Distribution of Plectidae (Nematoda: Araeolaimida) in pasture soils

Abstract

Across 88 sites 9 species were found, with Anaplectus granulosus at 56 sites, Plectus parietinus at 47, P. longicaudatus at 30, P. parvus at 15, P. cirratus and Wilsonema otophorum at 11, P. armatus and A. porosus at 4, and Tylocephalus auriculatus at 1 site. A key to Anaplectus males is given. For nine sites mean length of female A. granulosus is negatively correlated with mean annual air temperature. The most diverse fauna comprised six species in Kaitoke silt loam; it appears that faunal diversity increases with higher rainfall. Species apparently coexist through separation in size and time. Tylocephalus was only found in soils with a thermic soil temperature regime.     

Study of the genus Plectus Bastian, 1865 (Nematoda: Plectidae) from Iran

Three species of Plectus Bastian, 1865 viz., P. aquatilis and P. pusillus from Kerman province and P. velox from Alborz province, Iran are described and illustrated. Partial sequences of 18S region of ribosomal DNA gene were amplified for P. aquatilis and P. pusillus. The Blast results of population of P. aquatilis from Iran showed 8–10 nucleotides differences with populations of the same species (AF036602; GQ892827; AY284700) reported from the UK, Belgium and The Netherlands, respectively. Whereas Iranian population of P. pusillus showed 14–16 nucleotides differences with P. cf. pusillus (AY284705; AY284704) reported from The Netherlands. Molecular analysis revealed close relationship of the Iranian plectids with P. cf. parvus (AY284699) reported from The Netherlands. Phylogenetic relationships with other related species in the genus Plectus and closely related genera that are available in the GenBank are given.     

Comparative host reaction to Angiostrongylus malaysiensis (Nematoda) in three species of snails

Infection with Angiostrongylus malaysiensis was studied by means of tissue squash preparations and histological sections in three species of Malaysian aquatic snails: Lymnaea rubiginosa, Physastra sumatrana, and Melanoides tuberculata. Development to the third stage occurred normally in L. rubiginosa. The biphasic tissue reaction in this snail was similar to that described in Biomphalaria glabrata infected with A. cantonensis. However, the final architecture of the granuloma differed in the two hosts with the cells in the L. rubiginosa granuloma often appearing more vacuolated and less flattened. Nematode development in P. sumatrana was abnormal, with larvae beyond the early first stage occurring in only 21% of infected snails. The highly variable cellular reactions against larvae in P. sumatrana, even within the same snail, probably reflect the differing degrees of maturation attained by individual larvae. Except in one case, no infection of M. tuberculata occurred, presumably as a result of its impenetrable epithelia.     

Revision of Comesomatidae (Nematoda)

The gross and fine morphology of the family Comesomatidae is reviewed and the systematic position of its members revised. Significant differentiating characters of the Comesomatidae within the Chromadorida are: a copulatory apparatus provided with apophyses, a female reproductive system with outstretched ovaries, the presence of marginal tubes within the oesophagus, and a non-sclerotized and enlarged tail tip. For classification within the family the following three main characters are used: the structure of the buccal cavity, the structure of the copulatory apparatus, and the arrangement of the cephalic sense organs. Structure of the Sabatieria type is considered basic. The genera are rearranged in three subfamilies as follows: Sabatieriinae ( Cervonema, Laimelia, Pierrickia, Sabatieria (syn. Actarjania), Scholpaniella ), Dorylaimopsinae (Dorylaimopsis (syn. Mesonchium), Hopperia, Metasabatieria, Paramesonchium, Vasostoma ), Comesomatinae ( Comesoma, Metacomesoma, Paracomesoma. ) Six species of Comesomatidae are described from the øresund, Denmark: Cervonema macramphis sp.n.; Laimelia filipjevi nom. nov. (syn. Sabatieria longicaudata Filipjev, 1922); Sabatieria hilarula De Man, 1922; S. ornata (Ditlevsen, 1918); S. punctata (Kreis, 1924); Dorylaimopsis punctata Ditlevsen, 1918. Representatives of these species constitute more than 40% of the total number of nematodes in the region.     

