Paraeragia kiribatiensis, An & Zhang & Paulay, 2017

An, Jianmei, Zhang, Pengchi & Paulay, Gustav, 2017, A new genus and two new species of Argeiinae (Crustacea: Isopoda: Bopyridae) from the Indo-west Pacific, Journal of Natural History 51 (7 - 8), pp. 405-420 : 410-413

Paraeragia kiribatiensis gen. nov., sp. nov.

( Figures 1 and 2 )

Material examined

UF Arthropoda 42226: holotype ♀, allotype ♂, infesting Synalpheus gracilirostris de Man, 1910 ( UF Arthropoda 40882); Kiribati, Line Islands, Millennium Island , ‘tent site’, 12 m, host in live Pocillopora , 9.91° S, 150.21° W . 5 November 2013, coll., Francois Michonneau, Matthieu Leray, Nancy Knowlton.

Description of holotype female ( Figure 1 )

Length 2.62 mm, maximum width 2.54 mm, head length 0.58 mm, head width 0.84 mm. Body outline oval, slightly distorted ( Figure 1 (a,bHead quadrate, without frontal lamina, extending into pereomere 1 ( Figure 1 (a)). Black eyes on the anterolateral corners of the head ( Figure 1 (a)). Antennule of three articles; antenna of four articles; terminal article of antennules and antenna setose ( Figure 1 (c)). Barbula with two blunt lateral projections on each side, flat near centre ( Figure 1 (d)). Maxilliped triangular, articulated, with setose palp ( Figure 1 (e,f)).

Pereon broadest across third pereomere ( Figure 3 (a)). Pereomeres mostly distinct, pereomeres 2 and 3 fused on their left side ( Figure 1 (a)). Pereon wider than long, with reduced coxal plates on first four pereomeres on the left side and on the first three pereomeres on the right side ( Figure 1 (a)). Round tergal projection present only on the right side of pereomeres 2 and 3. Brood pouch widely open ( Figure 1 (b)). First oostegite with nearly smooth ridge and round posterolateral point ( Figure 1 (g,h)), and posterior margin of the first oostegite also smooth. Pereopods slightly larger posteriorly ( Figure 1 (i,j)), with blunt dactyli.

Pleon of six pleomeres, first five bearing lateral plates and small uniramous pleopods ( Figure 1 (b)). Uropods resembling lateral plates, uniramous.

Description of allotype male ( Figure 2 )

Length 1.40 mm, maximum width, across pereomere 3, 0.52 mm, head length 0.24 mm, head width 0.42 mm, pleonal length 0.26 mm. With scattered black pigmentation on dorsal surface of pereon and pleon.

Head oblong, black eyes near posterior margin ( Figure 2 (a)). Antennae extending beyond head, visible in dorsal view. Antennule of three articles, antennae of five or six articles, terminal articles of antennules and antennae setose ( Figure 2 (c)).

All pereon segments distinct ( Figure 2 (a)), pereomere sides parallel, subequal in width, lacking midventral projections ( Figure 2 (b)). First pereopods with longest dactyli, second pereopods with second largest dactyli, all seven pereopods with sharp, pointed dactyli ( Figure 2 (d–f)). Carpi increasing in size posteriorly ( Figure 2 (d–f)).

Pleon fused into single piece, but with faint lines suggesting demarcation of first three segments on dorsal surface ( Figure 2 (a)). Pleopods and uropods absent.

Etymology

The specific name, kiribatiensis refers to the type locality of Kiribati, Line Islands .

Remarks

These specimens are placed in Argeiinae because the female has a round body outline, a head without frontal lamina, a brood pouch that is widely open, a first oostegite with a simple internal ridge, and a pleon with six distinct pleomeres, whereas the male has a fused pleon. Among the eight currently recognized arginine genera, four have lateral plates on the pleon ( Argeia , Bopyrosa , Eragia , Stegoalpheon ), and four lack them ( Argeiopsis , Gareia , Parargeia , Stegoargeia ). Paraeragia has prominent lateral plates, but the uniramous pleopods and uropods distinguish it from Argeia and Stegoalpheon . Paraeragia differs from Eragia (based on Markham 1994; Williams and Boyko 2010) in the following characters (character states in Eragia given in parentheses): female: (1) triangular pleon, much shorter than pereon (quadrate pleon, pereon and pleon of equal length); (2) lateral plates extend posteriorly (extend laterally); (3) uropods paired, (uropods absent or present on right side only); (4) brood pouch widely open, (brood pouch almost closed); (5) oostegite 1 with blunt and round posterolateral point (with very slender and pointed posterolateral point); male: (1) faint lines demarcate anterior segments of pleon (pleon entire) (unique of species in the subfamily); (2) with black eyes (lacking eyes); (3) antennae with three articles (seven articles); (4) antennule with four articles (three articles); (5) pereopods decreasing in size from anterior to posterior (increasing in size); (6) body dorsally pigmented (unpigmented). Paraeragia differs from Bopyrosa in: (1) body about as long as wide (much longer than wide); (2) pleon much narrower than the pereon (wider than pereon because of large lateral plates); (3) lateral plates not conspicuously extended (markedly extended).

Figures

Figure 1. Paraeragia kiribatiensis sp. nov. Holotype female: (a) Dorsal view. (b) Ventral view. (c) Right antenna and antennule. (d) Right barbula. (e) Right maxilliped, external view. (f) Palp of right maxilliped. (g) Right oostegite 1, external view. (h) Right oostegite 1, internal view. (i) Left pereopod 1. (j) Left pereopod 7. Scale = 1 mm (a, b), 0.34 mm (c, f, i, j), 0.54 mm (d, e, g, h).

Figure 2. Paraeragia kiribatiensis sp. nov. Allotype male: (a) Dorsal view. (b) Ventral view. (c) Right antenna and antennule. (d) Left pereopod 1. (e) Left pereopod 3. (f) Left pereopod 7. Scale = 1 mm (a, b), 0.70 mm (c, d, e, f).

Figure 3. Argeiopsis guamensis sp. nov. Holotype female: (a) Dorsal view. (b) Ventral view. (c) Right antenna and antennule. (d) Right side of barbula. (e) Right maxilliped, external view. (f) Right oostegite 1, external view. (g) Right oostegite 1, internal view. (h) Left pereopod 1. (i) Left pereopod 7. (j) Ventral view of pleon (endopodites shaded). Scale = 1 mm (a, b), 0.18 mm (c, h, i), 0.39 mm (d), 0.32 mm (e, f, g), 0.40 mm (j).