Conditional lekking in ruff (Philomachus pugnax)

Summary In our study of ruff, a lekking shorebird, we found that the lek ratio — the proportion of the total population of males occurring on leks was low, averaging 12% over the breeding season (Fig. 1D). Off-lek males spent approximately the same proportion of time as lek males in displaying to females (Fig. 4). We defined three spacing tacties that male ruffs use to position themselves to court females: Following — directly pursuing females, and two types of lekking behavior, Intercepting — waiting for females at resource-rich sites, and True Lekking — waiting for females at places without any resources other than the males themselves. Males switched among these tactics, causing the lek ratio to vary over the season (Fig. 1 D). Lek ratio increased when the number of females present in the study area plummeted at the end of May, and was positively correlated throughout the season with the copulation rate of the preceding day, suggesting that males were tracking the behavior, as well as the number, of females available (Table 1, Fig. 1). Early in the season, males off leks spent most of their time feeding (Fig. 4), and lek ratio was positively correlated with temperature (Table 1), suggesting that some males may have been unable to lek during cold weather. Males on leks mated at significantly higher rates than Followers (Table 4). On average, males at our interception lek were less site faithful and less peristent than males at true leks, and the interception lek itself disappeared after females stopped coming to use its adjacent resource (Table 2, Fig. 5). The most successful individuals in our population were the True Lekking males, rather than the Interceptors.In addition to the conditinal lekking tactics described here, ruff display a dimorphism in behaviorat leks. Independent males defend small courts on leks, while Satellite males share courts and mutually display with independents Both independents and satellites may use all three conditional tactics. We propose that satellites evolved as specialized. Followers, adept at tracking the movements of females among leks.     

The normal fetus of an acardiac twin pregnancy: Perinatal management based on echocardiographic and sonographic evaluation

Experience with three prenatally diagnosed pregnancies complicated by an acardiac twin reveals that ultrasonography and echocardiography are helpful in detecting early signs of in-utero congestive heart failure in the normal twin. The use of Doppler blood flow analysis to determine direction of blood flow, post-mortem placental and fetal angiography, and umbilical cord blood gas determination provided proof that retrograde arterial perfusion occurs in the acardiac fetus. In a fourth pregnancy, an experimental approach to occlude the acardiac twin's umbilical cord was attempted, but was unsuccessful.     

Characterization of in vivo absorption features of chlorophyte,phaeophyte and rhodophyte algal species

Despite the plentiful diversity of macroalgae in coastal environments, few studies have examined the in vivo absorption features of common marine macrophytes. Here we report on results of a survey of 12 central California common intertidal and subtidal taxa, representing Chlorophyta, Phaeophyta and Rhodophyta carried out in the summer of 1988. Computer-assisted analyses were used to obtain fourth-derivative spectra from in vivo absorption spectra determined at room temperature to obtain spectral diagnostics for the different algal divisions and to provide a means to determine whether spectral features could be used to identify stress responses among these plants. Among the Chlorophyta, characteristic maxima for chlorophylls a and b were resolved in all species examined, and a spectral component attributable to siphonaxanthin-like carotenoid(s) was observed in two Ulva species and the coenocytic alga Derbesia marina. Representatives of the Phaeophyta were characterized by similar maxima for chlorophyll a and c, and for fucoxanthin. Among the Rhodophyta, maxima for chlorophyll a, as well as B- and R-type phycoerythrin were resolved. Differences in in vivo absorption features were detected for two tidal populations of Porphyra perforata and Mastocarpus papillatus. High-tidal thalli absorb less green light in regions characterized by phycoerythrin, but have enhanced carotenoid absorption compared with lowtidal thalli. Resolution of spectra by fourth-derivative analysis revealed significant differences in phycoerythrin and carotenoid contents. The spectral changes observed appear to reflect environmental and possibly populational characteristics of these algae. The spectral analyses described here provide robust, non-invasive means to characterize subtle responses of macroalgae to environment in ways not possible previously. Additional merits of these fourth-derivative analyses for use in environmental studies are discussed.This contribution is dedicated to the memory of Professor L. R. Blinks, a pioneer in photosynthesis research and algal physiology     

AN EFFICIENT METHOD OF APPLYING ALUMINUM SALTS FOR SEDIMENT PHOSPHORUS INACTIVATION IN LAKES1

ABSTRACT: Alum and sodium aluminate were injected into the hypolimnion of eutrophic Kezar Lake, New Hampshire, with a specially designed applicator mechanism. This new method of applying aluminum salts to achieve phosphorus inactivation included two separate chemical distribution systems mounted on a hydraulic weed harvester. The design of the applicator system is described, and its cost-effectiveness is compared with other aluminum salt injections.     

Distinguishing modes of dissolved organic carbon production in marine macrophytes by tracer kinetic analysis

Tracer kinetic analysis of radioisotope incorporation into dissolved organic compounds reveals two distinct patterns of photosynthate release by macroalgae. In experiments employing Sargassum lacerifolium, dissolved organic carbon was produced at a constant rate during light incubations. Steady state rates of production were never achieved in experiments employing either Ecklonia radiata (Turn.) J. Agardh. or Ulva lactuca L. Analysis of the time-varying radioactivity curves obtained in experiments using these algae always resulted in models consistent with dissolved organic carbon production being an autocatalytic process. Preincubation of U. lactuca in the dark resulted in a diminished (ca. 40%) rate of dissolved organic carbon production during the subsequent light incubations. In no case did the radioisotope content of the dissolved organic carbon approach a limiting value, indicating that in contrast to phytoplankton, uptake rates of photosynthate by macroalgae are always less than the rates of production.     

Glucosephosphate isomerase genotype frequencies,homozygous excess and size relationships in the sand flounder Rhombosolea plebeia

Genetic variation was studied at two polymorphic loci for 3 yr (November 1978–February 1982) in juvenile sand flounder (Rhombosolea plebeia) in Wellington Harbour, New Zealand. The Gpi-1 locus showed a heterogeneity in genotype frequencies, but this was not clearly related to season or to fish length. At the Gpi-2 locus, genotype frequencies were dependent upon length and showed a significant excess of homozygotes in juveniles but not in adults. This latter phenomenon has been reported previously in several species of marine molluscs, and so may be common to marine organisms producing large numbers of pelagic larvae. Reasons for the excess of homozygotes are discussed, and it is suggested that assortative mating is the most likely explanation and that this is an area of marine population genetic research which has been over-looked.