Ultrastructure of the forebody and foregut tegument and eccrine gland cells of Crepidostomum metoecus (Trematoda: Digenea: Allocreadiidae)

The forebody and foregut of Crepidostomum metoecus Braun, 1900 are invested with a tegument bearing regularly arranged surface tubercles comparable with the aspidogastrean surface structures. The tegument of the ventrolateral lobes and of the prepharynx is penetrated by ducts of eccrine gland cells. The frontal and prepharyngeal gland cells, localised in the parenchyma, discharge electron-dense granules. Their ducts are lined by peripheral microtubules and fixed to the tegument plasmalemma by a septate junction. The functional roles of these glands are discussed.     

Transmission electron microscopy of intra-tegumental sensory receptors in the forebody of Crepidostomum metoecus (Digenea: Allocreadiidae)

In the adult fish trematode Crepidostomum metoecus (Braun, 1900), four types of sensory receptors were observed inside the forebody tegument and one type beneath the tegument basal lamina. Two types of sensory receptors extend through the thickness of tegument and have a free cilium inside a pit (types I and II). Two types (III and IV) are nonciliate and entirely intra-tegumental in location. Type IV receptor with large horizontal and thin vertical rootlets was described earlier in aspidogastreans only. Below the basal lamina, nerve endings in close association with muscle fibres, comparable with those in the Aspidogastrea, were detected.     

Transmission electron microscopy of presumed sensory receptors in the forebody papillae of Crepidostomum metoecus (Digenea: Allocreadiidae)

Five types of presumed ciliate sensory receptors were detected in the forebody papillae of the adult fish trematode, Crepidostomum metoecus (Braun, 1900). The cilia are short and submerged in a tegumental pit. The apical bulb part of all types of receptors observed is supported by a dense collar and connected to the tegument basal plasma membrane by a circular septate junction. In sensory receptors types I and III no rootlet is present; the bulbs of sensory receptors types III and IV contain an electron-dense formation.     

External morphological differences between Crepidostomum farionis and Crepidostomum metoecus (Trematoda: Allocreadiidae), parasites of salmonids,as revealed by SEM

Scanning electron microscopy examinations of trematode specimens belonging to Crepidostomum farionis (O.F. Muller, 1784) and C. metoecus Braun, 1900, collected from brown trout, Salmo trutta fario L., in the Czech Republic, made it possible to study their surface morphology including details not described previously. The tegument of both species bears numerous characteristic papillae around the oral sucker (in C. metoecus also around the ventral sucker) and the ventral and dorsal surfaces of the forebody, exhibiting a high degree of variability in numbers and arrangement, with tegumental bosses forming lateral fields on the forebody and minute sensory receptors with submerged cilia scattered on the surface of the dorsal part of the oral sucker. In addition to marked differences in the size, shape and position of the oral muscular lobes, both species distinctly differ in the number of genital pores: two separate pores in C. farionis and a single pore in C. metoecus.     

The ecology of Crepidostomum species (Allocreadiidae: Digenea) in the salmonoids of Lake Yli-Kitka in northeastern Finland

Crepidostomum spp. were studied from 417 whitefish (Coregonus acronius Rapp, 1854), 220 vendace (Coregonus albula L.) and 38 brown trout (Salmo trutta m. lacustris (L.)) from Lake Yli-Kitka in northeastern Finland during 1980-1983.12.7% of the whitefish were infected with Crepidostomum with a mean intensity of 4.6 worms per infected fish. The species involvedare C. farionis (Müller, 1784) and Crepidostomum wikgreni Gibson et Valtonen, 1988, which differed from C. farionis in the number and size of the eggs. Both types were encountered in the gall-bladder and intestine, but were unable to be distinguished as immature stages. 21% of the brown trout harboured C. farionis in the intestine with a mean number of 1.5 worms per infected fish. Two C. farionis specimens occurred also in the intestine of one vendace. Whitefish smaller than 150 mm did not harbour Crepidostomum specimens, but in bigger fish the prevalence and the mean intensity of infection increased to a certain limit as the fish got larger. The prevalence of Crepidostomum infection also clearly increased during the three seasons in the three size-groups studied. The seasonal pattern of Crepidostomum in whitefish of the size greater than or equal to 150 mm was variable in that the lowest values, both in the prevalence and mean intensity of infection, occurred between September and December in 1980 and between April and August in 1982. Reinvasion was found throughout the year, although the main recruitment occurred during autumn and early winter. Eggs matured between late spring and early autumn. The smallest worms occurred mainly in the gall-bladder, and most of the gravid specimens were located in the intestine. Both the variance-to-mean ratio and the low values of the parameter k of the fitted negative binomial distribution reveal the Crepidostomum specimens are overdispersed in the whitefish of Lake Yli-Kitka.     

