Body Tegument Research Articles

Anthelmintic efficacy of Phlogacanthus thyrsiflorus leaf extract on juvenile and adult worms of Hymenolepis diminuta (Cestoda).

The leaves of Phlogacanthus thyrsiflorus are used as an anthelmintic remedy by the tribal communities of upper Assam in India. The present study was carried out to validate the anthelmintic credentials of this plant. Mature and larval Hymenolepis diminuta worms were exposed to varying concentration of methanolic leaf extract of plant and parasites were observed for paralysis and mortality. At the end of the experiment, worms were collected and processed for scanning electron microscopy (SEM) study to observe the effect of extract on tegument of parasite. The in vivo study was carried out in H. diminuta-rat model with 200, 400 and 800mg/kg concentrations of extract. The in vivo anthelmintic efficacy was assessed by reductions in egg per gram (EPG) and worm counts after necropsy of animals. In vitro studies revealed the earliest mortality of larval worms in 1.05 ± 0.04h by 30mg/ml concentration and of adult worms in 2.05 ± 0.08h. SEM study revealed extensive damage to the suckers, body tegument and microtriches of worms treated with 30mg/ml concentration of extract. In in-vivo studies, 800mg/kg dose of extract showed highest efficacy, with 59% and 54.25% reduction in EPG counts and worm count against juvenile worms, and 63.16% and 66.75% reduction in EPG counts and worm counts, respectively against adult worms. Although the effects were comparatively less than the reference drug, nevertheless this study reveals that P. thyrsiflorus possess anthelmintic efficacy and justify its use in traditional medicine against intestinal-worm infections.

Taxonomic study of Mesomeloe coelatus (Reiche amp; Saulcy, 1857) (Coleoptera: Meloidae: Meloini), with the description of an overlooked new species.

A new species of the genus Mesomeloe (Meloidae) is described from Qatar on the north-eastern coast of the Arabian Peninsula. Mesomeloe ottomerkli sp. nov., which is currently only known from the type locality, was previously identified as Meloe (Mesomeloe) coelatus. Both the morphological and molecular variability of M. coelatus across its wide distribution range are studied to determine the level of congruence between the morphological and genetic differentiation of M. coelatus and the new species. Mesomeloe ottomerkli is distinguishable from all other congeneric species in various traits: it presents a body tegument and appendages that are black in colour and shiny in appearance; an elytral surface absent of impressed longitudinal shallow ridges; a pronotal surface absent of depressed areas and longitudinal midline; and a pronotal base that is slightly arcuate. In addition, males of M. ottomerkli have antennae that gradually widen towards the apex; protarsomeres with a brush patch of yellowish setae on the ventral surface of the first two segments; genitalia in which the gonostyli, in lateral view, become slenderer towards the apex and an aedeagus that is relatively wide and rounded in the distal portion. The distribution records of M. coelatus are also updated and summarized.

Ultrastructural observations on the oncomiracidium epidermis and adult tegument of Discocotyle sagittata, a monogenean gill parasite of salmonids

During their different life stages, parasites undergo remarkable morphological, physiological, and behavioral “metamorphoses” to meet the needs of their changing habitats. This is even true for ectoparasites, such as the monogeneans, which typically have a free-swimming larval stage (oncomiracidium) that seeks out and attaches to the external surfaces of fish where they mature. Before any obvious changes occur, there are ultrastructural differences in the oncomiracidium’s outer surface that prepare it for a parasitic existence. The present findings suggest a distinct variation in timing of the switch from oncomiracidia epidermis to the syncytial structure of the adult tegument and so, to date, there are three such categories within the Monogenea: (1) Nuclei of both ciliated cells and interciliary cytoplasm are shed from the surface layer and the epidermis becomes a syncytial layer during the later stages of embryogenesis; (2) nuclei of both ciliated cells and interciliary syncytium remain distinct and the switch occurs later after the oncomiracidia hatch (as in the present study); and (3) the nuclei remain distinct in the ciliated epidermis but those of the interciliary epidermis are lost during embryonic development. Here we describe how the epidermis of the oncomiracidium of Discocotyle sagittata is differentiated into two regions, a ciliated cell layer and an interciliary, syncytial cytoplasm, both of which are nucleated. The interciliary syncytium extends in-between and underneath the ciliated cells and sometimes covers part of their apical surfaces, possibly the start of their shedding process. The presence of membranous whorls and pyknotic nuclei over the surface are indicative of membrane turnover suggesting that the switch in epidermis morphology is already initiated at this stage. The body tegument and associated putative sensory receptors of subadult and adult D. sagittata are similar to those in other monogeneans.

