Metatanais cylindricus Shiino, 1952

Blazewicz-Paszkowycz, Magdalena & Zemko, Karol, 2009, A new species of Metatanais Shiino, 1952 (Crustacea, Tanaidacea, Paratanaoidea) from Australian coral reefs, with a redefinition of the genus, ZooKeys 18 (18), pp. 129-141 : 132

Metatanais cylindricus Shiino, 1952

Figs 1 , 2

Metatanais cylindricus Shiino, 1952: 24–27 , figs 6–7; Larsen and Shimomura, 2007: 2.

Material examined: Lectotype female (dissected on slides) (NSMT-Cr 14507), among algae and on surface of sponges and compound ascidiae, coll. Sakata and Toshima, Seto, 9–12 May, 1948.

Diagnosis: Body three times as long as wide. Carapace shorter than wide. Antennule article 1 more than twice as long as wide. Pereopod 4–6 propodus slim (about five times as long as wide), with small setae ventrally.

Remarks: Metatanais cylindricus was described from 23 specimens found in shallow water off Seto (north-western coast of Japan) among aggregation of sponges and ascidiae, and catalogued as syntypes at the National Museum of Nature and Science in Tokyo. From this collection we have been loaned only one specimen which we have here designated the lectotype. It was partially dissected and drawn.

In the original species description Shiino stated that specimens studied by him were females as “Neither rudimental oostegites nor mare genital papillae …” were discovered. Based on the present knowledge about the tanaid life history we can assume that Shiino has deal with both sexes, where males had the rudimental pleopods (Shiino, 1952: 26, fig 7M), and females lacked them, as loaned lectotype.

M. cylindricus is morphologically almost identical to M. bipunctatus sp. n. It can be distinguished from the new species by most compact body, with cephalothorax clearly shorter than its length ( Fig 1 ). The antennule article 1 in M. cylindricus is almost three times as long as wide and ‘columnar’ according to Shiino (1952), while it seems to be more robust and just less than twice as long as wide in the new species ( Fig 2A ). The species also has much slimmer propodus in pereopod of the last three pairs (over four times as long as wide). Th e obvious difference between the species is the form of seta on ventral margin of the propodus in pereopod 4–6 that is small and weak seta in M. cylindricus ( Fig 2 G–I) and robust in the new species ( Fig 5 E–G).

Figures

Figure 1. Metatanais cylindricus Shiino 1952 female, lectotype A body, dorsal B body, lateral. Scale bar equals 1 mm.

Figure 2. Metatanais cylindricus Shiino, 1952, female, lectotype.A antennule B antenna C chela D pereopod 1 E pereopod 2 F pereopod 3 G pereopod 4 H pereopod 5 I pereopod 6. Scale bars equal 0.1mm.

Figure 5. Metatanais bipunctatus sp. n. paratype female. A cheliped B pereopod 1 B' pereopod 1 carpus detail B''pereopod 1 propodus detail C pereopod 2 C' pereopod 2 carpus detail C''pereopod 2 propodus detail D pereopod 3 E pereopod 4 F pereopod 5 G pereopod 6 H uropod. Scale bars equal 0.1mm for A–G; 0.01 mm for H.