The Comparative Cellular Architecture of the Female Gonoduct Among Tylenchoidea (Nematoda: Tylenchina)

The cellular architecture of the female gonoduct of 68 nematode populations representing 42 species belonging to Tylenchidae, Belonolaimidae, Hoplolaimidae and Meloinema is shown to have an overall similarity in cellular gonoduct structure. The oviduct consists of two rows of four cells; the spermatheca is comprised of 10 to 20 cells, and the uterus cells, except in the case of Psilenchus, are arranged in four (Tylenchidae) or three (Belonolaimidae, Hoplolaimidae and Meloinema) regular rows. Although the genus Meloinema is classified within Meloidogynidae, its spermatheca is clearly hoplolaimid-like and lacks the spherical shape with lobe-like protruding cells typical of Meloidogyne. Detailed morphology of expelled gonoducts may provide a valuable character set in phylogenetic analysis, and the cellular morphology of the spermatheca appears to be a distinguishing feature at species level, especially in the genera Tylenchus and Geocenamus. Ultrastructural data on the oviduct-spermatheca region of Meloidogyne incognita complement light-microscopic (LM) results. The combination of LM of expelled organs and transmission electron microscopy (TEM) on selected sections is put forward as a powerful tool to combine three-dimensional knowledge with ultrastructural detail.     

Negative influence of Gammarinema gammari (Nematoda) on the fecundity of Microphallus papillorobustus (Trematoda): field and experimental evidence

The gammarid amphipod Gammarus insensibilis frequently harbors adult individuals of the ectoparasitic nematode Gammarinema gammari as well as metacercariae of the trematode Microphallus papillorobostus. After the demonstration in a previous study of a negative relationship between the abundance of these 2 parasites, the nature of the relationship between these 2 parasites was explored in more detail by studying, in the field and in the laboratory, the influence of nematode abundance on trematode fecundity. In gammarids collected in the field, a negative relationship between metacercarial fecundity and the number of co-occurring nematodes was found. By manipulating the nematode abundance in the laboratory, it was confirmed that G. gammari has a negative effect on egg production in M. papillorobustus.     

No evidence for specificity between host and parasite genotypes in experimental Strongyloides ratti (Nematoda) infections

A key requirement for several theories involving the evolution of sex and sexual selection is a specificity between host and parasite genotypes, i.e. the resistance of particular host genotypes to particular parasite genotypes and the infectivity of particular parasite genotypes for particular host genotypes. Determining the scope and nature of any such specificity is also of applied relevance, since any specificity for different parasite genotypes to infect particular host genotypes may affect the level of protection afforded by vaccination, the efficacy of selective breeding of livestock for parasite resistance and the long-term evolution of parasite populations in response to these control measures. Whereas we have some evidence for the role of specificity between host and pathogen genotypes in viral and bacterial infections, its role in macroparasitic infections is seldom considered. The first empirical test of this specificity for a vertebrate–nematode system is provided here using clonal lines of parasite and inbred and congenic strains of rat that differ either across the genome or only at the major histocompatibility complex. Although significant differences between the resistance of host genotypes to infection and between the fitness of different parasite genotypes are found, there is no evidence for an interaction between host and parasite genotypes. It is concluded that a specificity between host and parasite genotypes is unlikely in this system.     

Arthrostoma miyazakiense (Nematoda: Ancylostomatidae) infection in raccoon dogs of Korea and experimental transmission to dogs

Arthrostoma miyazakiense (Nematoda: Ancylostomatidae) is a hookworm species reported from the small intestines of raccoon dogs (Nyctereutes procyonoides) in Japan. Five Korean raccoon dogs (N. procyonoides koreensis) caught from 2002 to 2005 in Jeollanam-do (Province), a southeastern area of South Korea, contained helminth eggs belonging to 4 genera (roundworm, hookworm, whipworm, and Capillaria spp.) and cysts of Giardia sp. in their feces. Necropsy findings of 1 raccoon dog revealed a large number of adult hookworms in the duodenum. These hookworms were identified as Arthrostoma miyazakiense based on the 10 articulated plates observed in the buccal capsule and the presence of right-sided prevulval papillae. Eggs of A. miyazakiense were 60-65 x 35-40 micrometer (av. 62.5 x 35 micrometer), and were morphologically indistinguishable from those of Ancylostoma caninum. The eggs were cultured to infective 2nd stage larvae via charcoal culture, and 100 infective larvae were used to experimentally infect each of 3 mixed-bred puppies. All puppies harbored hookworm eggs in their feces on the 12th day after infection. This is the first report thus far concerning A. miyazakiense infections in raccoon dogs in Korea, and the first such report outside of Japan.     

