Histopathological changes in fish gills infected with myxosporidian parasites of the genus Henneguya

Tissue reaction to invasion by two Henneguya species was studied in gills of three species of fish. Henneguya psorospermica and Henneguya creplini develop in secondary lamellar arterioles in perch ( perca fluviatilis ) and ruff ( Acerina cernua). In pike ( Esox lucius), H. psorospermica develops in the artery. During the growth of the vegetative stage, the gill tissue may undergo local atrophy or hyperplasia of the epithelium and displacement and disfiguration of the lamellae. After the myxosporidian cyst, surrounded by a host tissue capsule has reached maturity and contains fully-formed spores, an inflammatory reaction may set in which reduces the cyst to granulomatous tissue. This inflammatory process is essentially of the same type as that observed in mammals. There is evidence that inflammatory responses are of regular occurrence in the final stages of most myxosporidian infections. Transfer from low to room temperature provokes a rapid elimination of the cysts by granulomatous inflammation.     

Morphology of monogeneans parasitizing Amur River fish

Morphology of Bivaginagyrus obscurus from Pseudorasbora is described. B. obscurus differs from species of the genus Dacfylogyrus by 2 vaginae, shape of median hooks, seat of gill filament and length of additional ventral bar. Morphology of Silurodiscoides infundibulavagina and some other species of this genus parasitic on Parasilurus asotus is described. The morphology of Pseudoancylodiscoides from Pseudobagrus fulvidraco is characterized by 2 ventral bars and peculiar seminal vesicle. Morphology of Bychowskyella pseudobagri from Pseudobagrus fulvidraco is described. The testis in this type species is located more ventrally than the ovary.     

Specificity and specialization of congeneric monogeneans parasitizing cyprinid fish

Patterns and likely processes connected with evolution of host specificity in congeneric monogeneans parasitizing fish species of the Cyprinidae were investigated. A total of 51 Dactylogyrus species was included. We investigated (1) the link between host specificity and parasite phylogeny; (2) the morphometric correlates of host specificity, parasite body size, and variables of attachment organs important for host specificity; (3) the evolution of morphological adaptation, that is, attachment organ; (4) the determinants of host specificity following the hypothesis of specialization on more predictable resources considering maximal body size, maximal longevity, and abundance as measures of host predictability; and (5) the potential link between host specificity and parasite diversification. Host specificity, expressed as an index of host specificity including phylogenetic and taxonomic relatedness of hosts, was partially associated with parasite phylogeny, but no significant contribution of host phylogeny was found. The mapping of host specificity into the phylogenetic tree suggests that being specialist is not a derived condition for Dactylogyrus species. The different morphometric traits of the attachment apparatus seem to be selected in connection with specialization of specialist parasites and other traits favored as adaptations in generalist parasites. Parasites widespread on several host species reach higher abundance within hosts, which supports the hypothesis of ecological specialization. When separating specialists and generalists, we confirmed the hypothesis of specialization on a predictable resource; that is, specialists with larger anchors tend to live on fish species with larger body size and greater longevity, which could be also interpreted as a mechanism for optimizing morphological adaptation. We demonstrated that ecology of host species could also be recognized as an important determinant of host specificity. The mapping of morphological characters of the attachment organ onto the parasite phylogenetic tree reveals that morphological evolution of the attachment organ is connected with host specificity in the context of fish relatedness, especially at the level of host subfamilies. Finally, we did not find that host specificity leads to parasite diversification in congeneric monogeneans.     

Notes on the ultrastructure of the microconidium and stroma in Sclerotinia sclerotiorum

Summary An electron microscope study has been done on the structure of microconidia and stroma of Sclerotinia sclerotiorum. The microconidia showed the usual cell organelles already described for other species of this genus, e.g. a large nucleus and large lipid body, a few mitochondria and sparse endoplasmic reticulum. The stromatal ultrastructure presented hyphae with a rich content in lipid bodies and storage vacuoles as food reserve. Simple septa with plugged pores were occasionally seen. Although the existence of two kinds of hyphae, one with abundant food materials and the other type with a degenerated aspect, both hyphae showed a similar thickness in their cell walls approximately 0.2 , and the diameter of these hyphae was 1.5–3 .     

