Postparasitic Juveniles Research Articles

Acute Toxicity of Sodium Chloride, Nitrates, Ortho-Phosphates, Cadmium, Arsenic and Aluminum for Juveniles of the Freshwater Pearl Mussel: Margaritifera Margaritifera (L.1758)

The freshwater pearl mussel (FWPM) Margaritifera margaritifera (L.1758) is critically endangered in Europe and ecotoxicological studies on the species are scares. Here, 96 h acute toxicity tests were conducted at 16 °C with sodium chloride (NaCl), nitrates (NO3−), ortho-phosphates (PO43−), cadmium (Cd), aluminum (Al) and arsenic (As) on 13- to 28-month-old post-parasitic juveniles. The experimental protocol was developed according to conditions described in a standard guide and was modified in order to assess toxicity thresholds for the Dronne River. Results showed that juveniles were tolerant to concentrations of Al, Cd, As, PO43−, NO3− and NaCl, largely higher than those found in the Dronne river, since 96 h EC50s (effective concentrations) were >954 µg/L for Al; >110 µg/L for Cd; >127 µg/L for As; >5.01 mg/L for PO43−; between 1000 and 1500 mg/L for NO3− and were 1.19 and 1.33 g/L for NaCl. Moreover, the use of a substrate in experiments was found not to affect juvenile responses and younger juveniles seemed more sensitive than older individuals. This study thus provides new data about the tolerance of FWPM to environmental pollution and suggests that pollutant concentrations in the river are significantly lower than levels affecting them.

Acute and chronic toxicity of magnesium to the early life stages of two tropical freshwater mussel species

Magnesium (Mg) is a common contaminant in mine water discharges. Although Mg is an essential element in biological processes, increased concentrations from anthropogenic sources can stress aquatic ecosystems. Additionally, studies evaluating the effects of Mg on north Australian freshwater species have indicated that in very soft waters there is a high risk to some species. Freshwater mussels are an ecologically and culturally important taxon in many freshwater environments, but knowledge of their sensitivity to Mg is limited. In the present study, the acute and chronic sensitivity of two freshwater mussel species, Velesunio angasi and an undescribed Velesunio species, to Mg was assessed (using MgSO4) on their early life stages, larval glochidia and post-parasitic juveniles. Acute 24-h exposures with glochidia generated a mean median lethal (LC50) toxicity estimate of 284mg/L for the five tests with V. angasi, and a mean LC50 of 300mg/L for the three tests with Velesunio sp. Mean chronic 14-d toxicity estimates resulting in 50% (EC50) and 10% (EC10) growth rate reductions for juveniles were 241 and 88mg/L respectively for the three tests with V. angasi juveniles, and 232 and 87mg/L respectively for the three tests with Velesunio sp. juveniles.The results represent the first acute and chronic Mg toxicity data for tropical freshwater mussels, and indicated that V. angasi and Velesunio sp. exhibited similar sensitivity and were moderately sensitive to Mg when compared to other tropical species. These results are a valuable contribution to the small existing dataset for Mg toxicity to tropical freshwater species, which can be used to inform water management in areas where Mg is a contaminant of concern, and ensure the protection of these taxa.

RNAi of esophageal gland-specific gene Mi-msp-1 alters early stage infection behaviour of root-knot nematode, Meloidogyne incognita

Root-knot nematodes are economically important plant pathogens that cause considerable damage to agricultural crops worldwide. They secrete a range of effector proteins from their specialized gland cells to modify host cell physiology to favour parasitism of the host tissue. A deeper understanding of the roles of effectors in nematode parasitism is necessary to unravel the mysteries of plant–nematode interactions. Herein, mRNAs of Mi-msp-1 (or Mi-vap-1), a gene encoding venom allergen-like effector protein, was localized to the subventral esophageal glands of Meloidogyne incognita. Mi-msp-1 was highly transcribed in the pre- and post-parasitic juveniles of M. incognita, suggesting the association of this effector gene during early stage infection behaviour of nematode. The targeted knockdown of Mi-msp-1 using in vitro RNAi rendered the nematode less successful in penetrating the tomato root. Silencing of Mi-msp-1 also interfered with the development and reproduction of M. incognita in adzuki bean. Intriguingly, induced suppression of Mi-msp-1 significantly altered the transcription of cell-wall-modifying enzymes (CWMEs, effectors involved in early parasitic process) and vice versa in M. incognita, indicating a possible interaction among msp-1 and CWMEs during the early stage of nematode–plant interaction. Our results showed that Mi-msp-1 could be a potential target/choke point for developing anti-nematode strategies.

