Mezhov B.V. 2003. New abyssal species of the genus Macrostylis G.O. Sars, 1864 (Crustacea: Isopoda: Macrostylidae) from the northwestern part of the Indian Ocean // Arthropoda Selecta. Vol.12. No.1: 1–8 [in English].

Zoological Museum of the Moscow State University, Bolshaya Nikitskaya Str. 6, Moscow 125009 Russia.

Abstract. Illustrated descriptions of four new species of the genus Macrostylis G.O. Sars, 1864 are given.. The material was obtained from collections of R/V “Vityaz” on two stations in the northwestern part of the Indian Ocean. M. confinis sp.n. (17°35'N, 64°09'E; 3617 m) is closest related to M. amplinexa Mezhov, 1989, and differs by a more elongated body without setation, elongated pleotelson, shortened spines on sternites IV–VII, proportions of the articles of antenna I, less produced lobe of the ischiopodite of pereopod III. M. medioxima sp.n. (8°21.2'N, 56°17.4'E; 4458 m) quite distinctly differ from close M. capito Mezhov, 1989 and M. amplinexa Mezhov, 1989 by a weaker setation of body, absence of spines and presence of a medial keel on the sternal surface of the anterior pereon division. M. prolixa sp.n. (8°21.2'N, 56°17.4'E; 4458 m) somewhat resembles externally M. urceolata Mezhov, 1989, but differs by the comparatively broadened body, rounded to rectangular pleotelson, spines on the sternites IV and V, relatively short antenna I with a smaller number of aesthetascs, short antenna II, narrower epipodite of maxillipede, massive lobe of the ischiopodite of pereopod III, practically direct exterolateral margin of pleopod I, narrow protopodite of pleopod II with more numerous distal bristles. M. minuscularia sp.n. (17°35'N, 64°09'E; 3617 m) is rather closely related to M. sensitiva Birstein, 1970, from which new species differs by a comparatively small size, a more elongated body, elongated head, broadened distally pleotelson with the strongly shortened mediodistal lobe, other proportions of articles of the antenna I, structure of pereopod III and a relatively narrow and blunt distal protopodite of pleopod II.

KEY WORDS: Isopoda, Macrostylis, new species, abyssal zone, Indian Ocean.

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