The development of Myxobolus dispar Thélohan, 1895, a myxosporean parasite of the gills of common carp (Cyprinus carpio L.) was studied in experimentally infected oligochaetes Tubifex tubifex Muller. After infection of uninfected tubificids with mature spores of M. dispar, development of actinosporean stages was first observed light microscopically 21 days after initial exposure. In histological sections, early pansporocysts were located in the gut epithelium of experimental oligochaetes, while advanced stages occupied mostly the outer layers of the gut and the coelozoic space. Mature pansporocysts, each containing 8 raabeia spores, appeared 199 days after initial exposure. Following damage of the intestinal wall and rupture of the pansporocysts, free actinosporean stages were found in the gut lumen of the oligochaetes. Actinospores of hi. dispar emerged from the worms after 217 days of intra-oligochaete development. They were floating in the water and showed a unique raabeia form. Each raabeia spore had three pyriform polar capsules and a cylindrical-shaped sporoplasm with approximately 32 secondary cells. The spore body joined the three caudal projections without a style. Caudal projections were bifurcated at the end and the two main branches had further small bifurcations. The total length of the raabeia spore was approximately 158 pm. The prevalence of infection in 240 experimentally infected Tubifex specimens was 99.2%. No infection was found in the control oligochaetes.
The development of the nematode Procamallanus saccobranchi Karve, 1952, a parasite in the stomach of the fish Heteropneustes fossilis (Bloch), was studied in Mesocyclops crassus (Fischer) and Mesocyclops leuckarti (Claus). After being ingested by the copepods the nematode first-stage larvae penetrated into the haemocoel of the intermediate host; there they moulted twice (on days 3 and 5 p.i. at 28-30°C) attaining the third, infective stage. The definitive host H. fossilis acquired infection by feeding on copepods harbouring infcclivc-stage larvae; in the stomach of this definitive host, the larvae were observed to undergo two more moults. The third moult occurred on day 13 p.i. and the fourth moult on day 38 p.i. and day 66 p.i. in “male” and “female” larvae, respectively. The larval stages, including the moulting forms are described and illustrated.
The development of the swimbladder nematode Anguillicola crassus Kuwahara, Niimi et Itagaki, 1974 in the definitive host (eels) was studied under experimental conditions. Small eels, Anguilla anguilla (L.) with body length 8-16 cm were infected by feeding them intermediate host copepods (Cyclops strenuus Fischer) harbouring third-stage larvae of this parasite. These experiments showed that, at 20-22° C, the development from the third-to the fourth-stage larvae lasted approximately three weeks, but some retarding third-stage larvae occurred in the wall of the host’s swimbladder or hyperparasitizing in the cuticle of adult nematodes as late as three months p.i. Young adults developed in the lumen of the swimbladder within approximately one month and noneinbryonated eggs first appeared in females 6-7 weeks p.i. The prepatent period was about three months and the patent period could be estimated to last no more than a month. Females degenerated soon after oviposition. The experiments confirmed that the size of mature A. crassus depends on the body size of its definitive host (eel).
Larval development of the nematode Onchocamallanus bagarii (Karve et Naik, 1951), recovered from the intestine of the fish Bagarius bagarius (Hamilton) was studied under laboratory conditions. The cyclopoid copepods Mesocyclops leuckarti (Claus) and M. crassus (Fischer) were infected with first-stage larvae from female uteri and maintained at temperatures 29-30°C. After being swallowed by the copepods, first-stage larvae burrow through the intestinal wall and reach the haemocoel of the copepods and there they grow and moult twice to attain the third and infective-stage. First-stage larvae become ensheathed after 65 hours of infection and second-stage larvae first appeared on day 3 post infection (p.i.). The second moult occurred on day 5 p.i. The larval stages occurring during development are described.
Unfed nymphs of Ixodes ricinus (L.) can be divided into two morphological groups according to the length of idioso-ma, scutum, hypostome and palpal segment III, and the number of dorsal alloscutal setae. Specimens of greater body dimensions and more numerous dorsal alloscutal setae moulted predominantly into females. The frequency of different nymphal length categories in field-collected ticks followed a normal distribution. The length of unfed nymphs correlates well with the length (r = 0.7248 ± 0.0711, P < 0.001) and weight (r = 0.6519 ± 0.0782, P < 0.001) of engorged nymphs, however, it varies in ticks of different origin. In field-collected ticks, freshly engorged female nymphs were 2.30-2.94 mm long, male nymphs 2.14-2.46 mm long. Feeding period (P < 0.05) and premoulting period (P < 0,001 ) were significantly longer in female nymphs both in field-collected and laboratory-derived I. ricinus. The engorgement weight was found to be the best criterion for differentiation of male and female nymphs of ixodid ticks. In field-collected nymphs engorged on BALB/c mice, 98.6 % of females moulted from nymphs weighting more than 3.60 mg, while in laboratory-derived ticks, 98.4 % of females emerged from nymphs of 3.42 mg body mass or more.