An in vitro confirmation of the ethonopharmacological use of Senna plants as anthelmintic against rumen fluke Paramphistomum gracile

BackgroundParamphistomosis is a pathogenic disease of domesticated ruminants, causing great economic loss in dairy industry and meat production. It is considered as a neglected tropical disease with highest prevalence throughout tropical and subtropical regions, particularly in Africa, Asia, Europe, and Australia. There are few trematocidal drugs available in the market. Most are resistant and have elevated side effects. Therefore, alternative trematocidal drugs need to discover. This study was conducted to evaluate three plants leaf extracts (from Senna alata, S. alexandrina, and S. occidentalis) as effective remedies against gastrointestinal trematode parasite (Paramphistomum gracile) of ruminants. Live adult parasites were collected in 0.1 M phosphate-buffered saline (PBS) from fresh autopsied goat’s rumen. Parasites were incubated in leaf extracts of S. alata, S. alexandrina and, S. occidentalis individually and in combination (1:1) ratio at 37 ± 1°C. Treatment media contain extracts at different concentrations (10, 20 and 40 mg/mL) in 10 mL of 0.1 M PBS with 1% dimethylsulphoxide (DMSO). Parasites in control group were incubated in PBS without extract. The efficacy of three Senna extracts was evaluated on the basis of dose-dependent motility and mortality of the trematode. Immediately after paralysis, all treated parasites were collected for histology, SEM and biochemical study.ResultsDose-dependent efficacy was observed in terms of motility and time of mortality in all treated parasites after exposure in various concentrations of the Senna plant extracts. S. occidentalis and S. alexandrina showed better efficacy in combination than comparing with individual treatment groups. Histological study and scanning electron microscopic observations revealed conspicuous deformity of surface architecture in all treated parasites. Scanning electron micrographs also revealed shrinkage, vacuolization, infoldings and blebbings on the body surface of treated worms. Activities of tegumental enzymes were inhibited in all treatment groups compared to control.ConclusionThe overall findings from this study revealed that all three Senna leaf extracts individually and in combination showed potential antitrematocidal activity against Paramphistomum gracile by damaging body tegument and neural propagation. Thus, this study confirmed that all three Senna extracts can be considered as a potential drug-like candidate in indigenous system of traditional medicine against trematode infections in livestock.Graphical abstract

Ultrastructure of the anterior adhesive apparatus of the gill parasite Macrogyrodactylus clarii and skin parasite M. congolensis (Monogenea; Gyrodactylidae) from the catfish Clarias gariepinus

Transmission electron microscopy (TEM) was used for the first time to study the anterior adhesive apparatus of the monogeneans Macrogyrodactylus clarii Gussev, 1961 and M. congolensis (Prudhoe, 1957) Yamaguti, 1963 inhabiting gills and skin respectively of the same catfish Clarias gariepinus. Despite the different microhabitats occupied by these parasites, the present study revealed that they have a similar anterior adhesive system. In both parasites, the anterior adhesive apparatus consists of three types of gland cells: G1 cells that produce rod-shaped bodies (S1), G2 cells manufacture irregularly shaped bodies (S2) and G3 cells form mucoid-like secretions (S3). In the cytoplasm of G1 cells, a single layer of microtubules encloses each developing rod-shaped body. A unique feature of S1 secretory bodies is that some fully developed S1 bodies are attached to each other, forming large condensed globules in the cytoplasm of G1 gland cells and terminal portion of the G1 ducts, but none were detected in the adhesive sacs outside the ducts. In the adhesive sacs, G1 ducts open with multiple apertures whereas each of the G2 and G3 ducts have a single opening. The adhesive sacs are lined with two types of tegument (st1 and st2). A third tegument type (st3) connects the st2 tegument with the general body tegument. Only st1 has microvilli. Each adhesive sac is provided with a spike-like sensillum and single uniciliated sense organ. The possible functions of microvilli in increasing the surface area and assistance in spreading and mixing of the adhesive secretion, and the role of sense organs associated with the adhesive sacs are discussed.

