Fissarcturus rugosus (Nordenstam, 1933) Poore, 2003

Poore, G. C. B., 2003, Revision of Holidoteidae, an endemic southern African family of Crustacea, and re-appraisal of taxa previously included in its three genera (Isopoda: Valvifera), Journal of Natural History 37, pp. 1805-1846 : 1834-1837

Fissarcturus rugosus (Nordenstam, 1933) comb. nov.

(figures 12, 13)

‘ Microarcturus ’ rugosus Nordenstam, 1933: 163–167 , pl. 2 figure 14, text-figures 38a–e. Neoarcturus rugosus: Wägele, 1991: 183 , 188, figure 70B.

Material examined

Nordenstam (1933) mentioned 32 specimens from stn 17 of which he gave syntype status to a male of about 7 mm length and a female with marsupium of about 8.5 mm. SMNH ‘typsaml 798’ contains two males and one female, almost complete specimens, from stn 17. Twenty additional specimens, both sexes, from stn 17, some partially dissected, are also available ( SMNH Isopoda 7406). Thirty-six slides made by Nordenstam presumably from this material also exist but some contain limbs of both sexes. Parts of syntypes of Nordenstam’s ‘ Microarcturus ’ digitatus are almost certainly on slides and their carcases destroyed (see that species below). Presumably the same is true for this species so that today the syntypes and other material mentioned by Nordenstam are confused in the vials and slides. An intact specimen has been chosen for dissection and illustration but has no type status. SMNH ‘typsaml 795’ is Nordenstam’s male from stn 94, of which his figure 14 on pl. 2 is a photograph .

Figured specimen: Shag Rock Bank, between Falkland Island and South Georgia, 53°34∞ S, 43°23∞ W (Swedish Antarctic Expedition stn 17), 160 m (male, 11.4 mm).

Description of figured male

Body of male. Length 11.4 mm. Head with eyes lateral, pigmented. Major dorsal spination arranged in submedial, dorsolateral and lateral rows of spines; intermediate small spines and prickles irregularly scattered between rows. Head with anterolateral pair of spines; head and pereonite 1 together with four submedial, three dorsolateral and one lateral pair of spines. Pereonites 2–4 each with one submedial, one dorsolateral and one lateral pair of spines; pereonites 5–7 each with one submedial, four dorsolateral and one coxal pair of spines; pleonites 1–3 each with one submedial, one dorsolateral and one lateral pair of spines; remaining pleotelson with three submedial, two dorsolateral and two lateral pairs of spines of which last lateral pair is produced beyond acute apex of pleotelson, plus subapical mid-dorsal group of three small spines.

Limbs of male. Antenna 2 peduncle 54% of total body length; ratio of articles 3–5 and flagellum, 10:25:31:19; ratio of flagellum articles 100:66:40; antenna 2 with few setae along lower margin.

Mouthparts not dissected.

Pereopod 1 propodus oval, width 50% length; dactylus (including unguis) 92% propodus; ischium–carpus with long simple setae along and near posterior margin; propodus with eight posterior serrulate setae, 18 mesial facial simple and serrulate setae loosely arranged in oblique rows; dactylus mesial face with three setae near anterior margin, oblique row of three setae and two more near posterior margin; unguis 40% length of body of dactylus.

Pereopod 2 with anterodistal spine on ischium–carpus, proximal anterior spine on carpus; propodus as long as carpus; dactylus (including unguis) 1.13 times as long as propodus; unguis setiform, curved, 1.37 times as long as body of dactylus; secondary unguis absent; basis–propodus with setae along posterior margin, in five to six pairs of long setae accompanied by shorter one on carpus–propodus. Pereopod 4 with anterodistal spine on ischium–merus, more proximal anterior spines on basis; propodus 57% length of carpus; dactylus (including unguis) 1.5 times as long as propodus; unguis setiform, curved, 1.15 times as long as body of dactylus; secondary unguis absent; basis–propodus with setae along posterior margin, in five to six pairs of long setae accompanied by shorter one on carpus–propodus. Pereopods 5–7 progressively shorter, merus–propodus each with two, two and four posterior robust setae, respectively.

Penial plate tapering to rounded apex.

Pleopod 1 exopod 80% length of endopod; endopod with five plumose setae on distal margin; groove on posterior face opens on lateral margin three-quarters way along; an oblique margin distolateral to this defined proximally by shallow concavity and tuberculate corner; lateral margin with 18 marginal simple setae plus two stouter and shorter near opening of groove. Pleopod 2 exopod with 26 lateral and distal plumose setae; endopod exceeding exopod, with 13 distal setae; appendix masculina 1.2 times length of endopod, with acute apex, finely denticulate subdistally.

Uropod exopod articulating more proximal than larger endopod; reaching 60% of length of endopod, with two distal plumose setae; endopod with small distal setae.

Remarks

Fissarcturus rugosus has not been adequately illustrated previously. It differs from F. emarginatus and F. hirticornis in having the last pleotelsonic spine pair distant from the apex.