Marine nematodes play a vital role in the ecosystem of seas and estuaries as a diverse species, universally rich and
often showing sensitive responses to ecological changes. During present study, surveys were conducted at four
locations of Sindh coast viz., Kaemari, Korangi Creek, Ibrahim Haidry, Mubarak Village and two of Balochistan
coast viz., Gadani and Sonmiani beach. As a result, four new species Oncholaimus paraoxyuris n. sp.,
Metoncholaimus medispiculatum n. sp., Theristus (P) karachiense n. sp. and Theristus cylindricus n. sp. were
found. O. paraoxyuris, M. medispiculatum and T. karachiense were molecularly identified on the basis of 18S
ribosomal gene with accession numbers KY497017, KY979964 and KY979968, respectively.