Ultrastructure of the excretory system of Brachylaimus aequans (Trematoda: Brachylaimoidea)

The ultrastructure of the flame cell, excretory capillaries, ducts, collecting ducts, excretory bladder, and excretory pore of Brachylaimus aequans was studied 6-8 days p.i. The excretory ducts, collecting ducts and excretory bladder are provided with numerous lamellae on the luminal side. The cilia of lateral flames in the excretory ducts have a triated rootlet. The excretory pore is covered by a tegument identical with the body tegument. The syncytium of the excretory bladder is connected with the tegument of the excretory pore by means of a septate desmosome. No lipid or excretory corpuscles have been demonstrated in the excretory system.     

Ultrastructure of a new type of sensory ending in Echinostoma revolutum cercaria (Trematoda: Echinostomatidae)

Two pairs of hitherto unknown multiciliate sensory endings have been demonstrated in free-swimming cercariae of Echinostoma revolutum using transmission and scanning electron microscopy. This type of receptor consists of a bundle of 36--40 short, conically projecting cilia ensheathed by a collar formed by a circular evagination of tegument in shape of a cup. The cilia projecting from the centre of a widened nerve fibre, filled with electron-lucid vesicles, possess a well developed basal body and do not contain a ciliary rootlet. The function of this receptor is discussed.     

豆卜馍夜蛾触角感器的超微结构与分布

为了解豆卜馍夜蛾Bomolocha tristalis Lederer成虫触角感器的类型、超微结构、数量和分布,探索其化学感受机制。利用扫描电镜技术对豆卜馍夜蛾雌、雄蛾的触角感器进行观察。结果表明:在豆卜馍夜蛾触角上共观察到8种类型感器:B?hm氏鬃毛(两种亚型,BBⅠ型和BBⅡ型)、毛形感器、锥形感器、刺形感器、腔锥形感器、耳形感器、鳞形感器和栓锥形感器。其中毛形感器数量最多,其次是腔锥形,除刺形和栓锥形感器外,其他感器数量在触角鞭节从基部到端部呈现由少到多,再减少的趋势。毛形、锥形和耳形感器表皮具多孔属于嗅觉感器。雄蛾触角与雌蛾相比,鞭亚节多2～4节;毛形、刺形和鳞形感器明显长于雌蛾,耳形感器明显短于雌蛾;毛形和腔锥形感器数量均明显多于雌蛾。豆卜馍夜蛾触角感器种类丰富,数量较多,雌、雄蛾间存在性二型现象,B?hm氏鬃毛、刺形和栓锥形感器在结构和分布上存在有利其功能的特化现象。     

The life cycle of Echinostoma bolschewense (Kotova, 1939) (Trematoda: Echinostomatidae)

The life cycle of E. bolschewense, the species with 37 collar spines and closely related to E. revolutum, was experimentally studied. The following developmental stages are described: mother and daughter rediae, cercaria, metacercaria, and adult. The freshwater prosobranchiate snail Viviparus contectus was found to be the first intermediate host in nature. Under experimental conditions, the miracidia developed in V. contectus. They did not, however, penetrate into Bithynia tentaculata or into any of the pulmonate snails tested. The cercariae encysted in various Prosobranchia and Pulmonata. Adult worms were commonly obtained from hamsters (Mesocricetus auratus) and only exceptionally from chickens (Gallus gallus f. dom.). The species studied is considered to be conspecific with Cercaria bolschewensis described by Kotova (1939).     

Developmental cycle of Rubenstrema exasperatum (Rudolphi, 1819) (Trematoda: Omphalometridae).

The developmental cycle of the trematode Rubenstrema exasperatum (Rudolphi, 1819), a common parasite of insectivores of the family Soricidae, is described here for the first time. The first intermediate host in nature is the snail Planorbarius corneus. Metacercariae encysted experimentally in larvae of the mosquito Culex molestus; exceptionally, these were found encysted in daughter sporocysts. Adult specimens of R. exasperatum were found after experimental infections in the hamster Mesocricetus auratus. Daughter sporocysts, cercariae, metacercariae and adults are described in detail.     