Anomalomermis ephemerophagis n. g., n. sp. (Nematoda: Mermithidae) parasitic in the mayfly Ephemerella maculata Traver (Ephermeroptera: Ephermerellidae) in California, USA.

A new nematode, Anomalomermis ephemerophagis n. g., n. sp. (Nematoda: Mermithidae) is described from the mayfly Ephemerella maculata Traver (Ephermeroptera: Ephermerellidae) in California. The new species is characterised by six cephalic papillae and four additional disk papillae located on the head between the cephalic papillae and stoma. Additional diagnostic characters are: a terminal mouth opening; absence of X-fibers in the cuticle of both postparasitic juveniles and adults; paired, curved, medium-sized spicules; a straight barrow-shaped vagina and large eggs. Two infectious agents were present in some specimens. This is the first description of an adult nematode from a mayfly.

Large-scale production of the malaria vector biocontrol agent Romanomermis iyengari (Nematoda: Mermithidae) in Benin, West Africa.

The mermithid nematode Romanomermis iyengari is one of several natural control alternatives to synthetic pesticides for mosquito suppression. The commonly used mass rearing procedure of R. iyengari involves the use of coarse sand as a substrate for nematode maturation and oviposition. The coarse sand technique gives excellent nematode productivity in North America. However, under West African climatic conditions, this technique generates relatively lesser amounts of infectious worms. We evaluated coconut coir fibres as a replacement for coarse sand to improve yields in large-scale production of R. iyengari in Benin, West Africa. Culex quinquefasciatus was the host for the nematodes, and mosquitoes were blood-fed on chickens. Four days after blood feeding, egg rafts were collected and transferred into trays, each containing 2 l of water. The mosquito larvae were fed with fish food. When the mosquito larvae reached the second instar, preparasites (J2) were added (3 J2/larva) to the incubation trays. Eight days after infection, post-parasitic juveniles were separated from the water containing dead mosquito larvae and other debris using sieves and needles; 2 g of them were deposited in containers with coarse sand or coconut coir fibres and water. Three hours later, the water was drained, the jars covered and stored for eight weeks, after which J2 abundance was determined, using a total of 320 containers for each substrate. The abundance of J2 preparasites was also assessed 3-5 months after storage to determine the impact of long-term storage on the J2 yield. After 2 months storage, 2 g of post-parasites (~457 females and 583 males) yielded an average of 559,300±6094 J2 and 155,818±4427 J2 per container for coconut fibres and for coarse sand, respectively. During long-term storage, yields of J2 on coconut fibres substrate slowly decreased from 442,180±9322 J2 (3 months storage) to 163,632±12,416 J2 per container (5 months storage). On coarse sand substrate, the yield was relatively low and decreased from 49,812±1200 J2 at 3 months storage to 3046±229 J2 at 5 months storage. Under West African climatic conditions, coconut coir fibres gave significantly higher preparasitic nematode yields than the coarse sand technique.

The mermithid species Isomermis lairdi (Nematoda, Mermithidae), previously only known in Africa, found in Europe

The present work contributs to the knowledge on the aquatic mermithids (Nematoda, Mermithidae) occurring in black flies – an insufficiently studied group of parasitic nematodes. Isomermis lairdi Mondet, Poinar & Bernadou, 1977, described from larvae of Simulium damnosum Theobald, 1903 in Western Africa, is reported to occur in Bulgaria. The species was isolated from larvae of Simulium ornatum Meigen, 1818 in a local population of simuliids in a mountain stream near Jeleznitsa Village, Sofia district. Postparasitic juveniles of mermithids were obtained from the hosts and reared to the adult stage. The species was identified by morphological and morphometrical characters of postparasitic juveniles, and of male and female individuals. In the summer of 2012 a relatively high rate of mermithid infection in a local host population was detected (prevalence up to 44.1%). In August of the next year host abundance had considerably declined and other simuliid species, Simulium variegatum Meigen, 1818 and Simulium reptans (Linnaeus, 1758), predominated in the investigated locality. In West Africa, Isomermis lairdi is considered to be a potential biological agent for reducing the population density of the Simulium damnosum complex – the main vector of human onchocerciasis. In Europe, species of the Simulium ornatum complex are among the vectors of onchocerciasis of cattle and deer. The mermithids presumably play a certain role in the epidemiology of these diseases. A brief discussion on the taxonomy of the genus Isomermis Coman, 1953, and of the feasibility of molecular methods in mermithid taxonomy is provided. The species Isomermis lairdi is reported for the first time from Europe.

