Morphological and genetic description of Moniliformis necromysi sp. n. (Archiacanthocephala) from the wild rodent Necromys lasiurus (Cricetidae: Sigmondontinae) in Brazil.

A new species of Moniliformis Travassos, 1915 (Acanthocephala: Moniliformidae) is described from the hairy-tailed bolo mouse, Necromys lasiurus Lund, 1840 (Cricetidae: Sigmondontinae), captured in the Brazilian Cerrado, in Uberlândia, state of Minas Gerais, Brazil. The specimens were studied by light and scanning electron microscopy. Molecular phylogenies were inferred from partial nuclear large subunit ribosomal RNA gene sequences and partial mitochondrial cytochrome c oxidase subunit I gene. The new species is distinguished from other moniliformid species by the number of rows and number of hooks per row, size of the proboscis, size of the eggs, host species and geographical distribution. Molecular phylogenies and genetic distances analyses demonstrated that Moniliformis necromysi sp. n. forms a well-supported monophyletic group with sequences of other species of Moniliformis and is distinguished from them, which agrees with the morphological characteristics, allocating the new species to this genus and to the family Moniliformidae Van Cleave, 1924. This is the first moniliformid acanthocephalan described from a wild rodent in Brazil.

Morphological and molecular descriptions of Moniliformis saudi sp. n. (Acanthocephala: Moniliformidae) from the desert hedgehog, Paraechinus aethiopicus (Ehrenberg) in Saudi Arabia, with a key to species and notes on histopathology.

A new acanthocepohalan species, Moniliformis saudi sp. n. is described from the desert hedgehog, Paraechinus aethiopicus (Ehrenberg), in central Saudi Arabia. Fourteen other valid species of Moniliformis Travassos, 1915 are recognised. The new species of Moniliformis is distinguished by having a small proboscis (315-520 µm long and 130-208 µm wide) with two apical pores, 14 rows of 8 hooks each and small hooks, thre largest being 25-31 µm long anteriorly. Distinguishing features are incorporated in a dichotomous key to the species of Moniliformis. The description is augmented by scanning electron microscopical (SEM) observation and DNA analysis of nuclear (18S rRNA) and mitochondrial (cytochrome oxidase subunit 1; cox1) gene sequences. Attached worms cause extensive damage to the immediate area of attachment in the host intestine. This includes tissue necrosis and blood loss due to damage to capillary beds. Worms also obstruct essential absorbing surfaces.

Description of a new species of Moniliformis (Acanthocephala: Moniliformidae) from Peromyscus hylocetes (Rodentia: Cricetidae) in Mexico.

Moniliformis ibunami n. sp., is described from the intestine of the transvolcanic deermouse Peromyscus hylocetes Merriam 1898 (Cricetidae) from Parque Nacional Nevado de Colima "El Floripondio", Jalisco, Mexico. The new species can be distinguished morphologically from the other 18 congeneric species of Moniliformis by a combination of morphological and molecular characters including the number of hooks on the proboscis (12 longitudinal rows, each one with six to eight transversally arranged unrooted hooks), the proboscis length (230-270 µm), the female trunk length (159-186 mm) and egg size (40-70 × 20-40). For molecular distinction, nearly complete sequences of the small subunit (SSU) and large subunit (LSU) of the nuclear ribosomal DNA and cytochrome oxidase subunit 1 (cox 1) of the mitochondrial DNA of the new species were obtained and compared with available sequences downloaded from GenBank. Phylogenetic analyses inferred with the three molecular markers consistently showed that Moniliformis ibunami n. sp. is sister to other congeneric species of Moniliformis. The genetic distance with cox 1 gene among Moniliformis ibunami n. sp., M. saudi, M. cryptosaudi, M. kalahariensis, M. necromysi and M. moniliformis ranged from 20 to 27%. Morphological evidence and high genetic distance, plus the phylogenetic analyses, indicate that acanthocephalans collected from the intestines of transvolcanic deer mice represent a new species which constitutes the seventh species of the genus Moniliformis in the Americas.

Morphogenesis of the proboscis hooks of an archiacanthocephalan, Moniliformis moniliformis (Bremser 1811) Travassos 1915.

