Scyracepon polynesiensis An & Zheng & Liang & Paulay 2020, n.sp.
Creators: name: An, Jianmei
name: Zheng, Wanrui
name: Liang, Jielong
name: Paulay, Gustav
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Isopoda
Bopyridae
Scyracepon
Scyracepon polynesiensis

description: Scyracepon polynesiensis n.sp.
Figs 1, 2
Material examined. Holotype female, paratype male, UF Arthropoda 42203, infesting left branchial chamber of Xanthias lamarckii (H. Milne Edwards, 1834), UF Arthropoda 23676, French Polynesia, Society Island, Moorea Island, off Gump Cape, 50 meters north of bungalows, fringing reef flat, 1–1.5 meters, 17.4893°S, 149.8258°W, 24 October 2009, coll. A. Anker.
Description. Holotype female length 4.32 mm, maximum width 3.40 mm, head length 0.68 mm, head width 1.28 mm. Body suboval, sinistrally distorted (Fig. 1A).
Head oblate, with well-developed frontal lamina (Fig. 1A), with black eyes near junction of head and frontal lamina (Fig. 1A). Antennula of three articles; antenna of five articles; terminal article of both setose (Fig. 1B). Barbula with three, pointed, falcate projections on each side, without projections medially (Fig. 1C). Maxilliped with anterior article much larger than posterior article, extended into stout and curved palp fringed with setae, plectron poorly demarcated (Fig. 1D).
Pereon broadest across third pereomere, wider than long, last four pereomeres with middorsal bosses, anteriormost slightly smaller than others, pereomeres 2 and 3 with distinct tergal projections (Fig. 1A). Brood pouch completely closed. First oostegite with two nearly equal segments, internal ridge with large digitate projection and 3–5 small projections, posterolateral point sharp and projecting posteriorly (Fig. 1E, F). First two and last two pereopods smaller than others (Fig. 1G), propodi of pereopods 3–5 with ventral extension to accommodate pointed dactyli, making these appendages almost subchelate (Fig. 1G, H).
Pleon of six pleomeres, first five bearing lateral plates and biramous pleopods (Fig. 1A, I, J, K). All lateral plates and pleopods covered with tubercles, with tuberculated margins, and decrease in size posteriorly (Fig. 1A, I, J, K). Endopodites of pleopods oval and much smaller than exopodites. Uropods uniramous, resembling lateral plates and pleopod exopodites (Fig. 1L).
Paratype male length 1.96 mm, maximum width 0.83 mm, head length 0.23 mm, head width 0.34 mm, pleonal length 0.58 mm. Without pigmentation (Fig. 1M, 2A).
Head oblate, with small black eyes near posterior margin (Fig. 1M). Antennula of 3 articles, antenna of 4 articles, terminal three articles of both setose (Fig. 2B).
Pereon with distinct segments, sixth widest (Fig. 2A), sides truncate, curved ventrally (Fig. 2A). All pereomeres with midventral projections, peg-like in 1 and 2, bilobate in 3 and 4, broadly bilobate with broad, flat center in 5–7, increasing in size posteriorly (Fig. 2A, D, E), all with scales. Pereopods of similar size (Fig. 2A), with short but pointed dactyli, with few, small scales on meri, carpi and propodi (Fig. 2B, C), propodi with ventral, finger-like extension, covered with 4 or 5 scales with grooved sculpture that accommodate tip of dactyli (Fig. 2C).
Pleon somewhat coalesced, first three pleomeres separated by faint demarcations dorsally and ventrally, posterior three pleomeres fused; all pleomeres clearly demarcated by lateral indentations (Figs 1M, 2F). Lateral sides of pleomeres curved ventrally, ending in five pairs of hook- to tubercle-like pleopods (Fig. 2F). Uropods short, tubercle-like, terminating in a cluster of scales and setae (Fig. 2G).
Etymology. The specific name, polynesiensis, refers to the type locality of French Polynesia.
Remarks. The present specimens are placed in Scyracepon because the pleon of the male has pleomeres 4–6 fused.Among the 8 known species of Scyracepon, only two have middorsal projections on the last four pereomeres: S. hawaiiensis and S. quadrihamatum. The present species can be distinguished from S. hawaiiensis because the female lacks middorsal projections on pereomeres 2, 3 (present in S. hawaiiensis); head has a convex anterior margin (anterior margin of head is indented, giving a bilobate aspect, in S. hawaiiensis); lacks projections on the posterior margin of oostegite 1 (present in S. hawaiiensis). The female of the new species differs from S. quadrihamatum in that middorsal projections on the last three pereomeres are subequal (the last is much larger, extending to posterior end of body, in S. quadrihamatum), and has eyes (eyes lacking in S. quadrihamatum). Males can be distinguished in that the first three pleomeres are free (fused medially in both S. hawaiiensis and S. quadrihamatum). This is the first record of a species of Scyracepon parasitizing any host from the large family Xanthidae, expanding the host range of the genus to nine families.
description: Published as part of An, Jianmei, Zheng, Wanrui, Liang, Jielong & Paulay, Gustav, 2020, Three new species of Scyracepon Tattersall, 1905 (Isopoda: Bopyridae) from Pacific islands, with comments on the rarity of bopyrids parasitizing brachyurans, pp. 151-162 in Zootaxa 4851 (1) on pages 152-155, DOI: 10.11646/zootaxa.4851.1.6, http://zenodo.org/record/4407327