Alloglossidium demshini sp. nov. (Digenea: Macroderoididae) from leeches in Minnesota

Alloglossidium demshini sp. nov. is described based on specimens from leeches Haemopis grandis collected in northwestern Minnesota. The new species is morphologically closest to Alloglossidium schmidti. The two species can be readily differentiated based on several morphological characters. The cirrus sac in A. schmidti is almost entirely situated anterior to the ventral sucker while in A. demshini sp. nov. it is situated dorsal to the ventral sucker and its proximal end almost reaches the posterior end of ventral sucker or extends posterior to it. The new species has a prepharynx that is substantially longer than the esophagus while in A. schmidti the situation is the opposite. The two species also differ in the position of the ovary and the position of the testes and vitelline fields in relation to the ends of the ceca. Hirudineatrema oschmarini described from leeches in Eastern Palaearctic and Alloglossidium richardsoni described in North America demonstrate great morphological similarity. Nevertheless, Hirudineatrema cannot be synonymized with Alloglossidium at this point because of several peculiar morphological features of H. oschmarini such as a V-shaped excretory bladder and the apparent presence of a true seminal receptacle in the latter species. These features need to be re-evaluated before any taxonomic decision can be made.

Thryssatrema hanumantharaoi n. gen., n. sp. (Digenea: Fellodistomidae) from the longjaw thryssa, Thryssa setirostris (Clupeiformes: Engraulidae), of the Visakhapatnam coast, Bay of Bengal

Thryssatrema hanumantharaoi n. sp., representing a new genus of fellodistomid digenean, is described from a clupeoidfish, the longjaw thryssa, Thryssa setirostris, collected from the coast of Visakhapatnam, Bay of Bengal. The new genusis characterized by possessing a combination of the following features: An elongate body; poorly developed suckers; twooval, symmetrical testes situated in the posterior half of the hindbody; a cirrus sac that extends posterior to the ventralsucker; a bipartite seminal vesicle; a median genital pore situated immediately anterior to the ventral sucker; a lobed,pretesticular ovary; uterine coils that fill the entire hindbody; small eggs, elliptical vitelline follicles forming two zonesanterolateral to the ovary; and a V-shaped excretory bladder. The new genus shows affinities to Prudhoeus and Elopsiumbut differs from the former in the body shape (elliptical versus oval), and by having poorly developed suckers, moreposteriorly located gonads and elliptical vitelline follicles arranged in two lateral zones in front of ovary. It differs fromElopsium mainly in the body shape (elliptical versus rounded) and distribution of vitelline follicles and in the V-shaped excretory bladder.

Pathways for the influx of molecules into cercariae of Schistosoma mansoni during skin penetration

SUMMARYIt has been observed that fluorescent membrane-impermeant molecules can enter the cercariae as they penetrate mouse skin. The hypothesis to be tested was that such molecules, which included Lucifer Yellow and a variety of fluorescent dextrans, entered the parasite through the nephridiopore and excretory tubules as well as through the surface membrane. FITC-labelled poly-L-lysine (molecular weight 10 kDa), added at 4°C during syringe transformation, was found to enter the nephridiopore and labelled the excretory bladder and sometimes the excretory tubules. This finding indicates that macromolecules (10 kDa) can enter the nephridiopore. It was found that linoleic acid (a normal constituent of skin) greatly stimulated uptake of Lucifer Yellow and dextrans into the excretory/subtegumental region of 2-h-old schistosomula. This correlated with an increased uptake of membrane-impermeant propidium iodide at 37°C. Since increased uptake of propidium iodide occurs when membranes become permeable, the surface membrane could also be a pathway of transport of the membrane-impermeant molecules into the schistosomulum.

Metacercariae of Galactosomum lacteum (Jägerskiöld, 1896) Looss, 1899 (Heterophyidae) from marine teleosts in the Gulf of Cagliari (southern Sardinia, Italy)

Galactosomum lacteum (Jägerskiöld, 1896) Looss, 1899 metacercariae, encysted on the optic nerve, on the brain and/or on the muscle and the connective of the pharynx and oesophagus, were found in Spicara maena L., S. flexuosa Rafinesque, 1810, S. smaris L. (Centracanthidae), Gobius cruentatus Gmelin, 1789 (Gobiidae), Symphodus tinca L., S. mediterraneus L. (Labridae), Serranus cabrilla L. (Serranidae), Diplodus sargus L. and D. annularis L. (Sparidae) caught in the Gulf of Cagliari (southern Sardinia, Italy). Excysted specimens were identified by some distinctive morphological features: more or less expanded forebody, depending on whether the specimens were living or fixed; tubular excretory bladder extending to the posterior border of the ovary; two-chambered seminal vesicle; asymmetrical and parenchymatous ventral sucker with lines of spines within its cavity; and unarmed gonotyle. Comparison has been made with the congeneric species metacercaria, G. timondavidi Pearson & Prévot, 1971, also registered in the Mediterranean Sea.

