Guitartia tridentata n. gen., n. sp (monhysterida: xyalidae) and macrodontium gaspari n. gen., n. sp (chromadorida: microlaimidae), free-living marine nematodes from the Caribbean sea

Two new genera of free-living marine nematodes are described from the muddy bottom of Cienfuegos Bay, Caribbean Sea. Guitartia n. gen. (Xyalidae, Monhysterida) is characterised by three long tooth-like structures in the stegostom, second and third circle of anterior sensilla separate and posterior genital branch of the female restricted to a long post-vulvar sac. The type species is Guitartia tridentata n. gen., n. sp. Within the Xyalidae, Guitartia n. gen. is morphologically close to Amphimonhystrella, Cobbia, Elzalia, Scaptrella and Valvaelaimus, all being characterised by sclerotised structures in the stoma and transverse striation of the body cuticle. Main features for discrimination are the type of stoma structure, the shape and relative size of amphidial fovea, the presence of a post-vulvar sac and gubernacular apophyses and the absence of terminal setae on the tail. Macrodontium n. gen. (Microlaimidae, Chromadorida) is characterised by a heavily sclerotised stoma with one large dorsal tooth and two smaller subventral teeth, sexual dimorphism in size and position of the amphidial fovea and males with a single anterior testis. The type species is Macrodontium gaspari n. gen., n. sp. Within the Microlaimidae, Macrodontium n. gen. is similar to the genera Acanthomicrolaimus and Bolbolaimus due to sclerotised stoma and presence of large dorsal tooth. The new genus is similar to Aponema in sexual dimorphism in the size of the amphidial fovea, monorchic males, presence of a gubernacular apophysis and conico-cylindrical tail shape. Morphological characters of diagnostic value within the family are the ornamentation of the body cuticle, relative length of cephalic sensilla, stoma sclerotisation and number of testes

A morphometric analysis of the genus Terschellingia (nematoda, Linhomoeidae) with redefinition of the genus and key to the species

The cosmopolitan and often ecologically dominant genus Terschellingia (Nematoda, Linhomoeidae), with 37 nominal species, is taxonomically a problematic taxon. Its species show high morphological plasticity, possess few diagnostic morphological characters and identification keys are lacking. A revision of the genus was carried out based on morphological and morphometric data from the literature and from light and electron microscopic observations of specimens collected in Cienfuegos Bay, Caribbean Sea, Cuba. The diagnosis of the genus Terschellingia is emended. Of the current 37 nominal species, 15 are considered as valid species based on morphological characters related to size and position of amphidial fovea, presence/position of cephalic and cervical setae, presence/ size/ shape of oesophageal bulb, shape of spicular apparatus and shape of tail. Tabular and pictorial keys were provided based on these characters. Three sympatric species: T. communis, T. gourbaultae, and T. longicaudata were redescribed based on recently collected Cuban specimens. Each of them showed relatively large differences in body size in comparison with the respective type specimens, suggesting possible variation due to local environmental differences. The highest intraspecific variation pertains for the most widely spread cosmopolitan species T. longicaudata, suggesting that morphological plasticity enhanced adaptation to different environmental conditions. The notable taxonomic inflation within the genus (13 species inquirendae, 9 junior synonyms), probably also present in other highly specious genera of marine nematodes, can lead to an overestimation of the alpha-diversity for some taxa

Pathogenicity of indigenous entomopathogenic nematodes from Benin against mango fruit fly (Bactrocera dorsalis) under laboratory conditions

Bactrocera dorsalis fruit fly is the economically most significant tephritid pest species on Mango, Mangifera indica L., in Benin, and entomopathogenic nematodes (EPNs) represent good candidates for its control in the soil. In this study, the susceptibility of larvae and pupae of B. dorsalis to 12 EPN isolates originating from Benin was investigated. The effect of nematode concentrations (20, 50, 100, 200 and 300 Infective Juveniles (IJs)/B. dorsalis larva) and of different substrate moisture content (10, 15, 20, 25 and 30% v/w) on B. dorsalis mortality at the larval stage was studied. Also, the reproduction potential inside B. dorsalis larvae was assessed. Our results revealed that the susceptibility of B. dorsalis larvae was significantly different among the 12 tested nematode isolates with H. taysearae isolate Azohoue2 causing the greatest insect mortality (96.09 +/- 1.44%). The lowest insect mortality (7.03 +/- 4.43%) was recorded with Steinernema sp. strain Bembereke. Significant differences in insect mortality were recorded when EPNs were applied at varying IJs concentrations. A concentration of 100 nematodes of either H. taysearae Azohoue2 or H. taysearae Hessa1 per B. dorsalis larva was enough to kill at least 90% of B. dorsalis larvae. Larvae were less susceptible to nematodes at higher moisture content (25% and 30%). In addition, pupae were less susceptible to nematodes than larvae. Furthermore, the tested nematode isolates were able to reproduce inside B. dorsalis third instar larva with the Heterorhabditis isolates giving the greatest multiplication rate (59577.2 IJs +/- 14307.41)

