Corresponding author: Shoki Shiraki (
Academic editor: Sammy De Grave
We describe a new paranthurid isopod genus and species,
Species in the anthuroid isopod family
We collected a paranthurid individual lacking pereopod 7 from off the southern coast of Mie, Japan, but unlike the four known neotenous paranthurid genera, its mandible bears an acute incisor and 3-articulate palp, and its maxilliped bears an endite. Here we describe the species as new, establish a new genus for it, and provide a revised key to the genera in
A single specimen was collected in 2008 from Shima Spur off the southern coast of Mie prefecture, Japan, with a 3-m beam trawl at a depth between 805 and 852 m, during the cruise KT 08-3 of RV
Eyes present. Pereonite 7 reduced and hidden laterally. Pleonites 1–5 fused but with sutures. Pleonite 6 entirely fused dorsally to telson; pleotelson triangular, without statocyst. Mandible acute, with 3-articulate palp. Maxilliped with 4-articulate palp; endite present. Pereopod 7 absent on non-manca individuals. Uropodal exopod elongate triangular, tapering.
The generic name is a combination of the Greek letter
Like
Comparison of selected characters among the seven genera in
Characters | |||||||
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Eyes | Absent | Present/absent | Present | Present | Present | Absent | Present |
Pereonite 7 | Not hidden laterally | Not hidden laterally | Hidden laterally | Hidden laterally | Not hidden laterally | Not hidden laterally | Hidden laterally |
Pleonites 1–5 | Fused | Free or fused | Fused | Indicated by folds | 1 free, 2–5 fused | Free | Fused |
Pleonite 6 and telson | Fused dorsally | Not fused dorsally | Not fused dorsally | Not fused dorsally | Not fused dorsally | Not fused dorsally | Fused dorsally |
Mandible | Acute | Acute | Blunt | Blunt | Blunt | Blunt | Acute |
Mandibular palp | 3-articulate | 3-articulate | Absent | Absent | Absent | Absent | 3-articulate |
Maxillipedal endite | Present | Absent | Absent | Absent | Absent | Absent | Present |
Pereopod 7 in non-manca individuals | Present | Present | Absent | Absent | Absent | Absent | Absent |
Uropodal exopod | Tapering | Oval | Oval | Oval | Oval | Oval | Tapering |
References |
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Present study |
The neotenous species
The specific name,
Body relatively slender (Figs
Antennula (Fig.
Antenna (Fig.
Mandible (Fig.
Maxilla (Fig.
Maxilliped (Fig.
Pereopod 1 (Fig.
Pereopod 2 (Fig.
Pereopod 3 (Fig.
Pereopods 4–6 (Fig.
Pleopod 1 (Fig.
Pleopods 2–5 (Fig.
Uropod (Fig.
Our specimen lacks oostegites and an appendix masculina, but its pereon is expanded ventrally (Fig.
1 | Pereopod 7 present in non-manca individuals | 2 |
– | Pereopod 7 lacking in non-manca individuals | 3 |
2 | Pleonite 6 marked off dorsally from telson; uropodal exopod linear or leaf-shaped |
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– | Pleon and telson fused into single segment; uropodal exopod extremely reduced |
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3 | Pleonite 6 entirely fused dorsally to telson; pleotelson tapering, triangular; mandible acute, with 3-articulate palp | |
– | Pleonite 6 marked off dorsally from telson; pleotelson oval; mandible blunt, without palp | 4 |
4 | Pereonite 7 hidden laterally; head as long as wide | 5 |
– | Pereonite 7 not hidden laterally; head longer than wide | 6 |
5 | Pleonites 1–5 separated by integumental folds dorsally; pleonite 1 twice as long as pleonite 2 |
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– | Pleonites 1–5 fused, rarely with integumental folds dorsally; pleonites 1 and 2 similar in length |
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6 | Pleonites 2–5 fused; marine or estuarine; eyes present |
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– | Pleonites all free; hypogean or freshwater; eyes lacking |
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We thank the captain and crew of RV