Proboscis hooks of Moniliformis moniliformis were noted first as small protrusions on developing proboscides of 20- to 28-day-old acanthellae from hemocoels of experimentally infected cockroaches (Periplaneta americana). On the basis of proximity, residual connecting strands of tissue, and ultrastructural similarity, origin of the hooks has been determined to be from primordial muscle tissue. During development, primordial proboscis hooks extended into hypodermal tissue, but remained separated by the basement membrane and a characteristic space. Within this space, under the curvature of the hook, fibrous material began to accumulate at about 38 days during development. The fibrous material appeared to be produced at the distal end of the primordial hook as evidenced by the appearance of organelles in that area, and the compact, parallel nature of fibrous material immediately adjacent. Upon completion of development, the proboscis hook of the 46- to 54-day-old acanthella was observed to consist of a central core of parallel fibrous material, an outer layer of crisscrossed fibers, and a thin covering of hypodermis and cuticle.

Ultrastructural morphology of the neuropile of the cerebral ganglion of Moniliformis moniliformis (Acanthocephala).

The cerebral ganglion of Moniliformis moniliformis consists of an outer single layer of cell bodies and an inner core of neuropile occupied by cellular processes. Morphological characteristics of 5 types of cellular processes have been described. Most of the processes in the neuropile were of large size, although sites containing numerous small processes (neurites) were also observed. Small processes in the neuropile were the sites of synaptic interaction. The majority of presynaptic membranes were well defined by the presence of electron-dense material at the inner leaflet, while postsynaptic membranes appeared to lack marked postsynaptic density. Round or flattened lucent vesicles were concentrated around the presynaptic membranes. Electron-dense and dense-cored vesicles were usually separated from the clear vesicles and situated at some distance from synaptic sites.

Ultrastructural morphology of the nerve cells in the cerebral ganglion of the Acanthocephalan Moniliformis moniliformis.

The morphology of the cerebral ganglion of the Acanthocephalan Moniliformis moniliformis was studied in serial sections using electron microscopy. The organization of the cerebral ganglion was typical of other invertebrates with the cell bodies forming a rind, 1 cell thick, and their processes forming the central core of the neuropile. The ganglion was surrounded by a connective tissue capsule composed of collagen-like fibrils. Externally, the free surface of the cell bodies was covered by an electron-dense extracellular lamina. Seventy-six cells were identified in every ganglion examined and, on the basis of their cellular characteristics, they were divided into 5 distinct cell types, classified as type A, B, C, D and E cells. The characteristic morphological features of each cell type have been described, and the distribution of the different cell types in the cerebral ganglion was mapped.

Ultrastructural study of the host-parasite interface of Moniliformis moniliformis (Archiacanthocephala) in laboratory-infected rats.

The fine structure of the host-parasite interface of Moniliformis moniliformis in rats is described, comprising investigations on the ontogenic development of the presomal tegument, on the lesions caused by the worms, and on the host cellular reactions at the points of attachment of the worm. The presomal tegument of the worm contained more fibrous elements than the metasomal tegument. The sclerotization increased with the ages of the worms and toward the tip of the proboscis. The presomal surface coat was more coarsely structured and osmiophilic than that of the metasoma and was neither continuous with the contents of the tegumental crypts nor supported by lipids from necrotic host tissue. The surface coat occasionally detached from the proboscis, probably due to the activity of the surrounding granulocytes of the host. The proboscis hooks lost their tegumental covering during their larval development. Hooks of all worms from rats were invested with a semiliquid lipid coat, apparently derived from tegumental excretions at the base of the hooks. The invaginated area of excretion around the base of the hooks was rich in endoplasmic reticulum. The hooks seemed to renew their lipid coats at certain intervals by dipping into the excreted lipid. In rats all worms, irrespective of their age, attached superficially, penetrating only the intestinal mucosa and the tunica propria. No fibrous connective tissue was found in the lesions caused by the worms, indicating that they frequently changed their site of attachment. At 3-10 days postinfection the host's defense cells observed in the lesions consisted mainly of granulocytes, whereas plasma cells were the predominant leukocytes in lesions of older infections.

