Scyracepon polynesiensis, An & Zheng & Liang & Paulay, 2020

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, Zootaxa 4851 (1), pp. 151-162 : 152-155

publication ID	https://doi.org/ 10.11646/zootaxa.4851.1.6
publication LSID	lsid:zoobank.org:pub:2B3E81FE-D1DC-4087-B36D-80158A178638
DOI	https://doi.org/10.5281/zenodo.4407803
persistent identifier	https://treatment.plazi.org/id/03D91126-7D26-FFCE-FF30-FC73C060FC45
treatment provided by	Plazi
scientific name	Scyracepon polynesiensis
status	sp. nov.

Treatment

Scyracepon polynesiensis View in CoL n.sp.

Figs 1 View FIGURE 1 , 2 View FIGURE 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. GoogleMaps

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 View FIGURE 1 ).

Head oblate, with well-developed frontal lamina ( Fig. 1A View FIGURE 1 ), with black eyes near junction of head and frontal lamina ( Fig. 1A View FIGURE 1 ). Antennula of three articles; antenna of five articles; terminal article of both setose ( Fig. 1B View FIGURE 1 ). Barbula with three, pointed, falcate projections on each side, without projections medially ( Fig. 1C View FIGURE 1 ). Maxilliped with anterior article much larger than posterior article, extended into stout and curved palp fringed with setae, plectron poorly demarcated ( Fig. 1D View FIGURE 1 ).

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 View FIGURE 1 ). 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 View FIGURE 1 ). First two and last two pereopods smaller than others ( Fig. 1G View FIGURE 1 ), propodi of pereopods 3–5 with ventral extension to accommodate pointed dactyli, making these appendages almost subchelate ( Fig. 1G, H View FIGURE 1 ).

Pleon of six pleomeres, first five bearing lateral plates and biramous pleopods ( Fig. 1A, I, J, K View FIGURE 1 ). All lateral plates and pleopods covered with tubercles, with tuberculated margins, and decrease in size posteriorly ( Fig. 1A, I, J, K View FIGURE 1 ). Endopodites of pleopods oval and much smaller than exopodites. Uropods uniramous, resembling lateral plates and pleopod exopodites ( Fig. 1L View FIGURE 1 ).

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 View FIGURE 1 , 2A View FIGURE 2 ).

Head oblate, with small black eyes near posterior margin ( Fig. 1M View FIGURE 1 ). Antennula of 3 articles, antenna of 4 articles, terminal three articles of both setose ( Fig. 2B View FIGURE 2 ).

Pereon with distinct segments, sixth widest ( Fig. 2A View FIGURE 2 ), sides truncate, curved ventrally ( Fig. 2A View FIGURE 2 ). 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 View FIGURE 2 ), all with scales. Pereopods of similar size ( Fig. 2A View FIGURE 2 ), with short but pointed dactyli, with few, small scales on meri, carpi and propodi ( Fig. 2B, C View FIGURE 2 ), propodi with ventral, finger-like extension, covered with 4 or 5 scales with grooved sculpture that accommodate tip of dactyli ( Fig. 2C View FIGURE 2 ).

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 View FIGURE 1 , 2F View FIGURE 2 ). Lateral sides of pleomeres curved ventrally, ending in five pairs of hook- to tubercle-like pleopods ( Fig. 2F View FIGURE 2 ). Uropods short, tubercle-like, terminating in a cluster of scales and setae ( Fig. 2G View FIGURE 2 ).

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.