David J. Hunt

Entomopathogenic nematodes: systematics, phylogeny and bacterial symbionts.

The volume deals with history, morphology, taxonomy, and systematics of entomopathogenic nematodes (EPN) in the families Steinernematidae and Heterorhabditidae, molecular methods and bacteria associated with these nematodes.

Comparative morphometrics and ribosomal DNA sequence analysis of Longidorus orientalis Loof, 1983 (Nematoda: Longidoridae) from Spain and Iran

During recent nematode surveys in a muddy soil around undetermined graminaceous plants in El Rocio, Huelva Province, in southern Spain, and from the rhizosphere of date palm associated with graminaceous vegetation from Abadan, in Khuzestan Province, south-west Iran, populations of Longidorus orientalis were identified. Morphological and morphometrical studies on these populations fit the original description and represent the first report from Spain and Europe. Molecular characterisation of L. orientalis from Spain and Iran, using D2-D3 expansion regions of 28S rRNA, 18S rRNA and ITS-rRNA, is provided. Sequences of the D2-D3 expansion regions and partial 18S genes were analysed using maximum likelihood and Bayesian inference to reconstruct phylogenetic relationships within L. orientalis and other Longidorus species. The results revealed a closer phylogenetic relationship with L. goodeyi for the D2-D3 expansion region and with L. vineacola for the partial 18S region.

Nacobbus aberrans (Thorne, 1935) Thorne & Allen, 1944 (Nematoda: Pratylenchidae); a nascent species complex revealed by RFLP analysis and sequencing of the ITS-rDNA region

Twelve populations of Nacobbus aberrans, sensu lato, from Mexico, Bolivia, Peru, Ecuador and Argentina were subjected to molecular analysis of their genetic variability. RFLP banding patterns revealed three groups: i) Mexico, Ecuador and Argentina 1 populations; ii) Bolivia and Peru populations; iii) Argentina 2 population. These differences were confirmed by sequencing the ITS rDNA region. Depth of branching was strongly supportive of the presence of three separate species, thus supporting the hypothesis that N. aberrans s.l. is indeed a species complex. The populations from Mexico, Ecuador and Argentina 1 are attributed to N. aberrans s.s., although this requires confirmation by molecular characterisation of N. aberrans from the type locality in the USA; those from Bolivia and Peru are attributed to N. bolivianus Lordello, Zamith & Boock, 1961 with Argentina 2 regarded as representing another taxon. Nacobbus serendipiticus and N. batatiformis are removed from synonymy under N. aberrans s.l . and regarded as species inquirendae . Consistent minor banding patterns in the RFLP profiles may indicate that the genus reproduces predominantly by parthenogenesis.

Diversity and distribution of entomopathogenic nematodes in Chile.

A systematic programme of surveys for entomopathogenic nematodes (EPN) was done in Chile between 2006 and 2008. The survey spanned the principal ecosystems of mainland Chile as well as a number of islands, and covered a wide range of habitats including the Atacama Desert, Andean Altiplano, temperate rainforests and subpolar territory. Nearly 1400 soil samples were collected, of which 7% were positive for EPN. Of 101 EPN isolates obtained, 94 were Steinernema spp. and seven were Heterorhabditis sp. Of the 94 Steinernema isolates, 39 were identified as Steinernema feltiae , the remainder being distributed between two new species, S. unicornum (52 records) and S. australe (three records). The Heterorhabditis isolates, all designated as Heterorhabditis sp.1, are referred to herein as H . cf. safricana . Steinernema feltiae and S. unicornum were collected predominately in the south of Chile and were obtained from a range of habitats, including forests, open grassland, montane soils and coastal zones; neither species was recovered from the far north of the country ( viz ., desert soils in the Norte Grande region). Steinernema australe was found in only three soil samples, all from humid, cool, coastal localities in the south. Heterorhabditis cf. safricana was recovered from the northern regions, with most isolates found in or on the periphery of the Atacama Desert; they were not recovered from cooler, more humid regions of southern Chile. Molecular information indicated there were two subgroups of both S. unicornum and S. feltiae , with a geographical, intraspecific split of subgroups between the most southerly and the more central survey zones. All isolates were collected by ex situ baiting with waxmoth larvae and the natural hosts are unknown.

Steinernema australe n. sp. (Panagrolaimomorpha: Steinernematidae), a new entomopathogenic nematode from Isla Magdalena, Chile

A new species of entomopathogenic nematode, Steinernema australe n. sp., was isolated from a soil sample taken close to the beach on Isla Magdalena, an island in the Pacific Ocean, 2 km from mainland Chile. Morphologically the new species belongs to the glaseri-group and is characterised by morphometrics of the infective juvenile which has a very long body of 1316 (1162-1484) μm, excretory pore located far posterior to the anterior extremity (110 (95-125) μm), exceptionally long tail of 103 (92-114) μm, H% = 51 (42-61), E% = 107 (94-122) and a ratio = 35 (31-38). The first generation male has 72 (55-78) μm long spicules, a 45 (36-51) μm long gubernaculum and SW% = 172 (118-196). The first generation female can be recognised by well developed double epiptygmata, the lack of a prominent postanal swelling, a mucron on the tail tip and (in 60% of individuals) one to two subsidiary mucrons. Sequences of the ITS and D2D3 regions of the ribosomal DNA confirm that S. australe n. sp. is a valid species.

