Electron microscopy reveals novel external specialized organs housing bacteria in eagle ray tapeworms.

Nutritionally-based mutualisms with bacteria are known to occur in a wide array of invertebrate phyla, although less commonly in the Platyhelminthes. Here we report what appears to be a novel example of this type of association in two geographically disparate and phylogenetically distant species of tapeworms of eagle rays-the lecanicephalidean Elicilacunosus dharmadii off the island of Borneo and the tetraphyllidean Caulobothrium multispelaeum off Senegal. Scanning and transmission electron microscopy revealed that the grooves and apertures on the outer surfaces of both tapeworms open into expansive cavities housing concentrations of bacteria. This led us to reject the original hypothesis that these structures, and their associated mucopolysaccharides, aid in attachment to the host mucosa. The cavities were found to be specialized in-foldings of the tapeworm body that were lined with particularly elongate filitriches. Given tapeworms lack a gut and employ filitriches to assist in nutrient absorption, enhanced nutrient uptake likely occurs in the cavities. Each tapeworm species appeared to host different bacterial monocultures; those in E. dharmadii were coccoid-like in form, while those in C. multispelaeum were bacillus-like. The presence of bacteria in a specialized structure of this nature suggests the structure is a symbiotic organ. Tapeworms are fully capable of obtaining their own nutrients, and thus the bacteria likely serve merely to supplement their diet. Given the bacteria were also extracellular, this structure is more consistent with a mycetome than a trophosome. To our knowledge, this is not only the first evidence of an external symbiotic organ of any type in a nutritionally-based mutualism, but also the first description of a mycetome in a group of invertebrates that lacks a digestive system. The factors that might account for the independent evolution of this unique association in these unrelated tapeworms are unclear-especially given that none of their closest relatives exhibit any evidence of the phenomenon.

[The contribution of carbohydrases produced by symbiotic microflora to the digestive processes in cestodes and their host fishes].

The bacteria capable of producing the enzymes hydrolyzing carbohydrates of various degrees of complexity (from starch to sucrose) were found to be associated with the intestinal mucosa of fishes and tegument of cestodes. Presence of the bacteria displaying the sucrase activity is especially important for macroorganisms, as bacteriogenous glucose can be used by all members of the arising community. The greatest contribution to the hydrolysis of carbohydrates (both in host and parasite) is obviously made by those microorganisms which are more closely connected with the digestive-transport surfaces and are hardly removable from the intestines by peristalsis. The levels of total amylolytic activity of bacteriogenous enzymes and activity of their a-amylase under the experimental conditions are comparable to those of the enzymes involved in membrane digestion of the host and parasite, which can be evidence of the significant contribution of enzymes produced by symbiotic microflora to the digestive processes in macroorganisms.

Ovicidal activity of Paecilomyces lilacinus on Moniezia sp. eggs.

The ovicidal activity of Paecilomyces lilacinus was evaluated on Moniezia sp. eggs. Eggs of Moniezia sp. were incubated on plates with 2% agar-water inoculated with grown fungal isolates and a control treatment without fungus. After 5, 10 and 15 days post-inoculation, the eggs were removed and classified according to the following parameters: effect type 1, lytic effect without morphological damage to eggshells; effect type 2, lytic effect with morphological change in embryos and eggshells; and effect type 3, lytic effect with morphological change in embryos and eggshells, with hyphal penetration and internal colonization of eggs. Paecilomyces lilacinus showed percentages for ovicidal activity (P < 0.01), mainly type 3 effect, of 19, 20 and 23% on eggs of Moniezia sp., after 5, 10 and 15 days post-inoculation, respectively. Therefore P. lilacinus can be considered as a potential biological control agent for this cestode.

[The symbiotic microflora associated with the tegument of proteocephalidean cestodes and the intestines of their fish hosts].

The indigenous symbiotic microflora associated with the tegument of proteocephalidean cestodes and the intestines of their fish hosts has been investigated in morphological and ecological aspects. The indigenous microflora associated with the cestode tegument consists of the nannobacteria population, which was present obligatorily on the surface of tegument, and the "deep microflora". The deep microflora associates with some few species of parasites only. Each individual host-parasite micro-biocenosis includes specific indigenous symbiotic microorganisms, with the differing microfloras of host intestine and parasite. Physiology, biochemistry and/or diet of hosts apparently influence on the symbiotic microflora's structure of parasites. The least bacteria abundance and diversity of their morphotypes were observed in the parasites from baby fishes. The diversity and abundance of bacteria were increased with the fish host ageing and the formation of the definitive structure of its intestine. It is an evidence of the gradual invading of the intestinal parasites (cestodes) tegument by bacterial cells. The invading is realized on the base of the microflora that was present in the food of fish host. The symbiotic microflora has specific morphological features, can regulate the homeostasis of the cestodes and fish hosts and also can maintain equilibrium of alimentary and immune interrelations in the host-parasite system.

