Spathione asprosdovrima, Boyko & Van Der Meij, 2018

SPATHIONE ASPROSDOVRIMA SP. NOV.

( FIGS 3– 5, 10E)

urn:lsid:zoobank.org:act:94BB49B0-A076-485B-BAA4-9F1E60CB5B77

Type material

Indonesia: Mature non-ovigerous holotype female (3.48 mm), mature allotype male (1.8 mm) (RMNH. Crus.I.7749), ex abdominal marsupium of female Lithoscaptus tri ( Fize & Serène, 1956b) (4.0 mm long × 2.5 mm wide) (RMNH.Crus.D.54029), ex Echinopora lamellosa (Esper, 1795) ( Merulinidae ), Sulamadaha I Reef, Ternate, 00°52′03″N, 127°19′33″E, 6 November 2009, coll. S. E. T. van der Meij.

Japan: Immature paratype female (2.0 mm) (RMNH. Crus.I.7750), ex abdomen of male Xynomaia sp. (4.3 mm long × 3.8 mm wide) (RMNH.Crus.D.57234), ex Pectinia sp. ( Merulinidae ), Blue Tombs, Henza Island, Okinawa, 26°21′46″N, 127°59′50″E, 29 April 2016, coll. S. E. T. van der Meij.

Description

Female ( Fig. 3): Body length 3.4 mm, maximal width 2.6 mm, head length 0.71 mm, head width 0.78 mm. Pereon nearly straight, head slightly deflected sinistrally ( Fig. 3A, B). All body regions and pereomeres distinctly segmented.

Head subrectangular, approximately as broad as long, overlapping almost entire first pereomere medially, inflated dorsoventrally with very thin frontal lamina ( Fig. 3A, C). Eyes minute, lateral. Antennule of four articles; antenna of two articles ( Fig. 3D). First oostegite ( Fig. 3E) anterior lobe globular, posterior lobe slightly smaller than anterior lobe, ovate with rounded margins, distal projection lacking but with medially directed smooth lobe, internal ridge thick, smooth. Oostegites completely enclosing marsupium. Maxilliped ( Fig. 3F) with short subacute fleshy spur; palp lacking, anterior segment rounded, posterior segment triangular. Barbula of three short, rounded fleshy lobes ( Fig. 3G).

Pereon composed of seven pereomeres, broadest across pereomere V, gradually tapering anteriorly and posteriorly; pereomere I posterior margin under head, II weakly concave, III–VII medially concave. Coxal plates very small on anterior pereomers, pronounced, separated, tergal projections on pereomeres one to seven, those on one to four irregular in shape, those on five to seven smooth and rounded at ends (similar to appearance of lateral plates). Anteriormost pair of pereopods ( Fig. 3H) about half as large as other pairs ( Fig. 3I).

Five pleomeres plus pleotelson, lateral plates well developed, tubular, rounded distally and recurved ( Fig. 3J). Pleomeres I–IV with biramous, widely spaced, tubular pleopods as ventrally directed extensions of lateral plates; uniramous pleopods on pleomere V, bulbous uniramous uropods.

Male ( Fig. 5): Length 1.8 mm, maximal width 0.82 mm, head length 0.23 mm, head width 0.47 mm, pleon length 0.46 mm.

Head ovate, widest medially, distinct from first segment of pereon ( Fig. 5A, B); eyes present. Antennule of four articles ( Fig. 5C), distally setose, scarcely extending beyond margin of head; antenna of two articles, terminal article stout, distally setose ( Fig. 5C).

Pereomere V broadest, others gradually tapering anteriorly and posteriorly. Pereomeres I–V straight, VI and VII posteriorly concave, distal and ventral margins of all pereomeres rounded. All pereopods ( Fig. 5B, D, E) subequal; carpus and merus nearly fused, all other articles distinctly separated.

Pleon with four segments plus pleotelson. All pleomeres directed posterolaterally (in dorsal view; Fig. 5A), with distolateral margins rounded; extended ventrally (in lateral view). Midventral tubercles, pleopods and uropods lacking ( Fig. 5B).

Etymology

From a combination of the Greek απροσδόκητος (aprosdókiti), meaning unexpected, and εύρημα(evrima),meaning finding, because of the unexpected finding of a sister taxon to Rhopalione on a species of gall crab ( Cryptochiridae ).

Remarks

See under Remarks for the genus. The juvenile specimen (RMNH.Crus.I.7750; Fig. 4) already shows the overall body shape and pleopod formation seen in the adult female, and little additional modification to the body seems to occur between the immature and mature female forms. The occurrence of the juvenile female on a male host is perplexing, because the holotype female occupies the entirety of the female’s marsupium, hence the paratype female appears to have made a poor host choice because the male abdomen will not develop into an appropriate structure to hold the adult female. There is no evidence in the literature that bopyrids can markedly feminize their hosts à la rhizocephalans.

Known hosts

Lithoscaptus tri ( Fize & Serène, 1956b) View in CoL , Xynomaia sp.

Distribution

Known from Indonesia and Japan.

CRYPTONISCOIDEA KOSSMANN, 1880

CRYPTONISCIDAE KOSSMANN, 1880 View in CoL