New locality record of Monaxinoides austrosinensis (Mazocraeidea, Monaxinoididae) of finlet crevalle, Atule mate (Perciformes: Carangidae) from the Gulf of Thailand

Out of 203 Atule mate fish specimens examined, only 23 had parasitic monogeneans, Monaxinoides austrosinensis from the Gulf of Thailand. The prevalence and intensity of infection were 12.81% and 1.27%, respectively. Morphologically, the leaf-like body of M. austrosinensis was 5.88–8.07 mm long and 1.84–3.34 mm wide with a fan–shaped opisthohaptor at the posterior end. Numerous pores on the body tegument were observed using scanning electron microscopy. The muscular structure around the vaginal pore presented a number of sensory papillae. The opisthohaptor was one row of clamps which appeared similar in size. The presence of M. austrosinensis in this study is a new locality record in Thailand and is the first description based on scanning electron microscopy.

Dactylogyrus olfactorius n. sp. (Monogenea, Dactylogyridae) from the olfactory chamber of the fathead minnow, Pimephales promelas Rafinesque (Cyprinidae).

Dactylogyrus olfactorius n. sp. (Monogenea) is described from the olfactory chamber of the fathead minnow Pimephales promelas Rafinesque in Alberta, Canada. The new species resembles Dactylogyrus bychowskyi Mizelle, 1937, D. bifurcatus Mizelle, 1937 and D. simplexus Mizelle, 1937, all parasites of Pimephales spp. in North America, in overall size and shape of the anchors and hooks, and in having a male copulatory complex with a tapered tubular penis and bifurcate accessory piece. Diagnostically, D. olfactorius n. sp. has relatively small anchors, hooks of anchor length, and a thin, long dorsal bar and no apparent ventral bar nor 4A hooks. Scanning electron microscopy revealed the body tegument of D. olfactorius n. sp. to be microvillous and in shallow annular folds, while that of D. bifurcatus, occurring on host gills of the same fish, was avillous and in gill-like folds dorsally and ventrally. Partial 28S rDNA sequences revealed significant differences between the two species, supporting establishment of D. olfactorius n. sp. and dispelling the possibility of ecophenotypic effects of site of attachment on morphology.

Senna alexandrina Mill. induced ultrastructural changes on Hymenolepis diminuta.

Senna alexandrina Mill. has been used for antimicrobial activity. In the present study, the crude ethanolic extract of the plant and a synthetic compound Sennoside were tested in vitro on Hymenolepis diminuta to evaluate its potential anthelmintic efficacy through ultrastructural changes. Worms were maintained between rat model and beetle and the test parasites were exposed to different concentrations of crude ethanolic leaf extracts of S. alexandrina. Praziquantel was used as a reference drug. Dose dependent efficacy was observed in terms of motility and time of mortality in all treated parasites. Ultrastructural micrography revealed irrevocable destruction all over the body tegument accompanied with sloughing of microtriches and swellings of the basal lamina. Vacuolization of the syncytium along with sparsely cytoplasmic cytons and depletion of parenchymatous layer were observed accompanied by deformities in the cell organelles. Extensive deformities in the tegument indicates that the plant extract alter membrane permeability of the parasite leading to paralysis and subsequent death. Thus, S. alexandrina can be regarded as a potential anthelmintic agent.

Surface ultrastructural characteristics of Dictyocotyle coeliaca Nybelin, 1941 (Monopisthocotylea: Monocotylidae), an endoparasitic monogenean of rays.

Scanning and transmission electron microscopical observations were made of the surface topography of Dictyocotyle coeliaca (Nybelin, 1941) (Monopisthocotylea: Monocotylidae), a unique endoparasitic monogenean from the body cavity of the ray Amblyraja radiata (Elasmobranchii: Rajidae). Scanning investigation show the presence on the ventral side of the anterior body of smooth areas with pit-like depressions and shallow ridges, whereas the tegument of the middle and posterior regions of the body is extensively folded, and on the dorsal surface the tegument is smooth but interrupted by deep depressions. Transmission observation revealed the presence of invaginations of varying irregularity and depth, which form the various depressions of the tegumental surface. Non-ciliated, dome-shaped papillae occur singly or in groups and are common around the mouth and both the genital and vaginal pores, but exhibit no particular orientation. The haptor is much reduced, compared with that of ectoparasitic monocotylids, and is covered ventrally with an irregular array of 40-70 shallow loculi. Internal differences occur in the thickness of the syncytial tegumentary layer of the haptoral loculi and septa and also in the number of cytoplasmic inclusions. The locular surface has distinct ultrastructural characteristics, the most obvious of which are a honeycomb arrangement of small pockets measuring 0.6 × 0.75 to 1.0 × 1.7 μm in diameter, a terminal web beneath the surface plasma membrane and large outgrowths on the surface of the loculi filled with lysosome-like bodies. The surface specializations of the body and haptoral tegument of D. coeliaca are discussed in relation to their being adaptations to an endoparasitic environment.