Survey of slug-parasitic nematodes in East and West Flanders, Belgium and description of Angiostoma gandavensis n. sp. (Nematoda: Angiostomatidae) from arionid slugs

A survey for slug-associated nematodes in five locations of East and West Flanders in Belgium revealed the presence of one new and six known slug-parasitic nematodes, Agfa flexilis (Dujardin, 1845), Alloionema appendiculatum (Schneider, 1859), Angiostoma dentiferum (Mengert, 1953), Angiostoma limacis (Dujardin, 1845), Angiostoma norvegicum (Ross et al., 2017) and Phasmarhabditis hermaphrodita (Schneider, 1859). Angiostoma norvegicum and P. hermaphrodita are recorded for the first time in Belgium. The six known species are documented by light microscopy (LM) microphotographs and informative DNA sequences. Angiostoma gandavensis n. sp. (Angiostomatidae), discovered from arionid slugs, is described based on light microscopy, scanning electron microscopy (SEM) and molecular data. Based on analyses of D2D3 expansion segment of 28S and 18S rDNA sequences, this new species is found to be related to A. limacis, A. norvegicum, A. margaretae (Ross et al., 2011) and A. milacis (Ivanova and Wilson, 2009). The new species can be distinguished from these others based on morphological characters such as the distinctive mucronate structures at the tail tip of both sexes, presence of lateral ala, reflexed female ovaries and the number and arrangement pattern of male genital papillae

First report of Scutellonema brachyurus (Steiner, 1938) Andrassy, 1958 and occurrence of Meloidogyne incognita (Kofoid & White, 1919) Chitwood, 1949 in Belgium

A study of plant-parasitic nematodes in the Botanical garden at Ghent University in Belgium revealed the presence of two tropical nematode species, i.e. Scutellonema brachyurus and Meloidogyne incognita. Scutellonema brachyurus was recovered, only once, for the first time in Belgium from Musa basjoo and is morphologically characterized. M. incognita, forming galls on Hedychium greenii, was recovered in all seasons over three consecutive years and is morphologically and molecularly characterized. Although no unequivocal evidence was found to indicate that these nematodes pose a current threat in Belgium, in the light of climate change, it is crucial to improve our knowledge of potential tropical nematode activity in more Northern countries