On some cestodes parasitizing freshwater fish in Italy.

The paper presents a systematic survey of some cestodes parasitizing freshwater fish in Italy. The following eight species were recorded: Monobothrium wageneri, Cyathocephalus truncatus, Triaenophorus nodulosus (plerocercoids and adults), Bothriocephalus acheilognathi, B. claviceps, Ligula intestinalis (plerocercoids), Schistocephalus sp. (plerocercoids) and Proteocephalus percae from Perca fluviatilis which is reported from freshwater fish in Italy for the first time. All the tapeworms recovered are described and figured.     

Characteristics of the effect of cestodes parasitizing the fish intestine on the activity of the host proteinases

The activity and spectrum of proteinases in the intestines of host fishes change upon infestation with cestodes. Serine proteinases are found to make a greater contribution to the total proteolytic activity. The reduction of proteolytic activity is associated with adsorption of the enzymes of the host on the surface of cestodes, and the increase in the activity is caused by the injury of the intestinal mucosa by the attachment apparatuses of cestodes. The inhibition of proteainase activity indicates the possible participation of microbiota enzymes in protein hydrolyses.     

The dynamics of carbohydrase desorption from the surface of the intestines in fish and in their parasitizing cestodes

Data are obtained on the fixation strength of carbohydrases on the structures of digestive-absorptive surfaces of cestodes and intestines of their fish hosts. A dependence of the parasite's digestive activity on the activity of the host's enzymes has been established. General regularities of desorption dynamics of carbohydrases in studied animals and their specific peculiarities are noted.     

Luminous bacteria and light emitting fish: ultrastructure of the symbiosis

The luminescent fish Monocentris japonicus uses symbiotic luminous bacteria as a source of light. These bacteria live in light organs, complex tissue compartments, consisting of richly vascularized tubules or canals (in which the bacteria are cultured) lined with mitochondria-rich epithelial cells. The structure is consistent with a proposed model of symbiosis in which nutrients and oxygen are supplied by the vertebrate blood (vascular system). The nutrients, oxidized by the bacteria for growth and light production, are returned in part to the fish as pyruvate, which by reacting with mitochondrial oxygen regulates the light organ oxygen tensions. The luminous bacteria provide steady light that is modulated by passage through the melanocyte-containing dermis of the fish. Both the fish and the bacteria are highly adapted for their symbiotic coexistence.     

Further observations on Cryptobia dahli (Mastigophorea: Kinetoplastida) parasitizing marine fish.

Studies were conducted primarily to ascertain the mode of transmission of Cryptobia dahli parasitizing the digestive tract of lumpfish (Cyclopterus lumpus). Another flagellate, morphologically similar to C. dahli, was also observed in the gut of a deepsea fish (Macrourus berglax). Several invertebrates, which are food for lumpfish, were examined for flagellates, but were neither infected nor showed evidence of cystic stages. Parasites were more abundant in the stomach, especially at about pH 5, than in other areas of the digestive tract. Transmission was achieved by pipetting the parasites into the stomach of uninfected fish, by feeding food contaminated with flagellates, and also by holding infected and uninfected fish in the same aquarium. In nature, lumpfish probably acquire parasites during winter when they aggregate and regurgitate into seawater because parasites can survive for short periods outside their host.     

Effect of temperature on the development time and life-time fecundity of Trichopria anastrephae parasitizing Drosophila suzukii

The aim of this study was to evaluate the effect of temperature (10, 15, 20, 25, 30 and 35°C), on the development time and life-time fecundity of Trichopria anastrephae Lima, 1940 (Hymenoptera: Diapriidae) parasitizing Drosophila suzukii (Matsumura, 1931) (Diptera: Drosophilidae). D. suzukii pupae that were up to 24-hr old were submitted to T. anastrephae parasitism for 24 hr. They were placed in plastic containers (50 ml) (ten pupae per container) in climatic chambers at temperatures of 10, 15, 20, 25, 30 and 35°C ± 1°C with a relative humidity of 70% ± 10% and a 12 hr photoperiod. For the adult phase, T. anastrephae couples that were up to 24 hr old were each placed in plastic cages (300 ml) and kept at the same temperatures cited above until their deaths. The higher numbers of parasitism and offspring production were obtained at temperatures between 15 and 25ºC. At the temperatures of 10 and 35ºC, there was no emergence of individuals. The lower thermal threshold (Tt) for the egg to adult period was ≈ 14.6°C for males and females with thermal constants (K) of 384.61 and 432.90, respectively. In terms of the fertility life table, T. anastrephae at 20 and 25°C presented shorter generation time (T) and higher net reproductive rates (Ro) in relation to other temperatures. The data show the ability of T. anastrephae to adapt to different thermal conditions, which is important for biological control programmes of D. suzukii.     

