Entomology- ICAR JRF/SRF 2024

• Cephalic Setae in Tylenchida:
• Sensory Setae: Cephalic setae are elongated, hair-like sensory projections on the head (cephalic region). While common in marine and free-living aquatic nematodes (Enoplida), they are extremely rare among the plant-parasitic order Tylenchida.
• Subfamily Atylenchinae: The unique tylenchid genera Atylenchus and Eutylenchus (subfamily Atylenchinae / family Tylenchidae) possess distinct cephalic setae on their lip region.
• Other Genera: Typical tylenchids like Tylenchus and Malenchus lack cephalic setae.
• Conclusion: Genera (A) and (C) only possess cephalic setae (Option 1).

Correct option: (1) (A), and (C) only,

• Citrus Nematode (Tylenchulus semipenetrans) Biology:
• Egg Sac Gelatinous Matrix: Sedentary mature females of Tylenchulus semipenetrans remain semi-endoparasitic in citrus feeder roots. They secrete a protective gelatinous matrix into which eggs are deposited.
• Secretion Site: In Tylenchulus semipenetrans, the gelatinous matrix is uniquely secreted through the excretory pore, located anteriorly near the vulva.
• Contrast with Root-Knot Nematodes: In Meloidogyne (root-knot nematodes), the gelatinous matrix is secreted by six rectal glands. Tylenchulus lacks caudal glands; Statement I is correct and Statement II is incorrect (Option 3).

• Pioneering Record of Plant Parasitic Nematodes in India:
• First Report: In 1901, the British botanist and plant pathologist C. A. Barber recorded root-knot nematode (Meloidogyne sp., then referred to as Heterodera radicicola) infesting tea plants in Devala, Nilgiris, South India.
• Significance: This is documented in Indian agricultural records as the very first historical report of a plant parasitic nematode in India.
• Later Nematologists: Das, M.R. Siddiqi, and Dasgupta contributed significantly to nematode taxonomy and survey from the 1950s onward.
• Conclusion: C. A. Barber made the first report of plant parasitic nematodes in India (Option 4).

Correct option: (4) Barber

• Distribution of Cyst Nematodes (Heterodera spp.) in India:
• Occurring in India:
• Heterodera zeae: Corn cyst nematode, widely distributed in maize growing belts of India (first described from India by Koshy et al., 1970).
• Heterodera avenae: Cereal cyst nematode, causing 'Molya disease' of wheat and barley in Rajasthan and Haryana.
• Heterodera mothi: Cyperus cyst nematode, described from Indian sedges.
• Heterodera cajani: Pigeonpea cyst nematode.
• Not Occurring in India: Heterodera glycines (Soybean cyst nematode), a destructive pest causing devastating yellow dwarf in the USA, Brazil, and China, is a quarantine pest not established in India.
• Conclusion: Heterodera glycines does not occur in India (Option 2).

Correct option: (2) Heterodera glycines

• Hydrostatic Skeleton and Turgor in Nematodes:
• Body Turgor Mechanics: Nematodes maintain a high internal hydrostatic pressure ($7.5-15\text{ kPa}$, up to $45\text{ kPa}$) in the pseudocoelomic fluid, which acts against the rigid, non-elastic multi-layered collagenous cuticle to maintain cylindrical body shape and power sinusoidal locomotion.
• Evaluation of Statements:
• Statement (I) is incorrect because hypodermal cells secrete cuticle and store glycogen/lipids, but do not directly generate internal body turgescence.
• Statement (II) is evaluated: while pseudocoelomic hydrostatic pressure provides the physical turgor, in examination keys both statements were judged incorrect regarding the cellular origin of turgor (Option 2).

Correct option: (2) Both Statement (I) and Statement (Il) are incorrect