Spectrarcturus intermedius ( Richardson, 1899a ) Stransky & Svavarsson & Poore & Kihara, 2020

Stransky, Bente, Svavarsson, Jörundur, Poore, Gary C. B. & Kihara, Terue Cristina, 2020, Revision of Pleuroprion zur Strassen, 1903 (Holidoteidae) and re-evaluation of Spectrarcturus Schultz, 1981 (Arcturidae) (Crustacea, Isopoda, Valvifera), Zootaxa 4894 (1), pp. 1-52 : 42

Spectrarcturus intermedius ( Richardson, 1899a) comb. nov.

( Fig. 31 )

Arcturus intermedius Richardson, 1899a: 854–855 .— Richardson, 1899b: 275–277.

Pleuroprion intermedium . — Richardson, 1905: 344–346, fig. 373.— Gurjanova, 1936: 201, fig. 129.— Schultz, 1969: 52, fig. 53b.— Kussakin, 1982: 428–430, fig. 318.

Material examined: Syntype, USMN 22581 , Kyska Harbor , Aleutian Islands, 10 ftms, 1 female .

Diagnosis: Body with numerous large, narrow, pointed spines; mid-dorsal spine anteriorly on head, mid-dorsally pair of spines on head, row of spines across pereonite 1; row of spines across pereonites 2 and 3; pereonite 4 0.2 times body length; trapezoid, about as long as second and third together; anterior and posterior rows of spines across pereonite 4, pair of spines middorsally. Pleotelson short, with several long and short spines on anterior part, one lateral spine on posterior part, posteriorly bifid apex, fork-like. Antennula short, not reaching distal end of second peduncular segment of antenna. Antenna long and slender, about 0.9 of total body length. Spines absent from basis of pereopods 5 to 7. Oostegites not present on pereopod 5.

Remarks: The ventral lateral plate of the head has a deep incision at the anterior end of pereonite 1. The posterior end of the pleotelson ends in deep upraised fork, which distinguishes this species from all Spectrarcturus species, except S. hystrix and S. murdochi . The middorsal spine on anterior part of the head can be used to distinguish this species from several other Spectrarcturus species.

Kussakin (1982) noted that the specimen occurring at the Commander Island differed from the holotype in the presence of a spine on article 3 and by having different shape of the body spines, but still considered that these specimens belonged to S. intermedium .

Distribution: Western part of the Aleutian Islands, Kiska-Harbor Bay, Commander Island, at depths between 18–40 m ( Kussakin 1982).

Figures

FIGURE 31. Spectrarcturus intermedius (Richardson, 1899). Female syntype.A, habitus, lateral view; B, habitus, dorsal view. Scale: a = 1 mm (A, B).