Stichosome ultrastructure of the fish nematode Capillaria pterophylli Heinze, 1933

The stichosome (posterior glandular esophagus) of Capillaria pterophylli Heinze, 1933 consists of large gland cells (stichocytes) and lumenal epithelium with cuticular lining. Both structures are enclosed in a reticulum of muscle cells. The stichocyte cytoplasm contains small cisternae of rough endoplasmic reticulum, Golgi complexes, one kind of electron dense secretory granules, mitochondria and a branching system of intracellular collecting ducts without filament bundles around them.     

Changes in the plastid ultrastructure duringSedum rotundifolium leaf development

The ultrastructure of plastids was investigated in succulent leaves ofSedum rotundifolium to examine their changes during development. Leaves were categorized as etiolated, immature, young, and mature, based on their developmental stage and size. Of particular interest were the features of the tubular inclusion bodies (TIBs) and starch grains. These, along with vacuole size, showed remarkable changes over time. Etioplasts of unexposed leaves had prolamellar bodies, abundant starch grains, large TIB, few plastoglobuli, and thylakoid systems. Membranes of the thylakoids were still continuous with those of the prolamellar body. The plastids were often influenced by the presence and profile of inclusion bodies and starch grains throughout the early stages. Morphology was highly variable in the etioplasts but consistently hemispherical or ovoid in mature chloroplasts. TIB was most abundant in the etiolated leaves, but disappeared completely with development. Starch grains also became significantly reduced in size. Both young and mature mesophyll cells exhibited a normal chloroplast ultra-structure and huge central vacuoles, with an extremely thin peripheral cytoplasm. Grana were extensive and comprised a large portion of the chloroplasts. Traces of peripheral reticulum were also discovered in the chloroplasts of expanded leaves. The implications of these ultrastructural changes in the tubular inclusions and starch grains are discussed with relevance to Crassulacean acid metabolism (CAM).     

Influence of light and darkness on the ultrastructure of the pineal organ in the blind cave fish,Astyanax mexicanus

Ultrastructural changes of the pineal organ were investigated in the blind cave fish, Astyanax mexicanus, kept under continous artificial light (5000 lux), in continuous darkness, and under natural light conditions. The pineal end-vesicle of the fish kept under natural photoperiod consisted of photoreceptor cells and supporting cells mixed with a few ganglion cells. The photoreceptor cells possessed well-developed outer segments with regularly arranged lamellar membranes. The supporting cells contained a number of lipid droplets and large globular cisternae filled with fine granules. In the fish kept under continuous light or in darkness, the pineal end-vesicle displayed a dilated lumen, and the outer segments of the receptors showed signs of degeneration. Furthermore, alterations of cell organelles were observed in the photoreceptor and supporting cells.     

中红侧沟茧蜂在粘虫体内的发育 及畸形细胞发生

中红侧沟茧蜂Microplitis mediator的初产卵因受雌蜂产卵器的机械挤压,在形态上有别于未产出的卵,这种机械挤压激活了蜂卵的胚胎发育。产卵后 6 h,胚带和浆膜层开始分化,20 h胚胎成形,包裹在单层细胞的浆膜层内。32～34 h,幼蜂孵化,顶部的浆膜层立即分散形成畸形细胞,尾部的浆膜层则逐渐释放细胞。1龄幼蜂具一对角质的颚,用来消灭同种竞争者。寄生后108～113 h,1龄幼蜂蜕皮进入2龄。2龄幼蜂为无头型,尾囊发达。成熟的畸形细胞(受寄生日龄6天)表面密布微绒毛,细胞内部高尔基体丰富,内质网发达,细胞核多分支。在高尔基体的两侧和细胞膜附近分布了大量的分泌小池。