Deceptive use of alarm calls by male swallows, Hirundo rustica: a new paternity guard

Male swallows (Hirundo rustica) frequently gave alarm callswhen their fertile mates left the nest vicinity without themale during egg laying. Females engaged in extrapair copulationsduring such absences when they were not guarded intensely bytheir mates. However, males were sometimes able to disrupt extrapaircopulation attempts toward their mates by giving alarm calls,causing all nearby swallows to take flight. I experimentallytested the idea that male swallows gave alarm calls when theircertainty of paternity was at stake. When colonially breedingfemale swallows were temporarily chased away from their nestduring the egglaying period in the absence of their mates, malesnearly always gave alarm calls when they returned to the emptynest. In contrast, colonially breeding males rarely gave alarmcalls when their mates were absent during the prelaying or theincubation periods. Solitarily breeding males rarely gave alarmcalls in the absence of their mates, irrespective of the timein their nesting cycle. However, solitarily breeding males didgive alarm calls when their mates were absent from the nestif a male mount previously had been presented near their nestduring the egg-laying and the prelaying periods, but not duringthe incubation period. Deceptive use of alarm calls (in theabsence of any predators) by male swallows apparently was aneffective paternity guard.     

Cytochemical localization of lectin labeled vesicles in GERL region of hepatoma ascites cells.

The fate of lectin labeled internalized plasma membrane in the ascites tumor form of the Chang rat hepatoma growing under in vivo and in vitro conditions was investigated cytochemically. Ascites cells were incubated in Convanavalin A (Con A) and horseradish peroxidase (PO), either with or without prior glutaraldehyde fixation and subsequently treated with 3',3-diaminobenzidine. In cells fixed before Con-A-PO labeling the reaction product was localized as a continuous and even layer upon the external surface of the plasma membrane. If unfixed cells were treated with Con A, coupled with PO at 4 degrees C and reincubated in phosphate buffered saline at 37 degrees C for varying periods of time, the Con-A-PO layer was of irregular thickness. In as little as 15 min of reincubation endocytotic vesicles containing PO positive material were closely associated with GERL components of the Golgi Apparatus. Localization of acid phosphatase (ACPase) within GERL vesicles, similar in size and location to those containing Con-A-PO reaction product, indicates that the Con-A-PO labeled vesicles may be a component of the Golgi apparatus in hepatoma cells.     

An enzymatic, spectrophotometric glycerol assay with increased basic sensitivity

Glycerol can be assayed with good precision and accuracy in biological samples free of dihydroxyacetone using a series of four enzymatic reactions. Two moles of nicotinamide-adenine dinucleotide are reduced per mole of glycerol, thus doubling the basic sensitivity of existing enzymatic, spectrophotometric methods. The method was developed primarily for use in studies of adipose tissue. No deproteinization was required in samples obtained from incubation of isolated fat cells or pieces of adipose tissue.     

A sexually dimorphic basal anal-fin ray expansion in the weakly discharging electric fish Gnathonemus petersii

Male Gnathonemus petersii (Mormyridae) exhibit two structural, sexually dimorphic characters: anal-fin ray bone expansion and an indentation of the posterior ventral body wall (formerly described as anal-fin indentation). Females lack this bone expansion, but may show a slight indentation. Morphometric data on both characters were obtained from radiographs of 414 fish (males and females) ranging in size from 60 to 276 mm L_s. Both body wall indentation and bone expansion began to develop in males of about 120 mm L_s. At 160–180 mm, the sex ratio of fish with expansion to fish without expansion was 50 : 50. Androgens seem to affect the expression of both these sexual dimorphisms. Bone expansion may provide increased bone surface for muscle attachment and thus facilitate the anal-fin reflex during courtship behaviour.     

Predictive habitat modelling to estimate petrel breeding colony sizes: Sooty shearwaters (Puffinus griseus) and mottled petrels (Pterodroma inexpectata) on Whenua Hou Island

