Loki athanus, An & Chen & Paulay, 2020

An, Jianmei, Chen, Ruru & Paulay, Gustav, 2020, Three new species of abdominal shrimp parasites (Crustacea: Isopoda: Bopyridae Hemiarthrinae) from the Indo-West Pacific, Zootaxa 4845 (2), pp. 264-274 : 268-269

Loki athanus n. sp.

Figs 2 , 3

Material examined. Holotype female, ovigerous, 1.06 mm, paratype male, 0.5 mm, UF Arthropoda 18690, Madagascar, Nosy Be, across bay from CNRO complex, off Lokobe Reserve, 1–3 meters, 13.4139°S, 48.3056°E, coll. G. Bakary, H. Bruggemann, F. Michonneau, G. Paulay, and T. Werner, 16 May 2008. Infesting Athanas parvus de Man 1910 ( UF Arthropoda 14367) ( Fig. 2 ).

Description. Holotype female (UF 18690) length 1.06 mm, head length 0.29 mm, head width 0.35 mm, pleonal length 0.40 mm ( Fig. 3A ).

Head subquadrate, white, with black eyes near anterior margin. Antennulae with two articles, antennae with three articles, without setae ( Fig. 3B ). Barbula with one falcate lateral projection on each side ( Fig. 3C ). Maxilliped without palp, and with short, blunt plectron ( Fig. 3D ).

Pereon yellow. First three pereomeres merged into ring encircling the head. Other pereomeres distinct on short side of the body but fused on long side ( Fig. 3A ). Brood pouch pigmented, swollen, full of eggs, covering entire ventral surface of head and pereon. First oostegite with unadorned internal ridge, with broad notch along posterior margin ( Fig. 3E ). All pereopods of similar size and shape ( Fig. 3F ), with stout ischia and short, blunt dactyli. First two pairs of pereopods clustered near head; other five on short side in line along pereon, while on long side pereopod 3 is near middle of brood pouch, 4, 5 near posterolateral border of brood pouch, and 6, 7 near posterior end of brood pouch.

Pleon of five pleomeres ( Fig. 3A ), first four produced into uniramous lateral plates, with uniramous pleopods, fifth without lateral plates, with divergent pair of uniramous uropods.

Paratype male ( UF 18690 ) length 0.5 mm, maximum width (across pereomere 1) 0.19 mm, head length 0.09 mm, head width 0.15 mm, pleonal length 0.12 mm ( Fig. 3G, H ) .

Head semicircular, with large black eyes near posterolateral margin ( Fig. 3G ). Antennae visible from dorsal view, antennulae and antennae with 3 and 5 articles respectively, terminal articles setose ( Fig. 3I ).

Pereon with first segment fused with head, two to seven distinct laterally, but slightly fused near midline ( Fig. 3G ); with curved margins; first segment widest. Pair of pigmented lines extending from third to seventh pereomere ( Fig. 3G ). All pereopods with short dactyli; first two pereopods slightly larger than others, but similar in structure ( Fig. 3J, K ).

Pleon fused into triangular piece, narrower than last pereomere ( Fig. 3G, H ). Pleopods and uropods absent.

Etymology. The specific name, athanus , refers to the host genus.

Remarks. The present specimens are placed in the previously monotypic genus Loki because the female has 7 pairs of pereopods which on the long side have the following position: first two clustered around the head, third near middle of brood pouch, last four clustered around posterior of brood pouch. It further matches Loki because the fifth pleomere lacks lateral plates and has divergent uropods. The male fits Loki because it has a triangular pleon and the head is completely fused with the first pereomere. The new species differs from L. circumsaltanus Markham, 1972 in the following characters (character states in L. circumsaltanus given in parentheses): female with well-developed lateral plates on pleomere 4 (pleomere 4 with reduced lateral plates on short side, without lateral plates on long side) and with four pairs of uniramous pleopods (three pairs of uniramous pleopods); male with large black eyes (lacking eyes), and with pleon distinctly separated from pereomere 7 (pleon medially fused with pereomere 7). The new species extends the range of Loki from the west Atlantic to the Indo-West Pacific.

Figures

FIGURE 2. Athanas parvus (UF 14367) with type of Loki athanus n. sp. (UF 18690) attached; image of live specimens.

FIGURE 3. Loki athanus n.sp., holotype female (UF18690) (A–F), paratype male (UF18690) (G–K): A, dorsal view (lp = lateral plates; ur = uropods; pl = pleopod; pe1 = pereopod 1; pe2 = pereopod 2; pe3 = pereopod 3; eg = eggs); B, right antennula and antennae; C, right part of barbula; D, right maxilliped, external view; E, left oostegite 1, internal view; F, right pereopod 2; G, dorsal view; H, ventral view; I, right antennula and antenna; J, left pereopod 1; K, left pereopod 7. Scale bar: A = 1 mm; B, D–F = 0.63 mm; C, G, H= 0.44 mm; I–K=0.13 mm.