Limnoria aspera Yoshino &amp; Kambara &amp; Kajiwara &amp; Ohsawa 2021, sp. nov.
Creators: name: Yoshino, Hiroki
name: Kambara, Yuriko
name: Kajiwara, Shota
name: Ohsawa, Takeshi A.
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Isopoda
Limnoriidae
Limnoria
Limnoria aspera

description: <i>Limnoria aspera</i> Yoshino &amp; Ohsawa, sp. nov. Figs 1–8 <b>Material examined.</b> <b> <i>Holotype</i>:</b> male 2.6 mm, Kamogawa-shi, Chiba prefecture, Japan, 35°07’N, 140°10’E, subtidal zone (0–1 m in depth), <i>Sargassum ringgoldianum</i> holdfasts, Takeshi A. Ohsawa and Hiroki Yoshino, 9 September 2020 (CBM-ZC 16564). <b> <i>Paratypes</i>:</b> male 2.8 mm, Kamogawa-shi, Chiba prefecture, Japan, 35°07’N, 140°10’E, subtidal zone (0–1 m in depth), <i>Sargassum ringgoldianum</i> holdfasts, Yuriko Kambara, 14 July 2014 (CBM-ZC 16565). male 2.7 mm, Kamogawa-shi, Chiba prefecture, Japan, 35°07’N, 140°10’E, subtidal zone (0–1 m in depth), <i>Sargassum siliquastrum</i> holdfasts, Takeshi A. Ohsawa and Hiroki Yoshino, 9 September 2020 (CBM-ZC 16566). male 3.2 mm, Kamogawa-shi, Chiba prefecture, Japan, 35°07’N, 140°10’E, subtidal zone (0–1 m in depth), <i>Sargassum siliquastrum</i> holdfasts, Takeshi A. Ohsawa and Hiroki Yoshino, 9 September 2020 (CBM-ZC 16567). <b>Type locality.</b> Kamogawa-shi, Chiba Prefecture, Japan. <b>Description.</b> <i>Body</i> oblong, dark yellow to light brown in 70% ethanol (Figs. 1, 2A). <i>Head</i> almost globular. <i>Eyes</i> black in color, each with 8 ommatidia. <i>Pleonite</i> composed of 5 distinct segments. Pereonal segment 1 longest, approximately 1.5–1.7 times longer than segment 2 (Fig. 1), with 1 thinly V-shaped groove. Segments 2–4 subequal length. Posterior pereonal segments 4–7 progressively shorten. Coxal plates of pereonal segments 2–4 rectangular in shape and those of posterior segments prolonged acutely at posterior angle. <i>Pereonites 6, 7</i> and pleonites 1 to 4 each with transverse row of many small setae. <i>Pleonite</i> 5 approximately 0.6 times as long as pleotelson (Figs 2, 3A). Pleonite 5 dorsomedially with Y- or Ishaped indistinct longitudinal carina on which few scale spikes form line (Figs 2B, 3A). Pleonite 5 covered with fused scales, which make tile mosaics (Fig. 2C). <i>Pleotelson</i> 0.6–0.8 times as long as wide, medially with 1 tubercle on which few scale spikes follow its line (Figs 2, 3A). Pleotelson covered with fused scales, which present tiled pattern on surface (Fig. 2C). Lateral crests and posterior margin of pleotelson margined with sets of about 2–5 directed upward scale spikes. Posterior edge of pleotelson with fringe of long sheathed setae and many short setae (Fig. 3B). <i>Antenna</i> 1 with 4 flagellar articles; second article with 7 aesthetascs (Fig. 3D). Flagellum of antenna 2 with 4 articles (Fig. 3E). <i>Mandibular</i> palp lacking, replaced by single long stout seta (Figs 4A, B). Mandibular incisors lack rasp and file (Figs 4A–B, 8A). Lacinia mobilis of right mandible branched at intermediate point, branches gradually curving 90-degrees and serrated on anterior side (Fig. 4B). Posterior branch almost same length as anterior branch. Lacinia mobilis of left mandible with 1 serrated seta. Epipod of <i>maxilliped</i>, clavate, approximately 3 times as long as wide, reaching articulation of palp, with simple true setae (Fig. 4E). Secondary unguis on <i>pereopod</i> 1 undivided, without spinule or with 1–7 spinules (Fig. 5A). Secondary unguis on pereopods 2–6 undivided (Figs 5B, D, 6A–B) or slightly bifid (Fig. 5C). Secondary unguis on pereopod 7 undivided with 4–7 spinules (Fig. 6C). Ventral comb seta absent on merus and present on carpus of pereopods 6 and 7. Propodus of pereopods 3–5 with prominent barbed projection opposing secondary unguis, projection reduced on pereopod 2 (Figs 5, 6, 8B). <i>Pleopod</i> 2 with plumose setae up to 0.9 times length of exopod (Fig. 7B). Appendix masculina long, reaching beyond endopod tip, articulating near midlength of endopod. Endopod of pleopod 5, oval (Fig. 7C). Peduncle of pleopod 5 with simple seta laterally. Peduncles with coupling hook sequence 32220. <i>Uropod</i> exopod with laterally recurved apical claw (Figs 3C, 8C). Row of simple long setae on endopod placed apically. Uropod peduncle about 1.1 times as long as endopod, with many short simple setae and row of plumose setae. Exopod about 0.4–0.5 times as long as peduncle. <b>Molecular data.