Abstract

Between 2001 and 2006, we systematically sampled the entire coast of Whenua Hou, a rugged offshore island in southern New Zealand, to estimate the population densities of sooty shearwaters (Puffinus griseus) and mottled petrels (Pterodroma inexpectata) by counting the entrances of breeding burrows. A two‐step regression modelling process using binomial errors was used to predict the presence of a colony, and a normal general linear model was used to predict the density of entrances within colonies. Aerial photography, GIS and a Digital Elevation Model were used to extract relevant habitat and location variables, and a combination of both regression models was used to predict the density of breeding burrows within each 5.32 m² pixel on the island. This complex GIS and habitat prediction modelling approach gave population estimates very similar to a more traditional simple area extrapolation method and gave no improvement in precision. However, correction for the slope of the land increased our simple area estimates of population size by 11%. We estimate populations of sooty shearwater and mottled petrel breeding pairs at 173 000 (162 000–190 000) and 160 000 (123 000–197 000) respectively. Based on this number of breeding pairs, we calculate that Whenua Hou supports a total population of 868 000 (554 000–1 270 000) sooty shearwaters. Our estimate of the total mottled petrel population 202 000 pairs (162 000–242 000) is comparable with the only published estimate, but could be an underestimate because mottled petrels are sometimes found in large burrows. More research for robust estimation of population trends is needed to assess the conservation status of mottled petrels.     

The effects of androgens and estrogen on the external morphology and electric organ discharge waveform of Gnathonemus petersii (Mormyridae, Teleostei)

The effects of androgens and estrogen on the external morphology and electric organ discharge (EOD) waveform in Gnathonemus petersii, a weakly discharging electric fish, were investigated. Following preimplant data collection, juvenile and adult fish were gonadectomized and implanted with silastic capsules containing either high or low doses of testosterone (T), dihydrotestosterone (DHT), estradiol-17 beta (E2), or cholesterol. One group of fish was treated with high doses of DHT + E2. Radioimmunoassays revealed that low-dose implants resulted in plasma T levels comparable to and high-dose implants about sixfold greater than those found in adult males imported during breeding season. High-dose E2 implants resulted in higher plasma E2 levels in adults than those in juveniles. At either dose, both androgens induced male-like indentations in the dorsal margin of the anal fin of juveniles and adult females by 4 weeks postimplant. Both low and high doses of T decreased the peak power spectrum frequency (PPSF) of Fourier transformations of EODs and increased the durations of phases 2 and 3 of the EOD in juveniles and adults, but the high doses caused more rapid and profound effects. The two doses of T caused opposite effects on the durations of phases 1 and 4 juveniles. The low dose of T decreased the durations of phases 1 and 4, while the high dose increased them. In adults, the high dose of T increased the duration of phase 1, but had inconsistent effects on the duration of phase 4. Total EOD durations were increased by both doses of T in juveniles, while adults showed inconsistent effects possibly due to individual variability in hormone sensitivity. Compared to T, DHT exerted similar, but less dramatic effects on all measures, but only at high doses. E2 significantly increased adult PPSFs, the first such finding in a mormyrid species. E2 had no effects on juvenile PPSFs, or on adult or juvenile EOD phase durations. The effects of DHT + E2 on PPSF and phases 2 and 3 were similar to those of DHT alone. These findings demonstrate quantifiable steroid-dependent plasticity in the durations of individual phases of EODs in an electric fish and are the first to show that the external morphology in Gnathonemus petersii is androgen-dependent. The results are discussed with regard to methodological considerations and hormone studies involving sex differences in EODs reported for this and other species.     

The relative importance of size and asymmetry in sexual selection

Developmental stability reflects the ability of individualsto cope with their environment during ontogeny given their geneticbackground. An inability to cope with environmental and geneticperturbations is reflected in elevated levels of fluctuatingasymmetry and other measures of developmental instability. Bothtrait size and symmetry have been implicated as playing an importantrole in sexual selection, although their relative importancehas never been assessed. We collected information on the relationshipbetween success in sexual competition and size and asymmetry,respectively, to assess the relative importance of these twofactors in sexual selection. Studies that allowed comparisonof the relationships for the same traits' size and symmetryand success in sexual competition constituted the data, whichtotaled 73 samples from 33 studies of 29 species. The averagesample-size weighted correlation coefficients between matingsuccess or attractiveness and size and asymmetry, respectively,were used as measures of effect size in a meta-anatysis. Analysiswas conducted on samples, studies, and species separately. Wefound evidence of an overall larger effect of symmetry at thespecies level of analysis, but similar effects at the sampleor study levels. The difference in effect size for charactersize and character symmetry was larger for secondary sexualcharacters than for ordinary morphological characters at thelevel of analysis of samples. The results lend support to theconclusion that symmetry plays an important general role insexual selection, especially symmetry of secondary sexual characters.