Utriculimermis microcaudata n. gen., n. sp., a new genus and species of Mermithidae (Nematoda) of the rivers Lafnitz and Teigitsch in the southeastern Austrian Alps

AbstractUtriculimermis microcaudata n. gen., n. sp. (Nematoda: Mermithidae) is described from the hyporheic biotope of two running waters in southeastern Austria. The mermithids were sampled by pumping and with a modified 'Hess'-sampler. The characteristics of this new genus are: long body length, a very long pharynx which attains about 95% of the body length, six head papillae, mouth opening terminal, six hypodermal chords at midbody level, excretory pore present near the nerve ring, small cupshaped amphids, cuticula lacking cross fibres under light microscope, males with long slightly curved spiculum, very large number of genital papillae, vulva slightly curved to barrel-shaped with vulval flap, postparasitic juveniles with very short tail appendage often only present as a button-like nipple.

Gastromermis cordobensis n. sp. (Nematoda: Mermithidae) parasitizing Simulium lahillei Patterson & Shannon (Diptera: Simuliidae) in Argentina

Gastromermis cordobensis n. sp (Nematoda: Mermithidae) a parasite of larvae of the blackfly Simulium lahillei Paterson & Shannon (Diptera: Simuliidae) in Argentina, is described. Diagnostic characters of this species include a mouth ventrlly shifted; six cephalic papillae; eigh hypodermal chords; small and pear shaped amphids; a long and S-shaped vagina; a singl spicule, which is long, has non-uniform walls, and a tip with sculpture; three rows of genital papillae, the middle one with 18 pre-anal and 10 post-anal papillae, the lateral rows have 36 papillae each; oval eggs; and post-parasitic juveniles with long thin tails. Pre-parasitic and parasitic juveniles are included in the description.

Postembryonic growth of Romanomermis culicivorax Ross and Smith, 1976: an example of accretionary growth in the Nematoda

The postembryonic development of Romanomermis culicivorax was studied in experimentally infected Aedes aegypti larvae. During its 7-day parasitic phase the nematode increased 8-fold in length and 10-fold in width, and the number of somatic nuclei increased 30-fold. Mitosis was observed in the hypodermal, trophosomal (intestinal), and muscle tissues. Body length and body width were correlated with number of somatic nuclei (r = +0.95, p < 0.001 and r = +0.91, p < 0.001 respectively). Growth in R. culicivorax is associated with extensive nuclear division, and this is believed to be the first report of accretionary growth in nematodes. The number of lateral hypodermal chord nuclei is variable in postparasitic juveniles and adults (mean, 1206 ± 536; range, 610–2475) and is correlated with body length (r = +0.84, p < 0.001). The lateral hypodermal chord nuclei do not undergo a fixed number of divisions.

Parasitism of the simuliid (Diptera: Simuliidae) by Mermithidae (Nematoda) in western Africa. IV. Description of Isomeris lairdi, n.sp., parasite of Simulium damnosum

The present communication describes a new species of mermithid nematode, Isomermis lairdi, found parasitizing blackflies in the Ivory Coast, West Africa. This nematode is the most common mermithid parasite of Simulium damnosum Theobald and occurs in the larval, pupal, and adult stages of this blackfly in streams of various sizes. The diagnostic characters of the adults of I. lairdi are (1) terminal mouth. (2) strongly S-shaped vagina, (3) ratio of spicule length to anal body width (1.7–2.8), and (4) circular amphids and amphidial openings.The postparasitic juveniles of I. lairdi differ from those of I. tansaniensis Rubtsov, 1972, in having three or four rows of cells in the lateral cords and a longer tail appendage in the male.This is the third species of mermithid nematode described from blackflies (including Simulium damnosum) in West Africa, and the first of the genus.