[Hydrolytic activity of enzymes produced by symbiotic microflora and its role in digestion processes of bream and its intestinal parasite Caryophyllaeus laticeps (Cestoda, Caryopyllidea)].

Bacteria capable to secrete enzymes hydrolyzing proteins and carbohydrates proved to be associated with the digestive-transport surfaces of the bream intestine and tegument of cestode Caryophyllaeus laticeps. Apparently, the contribution of symbiotic digestion to the hydrolysis of polymers increases during active feeding of fishes, while at low feeding rate, bacteria can compete with the host and its parasite for the available monomers. Secretion of bacterial enzymes hydrolyzing both complex carbohydrates and disaccharides reduces the metabolic expenditures of the macroorganisms for the synthesis of their own hydrolases. Glucose resulting from hydrolytic activity of bacterial enzymes can be used by all members of the established community. While bacteria colonizing the digestive-transport surfaces of the host and parasite were generally similar, some specific features were also observed probably due to the structural peculiarities of the intestinal mucosa and cestode tegument.

[Indigenous microflora associated with the tegument of Triaenophorus nodulosus (Cestoda) and the intestine of its pike host].

Investigations of the indigenous microflora associated with the mucous intestines of fish and its cestode parasites have been for the first time carried out using the methods of transmission and scanning electron microscopy. New data on the bacterial biodiversity in the cestode and its fish host are obtained. Nanobacteria and spirochaetes are for the first time revealed in a fish host together with the previously known bacteria forming the intestinal microflora of fish. Spirochaetes were shown to be associated with the intestines of a pike host only, while nanobacteria cover abundantly the surface of the apical parts of the intestinal microvilli and the apical parts of the microtriches in the cestode tegument. The similarity of the bacterial floras associated with the apical surface of the parasite tegument and the intestine of the host should be noted. At the same time, deeper bacterial communities represented by obligate symbionts are specific. Thus, there is a normal indigenous microflora in cestodes, associated with the tegumental surface. This symbiotic microflora has specific morphological features and provides the balance of relations in the parasite-host system.

[Electron microscope investigation of bacteria associated with the tegument of the tapeworm species Eubothrium rugosum, a parasite of the intestine of burbot].

Bacteria associated with the tegument of the tapeworm species Eubothrium rugosum (Cestoda, Pseudophyllidea) parasitizing the intestine of burbot (Lota lota) were studied using transmission and scanning electron microscopy. Three morphological types of the bacteria were revealed. Bacteria of the first type are localized between microtrichia and fit to them closely. Bacteria of the second (gram-positive) and third (gram-negative) types are localized over microtrichia of the tegument and do not attach to the surface. Physiological functions of the bacteria are discussed.

[The role of alpha-amylase of symbiotic microflora in digestion by lower cestodes and their fish hosts].

The symbiotic microflora associated with the digestive-transport surfaces of the pike intestine and the parasitic cestodes Triaenophorus nodulosus proved capable of the initial stages of carbohydrate hydrolysis mediated by alpha-amylase. The products of hydrolysis by alpha-amylase can be used by both the host and the parasite, which decreases energy expenditures of the macroorganisms. The levels of the bacterial alpha-amylase activity are comparable to those of the analogous enzyme absorbed on the mucosa of the intestine and on the cestode tegument, which indicates a considerable contribution of enzymes of the symbiotic microflora to digestion by the host and the parasite. Apparently, this contribution depends on the fish diet.

Aspectos clínicos de la himenolepiasis en pediatría / Clinical aspects on hymenolepiasis in pediatrics

El presente estudio se realizó en 325 niños infectados con Hymenolepis nana, con el objeto de realizar un estudio clínico y de laboratorio de tipo integral. Los resultados mostraron que la himenolepiasis se encuentra entre las primeras cinco parasitosis intestinales en los niños escolares de la Ciudad de México, en la mayoría de los casos asociada a protozoos y otros helmintos, en especial con Giardia lamblia; generalmente la carga parasitaria es leve y sin embargo, la traducción clínica poco varía a pesar de ello. Las manifestaciones clínicas más importantes y constantes en los grupos de himenolepiasis pura y asociada son: dolor abdominal, hiporexia e irritabilidad. En cambio en las himenolepiasis en forma comparativa asociada a otras parasitosis con respecto a los casos donde no hay parásito intestinal, observamos que la pérdida de peso, meteorismo y flatulencia se presentan en las formas puras de himenolepiasis y en las asociaciones con G. lamblia; especialmente, la diarrea es una de las principales manifestaciones. Concluyendo, la himenolepiasis en nuestro medio es muy importante por su frecuencia en niños preescolares y escolares y tiene un cuadro clínico identificable en forma constante