Chaetotaxy of cercariae of Opisthioglyphe ranae (Fr?lich, 1791) (Trematoda: Plagiorchidae)

A detailed observation of the sensory apparatus of Opisthioglyphe ranae (Fr?lich, 1791) cercariae was carried out. The species was determined on the basis of an experimental study of the life cycle and morphology of sporocysts, cercariae, metacercariae, and adults. In contrast to other species of the family Plagiorchidae, no papillae were present in the positions CId1, CId2, CII0, CII3 and CII4. Papillae with markedly ventral situation on the postacetabular zone were found very rarely. Some of the cercariae possessed ventral papillae variously distributed in the preacetabular zone. A comparative analysis of the chaetotaxy revealed that the cercaria studied by us was very similar to Cercaria 4 of Richard, 1971, with the exception of the number of acetabular papillae and some groups of ventral papillae. Compared to the cercaria of O. ranae studied by Dobrovolskiy (1965). AID papillae and a part of ventral papillae were distributed differently. The chaetotaxy was identical with that of experimentally obtained cercariae of O. ranae from L. stagnalis and of cercariae of the same species obtained from Bulgaria.     

The life cycle of Paracardicoloides yamagutii Martin, 1974 (Digenea: Sanguinicolidae)

The sanguinicolids Paracardicoloides yamagutii Martin, 1974 and Plethorchis acanthus Martin, 1975 were obtained from their definitive hosts, Anguilla reinhardtii Steindachner and Mugil cephalus Linnaeus (respectively) in the tributaries of the Brisbane River, Queensland, Australia. Two putative sanguinicolid cercariae were collected from a hydrobiid gastropod, Posticobia brazieri Smith, in the same waters. The two cercariae differ markedly in size and the form of their sporocysts. Both putative cercariae develop in the digestive gland of Po. brazieri. The ITS2 rDNA region from these sanguinicolids and a Clinostomum species (utilised as an outgroup due to the close morphological similarities between the cercarial stages of the Clinostomidae and the Sanguinicolidae) were sequenced and aligned. Comparison of the ITS2 sequences showed one cercaria to be that of P. yamagutii. This is the first sanguinicolid life history determined by a molecular method. P. yamagutii is the fourth sanguinicolid known to utilise a freshwater hydrobiid gastropod as its intermediate host. ITS2 rDNA is effective in distinguishing sanguinicolids at the species level.     

草地贪夜蛾成虫触角感器的超微结构观察

草地贪夜蛾 Spodoptera frugiperda 于2018年12月入侵中国大陆,为害玉米等农作物。本研究采用扫描电子显微镜技术,对草地贪夜蛾成虫触角感器的形态结构进行了观察。结果表明:草地贪夜蛾触角呈丝状,由柄节、梗节和鞭节组成,雌雄成虫鞭节分别由63个和69个亚节组成,雌雄成虫触角被覆鳞片,共有11种感器类型,分别是:毛形感器、刺形感器、芽胞感器、鳞形感器、耳形感器、坛形感器、B?hm氏鬃毛、 锥形感器、栓锥形感器、 腔锥形感器和腔乳头状感器,多数感器又有不同的亚型。鞭节上感器类型较柄节和梗节丰富。雄蛾触角上的感器数量多于雌蛾。     

Observations on the bionomy of Allocreadium isoporum (Looss, 1894) (Trematoda: Allocreadiidae).

From October 1985 until July 1987, the bionomy of the trematode Allocreadium isoporum (Looss, 1894) was studied in the Rokytná River (the Danube basin), Czechoslovakia. While clams of the genera Sphaerium Scopoli and Pisidium Pfeiffer apparently serve as its first intermediate hosts, mayfly larvae Ephemera danica Müll. were found (prevalence 8%, intensity 1-5 metacercariae per mayfly) to be the only second intermediate host of A. isoporum in the locality. The most important definitive host is chub, Leuciscus cephalus (L.), in which the seasonal dynamics of A. isoporum occurrence and maturation was followed. The parasite exhibits here a distinct seasonal cycle of maturation which is shown mainly by quantitative changes in the ratio of young to mature worms containing eggs. The trematodes containing eggs occur almost throughout the year, but mainly in the spring and early summer (maximum in May), and after the oviposition they leave the host. New infections are acquired by chub all the year round. This seasonal periodicity is determined by ecological factors, mainly the temperature regime in the locality. A isoporum infections in chub in this locality are dependent on the body size of host fishes; the highest degree of A. isoporum infection occurs in fishes 20-25 cm long, the prevalence decreasing somewhat in larger fishes; infection is associated with changes in the food composition of chub of different size groups.     

