Gigantione rhombos, An & Yu & Markham, 2009

An, Jianmei, Yu, Haiyan & Markham, John C., 2009, First record of the genus Gigantione (Epicaridea: Bopyridae: Pseudioninae) from Chinese waters, with description of three new species, Journal of Natural History 43 (5 - 6), pp. 335-353 : 343-346

publication ID	https://doi.org/ 10.1080/00222930802590737
persistent identifier	https://treatment.plazi.org/id/03D9CC30-FFD0-BE00-FD93-C234330C44A9
treatment provided by	Felipe
scientific name	Gigantione rhombos
status	sp. nov.

Treatment

Gigantione rhombos View in CoL sp. nov.

( Figures 5 View Figure 5 , 6 View Figure 6 )

Material examined

Infesting Eucrate alcocki Serene. Determination of host, Huiliang Chen. Holotype: South China Sea, Stn 6062, 21 ° 45 9 N, 113 ° 30 9 E, 32 m, 8 October 1959, Coll. Yongliang Wang, 1♀, CIEG606201 GoogleMaps . Allotype: South China Sea, Stn 6062, 21 ° 45 9 N, 113 ° 30 9 E, 32 m, 8 October 1959, Coll. Yongliang Wang, 1 „, CIEG606202 . Paratypes: infesting Eucrate sp. South China Sea, Stn 6091, 20 ° 30 9 N, 112 ° 30 9 E, 78 m, 5 July 1959, Coll. Xiutong Ma, 1♀, CIEG609101 . 1 „, CIEG609102 GoogleMaps .

Infesting Heteroplax dentata Stimpson. Determination of host, Huiliang Chen. Beibu Gulf, Stn 7601, 19 ° 00 9 N, 105 ° 45 9 E, 13 m, 12 January 1962, Coll. Fuzeng Sun, 1♀, CIEG760101 GoogleMaps . 1 „, CIEG760102 .

Description of holotype (CIEG606201)

Length 6.8 mm, maximal width 8.42 mm, head length 1.89 mm, head width 2.41 mm, pleon length 1.59 mm. All body regions and segments distinct. No pigmentation ( Figure 5A,B View Figure 5 ).

Head oblate, wider than long, frontal lamina absent, posterior margin bilobate. Pointed anterolateral flaps projecting from each side of head. Eyes absent ( Figure 5A View Figure 5 ). First antenna of three articles, second antenna of five articles, both setose terminally ( Figure 5C View Figure 5 ). Maxilliped suboval, palpless, its anterior article three times larger than posterior one and marginally fringed by dense setae ( Figure 5D View Figure 5 ). Barbula with a pair of prominent falcate lateral projections on each side, many small projections encircled by lateral projections, prominent rhombic projection in centre ( Figure 5E View Figure 5 ).

Pereon broadest across third pereomere ( Figure 5A View Figure 5 ). Coxal plates well-developed on both sides of all pereomeres, margins distinctly dentate, small tubercles on ventral surface. Coxal plates on long side very long, wide and reflexed over dorsal surfaces of pereomeres; those on opposite sides short and narrow. Round dorsolateral bosses on first four pereomeres. Oostegites incompletely enclosing brood pouch ( Figure 5B View Figure 5 ). First oostegite ( Figure 5F,G View Figure 5 ) with much larger anterior article, deep groove separating it from posterior article externally; internal ridge bearing six to eight projections, posterolateral point absent. All pereopods hidden in dorsal view, of about same size ( Figure 5H,I View Figure 5 ), bases of second to seventh pereopods produced into prominent lobes along flexor margins.

Pleon of six pleomeres, first five bearing biramous pleopods and lateral plates, terminal segments retreating from body outline, and only short uropods visible in dorsal view. Lateral plates on long sides tuberculate and long, those on opposite sides smooth and much shorter. First pleopod lamellar, tuberculate, asymmetrical, that on left side much wider than one on right side ( Figure 5J View Figure 5 ). Second to fifth pleopods trifurcate, endopodites single lobes, but exopodites ramified into inner and outer lobes, tuberculate. Biramous uropods small.

Description of allotype (CIEG606202)

Length 3.36 mm, maximal width, across pleon 5, 1.13 mm, head length 0.45 mm, head width 0.84 mm, pleonal length 1.31 mm. All body regions and segments distinctly separated ( Figure 6A,B View Figure 6 ).

Head semicircular, with dark eyes near posterolateral corners ( Figure 6A View Figure 6 ). Antenna of four articles, with setae on distal articles; antennule of six or seven articles, terminal one setose ( Figure 6C View Figure 6 ).

Pereomeres 1–6 almost equally wide, with curved margins, lacking midventral projections ( Figure 6B View Figure 6 ). First pereopods much larger than other six pereopods ( Figure 6D,E View Figure 6 ).

Pleon of six pleomeres, first five with conspicuous pleopods, without midventral projections ( Figure 6B View Figure 6 ). Pleopods 1 and 5 rod-like and uniramous, pleopods 2–4 biramous. Sixth pleomere produced into uropods, middle region of uropods concave ( Figure 6B View Figure 6 ), small anal cone between two rami of uropods ( Figure 6B View Figure 6 ).

Variations

Paratype females agree in all respects with the holotype. A paratype male (CIEG760102) differs from the allotype in having pointed terminal uropods, and with setae on front edge of left side of the head.

Etymology

The specific name, the transliterated Greek noun rhombos used in apposition, refers to the presence of a prominent rhombic projection in the central region of the barbula of the female.

Remarks

The female of the new species, G. rhombos , is distinguished from those of the other 13 described species of Gigantione by the prominent dentate margin of its coxal plates, and by a prominent rhombic projection in the middle region of the barbula of the holotype and paratype females. Gigantione rhombos appears to be most closely related to G. petalomerae Markham, 1999 , which is known to infest Petalomera pulchra Miers. Females of the two species differ in that G. rhombos has distinct coxal plates, an asymmetrical body and a rhombic barbular projection. According to Markham (1999), the female of G. petalomerae has slender, smooth coxal plates on each side, an almost symmetrical body and a barbula with a single terete projection on each side and a triangular lobe in the centre.

Distribution and hosts

South Sea, China, infesting Eucrate alcocki Serene and Eucrate sp. ; Beibu Gulf, infesting Heteroplax dentata Stimpson.