Parental role division predicts avian preen wax cycles

Previous studies have shown that preen wax composition in some sandpipers shifts from the usual monoesters to diesters during the breeding season, possibly to reduce the ability of mammalian predators to find nests using olfactory cues. To investigate further the relationship between incubation and wax secretion, we examined seven sandpiper species with different incubation patterns (species in which both sexes incubate, in which only males incubate and in which only females incubate). During the breeding period, diester preen wax was secreted almost exclusively by the incubating sex in species with uniparental incubation, and by both sexes in species with biparental incubation. These findings suggest that diester preen waxes have a function that is directly related to incubation. Unexpectedly, in female-incubating Curlew Sandpiper Calidris ferruginea and Buff-breasted Sandpiper Tryngites subruficollis , some males also secreted diester preen waxes during the breeding period. This suggests that some males may in fact incubate, that these waxes may be a remnant from their evolutionary past when both sexes incubated, or that males need to be olfactorally cryptic because they are involved in the making of nest scrapes. The seasonal pattern of preen wax composition was also studied in captive male, female and female-mimicking male ('faeder') Ruff Philomachus pugnax . Captive female Ruff changed preen wax composition from monoesters to diesters in the spring despite the fact that no incubation took place. This suggests that circannual rhythms rather than actual incubation behaviour may trigger the shift to diester waxes. All captive male Ruff, including the faeders, continued to secrete monoesters, supporting the hypothesis that only the incubating sex secretes diesters.     

Identification of an Apically-Located Antigen That Is Conserved in Sporozoan Parasites

ABSTRACT. Sporozoan parasites of the phylum Apicomplexa all possess common apical structures. The current study used a monoclonal antibody (mAb-E12) to identify a conserved antigen in the apical region of merozoites of seven species of Plasmodium (including rodent, primate and human pathogens), tachyzoites of Toxoplasma gondii , bradyzoites of Sarcocystis bovis , and sporozoites and merozoites of Eimeria tenella and E. acervulina. The antigen was also present in sporozoites of haemosporinid parasites. Immunofluorescence studies showed that the antigen was restricted to the apical 3rd of these invasive stages. Using immunoelectron microscopy, labeling was demonstrated in the region of the polar ring, below the paired inner membranes of the parasite pellicle, and near the subpellicular microtubules radiating from the polar ring of merozoites and sporozoites of E. tenella . The majority of the antigen could be extracted with 1% Triton-X 100, but a portion remained associated with the cytoskeletal elements. The molecule has a relative rate of migration (M_r) of 47,000 in Plasmodium spp. and 43–46,000 in coccidian species. Since the epitope recognized by mAb-El 2 is highly conserved, restricted to motile stages, and appears to be associated with microtubules, this antigen could be involved in cellular motility and cellular invasion.     

Characterization of SSRs from the American lobster,Homarus americanus

The American lobster (Homarus americanus), a commercially important benthic marine crustacean, is widely distributed along the continental shelf of the western North Atlantic. The population substructure of this species remains poorly understood despite its economic value. Informative markers are required to clarify relationships between local populations. To this end, we developed eight polymorphic short sequence repeats (SSR) for the American lobster, which were derived from expressed sequence tags. Additionally, we tested four SSRs previously identified for the Norway lobster (Nephrops norvegicus L.) for cross‐species utility; only one of these showed polymorphism.     

Zooplankton in Rainbow Bay, a Carolina bay pond: population dynamics in a temporary habitat

SUMMARY.