The development of the nematode Syncuaria squamata (Linstow, 1883), a gizzard parasite of cormorants, was experimentally studied in the ostracod Notodromas monacha. After the eggs of this nematode have been swallowed by the ostracod, the toothed first-stage larvae of the parasite are released and penetrate through the intestinal wall into the haemocoel of the crustacean. Before attaining the infective third stage, the larvae moult twice in the body of the intermediate host (9-11 and 13-15 days after infection at water temperatures of 20-22° C). The fishes Alhumaides hipunctatus, Noemacheilus barbatulus, Oncor-hynchus mykiss and Poecilia reticulata were for the first time recorded as suitable experimental paratenic hosts of S. squamata third-stage larvae in which a slight growth of larvae may occur. The first recorded natural paratenic host of this nematode was tench, Tinca tinea, originating from a South-Bohemian pond where cormorants occur. Paratenic hosts are apparently the main source of S. squamata infection for cormorants.
The developmental stages and life cycle of the nematode Camallanus anabantis Pcarse, 1933 an intestinal parasite of Anabas testudineus (Bloch) arc described. The copepod Mesocyclops leuckarti (Claus) was used as experimental intermediate host. After being ingested by the copepods the nematode first-stage larvae enter its haemocoel, where they moult twice, 4 d.p.i. and 11 d.p.i., at 21-26°C, respectively to become the infective third-stage larvae. The definitive fish hosts become infected when feeding on copcpods harbouring infective larvae. In the fish host’s intestine the larvae undergo two more moults, the third on day 15 p.i. The fourth moult of “male” larvae occurred on day 68 p.i. and that of “female” larvae on day 86 pi. at water temperatures 24-36°C- A female with eggs and few larvae in the uteri was first observed on day 187 p.i.
An examination of a sample of European eels, Anguilla anguilla (L.), collected from Lake Bracciano near Rome in 1993, the only known European locality with the occurrence of the introduced swimbladder nematode Anguillicola novaezelandiae Moravec et Taraschewski, 1988, revealed for the first time the presence of two Anguillicola species, A. novaezelandiae and A. crassus. In view of the investigations carried out by current authors in Bracciano Lake in the years 1982-1992, it is apparent that the latter species has been introduced into the lake quite recently, where it quickly became a dominant species. The development of A. novaezelandiae was experimentally studied in the copepod intermediate host, Cyclops strenuus, for the first time. The copepods were infected with nematode second-stage larvae at 21-22°C; fully developed infective third-stage larvae were obtained 13 days p.i. The general morphology of individual larval stages of A. novaezelandiae was similar to that of larvae of the related species Λ. crassus.
Three species of planktonie crustaceans, Cyclops strenuus and Macrocyclops alhidus (Copcpoda) and Notodromas monacha (Ostracoda), were experimentally infected with the eggs and second-stage larvae of the swimbladder nematode Anguillicola crassus originating from eels from Neusiedler Lake in Austria. At 20-22°C, third-stage larvae of the parasite developed in all these invertebrate hosts within 16-20 days p.i. Ostracods harbouring the nematode third-stage larvae (33 days p.i.) were fed to small eels (Anguilla anguilla), while infected copepods (20 days p.i.) to seven other fish species. By these experiments, the larvae from ostracods proved to be infective for the definitive host and the ostracod was thus confirmed as a true intermediate host of Anguillicola crassus. Notodromas monacha represents a new experimental intermediate host of A. crassus and the second known invertebrate other than a copepod in which the larval development of this nematode up to the infective stage takes place. Five species of fish, cyprinids Tinca tinea, Alhumus alburnus, Gobio gobio and Albumoides bipunctatus (the latter representing a new host record), and guppy, Poecilia reticulata, were found to serve as experimental paratenic hosts for A. crassus, in which the live nematode infective larvae were recorded 49 days p.i.
The development of the nematode Anguillicola crassus, a swimbladder parasite of eels, was experimentally studied in copepod intermediate hosts Cyclops strenuus and Acanthocyclops vernalis. The copepods, kept at a laboratory temperature of 20-22 °C, were infected with nematode second-stage larvae; the second moult of larvae (the only one in the intermediate host) was observed to start 10 days p,i„ but third-stage larvae liberated from their cuticular sheath were first observed 20 days p.i. These proved to be infective for experimental eels. Free second-stage larvae as well as larvae from copepods were described. The morphology of A. crassus larvae and the mode of their development in the intermediate host were compared with those of other dracunculoid nematodes. From this point of view, Anguillicola members appear to represent an ancient group of dracunculoid nematodes.