Life Cycle of Isospora canis Nemeséri, 1959 in the Dog*

The life cycle of I. canis Nemeséri, 1959 was studied in experimentally infected dogs. Freshly sporulated oocysts were ovoid and 34–40 × 28–32 μm. The endogenous stages were found directly beneath the epithelium of the distal portion of the small intestinal villi. Most of the endogenous stages were in the lower 1/3 of the small intestine, but occasionally they were found in other portions of the small intestine. Three asexual generations were present. First-generation schizonts were 16–38 × 11–23 μm and contained 4–24 merozoites; mature 1st-generation merozoites were 8–11 × 3–5 μm. First-generation schizogony lasted up to 7 days after inoculation. Second-generation schizonts were 12–18 × 8–13 μm and contained up to 12 merozoites which were 11–13 × 3–5 μm. Second-generation schizogony was present on postinoculation days 6 and 7. Third-generation schizonts were formed by nuclear division of 2nd-generation merozoites. Most 2nd-generation merozoites underwent nuclear division without leaving the parasitophorous vacuole of the 2nd-generation schizont. Mature 3rd-generation schizonts were 13–38 × 8–24 μm and contained 6–72 merozoites. Third-generation merozoites were 8–13 × 1–3 μm. Third-generation schizogony was present on days 6–8 after inoculation. Mature macrogametes were 22–29 × 14–23 μm. Mature microgametocytes were 20–38 × 14–26 μm. Gametes were present on postinoculation days 7–10. Oocysts were present in tissue sections on postinoculation days 8–10 and 12. The prepatent period was 9–11 days.     

Four New Species of Eimeria (Protozoa: Eimeriidae) from the Pika Ochotona princeps from Alberta and O. pallasi from Kazakhstan1

SYNOPSIS. Eimeria worleyi n. sp. and Eimeria barretti n. sp. from the pika Ochotona princeps from Alberta and Eimeria pallasi n. sp. and Eimeria shubini n. sp. from the pika Ochotona pallasi from Central Kazakhstan are described. Oocysts of E. worleyi were 12–16 by 10–15 μ (mean 13.5 by 12.5 μ) and spherical to subspherical. E. barretti oocysts were ellipsoidal to slightly ovoid and 27–36 by 21–27 μ (mean 32.9 by 23.8 μ). Oocysts of E. pallasi were ellipsoidal or ovoid and 19–34 by 17–26 μ (mean 26.3 by 21.3 μ). E. shubini oocysts were spherical and 22 μ in diameter. E. kriygsmanni Yakimoff and Gousseff, 1938 of Svanbaev (1958) in O. pallasi, [non] E. kriigsmanni Yakimoff and Gousseff, 1938 in Mus musculus, is a synonym of E. pallasi. E. musculi Yakimoff and Gousseff, 1938 of Svanbaev (1958) in O. pallasi, [non] E. musculi Yakimoff and Gousseff, 1938 in Mus musculus, is a synonym of E. shubini.     

The role of lipids as feeding stimulants for shredding aquatic insects

SUMMARY.

• 1 Caddisflies (Trichoptera) that shred leaf detritus preferentially ingested lipid-coated detritus during the last larval in star. This is the interval when these insects accumulate the triglyceride reserves necessary for metamorphosis and reproduction. Early in star larvae, which do not accumulate lipids, showed no preference for any lipids. This behaviour indicates food selection based on changing nutritional needs.
• 2 Pure unsaturated 18- and 20-carbon fatty acids, either as free acids or triglycerides, were most strongly preferred. Crude lipid and the neutral lipid fraction from aquatic hyphomycete fungi, an important component of aquatic leaf detritus, were also preferred.
• 3 Tipula abdominalis (Diptera: Tipulidae) did not prefer any lipids during the last instar.