</b> We deposited the nucleotide sequences of COI region of mitochondrial genes (Acc. no. LC610781, LC610782) and 28S rRNA of nuclear genes (Acc. no. LC612562, LC612563) obtained from the holotype and paratype in GenBank. <b>Substrate.</b> <i>Sargassum ringgoldianum</i>, <i>S. siliquastrum</i> holdfasts. <b>Distribution.</b> Known only from the type locality. <b>Etymology.</b> From the Latin <i>aspera</i> (= rough; Gender feminine), referring to the rough exoskeleton on pleonite 5 and pleotelson. <b>Remarks.</b> Mandibular palp of <i>Limnoria aspera</i> <b>sp. nov.</b> is reduced to a seta. This feature is also found in 7 species: <i>L. bacescui</i>, <i>L. bituberculata</i>, <i>L. furca</i>, <i>L. nagatai</i>, <i>L. segnoides</i>, <i>L. uncapedis</i> and <i>L. zinovae</i> (Cookson 1991; Pillai 1957; Kussakin 1963; Menzies 1957; Nunomura 2012; Ortiz &amp; Lalana 1988; Yoshino &amp; Ohsawa 2019). Cookson 1991 stated that “ <i>L. uncapedis</i>, <i>L. segnoides</i> and <i>L. bituberculata</i> all share the following features: broad maxillipedal epipod, loss of mandibular palp, similar shape of the lacinia mobilis of the right mandible, and modification of the secondary unguis on pereopod 1”, and Yoshino &amp; Ohsawa (2019) said that the species of non- mandibular-palp group are algal-feeding and shared the broad epipod of maxilliped, except seagrass-feeding <i>L. zinovae</i>, the shape of epipod of maxilliped of which is unknown. <i>L. aspera</i> <b>sp. nov.</b> fits into this group, as an algalfeeding species that also has the broad epipod of maxilliped (Table 1). <i>L. bacescui</i>, <i>L. segnoides</i>, and <i>L. zinovae</i> differ from <i>L. aspera</i> <b>sp. nov.</b> by the number of flagellar articles of antenna 2, the secondary unguis on the pereopods, lacinia mobilis of right mandible, and the sculpturing of pleonite 5 and pleotelson. <i>L. aspera</i> <b>sp. nov.</b> is similar to <i>L. uncapedis</i> in the number of flagellar articles of antennae 1 and 2, secondary unguis of pereopod 1, lacinia mobilis of right and left mandible, and pereopods 2–5 with barbed projection on the propodus. However, <i>L. uncapedis</i> is pale yellow and has no carinae on pleonite 5 and pleotelson, while <i>L. aspera</i> <b>sp. nov.</b> is dark yellow and has Y- or I-shaped carina on pleonite 5 and 1 tubercle on pleotelson. Similarly to <i>L. aspera</i> <b>sp. nov.</b>, <i>L. bituberculata</i> has 4 flagellar articles of antenna 1, spinules on the secondary unguis of pereopod 1, and a dorsomedial longitudinal carina between 2 longitudinal grooves on pleonite 5. However, <i>L. bituberculata</i> is pale yellow and has 2 prominent tubercles on the pleotelson, while <i>L. aspera</i> <b>sp. nov.</b> is dark yellow and has 1 medial tubercle on the pleotelson. <i>L. aspera</i> <b>sp. nov.</b> seems to be most similar to <i>L. furca</i>, and <i>L. nagatai</i>. <i>L. aspera</i> <b>sp. nov.</b> is distinguished from <i>L. furca</i>, and <i>L. nagatai</i> by dark yellow body color (<i>L. furca</i>, and <i>L. nagatai</i> pale yellow), undivided or slightly bifid secondary unguis of pereopods (<i>L. furca</i> bifid or trifid, <i>L. nagatai</i> bifid), and the medial tubercle on the pleotelson lacks the attachment of two inverted V-shaped carinae (<i>L. furca</i>, and <i>L. nagatai</i> with medial tubercle followed by a pair of subparallel carinae).
description: Published as part of <i>Yoshino, Hiroki, Kambara, Yuriko, Kajiwara, Shota &amp; Ohsawa, Takeshi A., 2021, New species of Sargassum-boring Limnoria Leach, 1814 (Crustacea, Isopoda Limnoriidae) from Japan, pp. 119-130 in Zootaxa 4970 (1)</i> on pages 120-124, DOI: 10.11646/zootaxa.4970.1.4, http://zenodo.org/record/4756031
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