Trichodoridae, família de nematóides vetores de vírus

Os Trichodoridae são nematóides ectoparasitas de plantas, polífagos, que ocorrem com uma ampla distribuição mundial. Apesar da família ser pequena em número de gêneros e espécies quando comparada com outros taxons de nematóides parasitas das plantas, o grupo não é menos importante. Os Trichodoridae incluem não só espécies que podem causar danos diretos em numerosas plantas, como também, várias espécies que atuam como vetores naturais de tobravírus às plantas. Estes nematóides vetores de vírus têm recebido maior atenção por parte dos especialistas nas últimas décadas. A família Trichodoridae consiste em apenas cinco gêneros: Trichodorus, Paratrichodorus, Monotrichodorus, Allotrichodorus e Ecuadorus. As espécies vetoras de vírus têm sido registradas apenas nos gêneros didélficos, Trichodorus e Paratrichodorus, os quais têm uma ampla distribuição mundial. Os três gêneros monodélficos têm sido referidos, até hoje, apenas nas regiões neotropicais da América Central e do Sul. Na família Trichodoridae as espécies podem ser endêmicas, tal como a maioria das espécies da África do Sul, enquanto outras, como Paratrichodorus minor, se encontram amplamente distribuídas. Atualmente, no Brasil são conhecidas apenas 13 espécies (P. anthurii, P. minor, P. porosus, P. renifer, M. monohystera, M. samericus, A. brasiliensis, A. campanullatus, A. guttatus, A. longispiculis, A. loofi, A. sharmai e E. westindicus), apesar das numerosas referências acerca da ocorrência destes nematóides no País. A maioria dos registros refere-se apenas ao gênero ou refere Trichodorus em sentido lato. Das 13 espécies brasileiras, nove pertencem aos gêneros monodélficos e são consideradas endêmicas. Os Trichodoridae podem ser diferenciados facilmente dos outros nematóides parasitas das plantas principalmente pelo tipo de estilete e pela forma do corpo pós-morte. Enquanto os nematóides fitoparasitas em geral possuem um estilete oco, um estomatostilo ou um odontóforo, os nematóides tricodorídeos possuem um dente dorsal estiletiforme curvo, fechado na extremidade, que funciona apenas para perfurar a parede das células vegetais. Os tricodorídeos são nematóides relativamente roliços, arredondados em ambas as extremidades, o que levou os investigadores a atribuí-los a designação comum de nematóides em forma de charuto. Neste artigo, são fornecidas chaves politômicas pictórias para machos e fêmeas, que ilustram e codificam os caracteres diagnósticos. Os aspectos mais importantes são a forma e ornamentação dos espículos no macho e as peças da vagina esclerotizadas, nas fêmeas. Em seguida, apresenta-se também uma chave dicotômica ilustrada, para a identificação das espécies da América do Sul e Central. Uma vez que a identificação dos Trichodoridae nem sempre é fácil, as técnicas complementares, tais como dados sobre seqüências moleculares, parecem fornecerem dados adicionais extremamente úteis. O conhecimento destes nematóides é valioso não só na prevenção da entrada de novas espécies no país, mas, também, para se evitar a dispersão de espécies já existentes. As medidas de quarentena conhecidas para os nematóides vetores de vírus da família Longidoridae não se encontram estabelecidas para os tricodorídeos. Deveriam ser implementadas algumas medidas para o controle da troca de material eventualmente contaminado por estes nematóides ou tobravírus. As medidas de controle dos Trichodoridae são quer preventivas ou curativas. Além disso, o uso de alguns produtos químicos para o controle de parasitas das plantas está cada vez mais sujeito à regulamentação e sob restrição, por razões de natureza ambiental. Em geral, os prejuízos diretos causados por nematóides tricodorídeos são apenas severos quando as populações presentes são elevadas, enquanto a infecção por vírus necessita apenas de um espécime sendo, por isso, economicamente mais importante. As estratégias de controle em geral não visam especificamente os nematóides tricodorídeos. O controle genético ao nível da planta hospedeira através da produção de culturas resistentes ainda está pouco desenvolvido. O controle genético do nematóide tem sido dificultado pelo fato dos nematóides tricodorídeos serem polífagos, de se alimentarem do seu hospedeiro apenas por períodos muito curtos e por induzirem a formação de locais de alimentação pouco desenvolvidos.Trichodoridae are polyphagous ecto plant-parasitic nematodes occurring world-wide. Although the family is small in number of genera and species compared to other plant-parasitic nematode taxa, the group is not less important. The Trichodoridae include not only species which cause direct damage to numerous plants but also several species which act as natural vectors of tobra plant viruses. These virus vector nematodes have been receiving greater attention from specialists in the last decades. The family Trichodoridae consists of only five genera: Trichodorus, Paratrichodorus, Monotrichodorus, Allotrichodorus, and Ecuadorus. Virus vector species have only been recorded from the didelphic genera Trichodorus and Paratrichodorus which have a world-wide distribution. The three monodelphic genera have till now only been referred from the Neotropical Regions of Central and South America. Within the family Trichodoridae, species may be endemic such as most Trichodorus species of South Africa, other species such as Paratrichodorus minor are widely distributed. Currently, only thirteen species (P. anthurii, P. minor, P. porosus, P. renifer, M. monohystera, M. samericus, A. brasiliensis, A. campanullatus, A. guttatus, A. longispiculis, A. loofi, A. sharmai, and E. westindicus) are known from Brazil in spite of numerous reports on the occurrence of these nematodes in the Country. Most reports refer to genus level or very generally to Trichodorus as representative of the family Trichodoridae. Nine of the thirteen Brazilian species belong to the monodelphic genera and are considered endemic. Trichodoridae can easily be distinguished from other plant-parasitic nematodes mainly by the type of stylet and the habitus. While plant-parasitic nematodes in general possess a hollow stylet either a stomatostyle or odontostyle, trichodorid nematodes possess a curved stylet form dorsal tooth, closed at the tip just functioning to puncture plant cell walls. Trichodorid nematodes are rather plump nematodes, rounded at both ends, which lead researchers to use the common designation of cigar-shaped nematodes. Pictorial polytomous identification keys for male and females are provided, with illustration and coding the diagnostic characters; the most important features are the spicule shape and ornamentation in male and the sclerotized pieces at the vagina in females. Following, an illustrated dichotomous key is also provided for the identification of Central and South American species. Since identification of Trichodoridae is not always easy, complementary techniques, such as sequence data, appear to provide very helpful additional data. Knowledge about trichodorid nematodes is of great value not only to prevent entrance of new species in the country but also to avoid spreading of already occurring species. Quarantine measures known for longidorid virus vector nematodes are not established for trichodorids. Some measures for the control of changing of eventually contaminated material by these nematodes or tobra viruses should be implemented. The control measures of Trichodoridae are either preventive or curative. The use of some chemicals to control parasites of plants is more and more under regulation and restrictive for environmental reasons. Direct damage caused by trichodorid nematodes in general cause only severe damage when large populations are present. Virus infection needs only one specimen and is therefore an economically more important pest. Control strategies in general do not specifically target trichodorid nematodes. Genetic control at level of the host plant with the production of resistant crops is still not largely developed. Genetic control of the nematode is largely hindered by trichodorid nematodes being polyphagous, feeding for only very short time on its host and not inducing well developed feeding sites