     

Evolutionary Patterns in Advanced Snakes

One prevalent view of phylogenetic events in advanced snakesholds that the fangs evolved along at least two pathways one(e.g. elapids) from ancestors with enlarged anterior and theother (e.g. viperids) from ancestors with enlarged posteriormaxillary teeth. Selective forces driving these changes arepresumed to arise from the increasing advantages of teeth andglands in venom injection. In this paper another plausible viewof these events is proposed. First fangs of both elapids and viperids likely evolved fromreal maxillary teeth. In non-venomous snakes, differences intooth morphology and function suggest that there may be somedivision of labor among anterior and posterior maxillary teeth.Anterior maxillary teeth, residing forward in the mouth likelyserve the biological role of snaring and impaling prey duringthe strike. They are also conical frequently recurved and lacka secretion groove. On the other hand posterior teeth becauseof their geometric position on the maxilla and mechanical advantages,tend to serve as aids in preingestion manipulation and swallowingof prey. They are often blade shaped and occasionally bear asecretion groove along their sides. Although both front andrear maxillary teeth of nonvenomous snakes may be elongatedthis is likely to serve these different functional roles andhence they evolved under different selective pressures. Whenfangs evolved they did so several times independently but fromrear maxillary teeth. In support one notes a) the similar positionpostorbital of venom and Duvernoy s glands b) similar embryonicdevelopment of fangs and rear maxillary teeth c) secretion groovewhen present, is found only on rear teeth and d) similar biologicalroles of some rear teeth and fangs. For ease in clearance ofthe prey during the strike the fangs are positioned forwardin the mouth accomplished in viperid snakes by forward rotationof the maxilla and elapids by rostral anatomical migration tothe front of the maxilla. Second, the adaptive advantage first favoring initial rear toothenlargement likely centered not on their role in venom injectionbut rather on their role in preingestion manipulation and swallowing.However once enlarged, teeth would be preadapted for later modificationinto fangs under selection pressures arising from advantagesof venom introduction. This has implications for the function and evolution of associatedstructures. Besides possibly subduring or even killing of preythe secretion of Duvernoy's gland may be involved in digestionor in neutralizing noxious or fouling products of the prey.The presence or absence of constriction need not be functionallytied to absence or presence of venom injection. The phylogeneticpathways outlined herein were likely traveled several timesindependently in advanced snakes.     

Scanning Electron Microscopy of Tintinnopsis parva: Studies on Particle Accumulation and the Striae*

SYNOPSIS. Lorica building was studied experimentally for Tintinnopsis parva Merkle, an agglutinated tintinnid. This species incorporated either siliceous or Ca-rich particles. Evidence of agglutination was seen within 30 min after the addition of particles to cultures of the protozoa. Fully agglutinated loricae were produced by the proter; partially incrusted loricae attributed to an opisthe were also recovered. The cytoplasmic evaginations of unknown function called striae were seen in the scanning electron microscope in better relief than ever before. They may provide the mechanism whereby the enclosed capsules are brought into contact with prey organisms.     

Life Cycle and Host Specificity of Eimeria callospermophili Henry, 1932 From the Uinta Ground Squirrel Spermophilus armatus*

SYNOPSIS. Eimeria callospermophili was found in 6 species of ground squirrels and the white-tailed prairie dog. The hosts included Spermophilus armatus from Utah and Montana, S. richardsoni from Montana and Wyoming, S. beecheyi from California, S. lateralis and S. variegatus from Utah, and S. tridecemlineatus and Cynomys leucurus from Wyoming. Infections were generally transmissible from each species of ground squirrel to S. armatus and S. richardsoni. Oocysts from C. leucurus caused infections in S. armatus and S. richardsoni. No infections were found after inoculation of E. callospermophili oocysts into least chipmunks (Eutamius minimus), Mongolian gerbils (Meriones unguiculatus), or laboratory rats; however, excystation occurred in these animals. Resistance to infection did not develop in S. armatus, S. richardsoni, or S. variegatus, but did occur after 5 or more infections in S. lateralis. Eimeria callospermophili had little or no effect on the host in S. armatus, S. lateralis, or S. variegatus, but caused bloody diarrhea in severely infected individuals of S. richardsoni. The oocysts had an oocyst residuum consisting of several distinct bodies, which later coalesced to form a large homogeneous body. Each sporozoite had an unusually large refractile body. In experimentally infected specimens of S. armatus the prepatent period and patent period lasted for 5 and 9 days, respectively. Mature 1st-generation schizonts, first seen 2 days after inoculation, had 8–12 merozoites. Mature 2nd-generation schizonts, first seen 3 days after inoculation, had an average of 18 merozoites which were smaller than those of the 1st generation. Mature gametes were 1st seen 4 days after inoculation. Mature microgametocytes were only slightly larger than mature macrogametes.     