Taxonomic status of Ascocotyle (Phagicola) rara Arruda, Muniz-Pereira et Pinto, 2002 (Digenea: Heterophyidae)

Holotype and paratype of Ascocotyle (Phagicola) rara Arruda, Muniz-Pereira et Pinto, 2002, a heterophyid trematode recently described on the basis of two worms collected by Lauro Travassos in 1921 in the intestine of Ixobrychus exilis (Gmelin) from Brazil, were studied. The morphology of the worms revealed their conspecificity with Ascocotyle (Phagicola) angeloi Travassos, 1928 found in the same host. Both the taxa have a similar length (between 600 and 900 microm) and shape of the body (long pyriform), the long intestinal caeca reaching to the ovarian level, a long posterior muscular prolongation of the oral sucker and the prepharynx, transverse uterine loops situated between the ventral sucker and testes, and the gonotyl with more than 20 digitiform pockets. Consequently, A. (P.) rara is proposed as a junior synonym of Ascocotyle (Phagicola) angeloi.     

番茄潜叶蛾成虫触角及幼虫头部感受器的超微结构

为明确番茄潜叶蛾Tuta absoluta(Meyrick)成虫触角及幼虫头部感受器的种类、分布和形态结构,采用扫描电镜法观察番茄潜叶蛾雌雄成虫触角和4龄雌雄幼虫触角及口器上的感受器种类和形状。结果显示,番茄潜叶蛾成虫触角上共有8种类型感受器,分别为B?hm氏鬃毛、毛形感受器、鳞形感受器、锥形感受器（Ⅰ型和Ⅱ型）、刺形感受器、腔锥形感受器、栓锥形感受器和耳形感受器。其中,雌成虫的Ⅰ型和Ⅱ型锥形感受器数量、刺形感受器数量、B?hm氏鬃毛长度、鳞形感受器长度及基部直径、Ⅰ型锥形感受器长度及基部直径、Ⅱ型锥形感受器长度、刺形感受器臼状窝直径、腔锥形感受器基部直径和耳形感受器基部直径均显著大于雄成虫;而雄成虫的毛形感受器数量和腔锥形感受器中心锥长度显著大于雌成虫。幼虫头部共计有6种类型感受器,主要着生在触角、下颚和下唇上,分别为毛形感受器、锥形感受器、刺形感受器、栓锥形感受器、指形感受器和感觉锥;幼虫触角、下颚和下唇的感受器类型和数量在雌雄间完全相同。而雌性幼虫触角鞭节上的锥形感受器SB5和下颚须上的锥形感受器SB2的长度显著大于雄性幼虫;雄性幼虫下颚茎节上的刺形感受器Sch1和下颚须上的锥形...     

Toxicity of cadmium and zinc to the cercarial activity of Diplostomum spathaceum (Trematoda: Diplostomidae)

The toxicity of cadmium and zinc at concentrations ranging from 0.1 to 100 microg/l was investigated against the activity of Diplostomum spathaceum (Rudolphi, 1819) cercariae. Over a 24 h exposure period a significant reduction in cercarial activity occurred in solutions of cadmium, zinc, and a mixture of cadmium and zinc at all concentrations. Reduced cercarial activity also occurred in all toxicant solutions compared with controls after only 6 h exposure indicating that cercariae were vulnerable during the period of maximum cercarial infectivity (0-5 h). The mechanisms of metal toxicity and their importance to parasite transmission are discussed.     

绿翅绢野螟幼虫头部感器超微结构观察

为探讨和分析绿翅绢野螟Diaphania angustalis(Snellen)幼虫头部感器的功能及其作用机制,通过扫描电镜对其触角和口器上的感器进行了观察。结果表明:绿翅绢野螟幼虫头式为下口式,头部具有触角、上唇、上颚、下颚和下唇。触角短小,位于幼虫头部侧下方,分3节,其梗节和鞭节分布有4种类型的感器,即毛形感器、短毛感器、锥形感器和栓锥形感器。口器分为上唇、上颚、下颚和下唇4个部分,共具有6种类型感器,分别为毛形感器、刺形感器、指形感器、锥形感器、栓锥形感器和小感觉锥。刺形感器数量较多,分布范围广,口器上各部位均有分布;毛形感器仅分布于上唇;指形感器仅分布于内唇;锥形感器仅分布于下颚;栓锥形感器在下颚和下唇皆有分布;指形感器为内唇所特有。