Chiloplectus masleni sp. nov. and variability in populations of Plectus acuminatus Bastian 1865 (Nematoda: Plectidae) from the nunatak Basen,Vestfjella, Dronning Maud Land,East Antarctica

 A new species, Chiloplectus masleni sp. nov., and 12 populations of Plectus acuminatus are described from the nunatak Basen, Vestfjella, Dronning Maud Land, East Antarctica. C. masleni sp. nov. is distinguished from the closely related C. loricatus by a broader lip region, longer stoma, the more posterior position of amphids, a pear-shaped basal bulb, more narrow annuli, anterior annuli that are evenly rounded and a larger number of tail setae. New information is provided on internal and external morphology of specimens of P. acuminatus from Basen. Received: 20 December 1995/Accepted: 17 March 1996     

Tubulin and benzimidazole-resistance in Trichostrongylus colubriformis (Nematoda)

Benzimidazole treatment produced greater effects on microtubule-dependent acetylcholinesterase secretion, the presence of microtubules in intestinal cells, and colchicine binding in susceptible compared with benzimidazole-resistant Trichostrongylus colubriformis. In addition, the binding of benzimidazoles was markedly reduced in preparations from the latter strain, indicating that the mechanism of resistance to benzimidazoles in this nematode involves a reduced affinity of tubulin for benzimidazoles.     

Molecular basis of hyperlipidemia in golden hamsters during experimental infection with Ancylostoma ceylanicum (Nematoda:Strongylidae)

An infection of golden hamsters with Ancylostoma ceylanicum, a hookworm parasite, induced profound hyperlipidemia, particularly hypertriglyceridemia, and the effect was directly related to the degree of infection. A significant increase was also noticed in serum cholesterol and phospholipid levels. The appearance of lipoprotein-X, an abnormal low density lipoprotein, was detected in the serum of hookworm-infected animals. The hyperlipidemia was further characterized by an increase in very low density lipoproteins (VLDL) and low density lipoproteins (LDL) with a concomitant decline in high density lipoproteins (HDL). Decreased lipolytic activities, especially triglyceride lipase, in hepatic tissue and induction of lipolytic activities in intestine and adipose tissues indicated mobilization of fats from adipose and jejunum with a defective removal of triglyceride-rich lipoproteins in hepatic tissues. Accumulation of lipids in liver and depletion in adipose tissue supported these results. The derangement may have a significant effect on host parasite interaction and is an important pathophysiological feature occurring during experimental ancylostomiasis.     

Comparative effects of Steinernema feltiae (Nematoda: Steinernematidae) and insecticides on yield and cropping of the mushroom Agaricus bisporus

In a mushroom crop (Agaricus bisporus) affected by a very low level of sciarid fly (Lycoriella auripila) infestation, the effects of an indigenous isolate of insect-parasitic nematode (Steinernema feltiae) and of two commonly used insecticides (diazinon and diflubenzuron) were studied. When compared with untreated plots, nematodes applied to the casing had no adverse effects on mushroom yields whereas insecticides decreased yields. At a rate of 3 × 10⁶ infective juveniles per tray (surface area = 0.56 m²), S. feltiae elicited increases of 28.5% and 19% in the mean total numbers and weights of mushrooms respectively. Treatment only with diflubenzuron resulted in 14.6% and 6% reductions in mean total numbers and weights of mushrooms, respectively; treatment with both diazinon and diflubenzuron caused 18.5% and 9.4% losses. Application of nematodes generally reduced the mean weight per mushroom whereas insecticides increased it; nematodes delayed the onset of mushroom production (first flush) whereas diflubenzuron delayed the third and fourth flushes. Nematode contamination of sporophores was minimal when S. feltiae was applied at casing. Although their numbers declined with time, the nematodes persisted, in the casing layer, throughout the cropping period of seven weeks. It is concluded that yield benefits associated with nematode application can result mainly from nematode effects on A. bisporus and not solely from suppression of a damaging pest population.