• 1 Rainbow Bay is a temporary freshwater pond in South Carolina, U.S.A., that typically fills in winter and dries in spring or summer. We studied population dynamics of zooplankton in 1984 and 1985 when it held water for 282 and 57 days, respectively. The zooplankton were diverse, including one species of calanoid copepod, nine or more cyclopoid copepods, nineteen or more cladocerans, and twelve or more rotifers. The community was initially dominated by the copepods Diaptomus stagnalis and Acanthocyclops vernalis or Diacyclops haueri, later by cyclopoids and cladocerans including Daphnia laevis and Simocephalus spp.
• 2 Laboratory experiments with sediments from the dry pond support the inference from field data that time of emergence from resting stages was a proximate cause of the initial succession of species. The experiments also showed that eggs of the calanoid copepod, Diaptomus stagnalis, were inhibited from hatching in early November, but became ready to hatch by late November. A similar inhibition was not observed for cladocerans or cyclopoid copepods.
• 3 Food limitation appeared to influence population dynamics following emergence. For the cladocerans Daphnia laevis and Simocephalus spp., great reductions in size-specific fecundity occurred 1 month (1985) or 3 months (1984) after the pond filled and were associated with disappearance of the rotifer Conochilus hippocrepis. The cladocerans produced ephippia when their fecundities declined. Reproduction of Diaptomus occurred before cladoceran fecundities decreased in 1984, but during their decline in 1985. Broods of Diaptomus were smaller in 1985.
• 4 The impact of invertebrate predators was probably greater than that of vertebrate predators, but neither was sufficient to prevent over-exploitation of food resources. Prey consumption rates by salamander larvae were estimated from diets and population densities of the larvae in 1984 (Taylor et al., 1988). Their impact on the zooplankton was low in February, increased in March and April as the larvae grew, and then

     

An example of Holocene vegetation stability from Camerons Lagoon,a near treeline site on the Central Plateau,Tasmania

Abstract A discontinuous record of vegetation over the past 7500 years was obtained through pollen analysis of pond sediments from an extensive treeless plain on the relatively dry Central Plateau of Tasmania. The results demonstrate continuity of treeless conditions, which probably persisted from the Pleistocene throughout the Holocene, up to the present day. Some changes to the structure of the grassland were observed, especially over the past 200 years. Analysis of carbonized particles showed that fires had been infrequent over the period examined. It seems that this area, close to the altitudinal tree limit, has remained a natural grassland, and the hypothesis of Jackson (1973), that unreliable summer conditions may be a major factor in maintaining open conditions, is supported. Parts of the Central Plateau may thus preserve plant communities with some of the floristic elements and structure of widespread Bassian grasslands of the Late Pleistocene.     

D- AND L-STEREOISOMERS OF ALLYLGLYCINE: CONVULSIVE ACTION AND INHIBITION OF BRAIN L-GLUTAMATE DECARBOXYLASE

DL-Allylglycine was resolved into the L- and D-stereoisomers using hog kidney acylase. Both isomers were active as convulsants after administration to mice. The dose of D-allylglycine required to induce convulsions was greater than that of the L-isomer. Studies on the concentration of the two isomers in brain suggest that the lower effectiveness of D-allylglycine is partially due to its slower penetration into the brain through the blood-brain barrier. Both isomers of allylglycine inhibited brain glutamate decarboxylase in vitro to approximately the same extent, however, in vivo L-allylglycine inhibited the enzyme more strongly than the D isomer. Concentrations of allylglycine which caused a significant inhibition of L-glutamate decarboxylase in vivo were ineffective in inhibiting the enzyme in vitro. Oxidation products derived from L- or D-allylglycine by the action of either L- or D-amino acid oxidase caused an almost complete inhibition of the enzyme in vitro. It is suggested that a common intermediate derived from the two isomers (possibly 2-keto-4-pentenoic acid) is responsible for the in vivo inhibition of L-glutamate decarboxylase and possibly also for the induction of convulsions.     

The cranial anatomy and relationships of Secodontosaurus, an unusual mammal-like reptile (Synapsida: Sphenacodontidae) from the early Permian of Texas

The cranial anatomy of the Early Permian sphenacodontid synapsid Secodontosaurus is redescribed. There is no evidence for recognition of more than one species of Secodontosaurus, and S. willistoni is declared a junior subjective synonym of S. obtusidens. Numerous derived characters (autapomorphies), mainly related to the unusually slender and slightly elongated skull, distinguish Secodontosaurus. The cranial specializations are interpreted as an adaptation toward a feeding strategy which involved preying upon small tetrapods that attempted to avoid capture by hiding in crevices and burrows. A cladistic analysis supports the following hypotheses of relationships: (a) the Sphenacodontidae is the nearest sister taxon of Therapsida; (b) Secodontosaurus, Sphenacodon, Ctenospondylus and Dimetrodon share a more recent common ancestor with one another than any of them do with Haptodus, and (c) Secodontosaurus shares a more recent common ancestor with Dimetrodon than with either Sphenacodon or Ctenospondylus. The latter hypothesis suggests that the sphenacodont subfamily 'Sphenacodontinae' is paraphyletic and, therefore, invalid.