Observations on the biology of the trochid gastropod Austrocochlea constricta (Lamarck) (Prosobranchia). II. The effects of available food on shell-banding pattern

The trochid gastropod Austrocochlea constricta (Lamarck) shows a variable pattern of shell banding. The concentration of the major shell pigment, uroporphyrin I, has been shown to differ between stripe-classes and, within each stripe-class, between shores. This paper describes the relation between amount of available food and shell pigmentation on six shores.Qualitative and quantitative methods were used to determine the concentrations of chlorophyll pigments in the substratum of each shore. Thin-layer chromatography showed differences in the type of microalgae present. Quantitative, spectrophotometric determinations of the chlorophyll concentrations of acetone extracts of scrapings of the substratum showed significant differences in total chlorophyll between the six shores. A uroporphyrin index gives an estimate of the total amount of uroporphyrin/unit area on each shore, and enables the wet wt/animal, density/area, and proportions of the population in different stripe-classes to be related to the concentrations of uroporphyrin/g shell within the stripe-classes. There was a highly significant linear regression of the uroporphyrin index on total chlorophyll concentration. This provides evidence for the effect of amount of available food on shell pigmentation. The mean concentration of pigment/g shell increased as the chlorophyll content of the substratum increased.A hypothesis is proposed to explain the observed differences in banding-pattern frequencies between shores; this represents the frequency distribution of animals with different concentrations of pigment/g shell as a normal distribution, with increasing mean and standard deviation as the concentration of chlorophyll in the substratum increases. Theoretical distributions are given to show that similar banding pattern frequencies to those observed on the six shores can be produced under this hypothesis. Neither a more complex hypothesis, nor selective nor genetic mechanisms are necessary to explain the observed distributions of banding pattern in Austrocochlea.     

Parameters of brown-headed cowbird Molothrus ater egg discrimination in warbling vireos Vireo gilvus

We examined which egg parameters warbling vireos Vireo gilvus use to discriminate brown-headed cowbird Molothrus ater eggs and, by comparing our results to other studies, tested the prediction that ejecter species with eggs more similar in appearance to cowbird eggs will be less tolerant of foreign eggs. In addition, we tested the hypothesis that egg characteristics influence the cost of ejection and probability of committing ejection errors. Warbling vireos ejected 100% of eggs with a cowbird spot pattern and only spot pattern significantly influenced the probability of ejecting a foreign egg, whereas size and nest stage did not. Foreign eggs that differed in two parameters were not ejected significantly more than those that differed in one parameter. Thus, warbling vireos appear to be less tolerant of foreign eggs than species with eggs more divergent from cowbird eggs. There was no significant difference in the number of vireo eggs that were damaged when foreign eggs of different sizes and spot patterns were ejected, which is counter to the assumptions of the evolutionary equilibrium hypothesis. Similarly, foreign egg characteristics did not significantly influence the probability of ejection errors. Finally, egg discrimination in warbling vireos appears to have evolved directly to counter cowbird parasitism because all conspecific eggs switched into their nests were accepted.     

Pineal melatonin rhythms in the lizard Anolis carolinensis: II. Photoreceptive inputs

The pineal organ of the lizard Anolis carolinensis acts as a transducer of photoperiodic information, since light can affect the pineal melatonin rhythm (PMR). The synthesis and secretion of melatonin may be a major mechanism whereby a circadian pacemaker within the pineal can control circadian clocks located elsewhere. An investigation into potential routes by which light could affect the PMR showed that (1) removal of the photosensory parietal eye did not affect the PMR as compared to controls under either a light-dark (LD) 12:12 cycle and a constant temperature (32 degrees C) or an LD 12:12 cycle and a daily temperature cycle (32 degrees C/20 degrees C); (2) removal of both the parietal eye and the lateral eyes did not affect the PRM of anoles held in LD 12:12 (constant 32 degrees C); (3) the PMR of blinded anoles re-entrained to a 10-hr shift in the phase of the LD cycle as rapidly as that of sighted anoles; (4) blocking light penetration to the brains of anoles, but leaving the lateral eyes exposed, blocked the ability of anoles to re-entrain to a 10-hr shift in the phase of an LD cycle. The data support the hypothesis that light directly affects the PMR in Anolis and that other potential photic inputs (parietal eye, lateral eyes) play little or no role. This conclusion is supported by previous neurophysiological and ultrastructural studies showing that the lizard pineal possesses functional photoreceptors.     

Supply-side ecology and benthic marine assemblages

Many marine invertebrates have a planktonic stage of their life history during which widespread dispersal and much mortality occur. The numbers surviving to recruit into habitats occupied by adults are therefore very variable in time and space. Models for the structure and dynamics of benthic assemblages tend to focus on processes causing death - often assuming consistent arrivals of recruits. Supply-side ecology is a newly fashionable term to describe recent interest in the long-realized consequences of variations in recruitment. Such variations have important influences on theory and empirical research in these assemblages.     

Substituted piperidin-2-one biphenyltetrazoles as angiotensin II antagonists

A novel series of substituted piperidine-2-ones has been identified as antagonists of angiotensin II. These compounds showed high affinity for the receptor in bovine adrenal cortex binding assays with IC₅₀'s as low as 20nM. They are potent inhibitors of angiotensin II induced contractions in rabbit aortic rings, with pA₂ values as high as 9. A number of these compounds are also orally active as antihypertensives in spontaneously hypertensive rat preparations.     

