Ageing in the nematode Caenorhabditis elegans is unusual in terms of the severity and early onset of senescent pathology, particularly affecting organs involved in reproduction (Ezcurra et al., 2018; Garigan et al., 2002; Herndon et al., 2002). In post-reproductive C. elegans hermaphrodites, intestinal biomass is converted into yolk leading to intestinal atrophy and yolk steatosis (Ezcurra et al., 2018; Sornda et al., 2019). We recently showed that post-reproductive mothers vent yolk which functions as a milk (yolk milk), supporting larval growth that is consumed by larvae (Kern et al., 2020). This form of massive reproductive effort involving biomass repurposing leading to organ degeneration is characteristic of semelparous organisms (i.e. that exhibit only a single reproductive episode) ranging from monocarpic plants to Pacific salmon where it leads to rapid death (reproductive death) (Finch, 1990; Gems et al., 2020). Removal of the germline greatly increases lifespan in both C. elegans and Pacific salmon, in the latter case by suppressing semelparous reproductive death (Hsin and Kenyon, 1999; Robertson, 1961). Here we present evidence that reproductive death occurs in C. elegans, and that it is suppressed by germline removal, leading to extension of lifespan. Comparing three Caenorhabditis sibling species pairs with hermaphrodites and females, we show that lactation and massive early pathology only occurs in the former. In each case, hermaphrodites are shorter lived and only in hermaphrodites does germline removal markedly increase lifespan. Semelparous reproductive death has previously been viewed as distinct from ageing; however, drawing on recent theories of ageing (Blagosklonny, 2006; de Magalhães and Church, 2005; Maklakov and Chapman, 2019), we argue that it involves exaggerated versions of programmatic mechanisms that to a smaller extent contribute to ageing in non-semelparous species. Thus, despite the presence of reproductive death, mechanisms of ageing in C. elegans are informative about ageing in general.

A new population of Metarhabditis amsactae from India is morphologically, morphometrically, and molecularly characterized. This material is characterized by having 0.65 to 1.14 mm length, lips rounded, and grouped in pairs, stoma with metastegostoma bearing setose denticles, pharynx with metacorpus slightly swollen and fusiform, nerve ring, and excretory pore located at isthmus level, female reproductive system didelphic-amphidelphic with vulva equatorial, female tail conical-elongate with acute tip, male tail conical with large and robust posterior filiform part, spicules free with hooked manubrium slightly bent ventrad, gubernaculum with narrow corpus, bursa open leptoderan with eight genital papillae and phasmids posterior to the GP8. Molecular studies based on 18S and 28S rDNA genes are provided for the first time for the species. In addition, integrated morphological, morphometrical, and molecular characters are compared with other previous records of the species. According to our analysis, Metarhabditis longicaudata and other material described as different species are proposed as new junior synonyms of M. amsactae .

Background In India, application of entomopathogenic nematodes (EPNs) as a bio-agent against insect pests was known since 5–6 decades with the application of the exotic species Steinernema carpocapsae (DD-136 Strain). EPNs have a strong potential to control the soil-borne insect pests. In the present study isolated strain was identified as Steinernema abbasi and docketed as CS-39. The efficacy of the isolated strain was tested against the American bollworm, Helicoverpa armigera (Hub.) (Lepidoptera: Noctuidae). Results Laboratory bioassay revealed that the median lethal concentration (LC50 = 83.21 IJs) of the S. abbasi isolate CS-39 was quite sufficient to achieve 100% mortality after 24 h of exposure. Mean mortality percentage was estimated > 75% at all concentrations, i.e., 25, 50, 100 and 200 IJs/larva, and 100% mortality was achieved at 200 IJs/larva after 24 h of concentration exposure. Positive relationship was found at every concentration of exposure and % mortality of the insect pest (H. armigera) after 36 (p < 0.01) and 48 h of exposure (p < 0.02). Conclusions Steinernema abbasi isolate CS-39 found to be highly virulent to H. armigera. As the result urged, 200 IJs / larva showed 100% mortality at 36 h, whereas 100 IJs / larva showed 100% mortality at 60 h. Difference in time duration might be because of action of bacterial symbionts which were the main precursor of pathogenicity. Extensive study of secondary metabolites of the bacterial symbionts may extend the present study to the new dimension.

National loss of Rs. 21,068.73 million has been estimated due to plant-parasitic nematodes in India. Among plant-parasitic nematodes, one of the major nematodes, root-knot nematodes (RKNs), are well-known diseases causing major losses in vegetable crops. An in vitro experiment was conducted to evaluate the nematicidal activities of the cell-free culture filtrate (CFCF) of entomopathogenic bacteria Photorhabdus spp. and Xenorhabdus spp. isolated from entomopathogenic nematodes Heterorhabditis indica (DH3) and Steinernema abbasi (CS-39), respectively. The applied doses were 90, 50, 25 and 10% CFCFs. The experiment was performed on the plant-parasitic nematode Meloidogyne incognita, and the % mortalities were determined at 6, 12, 24 and 48 hr intervals. The results of the present study revealed that 100% mortality was achieved after 48 hrs with a 10% filtrate of H. indica isolate DH3, while no significant result was achieved even after 48 hrs and at 90% CFCF of isolate CS39. Therefore, 10% CFCFs may be recommended for application in root-knot nematode-infected fields for the control.