Aporocotyle michaudi n. sp. (Digenea: Aporocotylidae) from the emerald rock cod, Trematomus bernacchii (Teleostei: Perciformes) in Antarctica

Aporocotyle michaudi n. sp. is described from the gill blood vessels of the emerald rock cod Trematomus bernacchii in the Ross Sea, Antarctica. It is distinguished from all other species of Aporocotyle by its body tegument showing single conical spines, spinous buccal capsule, and genital atrium positioned medially; all congeners described to date are characterized by clusters of tegumental spines, unspined buccal capsule and genital atrium located in the lateral part of the body. Aporocotyle michaudi n. sp. clearly differs from A. notothenia (the only other species of Aporocotyle found in a perciform fish) in its shape and arrangement of tegumental spines, buccal capsule features, location of genital atrium, body size, ratio of esophagus/body length, anterior caeca/posterior caeca ratio, number of testes, cirrus sac and ovary size and shape, and host. The new species is easily distinguished from A. argentinensis (the species that most closely resembles A. michaudi) by the shape and arrangement of tegumental spines, buccal capsule features, genital atrium location, left anterior caecum longer than right, esophagus/body length ratio, number of testes, cirrus sac size and shape, host and molecular analyses. Phylogenetic analyses of partial 28S rDNA genetic data showed that sequences representing the new species form a distinct clade with all other sequences for species of Aporocotyle and appear basal within the genus. Aporocotyle michaudi n. sp. represents the only species of genus described in Antarctica.

Ultrastructural characteristics of the vaginae of the basal monogenean Chimaericola leptogaster (Leuckart, 1830)

In the first study of the vaginal ultrastructure of any monogenean, the paired vaginae of Chimaericola leptogaster, a basal polyopisthocotylean from the gills of a holocephalan, are described. Each vagina opens laterally. A unique feature of this relict parasite is a short vagino-intestinal connecting duct, the lining of which is separated by septate junctions from the linings of the vagina and the intestine. After giving rise to this vagino-intestinal duct, each vagina travels in a posterior direction and opens into the vitelline collecting duct. The lining of each vagina close to the vaginal pore resembles the body tegument, the syncytial lining of which measures about 2.5μm in thickness and has a dense surface layer 0.2μm in thickness and different apical projections. Proximal to this and before the entrance to the vaginal-intestinal duct, the vaginal lining is characterised by: uniformly distributed electron-dense, lanceolate, spine-like surface structures of about 1.7μm in length; three kinds of surrounding glands with three kinds of secretory granules (abundant oval or rounded electron-dense granules 0.7-2.5μm in length, much less numerous spheroidal, vesicular granules 0.3-0.4μm in diameter, and tightly packed, spheroidal granules 0.8μm in diameter and containing fine particulate material of low density); and four kinds of sensory receptors (three uniciliate and one aciliate). These features are absent from the rest of the vagina. The likely roles of the vagino-intestinal connection, the different gland cells, sensory structures, and the armament of the distal vaginal regions are discussed. Considering the suggested polyopisthocotylean ancestor for the Neodermata, the relict parasite fauna of holocephalans and the unique vagino-intestinal connection in C. leptogaster, which is also known in turbellarians, an ancient origin for chimaericolids is supported.

Emerging roles of TRPA1 in sensation of oxidative stress and its implications in defense and danger

Transient receptor potential ankyrin subtype 1 (TRPA1) is a well-known ion channel that play a central role for pain sensation. In the peripheral sensory nerve terminals innervating the body tegument or organs, TRPA1 detects and is activated by diverse harmful environmental and internal stimuli. The TRPA1 activation results in neuronal firing, which finally sends a warning signal to our brain. However, sensitization or sustained activation of TRPA1 often causes plastic changes both in the neural pathway and in the peripheral tissues, leading to a pathologic state in tissue health and pain mediation. Recently, a unique covalent detection mode for reactive biological attacks was uncovered in the sensory mechanisms of TRPA1. Notably, the pool of the newly found reactive stimulators for TRPA1 includes oxidative stress. Here, we overview the nature of this interaction, and try to find biological meanings of the participation of such a rapid ionotrophic component in disease exacerbations. Acutely, its relatively rapid response can be understood in terms of efficiency for avoiding harmful milieu as quickly as possible, as implicated in the raison d'etre of the pain mechanism. Nonetheless, complex situations in a chronic disease progress may occur. As well, multiple interplays with known molecules on the redox defense mechanism are anticipated. At a therapeutic angle, how to control TRPA1 for promoting body's defensive potential will be a practical question but remains to be answered. Future investigations will likely give more detailed insights to understand the roles and target validity of TRPA1.