The life cycle of Hapladena gymnocephali sp. nov. (Digenea: Haploporidae) from the bald glassy perchlet Ambassis gymnocephalus in Kerala, India

The life cycle of a new haploporid digenean, Hapladena gymnocephali sp. nov., infecting the bald glassy perchlet Ambassis gymnocephalus from the Chaliyar and Kadalundi rivers of Kozhikode district, Kerala, India, is elucidated. The new species is described in detail, its systematic position discussed and compared with related species, H. acanthuri Siddiqi & Cable, 1960 and H. spinosa Manter & Pritchard, 1961. Hapladena gymnocephali is distinctly different from the two latter species in the shape and size of body, nature of testis, extent of vitelline field and excretory bladder. Hapladena gymnocephali has a typical haploporid, two-host life cycle: the gymnocephalous, bi-ocellate, distome cercariae released by the snail Gabbia travancorica are ingested by the fish and develop directly into adults without undergoing a metacercarial stage of development. This is the first report of the genus Hapladena from India, and also the first report of the life cycle of the genus.

An ultrastructural study of the cercarial excretory system in Bucephaloides gracilescens and Prosorhynchus squamatus

The ultrastructure of the flame cells, capillaries, collecting tubes, excretory bladder, excretory atrium, caudal vesicle, lateral caudal ducts and excretory pores of cercariae of Bucephaloides gracilescens (Rudolphi, 1819) Hopkins, 1954 and Prosorhynchus squamatus Odhner, 1905 (Digenea: Bucephalidae) is described. Both species are essentially similar except for some details. The terminal parts of the protonephridia have all the structural features that are typical of trematodes. The collecting tubes in the cercarial body are composed of cells that are wrapped around the lumen. The main collecting tubes are joined to the excretory bladder syncytium by septate junctions. Features of P. squamatus excretory bladder epithelium indicate that it is involved in secretory activity, but this is not the case in B. gracilescens. In both species the luminal surface of the excretory bladder epithelium is increased by lamellae, and the basal plasma membrane forms invaginations. In the bladder syncytium of P. squamatus both apical lamellae and basal invaginations are more developed and mitochondria are also more numerous. The excretory atrium is lined by a syncytium with nucleated cytons located in the surrounding parenchyma. The atrium lining is not continuous with the body tegument and possesses specific secretory inclusions and a thick glycocalyx. Septate junctions connect the atrium syncytium to the excretory bladder epithelium at its anterior end and to the syncytial excretory epithelium lining the caudal vesicle and the lateral caudal ducts at its posterior. In the excretory pores the caudal duct syncytium is joined to the tegument by septate desmosomes.

Excretion of fluorescent substrates of mammalian multidrug resistance-associated protein (MRP) in theSchistosoma mansoniexcretory system

The protonephridium of platyhelminths includingSchistosoma mansoniplays a pivotal role in their survival by excretion of metabolic wastes as well as xenobiotics, and can be revealed in the living adult parasite by certain fluorescent compounds which are concentrated in excretory tubules and collecting ducts. To determine the presence of the multidrug resistance-associated protein (MRP) as a possible transporter in protonephridial epithelium, adult schistosomes were exposed to a fluorescent Ca2+indicator, fluo-3 acetyloxymethyl ester, which is a potential substrate of mammalian MRP. Specific fluorescence related to fluo-3/Ca2+chelate delineated the whole length of the protonephridial system. Simultaneously, a fluorescent substance was accumulated in the posterior part of collecting ducts and the excretory bladder. Similarly, when other fluorogenic substrates for mammalian MRP such as monoclorobimane, fluorescein diacetate, and 5(6)-carboxyfluorescein diacetate were applied to adult schistosomes, these fluorescent markers were observed in the excretory tubules through to the excretory bladder. The excretory system of mechanically-transformed schistosomula was not labelled with any of these 4 fluorescent markers. These findings suggest that the protonephridial epithelium of adult schistosomes, but not schistosomula, might express the homologue of the mammalian MRP transporting organic anionic conjugates with glutathione, glucuronate or sulphate as well as unconjugated amphiphilic organic anions.

The structure and formation of metacercarial cysts in the trematode family Microphallidae Travassos 1920

This study deals with the formation of the metacercarial cysts of four microphallid trematodes, Maritrema subdolum, M. arenaria, Levinseniella brachysoma and Microphallus claviformis. The first observable cyst was present around Maritrema arenaria 18 h p.i. (post-infection). The other species had not developed a cyst by day 8 p.i. but their cysts were apparent by day 16 p.i. These were bi-layered and that of M. subdolum was thicker than those of L. brachysoma and Microphallus claviformis of the same age. The structure of older cysts varied substantially between the four species. Microphallus claviformis and Maritrema subdolum cysts were fully formed at 30 days p.i. Like those of M. arenaria they were bi-layered, the outer layer (up to 3 μm thick) being electron-dense and the inner one (up to 7 μm thick) being less electron-dense. The cysts of fully formed L. brachysoma metacercariae were much more complex, composed of four layers, one of which was divisible into three sub-layers. It was concluded that the outer cyst layer was the product of secretory granules which were previously identified in cercarial tegument. The inner, thicker layer was derived from several sources. These included small tegument vesicles produced over the entire surface of the metacercariae, larger fragments of tegument released from the anterio-ventral region and material liberated from the metacercarial excretory bladder. This heterogeneous material accumulated in the cyst lumen for some time before becoming polymerized to form the thick inner layer or layers of the metacercarial cysts.