Parasite faunas,testosterone and secondary sexual traits in male red-winged blackbirds

Summary We examined associations among parasite infections, secondary sexual traits and testosterone in male red-winged blackbirds sampled at the start of the breeding season. Parasites quantified included ectoparasitic lice and mites and endoparasitic blood protozoans, nematodes, trematodes and cestodes. Secondary sexual traits that we quantified included body size, epaulet size and color, song repertoire size and song switching rate, and behavioral responses to male and female models. Overall we found few significant associations between parasites and secondary sexual traits, between secondary sexual traits and testosterone, or between parasites and testosterone. In addition, most parasite taxa appeared to infect birds independently, although the low prevalence (<50%) of many of the parasites meant that our sample sizes were too small to detect weak associations. Our most promising results were obtained for ectoparasitic mites, which tended to occur on birds uninfected with other parasites, on birds with longer epaulets, and on birds with higher levels of testosterone. Epaulet length and testosterone are both probable correlates of dominance in this species. Further research will be required to determine whether there is a causal link between the immunosuppressive effects of testosterone and the mite infections, and between testosterone, epaulet length and male mating success. Correspondence to: P. Weatherhead     

Simulated green turtle grazing affects nutrient composition of the seagrass <Emphasis Type="Italic">Thalassia testudinum</Emphasis>

Before populations of green turtles (Chelonia mydas) were severely reduced by human overexploitation, the seagrass Thalassia testudinum was intensively grazed by green turtles in the Caribbean. To explore how nutrient composition of T. testudinum pastures responds to intense grazing pressure, we simulated green turtle grazing in 15 plots (each 3 m × 3 m) for 16 months in the central Bahamas. Comparisons of clipped plots with 15 adjacent control (unclipped) plots revealed that simulated grazing resulted in significantly higher energy, nitrogen, phosphorus, lignin, cutin, and condensed tannin content in blades in clipped plots, but sediment organic content was not affected. By continually re-cropping blades in grazing plots, turtles ingest young, actively growing blade tissue with higher energy, nitrogen, and phosphorus concentrations. Our 16-month clipping trial did not generate the expected decline in nutrient content in T. testudinum blades under intensive grazing. However, significant decreases in nitrogen and organic matter reserves in rhizomes, with declines apparent after 16 and 11 months, respectively, indicate that nutrient content of blades and/or blade productivity may decline under continued clipping.     

Habitat influences on reproductive allocation and growth of the mummichog (<Emphasis Type="Italic">Fundulus heteroclitus</Emphasis>) in a coastal salt marsh

To determine whether life history differences can occur in salt marsh fishes that occupy different habitats within the same marsh, we compared reproductive allocation in female mummichog (Fundulus heteroclitus) inhabiting creeks and ponds of a coastal salt marsh in southern New Jersey, USA during the spring and summer of 2001 and 2002. Females were collected in phase with the lunar spawning cycle from four sites of each habitat type, and assessed for gonad-to-body-mass ratio and growth increment. Annual reproductive allocation, expressed as a percent of somatic mass, was estimated for each site and year from the gonadosomatic indices of individuals collected during each spawning period. Mummichogs from creeks showed little change in annual reproductive allocation from 2001 to 2002, whereas those inhabiting ponds showed a significant increase between these years. Seasonal reproductive patterns indicated that pond females cease spawning at least one lunar cycle earlier than creek fish. While ponds experienced considerably higher maximum summer temperatures than creeks as well as near-anoxic pre-dawn conditions, neither of these variables explained a significant amount of variation in annual reproductive allocation. In contrast, annual reproductive allocation of mummichogs in a pond correlated with its flood frequency in both years of study. Our results suggest that while the length of the spawning season differs in mummichogs inhabiting marsh creeks and ponds, annual reproductive allocation depends more upon the hydrodynamic conditions of the particular waterbody than its habitat type per se.     

Social spider defense against kleptoparasitism

Summary Because of the large amount of webbing they provide, social spider colonies often host other satellite spider species referred to as kleptoparasites or food stealers. Such kleptoparasites may take advantage of increased prey capture rates associated with large spider aggregations. This study investigated the relationship between a cooperatively social spider species, Anelosimus eximius (Araneae: Theridiidae), which lives in the undergrowth of tropical rainforests in Peru, and its kleptoparasite, Argyrodes ululans (Araneae: Theridiidae), which specializes in foraging in An. eximius webs. Although large aggregates of spiders may be more attractive to kleptoparasites, the benefits of group defense may offset this cost. Natural colonies were observed, and enclosed field colonies containing fixed numbers of host spiders were manipulated in order to determine whether kleptoparasite success is affected by the number of social spiders that are available for defense. Prey was less likely to be stolen by Ar. ululans when a greater number of host An. eximius spiders were involved in prey capture. When hosts detected a kleptoparasite earlier and chased it more often, prey was more likely to be successfully defended. Ar. ululans was more successful in stealing small prey items in all colonies and gave up more readily on very large prey (> 11 mm). I conclude that communal living and group defense in An. eximius confer protection from the kleptoparasite Ar. ululans.     

