Ultrastrukturen Und Cytochemie Der Pellikula Und Des Apikalkomplexes Der Kineten Von Babesia Bigemina Und Babesia Ovis In Hämolymphe Und Ovar Von Zecken*,†

SYNOPSIS The term kinete is used in this paper for the cigar-shaped, motile development stages (“vermicule”) of Babesia occurring intra- and extracellularly in hemolymph and ovary (including oocytes) of vectors, hard ticks (Ixodoidea). The structure of, and cyto-chemical activities of hydrolases (acid phosphatase, nonspecific esterase) in the pellicle and the apical complex were studied at the fine-structural level in kinetes of Babesia bigemina Smith & Kilborne, in hemolymph of female Boophilus microplus Canestrini. The cytochemistry of acid hydrolases was studied also in kinetes of Babesia ovis (Babes) Starcovici, in hemolymph and ovary of Rhipi-cephultis bursa Canestrini & Fanzago. The pellicle of the B. bigemina kinetes is composed of 3 membranes (pellicular complex): an outer membrane, ?8 nm thick (the plasmalemma) and 2 inner ones, each ?6 nm thick, lying closely together. The outer membrane appears to be covered by a structureless coat, 3 nm thick. The space between the inner double membrane and the plasmalemma is 7.5 nm. The whole pellicular complex is 30 nm in diameter. The 2 inner pellicular membranes appear to be derived from the endoplasmic reticulum (ER) for the following reasons: (a) a layer of hydrolase-active material is enclosed by these membranes; (b) in the spheroid parasite stages which transform from kinetes inside hemocytes, the inner double membrane is apparently replaced by an ER cisterna; (c) the thickness of each of the inner pellicular membranes is approximately the same as that of the ER membrane. There are circular openings in the pellicular double membrane with average diameters of 100 nm; despite some similarity to micropores, they have a specific structure. The term Intrapellikularfenster (IPF) (intrapellicular windows) or pseudomicropores is proposed for these pellicular differentiations. The margin of an FPF is formed by the 2 inner membranes folding into each other; cytoplasmic, electron-dense material is accumulated alongside this edge. Unlike that of micropores, the plasmalemma of the IPF is not invaginated. The IPF appears as a single, dark ring in tangential sections. At times, rhoptry-like bodies are associated with the openings. The function of the IPF is not known. An intrapellicular opening similar to the IPF, although wider, is present at the apex of the parasite. Its margin coincides with the inner edge of the apical ring. Typical subpellicular microtubuli were not observed in the Babesia kinetes. The apical complex of the B. bigemina kinetes consists of an Apikalschirm (apical umbrella), a crown of microtubuli beneath it, and rhoptries: micronemes are also present in large numbers. The Apikalschirm is located beneath the pellicle of the apical pole of the parasite. It is a wheel-like structure composed of spokes radiating from a wide, hub-like central ring (apical ring). It should be stressed that the apical ring is not identical with the polar ring described as an integral part of the pellicular complex in other Apicomplexa. Beneath each “rib” of the Apikalschirm there is one microtubule (subcostal microtubule). In kinetes of B. ovis the “ribs” are less well developed. In addition, the Apikalschirm is more pointed in kinetes of this species in tick oocytes and ova. The rhoptries of the kinetes are spindle-shaped and largely located directly beneath the Apikalschirm. They are arranged radially, each row being associated with a “rib”. A conoid was not observed. Occasionally, low hydrolytic activity could be detected in micronemes. The rhoptries and the Apikalschirm were always negative for phosphatase and esterase activity. With regard to the number and arrangement of its membranes and to its hydrolase activity, the pellicle of the kinetes of Babesia closely resembles the pellicular complex of the Coccidia. It differs from the latter by the presence of the IFF and by the lack of micropores and of true subpellicular microtubules. In the complexity of their pellicle and in some details of the organization of their apical complex (lack of a conoid; umbrella-like structure), the kinetes of Babesia resemble the ookinetes of the Haemosporidia.     

The Effect of 2-Chloro-4-ethylamino-6-isopropyl-amino-s-triazine (Atrazine) on Distribution of 14C-Compounds Following 14CO2 Fixation in Excised Kidney Bean Leaves

Excised leaves of kidney bean plants treated with various concentrationsof atrazine for different periods were allowed to fix ¹⁴CO₂CO₂ fixation was inhibited by atrazine. The ¹⁴C-labelling patternof atrazine-treated leaves resembled dark Co₂-fixation patterns.The carbon-I-carboxyl group of ¹⁴C-aspartic acid from atrazine-treatedand ‘dark’ leaves showed no significant differencesin total radioactivity. Although atrazine disrupted the photosyntheticapparatus, it seemed to have no effect on non-photosyntheticCO₂ fixation.     

Cannibalism and Coprophagy Are Modes of Transmission of Blastocrithidia triatomae (Trypanosomatidae) between Triatomines

Transovarial transmission was not detectable among Blastocrithidia triatomae- infected Triatoma infestans . Rather, B. triatomae was transmitted directiy between triatomines by cannibalism and coprophagy. Cannibalism conditions that excluded coprophagy always resulted in an infection of Dipetalogaster maxima . The efficiency of transmission was not influenced by the blood source—mice or chickens—fed to the infected donor bugs although chicken blood lyses the epimastigotes of the stomach population. Triatoma infestans was infected by coprophagy only if fed, not if unfed. Blastocrithidia triatomae in dry feces was taken up only if the feces were redissolved in fresh feces. Infections also appeared in groups of bugs fed on chickens previously used for feeding infected bugs.     

Structural refuges in two stem-boring weevils on Rumex crispus

Abstract.

• 1 Differences in feeding positions, parasitoid complexes and parasitization rates of the two dominant insect species in stems of Rumex crispus were investigated. Apion miniatum (inhabiting the lower 10% of the stem) and Apion violaceum (occurring all along the stem) exploited distinctly different feeding positions, partly due to differences in time of oviposition.
• 2 A.miniatum suffered less parasitization thanA.violaceum, measured both by number of parasitoid species and parasitization rates. Its feeding position constitutes a refuge.
• 3 Parasitization of A.violaceum was least in individuals feeding in basal, thick parts of the stem. There is a trend that the developed refuge increases with increasing stem diameter.
• 4 The refuge of A.violaceum in basal positions only affected idiobiont ectoparasitoids, because koinobiont endoparasitoids attack the weevils before they enter the stem. Moreover, the koinobiont did benefit from the refuge itself by avoiding hyperparasitism.
• 5 Densities of A.violaceum increased with plant size, whereas percentage parasitism did not differ. Its three most abundant parasitoid species showed small-scale density-independent patterns of attack over all plants. Therefore a constant proportion of weevil larvae mine within the refuge independent of its potential size.
• 6 Synchronization between weevils and plants, as well as between parasitoids and hosts, appears to be the dominant factor for the spatial community structure of the stem borers of Rumex crispus and their enemies.