A new species of polychaete, Armandia sampadae was collected from shallow sandy sediments off Rutland Island (57 m depth) and off North Andaman (52 m depth) during a benthic survey along the continental shelf of Andaman and Nicobar Islands. The major character which distinguishes this species from other members of the genus Armandia is the presence of a pair of large, flattened, rounded, stalked, pigmented, leaf-shaped ventral papillae at the ventral base of the ringed anal funnel and the occurrence of a pair of sub-triangular black pigmented spots in the basal portion of the ventral papillae.

The present study reports the first record of Herviella mietta from the Andaman Sea, Indian Ocean, more precisely from the Andaman and Nicobar Islands, India. The species is identified by colour pattern, morphological characters and microscopic investigation of the radula and the lateral denticles. The important diagnostic characters are the carrot-shaped cerata that are predominantly black in colour, black pigment on the body, and 8–9 denticles on each side of the small central cusp of each tooth.

Halieutopsis stellifera was previously reported only from the northern Celebes to the Philippine archipelago and Okinawa Trough. The present study reports Halieutopsis stellifera from the eastern Indian Ocean based on three specimens from Andaman waters (depth range 480 to 580 m).

Damiria toxifera has been recorded for the first time in the Andaman Sea region. It has not been found elsewhere since its discovery and description from the Seychelles. The distinguishing features of this species in the Andaman and Nicobar Islands are depicted in detail.

The identity of a dotillid intertidal crab from exposed sandy beaches within the Laem Son National Park along the Andaman Coast in Thailand was investigated. The species was identified as Dotilla intermedia De Man, 1888, which represents the first record of this species from Thailand. A description of the species is provided and a lectotype is designated from the type series.

Suctorian epibionts Thecacineta calix attached on the cuticle of nematodes Desmodora sphaerica and D. pontica are reported here from the deep-sea hexactinellid sponge Pheronema sp. from the Andaman Sea (Indian Ocean). The epibiont T. calix is reported here for first time from the Andaman Sea.