A new genus of Carnoyidae (Nematoda: Rhigonematida) with descriptions of Cattiena trachelomegali gen. n., sp. n. and C. trigoniuli gen. n., sp. n., parasites of Spirobolida (Diplopoda) from Vietnam

Cattiena gen. n., a new genus from the Carnoyidae, is described from the posterior gut of two genera of spirobolid diplopods from Vietnam. The new genus is characterised by: presence of eight somatic spine rows in the cervical region of both male and female, the four sublateral spine rows being better developed; presence of six cuticularised plates around the female oral opening; extremely posterior vulva; two anteriorly directed ovaries; isomorphic and isometric spicules; boat-shaped gubernaculum of similar form to the spicules; gubernaculum with a dorsal hole; well developed, smooth cephalic cap in the male and 15 copulatory papillae with three pairs located lateral, sublateral or subdorsal. The new genus has morphological affinities with Raonema Kloss, 1965, a poorly known genus from India, but is easily differentiated by the extremely posterior vulva and the presence of spine rows in the male. Two new species are described in the genus: the type, C. trachelomegali gen. n., sp. n. from Trachelomegalus sp. and C. trigoniuli gen. n., sp. n. from Trigoniulus sp. The two species differ primarily in the position of the vulva (consistently more anterior in the latter species), degree of development of the vulval flap, body length, tail length and in the relative development of the somatic spine rows.

Agricultural nematology in East and Southern Africa: problems, management strategies and stakeholder linkages

By 2050, Africas population is projected to exceed 2 billion. Africa will have to increase food production more than 50% in the coming 50 years to meet the nutritional requirements of its growing population. Nowhere is the need to increase agricultural productivity more pertinent than in much of Sub-Saharan Africa, where it is currently static or declining. Optimal pest management will be essential, because intensification of any system creates heightened selection pressures for pests. Plant-parasitic nematodes and their damage potential are intertwined with intensified systems and can be an indicator of unsustainable practices. As soil pests, nematodes are commonly overlooked or misdiagnosed, particularly where appropriate expertise and knowledge transfer systems are meager or inadequately funded. Nematode damage to roots results in less efficient root systems that are less able to access nutrients and water, which can produce symptoms typical of water or nutrient deficiency, leading to misdiagnosis of the underlying cause. Damage in subsistence agriculture is exacerbated by growing crops on degraded soils and in areas of low water retention where strong root growth is vital. This review focuses on the current knowledge of economically important nematode pests affecting key crops, nematode control methods and the research and development needs for sustainable management, stakeholder involvement and capacity building in the context of crop security in East and Southern Africa, especially Kenya, Tanzania, Uganda and Zimbabwe.

The African Rhigonematoidea (Nematoda: Rhigonematida). 2. Six new species of Rhigonema Cobb, 1898 (Rhigonematidae)

Six new species of Rhigonema are described from the gut of various African diplopods. Rhigonema fecundum sp. n., from South Africa, is characterised by medium to fairly long body length, finely pilose anterior region, posterior margin of cephalic collar smoothly fused to body contour, Type 2 genital tract with a long ovejector, presence of a long, closely adpressed, vulval flap, tail shape in both sexes, broad spicules of medium length and complement of 23 copulatory papillae of which three pairs are subdorsal or sublateral in position. Rhigonema oxydesmi sp. n., from Oxydesmus platycercus concolor, Zaire, is characterised by medium body length, slightly projecting cephalic collar, finely pilose anterior region, Type 2 female genital tract with a long ovejector, presence of a short, adpressed, vulval flap, tail shape in both sexes, medium length spicules with a hamate capitulum and complement of 23 copulatory papillae, three pairs of which are subdorsal or sublateral in position. Rhigonema peziphorum sp. n., from Sphaerotherium selindum, Zimbabwe, is characterised by medium body length, prominently projecting cephalic collar, finely pilose anterior region, Type 1 female genital tract with a medium length ovejector, rather large eggs, absence of a prominent vulval flap, presence of a spermatophore, tail shape in both sexes, unusually short spicules with a weakly hamate capitulum and complement of 23 copulatory papillae. It is the only known Rhigonema species to form a spermatophore. Rhigonema rostrellum sp. n., from Ivory Coast, is characterised by medium body length, finely pilose anterior region, Type 2 genital tract with a very long ovejector, presence of a closely adpressed vulval flap, tail shape in both sexes, broad spicules of medium length and complement of 23 copulatory papillae of which three pairs are subdorsal or sublateral in position. Rhigonema spicatum sp. n., from Congoromus flabellatus, Zaire, is characterised by medium body length, slightly projecting cephalic collar, densely pilose anterior region, Type 2 female genital tract with a long ovejector, presence of an adpressed vulval flap, tail shape in both sexes, relatively short spicules with a hamate capitulum and complement of 23 copulatory papillae. Rhigonema xiphiurus sp. n., from Oxydesmus sicarius, Zaire, is characterised by medium body length, projecting cephalic collar, coarsely pilose anterior region with bristly microtrichs, microtrichs extending down body to beyond vulval level in female and a similar relative position in the male, Type 2 female genital tract with a long ovejector, elongate female tail, convex conoid male tail with an exceptionally well developed subulate projection, very short spicules and disposition of the 23 copulatory papillae, three pairs of which are dorsal or sublateral in position. A synopsis of the other eight nominal species of African Rhigonema is appended.