Surface features of the monogenean gill parasites Pseudodactylogyrus anguillae and Pseudodactylogyrus bini from the European eel Anguilla anguilla in Egypt

In the present study, scanning electron microscopy is used to demonstrate the surface features of Pseudodactylogyrus anguillae Yin and Sproston (1948) Gussev, 1965 and Pseudodactylogyrus bini Kikuchi (1929) Gussev, 1965 from the European eel Anguilla anguilla. Specimens of the eel A. anguilla were collected from the River Nile, near Mansoura, Dakahlia Province, Egypt. Morphologically, P. anguillae could be distinguished from P. bini based on the total length, the shape and size of the haptor, and the constriction between the haptor and body proper. The general body tegument and the haptoral tegument of both species are microvillous. Possible functions of the microvilli associated with the tegument covering the anterior adhesive areas are discussed. The region of the body proper just anterior to the haptor of P. anguillae, appears to be highly folded and provided with many projections forming scale-like structures. Many surface ciliary sensilla presumed to be sensory structures are found on the tegument of the anterior adhesive area of P. anguillae. Secretory bodies and mucus-like substances are recorded on the tegument covering the anterior adhesive areas of P. anguillae and the haptor of P. bini. The possible role of these secretions in the attachment of the anterior adhesive areas and the posterior attachment haptor to the host tissues are also discussed.

Ultramorphological characteristics of immature stages of Chrysomya albiceps (Wiedemann 1819) (Diptera: Calliphoridae), a fly specie of forensic importance

Forensic entomology is an area of science that serves as a tool in crime scene investigations. Usually, flies are the first insects to reach a dead body and can oviposit just a few hours after arrival. Therefore the knowledge of immature stages is essential for correct identification of the species found on corpses. Scanning electron microscopy gives detailed information about morphological characters helping to identify the immature forms and consequently serves as a tool in crime scene investigations. C. albiceps is a very important fly for forensic entomologists because its larvae are almost always present on a dead body and it is facultative predators and therefore can alter the composition of species present at the carcass. The aim of this study is to identify eggs, larvae, and puparia of C. albiceps using SEM. Eggs were elongated with the anterior region ending in a "Y" shape and the posterior end was tapered. The micropyle was a well-adorned orifice with some projections around it. The first instar larva was composed of 12 segments separated by spines. Only one spiracular opening could be seen at the posterior spiracle. Body tegument was smooth and tubercles were not seen. Antennae and maxillary palps were visible. Second and third larval instars were very similar to first instar, except for the presence of anterior spiracle. However, body tegument was composed of net-like patches and tubercles were visible. Tubercles present at the third instar larvae were robust and erect. Puparia showed a retracted cephalic region and curved tubercles.

Ultrastructural observations on Fasciolopsis buski and its alterations caused by shoot extract of Alpinia nigra

The ultrastructural alterations in the tegument of Fasciolopsis buski in response to incubation in the alcoholic extract of Alpinia nigra were evaluated using transmission electron microscopy. The body tegument of the trematode is composed of an external syncytial layer, musculature, and an inner layer containing tegumental cells. The syncytium comprises various organelles like mitochondria, lysosomes, and tegumentary bodies of the type 2 kind with rare sighting of the type 1. Severe distortion and disorganization of the tegument was revealed in the parasite exposed to the A. nigra extract in the current study. The extent of vacuolization was such that vacuoles proceeded down to the basal lamina causing the syncytium to separate from the tegument at different places. There was depletion of parenchyma material and loss of connecting tubules running down from the syncytium to the tegumental cells causing the cells to be deprived of any proper boundaries.