Low genetic but high morphological variation over more than 1000 km coastline refutes omnipresence of cryptic diversity in marine nematodes

Background: The resilience of ecosystems to negative impacts is generally higher when high gene flow, species diversity and genetic diversity are present. Population genetic studies are suitable to investigate genetic diversity and estimate gene flow between populations. Seaweed beds form a dynamic shallow water ecosystem influenced by climate change and human exploitation, as such, seaweed beds are a particularly powerful model to investigate ecosystem resilience in coastal areas. We studied the population genetic structure of the new nematode species Paracanthonchus gynodiporata associated with seaweeds in northeastern Brazil. Nematodes are generally believed to have a limited dispersal capacity because of the lack of planktonic larvae. Yet, they can drift on seaweeds, and water currents might be a natural barrier for their dispersal. Populations of P. gynodiporata were sampled over more than 1000 km coastline in regions across major oceanic currents with and without historical exploitation of seaweed. Results: P. gynodiporata is described in an integrative way using mitochondrial and nuclear sequences and morphological data. The 3D model of the head region shows for the first time a detailed view of the ventrosublateral teeth, a character often overlooked in older taxonomic studies of the genus. A total of 17 mitochondrial COI haplotypes were found with one haplotype representing 63 to 83% of the frequencies in each population. AMOVA showed overall little population genetic structure (F-ST = 0.05204), and no genetic subdivision between the populations under the influence of the two different water currents were found. Effects of historical seaweed exploitation on population genetic diversity were not detected. In contrast, significant differences between populations were found in morphometric characters. This discrepancy in genetic and morphological differentiation between populations across 1000 km of coastline is surprising in view of the frequently observed presence of several cryptic species at small geographical scale in other macroalgal associated nematodes. Conclusions: Our results show that cryptic species are not omnipresent in marine nematode species, suggesting that nematodes associated with seaweeds have been able to disperse over large distances across well-known biogeographic barriers

Biodiversity patterns of free-living marine nematodes in a tropical bay: Cienfuegos, Caribbean Sea

Spatial and temporal biodiversity patterns of free-living marine nematodes were studied in Cienfuegos Bay, a tropical semi-enclosed basin in the Caribbean Sea. Taxonomic (to species level) and functional (biological trait) approaches were applied for describing the assemblage structure and relating it to abiotic environment based on a sampling scheme in six subtidal stations and three months. Biological trait approach added relevant information to species pattern regarding relationships between diversity patterns and the abiotic environment. The most common morphotypes were deposit feeding nematodes, with colonising abilities of 2–3 (in a scale from 1 to 5), tail conical cylindrical or filiforme and body slender; and their abundance were correlated with depth, organic matter and silt/clay fraction. In spite of a high turnover of species, functional diversity of assemblages did not change notably in space and time. A result probably due to sampling of the habitat pool of species and to low heterogeneity of the studied muddy bottoms. Chemical pollution (organic enrichment and heavy metals) and hydrodynamic regime possibly drove the biodiversity patterns. Spatial distribution of assemblages support the existence of two well differentiated basins inside the bay, the northern basin more polluted than the southern one. The low hydrodynamic regime would determine a poor dispersion of nematodes resulting in high spatial variance in the assemblage structure; and also the associated hypoxic conditions and pollutants in sediments can explain the dominance of tolerant nematode species such as Daptonema oxycerca, Sabatieria pulchra, Terschellingia gourbaultae, and Terschellingia longicaudata. A comparison of spatial– temporal patterns of biodiversity between Cienfuegos Bay and other semi-enclosed bays in temperate regions suggests several similarities: nematode assemblages are strongly influenced by anthropogenic disturbance, temporal trends are weak or overridden by spatial ones, and few cosmopolitan genera/ species tolerant to pollution and hypoxic conditions are dominant