The African Carnoyidae (Nematoda : Rhigonematida). 1. Brumptaemilius brevispiculus sp. n. from Ghana with observations on copulatory plugs and spermatophore development

Brumptaemilius brevispiculus sp. n. from the gut of a spirostreptid diplopod from Ghana is described and illustrated with the aid of SEM. The species is characterised by the structure of the male area rugosa, particularly the ventral extension of the rugosities on to the tail spike and the transverse rows of imbricate spines in the postcloacal region, the tail spike ca 1-1.5 gubernaculum length long, the very short spicules bearing relatively few transverse striae, the form and disposition of the copulatory papillae and the presence of an external, pedunculate spermatophore. It is distinguished from the other nominal species in the genus, including all of the ten species inquirendae, principally by a combination of the unusually short spicules, the form of the area rugosa, vulval position and the extent of the lateral alae in both sexes. The development of copulatory plugs and spermatophores within the African Carnoyidae is discussed. Simple copulatory plugs exist in Gilsonema and Waerebekeia, but specialised spermatophores occur in Afrocarnoya and Brumptaemilius. The most complex spermatophore is found in Brumptaemilius and comprises an oval structure containing sperm connected by a hollow peduncle to the vulval/vaginal region of the female, the peduncle being inserted under the anterior vulva lip and firmly cemented into position by a copulatory plaque. This is only the second report of spermatophore development within the Nematoda.

The African Rhigonematoidea (Nematoda: Rhigonematida). 1. Trachyglossus quintus gen. n., sp. n. (Xustrostomatidae fam. n.) with redescription of Rhigonema multipapillatum (Skrjabin, 1916) and designation of a neotype

Trachyglossus quintus gen. n., sp. n. is described from Charactopygus frequens from Zaire. The new genus is characterised by having a dorsoventrally elongate oral aperture with the dorsal jawplate developed into a tongue-like rasp extending over halfway down the corpus lumen; a hypertrophied corpus and isthmus; well developed, lobate caudal alae in the male; hypertrophied, lobiform, vulval flap and by the form of the spicules and disposition of the copulatory papillae. It is closest to Xustrostoma, a genus with which it shares the development of a tongue-like rasp, but differs principally in the hypertrophy of the pharyngeal components: in Trachyglossus gen. n. it is the corpus and isthmus which are enlarged whereas in Xustrostoma it is the basal bulb. Trachyglossus gen. n. also differs in having strongly developed, lobate, caudal alae in the male (vs absent) and in possessing a lobiform anterior vulval lip. It differs from Obainia in having the dorsal jaw plate modified to form a tongue-like rasp, corpus and isthmus region of pharynx hypertrophied (vs basal bulb in African species of Obainia), hypertrophied vulval flap, form of spicules, distribution of copulatory papillae and presence of caudal alae in the male. From Zalophora it differs in the form of the pharynx, development of a tongue-like dorsal rasp instead of numerous teeth on the dorsal jawplate, presence of a hypertrophied vulval lobe and in being amphimictic instead of parthenogenetic. Xustrostomatidae fam. n. is proposed for all those genera (formerly included in the Rhigonematidae) with the cephalic capsule laterally compressed to form a dorsoventrally orientated oral aperture. Rhigonema multipapillatum (Skrjabin, 1916), previously known only from the original description, is redescribed and established as a valid species on the basis of material from Uganda. A neotype is proposed. The species is characterised by medium body size; posterior margin of cephalic collar fused to body; presence of fine microtrichs in the cervical region; cuticularised mouth plates clothed in minute spine-like structures; Type 1 female genital tract; conoid spicate tail shape in both sexes; form of the long, slender spicules and disposition of the 31 copulatory papillae, three postcloacal pairs of which being subdorsal or sublateral in position.