SI × VI × GY. SI is a soil index to characterize the relative effect of soil texture on emission and is linked with soil sand percentage. VI is a variety index to identify the intervarietal difference in methane emission and is related to the amount of methane emission per unit grain yield. GY is grain yield (g m^–2). Constant 0.048 was derived from the measurements of 10 cultivars planted in 1993. Computed emission applying the relationship is well matched with measured data. The comparison of computed with measured seasonal methane emission over an 80-day period using a total of 32 data sets yields a correlation coefficient r ² of 0.800. In addition, the ratio of seasonal methane emission to net primary productivity was calculated on a carbon to carbon basis, which produces an average value of 2.8%, ranging from 1.2% to 5.4%. A further investigation indicated that the ratio is soil and variety dependent and can be quantitatively explained by C[CH₄]/C[NPP] (%) = 3.21 × SI × VI + 0.12 ( r ² = 0.738, n = 32). Under the condition of 30% soil sand, this ratio is ≈ 3% for the majority of cultivars.     

Chaetetid growth form and its controlling factors

Chactetid sponge morphology is examined to provide details on growth styles and their controlling factors. Chactetid growth forms range from laminar to domical. bulbous. columnar and complex branching in a variety of sizes. The chactetid skeleton began as a laminar unit comprising growth of many calicles across the substrate at the same time. Several styles of early growth. involving differential calicle growth rates and varying directions of adjacent calicle growth. are recognized. and result in complex arrangements of caliclcs in the skeleton. Despite this. the cross-sectional protile of the gross morphology at any stage of growth is usually a simple outline. implying that internal complexities of calicle development are modulated to produce an optimum cross-sectional outline for the individual chactetid. The morphological range of chactetids is similar to stromatoporoids. some tabulate. heliolitid and colonial rugose corals. some bryozoans. stromatolites. encrusting foraminifera and calcareous algae: the common environmental controlling factors of sedimentation and turbulence profoundly influenced growth form in all these organisms by virtue of their common sessile shallow marine habit. Chactetid growth forms show a general relationship to the environment: columnar and branching forms grew in quiet water. while laminar and domical were better adapted to environments of higher energies. The environmental adaptations of laminar forms. however. remain problematic. because they are found in both high and low energy facies. and interpretation depends strongly on facies study. Also. interpretation of all growth forms is suspected to relate to taxonomic aspects. as has been recognized for other groups. Unfortunately. chaetetid taxonomy is in need of revision. and at present no certain relationship has been demonstrated between taxonomy and growth form. Some modern calcareous sponges with a chaetetiform architccture also show similarities in growth form to fossil types. and may be subject to similar controls. □Chaetetid. calcified sponge. growth form. Pennsyloanian. North America.