Reproductive Advantages for Common Loons Using Rafts

Abstract: Artificial nesting islands, or rafts, are often deployed in common loon (Gavia immer) breeding territories to decrease negative impacts of mammalian predation and water-level fluctuations on nesting success. The management value of rafts has been demonstrated in other studies; however, no published studies have quantified the use or associated reproductive benefits of rafts on lakes exhibiting water-level fluctuations. These lakes constitute a major portion of loon nesting habitat in New England and the Midwest. We used long-term data sets from loon survey and raft management efforts on lakes with stable (SWL) and fluctuating water levels (FWL) in New Hampshire and Maine, USA, to compare raft-use patterns on both types of lakes. We then modeled the influence of percentage of nesting attempts on rafts, lake fluctuation type, and human development index on nesting success as a function of the number of nesting attempts. Loons used 76% of all rafts for nesting, and initial use patterns were similar between SWL and FWL lakes. Half (51%) of rafts used for nesting were first used during the initial year of deployment and 90% of those used were used by the third year. Based on our model, we would expect to see an 8.6% increase in nesting success associated with each successive categorical increase in raft use (0–33%, 33–60%, 60–100%). Nesting success varied with lake fluctuation type, increasing by 21.4% from FWL to SWL types. Our model estimated a 12.8% decrease in nesting success associated with an increasing human development index. Naturally nesting loons on FWL lakes are likely to display mean nesting success levels lower than those needed to sustain populations. We suggest that natural nesting habitat on lakes with fluctuating water levels during the loon nesting season may constitute an ecological trap warranting consideration of raft management. Findings in this study are germane for managing breeding loon populations, particularly those on reservoirs requiring permits from the Federal Energy Regulatory Commission.     

Experimental Infection of Triatoma infestans and Rhodnius prolixus with Trypanosomatidae of the Genera Crithidia and Blastocrithidia*

SYNOPSIS. Dissections of Triatoma infestans and Rhodnius prolixus at various intervals after experimental infection with insect Trypanosomatidae of the genera Blastocrithidia and Crithidia (B. euschisti, C. luciliae, C. acanthocephali and C. mellificae) disclosed the protozoa to be surviving and in most instances undergoing reproduction in the experimental bugs for as long as 2 months following infection. Epimastigotes and amastigotes were seen in bugs infected with B. euschisti and choanomastigotes and amastigotes were observed in insects experimentally infected with the Crithidia. Since C. acanthocephali and C. luciliae were from clones, this is the 1st finding of these 2 structural types in this genus using cultures originating from a single choanomastigote. In view of the loose host specificity of the insect Trypanosomatidae as further emphasized by this work, it would appear that the necessity is increased for field workers in trypanosomiasis and leishmaniasis areas of the world to become well acquainted with the infective potentialities of the insect trypanosomatids of their areas for the vectors of Trypanosoma and Leishmania along with the possible association in nature of these vectors with insects which might harbor insect-limited Trypanosomatidae.     

The production of pure stocks of self-pollinating cereal varieties

The method of cereal pure stock production used at the Plant Breeding Institute is described. Multiplication from fifty plants to commercial seed stocks takes 5 years; individual ears are inspected each year and an ear-row/ear-row progeny system is used. An accelerated system reducing the period of multiplication to 4 years is also described. The advantages and disadvantages of other multiplication methods are discussed.     

Some Complicating Factors in the Study of the Calcium Metabolism of Teleosts

A number of factors which may complicate studies dealing withthe calcium metabolism of teleosts are pointed out. Thus, lowenvironmental levels of calcium markedly affect both gill RNAand sodium metabolism in dilute sea water, and the absence ofmonovalent cations affects calcium metabolism in dilute environments.Hypophysectomy is not always followed by the disappearance ofcortisol from the plasma, and prolactin—which is requiredfor the survival of either hypophysectomized or intact animalsin a divalent ion-free environment—stimulates cortisolproduction. It is also pointed out that Fundulus kansae can be maintainedin divalent ion-free environments for long periods, and thatcalcium is mobilized from internal reservoirs such as acellularbone and scales. Failure to survive in such environments isdue to the regulatory effect of environmental calcium on sodiummetabolism rather than on calcium metabolism per se. Finally,it is pointed out that while one parameter of calcium metabolism—suchas plasma calcium levels in male fish—may remain constantthroughtout the year, other parameters such as calcium uptakemay vary considerably. Seasonal differencees in responses tomammalian calcitonin have also been noted.     

Growth and Reproduction of Leptomonas oncopelti in the Milkweed Bug, Oncopeltus fasciatus

SYNOPSIS. A laboratory colony of Oncopeltus fasciatus was found to be infected with Leptomonas oncopelti. Inasmuch as the parasite is transmitted from parent to offspring an opportunity presented itself to study the biology and transmission of this parasite under controlled laboratory conditions. An apparatus for observing individual bugs was designed and the presence or absence of flagellates in the feces determined. Flagellates were not shed until the bugs became adults after which they appeared in every defecation. Dissection of infected bugs revealed that flagellates were not present in the rectum until adulthood. Further studies indicated that in the midgut of the insect there is a departure from binary fission to budding. The nucleus divides and one of the newly formed nuclei migrates toward a newly formed kinetoplast. Rarely there is still another kinetoplast/nucleus division. In the event the new axoneme grows within the cytoplasmic sheath of the parent flagellum, smaller organisms produced by unequal cytokinesis remain attached. If the axoneme grows free, the smaller daughter organisms become free-swimming. Passage into the rectum of the adult bugs causes a rounding up of all parasites although the leishmaniform organisms continue to divide. It is presumed that infection of clean bugs is accomplished by the ingestion of leishmaniform organisms through a common water source. The reason for the presence of flagellates in the rectum of the adult but not in the nymphal insect and the mechanism responsible for the change from binary to unequal fission are not known.     

Transfer and Localisation of Maternal Serum Antigens by Mouse Preimplantation Embryos and Oviductal Epithelium

Two hours after systemic injection of bovine plasma albumin (BPA) into pregnant mice, albumin-like antigen was detected by indirect immunohistological methods within the cytoplasm of oviductal and preimplantation uterine embryos whether ovulation was spontaneous or induced by hormone injection. Although fluorescence, localising antigen similar to or identical with the systemically injected foreign protein, was present in embryos in all oviductal regions and at all cleavage stages, the intraembryonic location of the transferred serum molecules differed with embryo stage. Most ootids and two-celled blastomeres contained large intracytoplasmic areas of intense fluorescence randomly associated with non-fluorescent or dimly fluorescent areas in the same cell. By four- and eight-celled stages, albumin-like antigen was localised at the periphery of blastomeres; less was found deep within embryos. By morula and blastocyst stages, blastomeres differed from each other in fluorescence intensity although intracellular fluorescence was homogeneous. Transferred BPA antigen, present in both pronuclei, probably was absent from blastomere nuclei. Ootid zonae pellucidae contained BPA antigen but none was detected in zonae surrounding cleaving embryos. Little foreign albumin was detected in oviductal epithelium.
It is concluded that morphological, as well as biochemical, differentiation occurs during mammalian cleavage and it is suggested that maternal macromolecular contributions to mammalian preimplantation embryos may be necessary for normal development in vivo .