Fine structure of the anterior adhesive apparatus (head organs) of Bravohollisia gussevi Lim, 1995 (Monogenea: Ancyrocephalidae)

A study of the anterior adhesive apparatus (head organs) of Bravohollisia gussevi Lim, 1995 was carried out using light and electron microscopy. The anterior adhesive apparatus or head organs in B. gussevi comprise 6 circular openings or apertures in the antero-lateral region, associated pits lined with specialized microvillous tegument that differ from the general body tegument, a bundle of ducts, and uninucleate gland cells located lateral to the pharynx. The uninucleate glands of the anterior adhesive apparatus (head organs) comprise 2 types of cells, one kind of cell producing rod-like bodies (S1) and the other oval bodies (S2). The S1 bodies are filled with numerous, less electron-dense vesicles in an electron-dense matrix, while S2 bodies have no vesicles but contain a more homogeneous electron-dense matrix. Interlinking band-like structures were observed between S1 bodies. Similar band-like structures were found between S2 bodies. The formation of S1 bodies was followed by transmission electron microscopy. However, the formation of S2 bodies was unclear and could not be resolved. Uniciliated structures were also observed around the openings of the anterior adhesive apparatus. Each uniciliated structure is usually associated with an opening of a gland cell producing granular, electron-dense, secretory bodies, which differ from the secretions produced by the lateral gland cells of the anterior adhesive apparatus.

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.

Anterior adhesive areas and adjacent secretions in the parasitic flatworms Decacotyle lymmae and D. tetrakordyle (Monogenea: Monocotylidae) from the gills of stingrays

Abstract. The monogeneans Decacotyle lymmae and D. tetrakordyle (Monocotylidae: Decacotylinae), from gills of the dasyatid stingrays Taeniura lymma and Pastinachus sephen, respectively, have a single aperture for adhesive secretion on each side of the anterior ventrolateral region. Rod‐shaped bodies (S1) and electron‐dense spherical secretion (S2) exit through specialised ducts opening adjacent to one another within these apertures. The S1 bodies are 230 ± 11 nm wide and ≥4 μm long in D. lymmae and 240 ± 9 nm wide and ≥3.3 μm long in D. tetrakordyle. The S2 bodies have a diameter of 88 ± 7 nm in D. lymmae and 65 ± 6 nm in D. tetrakordyle. The apertures are unusual in being extremely small (internal diameter, 3–5 μm). Each aperture has a slit‐like surface opening as small as 160 nm wide, surrounded by muscle fibres indicating that they may be opened and closed. The aperture is also surrounded and underlain by muscle fibres that may aid in secretion from, or even eversion of, the tissue within the aperture. Sensilla/cilia are also found within the apertures. Additional secretions from anteromedian and anterolateral glands (body glands), each containing granular secretions, occur in profusion and exit anteriorly and posteriorly to the position of the apertures, through duct openings in the general body tegument. These granular secretions do not appear to be associated with anterior adhesion. Both species show similarities in aperture, underlying tissue, sense organ, and secretion detail, in accordance with findings from other monogenean genera, and which supports the importance of such data for phylogenetic studies.

Ultrastructure of the tegument of Metamicrocotyla macracantha (Alexander, 1954) Koratha, 1955 (Monogenea, Microcotylidae).

The ultrastructure of the body tegument of Metamicrocotyla macracantha (Alexander, 1954) Koratha, 1955, parasite of Mugil liza from Brazil, was studied by transmission electron microscopy. The body tegument is composed of an external syncytial layer, musculature, and an inner layer containing tegumental cells. The syncytium consists of a matrix containing three types of body inclusions and mitochondria. The musculature is constituted of several layers of longitudinal and circular muscle fibers. The tegumental cells present a well-developed nucleus, cytoplasm filled with ribosomes, rough endoplasmatic reticulum and mitochondria, and characteristic organelles of tegumental cells.

Cladistic analysis of Simulium (Trichodagmia) and Simulium (Thyrsopelma) (Diptera: Simuliidae)

A cladistic analysis of Simulium (Trichodagmia) sensu Crosskey and Howard, using 34 morphological characters of larvae (6 characters), pupa (5) and adults (23), yields nine most parsimonious trees under equal weights (length 101 steps CI 0.49 RI 0.73). Successive weighting based on the maximal rescaled consistency index preferred one of the nine (31.37 steps CI 0.62 RI 0.87 total fitcon3=235.8), which was also one of two trees found under implicit weights with concavity values of 3–6. The cladogram justifies the recognition of two subgenera. Simulium (Trichodagmia) sensu stricto (containing S. muiscorum, sumapazense, S. wygodzinskyorum, S. nigrimanum, S. chalcocoma, S. huairayacu and S. lahillei) is supported by the branchial tip sclerotization and the presence of cibarial teeth, larval body tegument covered with lanceolate hairs, female with simple claw, and gonapophysis size. Simulium (Thyrsopelma) (containing S. scutistriatum, S. hirtipupa, S. orbitale, S. guianense, S. perplexum and S. itaunense) is supported by the hypostomial teeth.