Empidomermis cozii n.gen., n.sp. (Mermithidae: Nematoda) a parasite of Anopheles funestus (Culicidae: Diptera) in West Africa.

A new genus and species of mermithid nematode parasitizing adult females of Anopheles funestus (Giles) in Upper Volta is described. The new genus Empidomermis is characterized by having six head papillae, eight hypodermal cords, cuticle without noticeable cross fibers, two short slightly curved spicules (equal to or less than body width at cloaca), a relatively short S-shaped vagina, small amphids, and postparasitic juveniles with a well-developed tail appendage.The nematodes could only be successfully reared to maturity if the hosts were held on glucose 3–4 days after the blood meal. Postparasitic juvenile mermithids molted to the adult stage about 17 days after leaving their mosquito hosts and mating and oviposition occurred immediately afterwards. The eggs hatched about 54 days after oviposition when mosquito larvae were added to the container. Parasitized adult female A. funestus were sterilized and died soon after the nematodes emerged.

Biology and Redescription of Pheromermis Pachysoma (V. Linstow) N. Gen., N. Comb. (Nematoda: Mermithidae), a Parasite of Yellowjackets (Hymenoptera: Vespidae)

Pheromermis pachysoma (von Linstow) n. gen., n. comb., a parasite of the yellowjacket, Vespula pensylvanica (Saussure), is described from California. The genus, Pheromermis, is characterized by the presence of four submedian cephalic papillae; large anteriorly placed cup-shaped amphids; an S-shaped vagina not bent in a transverse plane to the body; six hypodermal cords; paired, short, separate spicules; cuticle with cross fibers; and eggs lacking processes. The development of P. pachysoma is unique because a paratenic or transport host is required for completion of the life cycle. The adult nematodes occur in water or saturated soil and the eggs are fully embryonated at oviposition. The eggs hatch in the gut of various insects and infective stage juveniles penetrate the gut wall and enter a quiescent state in the tissues of these paratenic hosts. Wasp larvae are probably infected when they are fed paratenic hosts captured by worker yellowjackets. Postparasitic juveniles of P. pachysoma emerge from adult wasps when the latter visit wet sites after their fall emergence from the nest. The ant parasite, Mermis myrmecophila Baylis, is transferred to the genus Pheromermis.

Field and Laboratory Observations of Hexamermis arvalis (Nematoda: Mermithidae) a Parasite of Cutworms1

In Missouri and adjacent States, the nematode Hexamermis arvalis Poinar & Gyrisco was commonly found in clover and alfalfa fields parasitizing the dingy cutworm, Feltia subgothica (Haworth), the black cutworm, Agratis ipsilon (Hufnagel), and the bristly cutworm, Lacinipolia renigera (Stephens) (Lepidoptera: Noctuidae). Other noctuid larvae occurring in the same habitat were never found parasitized, and young nematodes found in larvae of the clover leaf weevil, Hypera punctata (F.), always succumbed to encapsulation by blood cells of the host. H. arvalis proved to be univoltine. Infective juveniles parasitized overwintering 1st- and 2nd-stage lepidopterous larvae in the fall, completed their development, and emerged from 4th- and 5th-stage larvae in late spring of the following year, entered the soil, molted to adults in about 1–2 months, mated, and laid eggs that apparently aestivated. A method of rearing postparasitic juveniles to adults was devised, and a method of sampling field population of the nematode was successful. The nematode reared from the cutworms may be different from H. arvalis described from Hypera postica (Gyllenhal).

On the Occurrence of Protein Platelets in the Pseudocoelom of a Nematode (Hydromermis Sp.; Mermithidae)

Disc-like protein platelets are described from the pseudocoelom of free living post-parasitic juveniles of Hydromermis sp. (Mermithidae). These platelets have an average diameter of 23.2 μ and an average width of 5.5 μ. They appear hyaline and homogeneous under bright field and are not refringent. They lack a nucleus and possess an indistinct limiting membrane. Electron micrographs showed the platelets to consist of a highly organized pattern of parallel, dense lines, evenly spaced at about 270 A. The entire platelet gave a strong positive reaction for protein while tests for tyrosine and uric acid were negative. On the basis of this study, it is concluded that similar objects previously reported from the pseudocoelom of mermithid nematodes and listed in Table I of this paper are probably also protein platelets.