Observations on the development of the ovarian balls of Moniliformis (Acanthocephala).

Observations have been made on the ultrastructure of objects identified as ovarian balls from female Moniliformis after 1, 3, 5, 7 and 9 days in the rat. Similar objects are present in the body cavity of female cystacanths from cockroaches. The ovarian balls from 1-day-old worms are formed of several cells which are enclosed within a surface coat. During development, the ovarian balls increase in size and cell number and the interval organization appears to become more complex. After 9 days of development in the rat, the surface coat of the ovarian balls can no longer be observed and microvilli are present. It also appears that the supporting syncytium has been formed by this time.

Observations on the surface morphology of the ovarian balls of Moniliformis (Acanthocephala).

The surface morphology of fixed ovarian balls from female Moniliformis dubius, agd 12, 18, 26, 28, 42, 77, 105 and 118 days, has been examined by means of scanning electron microscopy. The appearance of the surface has been found to be variable between ovarian balls from worms of the same and different ages. Some parts of the surface are seen to possess micro-projections, cavities and ridges while other parts have the appearance of an irregular meshwork of fibres. Various protruding features have been observed to extend from the surfaces of the ovarian balls taken from the inseminated female worms. In most cases, the surfaces of the protruding features differ in appearance from the surrounding surfaces of the ovarian balls. Some of these features have been assumed to represent growing zygotes and developing eggs covered by the supporting syncytium of the ovarian ball. Single or several thread-like structures have been observed in association with the surfaces of ovarian balls taken from the inseminated female worms. At present, the thread-like structures are believed to be portions of spermatozoa. By means of light microscopy, preliminary observations have been made on what is considered to be the division process of ovarian balls taken from uninseminated and inseminated worms varying in age from 7 to 98 days.

Localization of phenoloxidase in the midgut of Periplaneta americana parasitized by larvae of Moniliformis moniliformis (Acanthocephala).

In cockroaches infected with Moniliformis moniliformis, the melanogenic enzyme phenoloxidase (PO) was histochemically localized in the posterior midgut and in haemocytes. Midguts were incubated with either 3-hydroxytyramine-HCl (dopamine) or 3-(3,4-dihydroxyphenyl)-L-alanine (dopa), and the resulting electron-dense reaction products of PO activity were found to be homogeneously distributed in the cytoplasm of both midgut cells and haemocytes. Following experimental infection, the first acanthors that reached the outer surface of the gut elicited a haemocyte response similar to that observed during wound healing. Larvae that remained attached to the gut became melanized or developed successfully. PO activity gradually decreased as the course of infection proceeded (10-50 days post-infection) but was apparently not inhibited in either midgut cells or haemocytes that were closely associated with the parasites. PO was lacking in the midgut cells of uninfected cockroaches. The results of the present study are discussed with respect to the defence reactions of the host and the survival mechanisms of the parasite.

Evasion of the insect immune response by Moniliformis dubius (Acanthocephala): further observations on the origin of the envelope.

The envelope around larvae of Moniliformis dubius appears to protect the parasite against immune recognition and encapsulation by the insect host's haemocytes. The origin of this envelope has been the subject of controversy although most evidence suggests it is parasite-derived. If host-derived, the envelope would be expected to share surface properties with host tissue. Thus, experiments were undertaken, transplanting parasites and host tissue to other insects and using haemocytic encapsulation as an assay for immune recognition, in order to compare the response to host tissue and to the parasite's envelope. Parasites without their envelopes, and pieces of tissue (ventral nerve cord) from the experimental host (the locust Schistocerca gregaria) were recognized as foreign and encapsulated in the cockroach, Periplaneta americana. The majority of parasites with their envelopes were unencapsulated or only partially encapsulated on transfer to their normal host, P. americana, indicating that the envelope does not have surface similarity to locust tissue. Cockroach-derived parasites with or without envelopes were not encapsulated in S. gregaria, suggesting that the larva itself can evade or inhibit the locust's recognition mechanism. However, since larvae which develop in S. gregaria are enclosed in an envelope, the formation of the envelope would seem to be an inherent feature of the parasite's development.