The Relation of Phosphate Metabolism to Oxidative Assimilation of Acetate by Euglena gracilis var. bacillaris. Effects of 2,4-Dinitrophenol*

SYNOPSIS. Oxidative assimilation of acetate by Euglena gracilis var. bacillaris occurs without appreciable net transfer of inorganic phosphate between cells and medium. Low concentrations of the “uncoupling agent” 2,4-dinitrophenol (2–5 μM, pH 5) stimulate acetate oxidation and inhibit acetate assimilation. These dinitrophenol concentrations have no measurable effect on edogenous respiration. Higher concentrations inhibit respiration on acetate, and still higher concentrations inhibit endogenous respiration. Dinitrophenol concentrations which stimulate acetate oxidation produce no measurable change in the total ATP content of the euglena cells. Higher concentrations (50–100 μM) cause progressive decrease in the ATP content. A hypothetical mechanism is proposed which accounts for the normal, constant oxidation-assimilation ratio for acetate as the result of coupling of oxidative ATP synthesis with assimilatory ATP consumption. The data are consistent with this mechanism if it is additionally assumed that oxidation and assimilation of acetate occur in an intracellular “compartment” separated from other sources and sinks of ATP.     

High diversity and regional endemism in land snails of eastern Tanzania

In February/March 1995 we collected land snails (including slugs) at 12 stations in eastern Tanzania. A total of 571 person-hours yielded 9174 snails assigned to 159 morpho-species. The richest two sites each (<4ha of uniform forest) had 50 species (Amboni Cave) and 48 species (near Amani, Usambaras), nearly as great as the most species-rich sites known in the world; sieving of litter and soil would probably yield more species. In lowland (coastal) forests, both diversity and endemism seemed to decrease from north to south. Most snail species were found within only one of four coastal or one montane geographic regions, indicating substantial regional endemism. Only one species (Achatina fulica) appeared in all five regions, and 84% of all other species were found in only one (61%) or two regions (23%). The predatory streptaxids comprised about half the species and a third of the individuals at the Usambara site, an extremely high ratio of carnivores. Small snails (< 5mm greatest adult shell dimension) – many of which are probably undescribed species – comprise a substantial proportion of Tanzanian molluscan diversity; more surveys are needed, especially because of human pressures on the few forest patches remaining.     

Polygyrid relations: a phylogenetic analysis of 17 subfamilies of land snails (Mollusca: Gastropoda: Stylommatophora)

The family of polygyrid land snails in North America is significant for its sympatric shell convergences, diversity of mating systems and complex zoogeography; its monophyly and its relation to other families has long been questionable. Cladistic analysis has been performed on one representative each of 17 subfamilies, including all three polygyrid subfamilies and one or more subfamilies each from all ten of the families that have been proposed as the polygyrid sister groups. Eighteen anatomical synapomorphies are used, of which eight are newly discovered, four are differently assessed from previous studies, and six are traditional. The resulting strict consensus tree of alternative maximum-parsimony cladograms is: (Acavidae (Ammonitellidae Corillidae ((Discidae Oreohelicidae) (Helminthoglyptidae Bradybaenidae Polygyridae (Thysanophoridae (Camaenidae Sagdidae)))))).
According to this working hypothesis, the Polygyridae are monophyletic, and their sister group remains unresolved, although the Acavidae, Ammonitellidae, Corillidae, Discidae and Oreohelicidae can be ruled out. Of the five classifications of stylommatophoran families that have been proposed in the past 12 years, the consensus tree is closest to that of Nordsieck. For future morphological work, three regions are recommended as potentially rich in unused phylogenetic information: the fertilization pouch-seminal receptacle complex, the ureter at the pneumostome and the ventral-chain ganglia. Simultaneous dissection, wkh side-by-side comparisons, is recommended over other methods for detecting homologies in land snails. Molecular characters should be exploited, because of the scarcity and the frequent homoplasy of morphological characters.