The localisation of an Mr 74,000 major chromatin antigen on native salivary chromosomes of Drosophila melanogaster

An antigen making a major contribution to the immune response to Drosophila melanogaster chromatin resides primarily on a nonhistone charge-class family of proteins of Mr 74,000. Immunofluorescence detects this antigen at interbands, puffs and diffuse bands of D. melanogaster salivary chromosomes isolated without exposure to acid fixatives, and on nucleoplasmic ribonucleoprotein droplets. In the electron microscope, gold labelling reveals the binding of monoclonal antibodies specific for the antigen at chromosomal loci generally bearing putative ribonucleoprotein (RNP) particles. However, the locus 3C 11–12 is remarkable in that it bears putative RNP particles but is virtually unlabelled, suggesting protein specificity at different active loci.     

Efficient purification of somatomedin-C/insulin-like growth factor I using immunoaffinity chromatography

Somatomedin-C/insulin-like growth factor I was purified from human plasma using a monoclonal antibody affinity column. Combining immunoaffinity chromatography with standard protein purification methods resulted in an overall recovery of 18%. The 35 micrograms of somatomedin-C/insulin-like growth factor I purified from 500 ml of plasma appeared as a single band when analyzed by polyacrylamide gel electrophoresis and could be used in radioimmunoassay and receptor binding studies.     

Rearing a second generation of cotton-top tamarins (Saguinus oedipus oedipus) in captivity

The average age at first parturition in captive-born female cotton-top tamarins was 31 months. Only 18% of full-term young born were successfully reared by primiparous females, but success increased with parity and 71% of babies born at 4th and 5th pregnancies were raised. 15% of litters were single births, 61% were twins and 24% were triplets. There was a seasonal distribution of births, with a clear peak in the spring months. The average interbirth interval was 294 days.     

The effects of tidal height,wave-exposure,seasonality and rock-pools on grazing and the distribution of intertidal macroalgae in New South Wales

The effects of grazers (mostly gastropods), height on the shore, wave-exposure, season of the year and the presence of shallow rock-pools on the abundance of intertidal macroalgae were examined on shores at Cape Banks (Botany Bay). At the beginning of each of the four seasons, experimental plots with and without grazers were cleared at four heights on three shores, of increasing exposure to waves, The colonization and growth of algae in these plots were monitored (by measurement of per cent cover and dry wt) for approximately the next 3 months in each season.In grazed plots, foliose algae only grew at the lowest levels on the shores. They were more abundant where wave-action was greater, and during the cooler periods of the year, when growth of the plants was enhanced. Higher on the shore, there was a positive correlation between algal cover in grazed plots and the amount of rainfall during the previous 10 days. In all seasons, there was much greater colonization of foliose algae where grazers were excluded. There was greater algal growth at lower levels on the shore, and where wave-action was stronger. Less algae grew in sheltered areas during warmer times of the year. The major seasonal difference found was the more rapid growth and occupancy of the rock by algae during the cooler seasons of the year.Experimental rock-pools were colonized more rapidly at lower levels on the shore, and during the winter. There was no difference between pools and control (non-pool) areas during winter. During summer, however, there was a greater per cent cover and biomass of algae in pools from which grazers had been excluded than in similar control areas.The results can be interpreted as being due to the greater survival and more rapid growth of algae under conditions of increased moisture, decreased emersion and decreased temperatures and light regimes during low tide (i.e. when physical stresses were reduced). These physical factors were, however, less important to the distribution of the algae than were the effects of grazers. Although few algae were present in any experimental plot, the number of species of algae per plot was considerably reduced in grazed areas.The results confirm that the patterns of vertical distribution and abundance of algae on rock-platforms in New South Wales are primarily the result of the activities of grazers. All algae in the present study were capable of living higher on the shore than they were normally found. Much of the variation along a gradient of wave-exposure, from season to season, and small-scale variation from place to place at any time can be explained by the complex interactions between the activities of grazers, and the effects of variations in the physical environment that influence the recruitment, survival and growth of the algae.     

Plasma 13,14-dihydro-15-keto-PGF alpha (PGFM) in pregnant and nonpregnant heifers prior to and during surgery and following intrauterine injection of PGF2 alpha

On day 17 postestrus or postmating, heifers were given intrauterine injections of saline (2 pregnant, 2 non-pregnant) or 200 micrograms PGF2 alpha (7 pregnant, 6 nonpregnant) through cannulae installed surgically into the uterine horn ipsilateral to the corpus luteum bearing ovary. Jugular blood samples were collected prior to the laparotomy at which the cannulae were installed during surgery, and for 90 min following the intrauterine injection. Plasma was assayed for progesterone and 13,14-dihydro-15-keto-PGF2 alpha (PGFM). Laparotomies were reopened to confirm proper cannula placement and to determine if blastocysts were present in mated heifers. Concentrations of PGFM were higher in pregnant compared to nonpregnant heifers during the presurgery (68 +/- 26 vs 24 +/- 26 pg/ml; P less than .025) and surgery (186 +/- 47 vs 65 +/- 17 pg/ml; P less than .05) periods. Pregnancy status did not alter the mean concentrations of PGFM (pregnant, 554 +/- 70 pg/ml; nonpregnant, 422 +/- 81 pg/ml) or the half-life of its decline in concentration (18 min) following intrauterine injection of PGF2 alpha. Pregnancy at 17 days in cattle does not appear to influence PGF2 alpha transport from the uterine lumen or its metabolism in the uterus or elsewhere in response to an acute intrauterine injection.