Archaeochlus Brundin: a midge out of time (Diptera: Chironomidae)

Abstract. Archaeochlus , a plesiomorphic genus of Podonominae (Chironomidae), is revised and two new species (biko from Namibia and brundini from southwestern Australia) described. The systematic status of the genus and the tribe Boreochlini is reassessed. Biogeographic evidence, sustained by a fossil record, dates the genus at least to the Upper Jurassic. The ecology of early Chironomidae is suggested to be eurythermic and hygropetric rather than cold stenothermic in lotic waters.     

Amoeboflagellate Transformations and the Gibbs-Donnan Ratio*

SYNOPSIS. A number of protozoa may have amoeboid, flagellated, or intergrade forms. At the present time several mechanisms have been proposed for inducing the formation of each of the above forms, but a definite triggering mechanism has not been elucidated. However, some change in the environment precedes the transformation of the cell from one form to another. Jahn (1962) and Czarska (1964), respectively, correlated ciliary reversal and water expulsion vesicle activity with alterations in the ionic environment. In both cases the processes involved are correlated with changes in the Gibbs-Donnan (G-D) relationship rather than direct ratios or molarities. It seems reasonable to assume that additional environmentally induced phenomena may also be based on changes in the relationship. The assumption is here made that an amoeboid cell, possessing the necessary genetic and physiologic potentials, can respond to certain changes in its environment by enflagellation. The following hypothesis is being considered: a change in the environment that increases the relative concentration of associated divalent cations is perhaps one of the main triggers for amoeba-to-flagellate transformations. Thus, in accordance with the G-D theory, this transformation would be expected to occur when a given ionic environment is diluted. In addition, the transformation is discussed in relation to pH, population density, and other environmental parameters that alter the Gibbs-Donnan ratio.     

Reconstitution of Embryo-Like Structures from Sea Urchin Embryo Cells: Distinction Between Cell-Cell and Cell-Substrate Associations

Sea urchin embryos can be dissociated into a suspension of single cells that reconstitute embryo-like structures. When reconstitution is conducted in stationary cultures the first step is attachment of the cells to the culture plate, which requires calcium and metabolic energy but not protein synthesis. We have found that protease treated cells form cell-cell associations in stationary cultures without attaching to the culture plates, and that cell-plate attachments are unaffected by inhibition of protein synthesis. These data suggest that cell surface proteins are needed for cell-plate attachment and that these proteins are present on freshly dissociated cells. We also demonstrated that butanol extracted cells attach to the plates, but do not form functional cell-cell associations unless the butanol extracted material is restored to them. We conclude that sea urchin embryo cells contain two classes of attachment components. The first class functions in the cell-plate attachments, is protease sensitive, and not extracted by butanol; the second class is necessary for cell-cell associations, is protease insensitive, and extracted by butanol. Since protease treated cells reconstitute embryo-like structures without attaching to the culture plates, only the second class of attachment components is necessary for embryo reconstitution.     

Potential interspecific competition and host specificity: hispine beetles on Heliconia

Abstract. 1. Adults of rolled-leaf hispine beetles (Chrysomelidae, Coleoptera) spend their lives in the scrolls formed by immature leaves of Heliconia (Heli-coniaceae, Monocotyledonae) in Tropical America. As many as eight hispine species can intermingle in the host scrolls at a single site. Scrolls of single host species are invariably occupied by adults of more than one hispine species, and as many as five species can simultaneously occupy one scroll.
2. I made virgin scrolls, which had never contained any insects, by growing leaves under the cover of plastic bags.
3. Thirty-seven combinations of single hispine and Heliconia species were experimentally created in the virgin scrolls, at two sites and in two seasons, in Costa Rica. Combinations included all abundant host species at the sites.
4. All beetles left all leaves of the twenty-eight unnatural beetle—host combinations, within 24 h. On the other hand, none of the nine natural combinations was completely abandoned within the experimental period.
5. Thus, host specificity is not broader in the absence of similar hispine species that might be competitors, and interspecies competition does not affect this obvious aspect of resource utilization for these phytophagous insects.     

Effect of Acetaldehyde on Growth in Succinate Media and Labeling RNA with 14C Succinate in Polytomella caeca

SYNOPSIS. Acetaldehyde had been shown to prevent growth of Polytomella caeca in acetate media when present at 4 mM and to depress labeling of RNA with acetate-2-¹⁴C. In order to avoid inhibition by acetaldehyde of possible malate synthase activity believed necessary for incorporation of acetate, succinate was substituted for acetate. Acetaldehyde had the same effect on growth in succinate media and labeling of RNA with succinate-2-¹⁴C as it had on utilization of acetate.     

Infection of Macrophages in Culture by Leptomonads of Leishmania donovani

SYNOPSIS. Peritoneal macrophages from hamsters were monolayered on coverslips in Leighton tubes. Twenty-four hours later these were transferred to a perfusion chamber. Leptomonads were added with fresh medium and the infection process observed with the aid of phase contrast. In the perfusion chamber free-swimming leptomonads attached to the macrophage by the tip of their flagella. Shortly after this initial attachment the macrophage extended a narrow pseudopodium around the flagellum which eventually reached and enveloped the body of the parasite. Upon complete envelopment the pseudopod containing the leptomonad was retracted into the central body of the macrophage. When first seen in the granular endoplasm of the macrophage, most of the leptomonads appeared to be surrounded by vacuoles. In most cases these vacuoles disappeared in a few minutes making it difficult to distinguish the parasite from the host cell cytoplasm.
Leptomonads also were added directly to Leighton tube cultures, and the coverslips with the adherent macrophages and parasites were removed, fixed and stained periodically during the infection process. In these preparations most of the parasites were in clumps in the vicinity of macrophages. Details of the ingestion of the clumps could not be seen, but occasionally a single organism was seen with its flagellum and part of its body enclosed by an extended pseudopod. Most of the intracellular leptomonads were in large vacuoles. Forms intermediate between elongate leptomonads and LD bodies were surrounded by smaller vacuole-like spaces. The halo-like vacuoles most frequently seen around LD bodies may have been fixation artifacts. Under favorable conditions the leptomonads transformed to LD bodies in 1–4 hours, but it was 48 hours before a population increase could be found.     

Notes on the biology of Trypanosoma ambystomae Lehmann, 1954. II. The Life Cycle in the Invertebrate Host.

SYNOPSIS. The leech, Erpobdella sp., is a suitable invertebrate host for Trypanosoma ambystomae. The developmental cycle involves a mononucleate, rounded body derived from the bloodstream form; this body then transforms into a large plump crithidia. Subsequent divisions yield medium crithidia, small crithidia, and ultimately, metacyclic trypanosomes.     

Paternal Behavior in Rodents

The literature on paternal behavior in rodents includes reportsof many species; however, paternal behavior appears more prevalentamong muroid and hystricomorph rodents than in the sciurids.Many reports of paternal behavior are based on small numbersof animals observed under special conditions. Where systematicstudies have been conducted, the most salient feature of rodentpaternal behavior is its lability. The occurrence varies withobserver constraints, genotype, experience, social conditionsduring observation, and stimulus characteristics. This intraspecificvariability renders application of the comparative method inunderstanding evolution difficult but may provide a key in theremarkable adaptation of rodents to diverse habitats. Althoughspecies differences exist the evolution of rodent paternal behaviorappears to entail changes in the thresholds and conditions forthe occurrence of a relatively few basic motor patterns of paternalcare.