Genetic Analyses to Establish Captive Breeding Priorities for Endangered Snake River Sockeye Salmon

The plight of the Snake River sockeye salmon presents a challenging genetic puzzle for conservation biologists. Although the Snake River sockeye has been declared endangered, assessment of captive breeding strategies are complicated because a healthy non-migratory strain of O. nerka (kokanee) resides in Redfish Lake, Idaho—the same lake the anadromous fish return to for spawning. The migration of 1-year-old fish (outmigrants) from the lake each year and the observation of non-migratory fish spawning in areas previously used by the sockeye further complicate the issue. We estimated the relatedness of these strains by direct examination of their genetic similarity. Mixed DNA fingerprint analyses suggested that the outmigrants were more closely related to the anadromous sockeye than to the kokanee. Closer analysis using a probe, One-HO.8, to examine allele frequencies at a single locus revealed polymorphism in a number of O. nerka populations. Within the Redfish Lake populations this probe detected an allele present at 0.21 frequency in the kokanee (n = 43), 0.01 (n = 324) in the outmigrants, and absent among 13 anadromous fish. These results support a close genetic relationship of the outmigrants to the anadromous sockeye and the probable utility of the outmigrants in a captive breeding program to restore the anadromous strain.     

Source of lead in humans from Broken Hill mining community

This paper documents the first precise lead isotope measurements for men, women and children from the same family in an attempt to determine the source of lead in their blood. The subjects reside in one of the world's largest lead mining cities, Broken Hill, NSW, Australia. Biological and environmental samples have been compared using isotopic compositions and lead contents. Adult males have isotopic profiles (or compositions) which appear to be related to their occupations. Adult females have low blood leads (<10 g dL^–1) and their main source of lead is not from the mine dumps around which the city is built but probably from a mixture of petrol, food and perhaps water. The blood lead contents in children from 1 to 14 years old vary and are partly dependent on age. There is a moderate correlation of blood lead and isotopic compositions (r = 0.73) indicating that a significant component of blood lead derives from the mine dumps in children with elevated blood leads. Some children with blood leads <20 g dL^–1, however, also have a dominant component of mine lead in their blood     

Color bands function as secondary sexual traits in male red-winged blackbirds

Summary We present the first experiment to assess band color effects in a natural bird population. 38 territorial male red-winged blackbirds (Agelaius phoeniceus) were randomly assigned to 1 of 2 banding treatments. They received either all red bands (to match their epaulets) or all black bands (controls). Over half the red-banded males lost their territories while all black-banded males retained their territories. Red and black-banded males did not differ morphologically. However, among red-banded males, those that lost their territories had larger epaulets and were in poorer condition than those retaining their territories. Red-banded males suffered much higher intrusion rates, particularly by neighbors, than black-banded males. We propose that red color bands exaggerated the males' natural aggressive signal beyond the point where the signal was reliable. Our results suggest that signal reliability is maintained by regular testing, particularly of those males most likely to be signalling dishonestly. Offprint requests to: K.J. Metz     

Alpha-fetoprotein and acetylcholinesterase are not predictive of fetal junctional epidermolysis bullosa,Herlitz variant

Junctional epidermolysis bullosa, Herlitz variant (junctional EB-Herlitz) is a lethal autosomal recessive skin disorder currently amenable to prenatal diagnosis only by direct analysis of fetal skin. However, elevated levels of alpha-fetoprotein, as well as the presence of acetylcholinesterase in amniotic fluid, have been associated with other severe fetal genodermatoses. Fetal skin samplings were performed in ten pregnancies at risk for fetal junctional EB-Herlitz, with three fetuses affected on the basis of electron microscopic detection of blisters within the lamina lucida and abnormal hemidesmosomes. In neither affected nor unaffected pregnancies were maternal serum or amniotic fluid alpha-fetoprotein levels elevated. Moreover, alphafetoprotein levels in both maternal serum and amniotic fluid were not statistically different comparing affected and unaffected fetuses. Acetylcholinesterase was not present in the amniotic fluid samples of the three affected pregnancies. Unlike other severe fetal genodermatoses, neither alpha-fetoprotein nor acetylcholinesterase was predictive of junctional EB-Herlitz.     

Anaerobic microbial degradation of poly (3-hydroxyalkanoates) with various terminal electron acceptors

The microbial degradation of poly (3-hydroxyalkanoates) (PHAs) under anaerobic conditions with various terminal electron acceptors was examined. Nitrate-reducing consortia were established using activated sludge, and PHAs were shown to be biodegradable under these conditions. A positive correlation between carbon dioxide production and nitrate reduction was demonstrated. Nitrous oxide accumulated as the main N-containing product of nitrate reduction. The amount of PHAs in activated sludge cultures decreased approximately 20% within 40 days of incubation. Attempts were made to establish iron- and sulfate-reducing consortia from spring water, yet it could not be demonstrated that the mixed cultures were capable of degrading PHAs. Pure cultures of iron- and sulfate-reducing bacteria could not utilize PHAs as sole carbon sources. Methanogenic environments sampled included pond sediment and rumen fluid. PHAs were fermented to methane and carbon dioxide after 10 weeks by a sediment consortium, with 43 to 57% of the substrate carbon transformed to methane. Although it could not be demonstrated that PHAs were biodegraded by a rumen fluid consortium, a facultative anaerobic bacterium, identified as aStaphylococcus sp., that could grow on PHAs was isolated from rumen fluid.