Fissarcturus sandwichi, Brandt, 2007

Brandt, Angelika, 2007, Three new species of Fissarcturus (Isopoda, Antarcturidae) from the Southern Ocean, Zoological Journal of the Linnean Society 149 (2), pp. 263-290 : 269-281

FISSARCTURUS SANDWICHI SP. NOV. ( FIGS 11–20 )

Material examined: Holotype, male (8.2 mm), Station ANDEEP 143-3, 65°18.55′S, 51°31.95′W, 2893− 2894 m, South Sandwich Islands, 6 March 2002, RV Polarstern ( ZMH K-40894).

Paratypes: Female (9 mm – illustrated), station ANDEEP 143-3, same locality as holotype, RV Polarstern ( ZMH K-40895); further paratype material from the same station: male (juveniles 7, 7.5, adult 10 mm), female (2 ovig: 8 mm), Manca (2.8, 3, 3, 3.8, 4, 4.8, 5, 5.2, 5.2 mm), juveniles (6.3, 6.5, 7 mm) .

Distribution: Southern Ocean, South Sandwich Islands.

Etymology: The species name is derived from the name of the type locality, the South Sandwich Islands. The gender is masculine.

Diagnosis: Strong frontally bent supraocular spines (females with second cephalic spines) and dorsum covered with flat, cauliflower-like elevations in submedial, lateral and coxal rows.

Description of the holotype male: Body ( Fig. 11 ) length 8.2 mm. Eye rounded. Eye 0.2 of lateral length of head. Preocular spine absent. Supraocular spine long, blunt, strongly curved frontally. Second cephalic spine shorter than supraocular spine, boss-like, with spinules or tubercles. Second cephalic spine hemispherical bosses. Other spines on head absent. Body long, slender ( Fig. 11 ). Pereonites 1–3 of about same length, pereonite 4 longest, anterior pereonites of about same width. Pereonites 5–7 slightly narrowing in width. Pereonal spination comprising elements in submedial, dorsolateral and coxal rows. Submedial spines present on pereonites 1–4, dorsolateral spines present on pereonites 1–3. Submedial spines present on pereonites 5–7 absent in male. Spines present on 1–7, of cauliflower shape (except for supraocular ones), two pairs on pereonites 1–3. Dorsolateral spines present on 1–3, of cauliflower shape. Three or four contiguous marginal spines on coxa 1, frontally directed, pereonites 5–7 only with tubercles in both sexes. Intermediate ornamentation on pereonites absent. All pleonites fused with pleotelson. No submedial spines on pleotelson. Position of lateral spines on pleotelson at half length. Pleotelson length 0.35 body length. Pleotelson width 0.3 total pleotelson length. Pleon spination, male only with small scattered tubercles. Position of most posterior lateral spines 55% of pleotelson length in male. Pleotelson apex prominent, triangular, caudally rounded.

A1 ( Fig. 12 ) first peduncular article broadest and shorter than second, first and second both with medial feather-like setae. Peduncular article 3 0.4 length of article 2. Antenna 1 flagellum, one proximal single, six groups of two and three apical ones in male.

A2 ( Fig. 12 ) peduncle 0.8 body length. Antenna 2 peduncle scattered tubercles on articles 2– 4 female. Antenna 2 flagellum with five articles.

Mandibles ( Fig. 12 ) without palp, asymmetrical. Pars incisiva and lacinia mobilis of lMd with three teeth.

Mx1 ( Fig. 12 ) of two endites, both slightly narrowing distally, lateral one distally curved medially, apex with 11 strong smooth spines. Medial endite shorter, with three stout setulated setae.

Mx2 ( Fig. 12 ) consisting of three endites. Outer, lateral, endite with three long setulated setae, medial endite also with three setulated setae, inner endite with a rows of eight shorter setulated setae.

Mxp ( Fig. 12 ) with long, oval epipod slightly waisted laterally in distal third, rounded endite and a five-segmented palp. Endite distodorsally with six spine-like setae, one being setulated. No coupling hooks. Third palpal article longest, slightly longer than fourth, first and last smallest, dense medial brush of long sensory setae, especially on third to fifth articles.

P1 ( Fig. 13 ) basis about as long as propodus, carpus trapezoidal, propodus subchelate and slender. Pereopod 1 propodus, length 1–1.4 of total width. Dactylus shorter than propodus, with one long, strong distal claw. Propodus and dactylus densely setose. Ventral surface of propodus with few setae, most on medial part and on palm. Mediodorsal side of propodus forming a concave ‘spoon’, curved dorsolateral surface with long setae, arranged in five parallel transverse rows of combs, dorsal part of palm bearing many medially directed sensory setae.

P2–4 ( Figs 13 , 14 ) similar, P2 shortest, P4 longest. Eight, 8, 7–9 setal groups on carpus of pereopods 2–4, and 6–8, 6–7, 5–6 setal groups on propodus of pereopods 2–4. Dorsal ornamentation of basis tubercles and denticulate spines in males. Pereopods 2–4, ornamentation on ischium-carpus tubercles in male only on pereopod 4. Pereopods 2–3 dactylus, length 0.4–0.5 length of propodus. Unguis as long or longer than dactylus. Pereopods 2–3 unguis, length 1.2–1.3 that of dactyus. Pereopod 4, dactylus, length 0.4–0.5 that of propodus, and 0.7–1 length of dactylus. Pereopod 4 dactylus of male without setae.

P5–7 ( Figs 13 , 14 ) similar in shape and setation and shorter and stouter than P2–P4. Pereopods 5–7 progressively shorter, with tubercles on basis. Basis of P5–P7 longest article. Basis of P6 and P7 with one feather-like seta. Merus, carpus and propodus with ventral strong setulated setae. Propodus dorsally with one feather-like seta and some simple setae of varying lengths. Dactyli with two short claws, dorsal one much longer than ventral one.

Plp1 ( Fig. 15 ) sympod 0.8 as long as rami, with four coupling setae. Male pleopod 1 exopod length 1 endopod. Male pleopod 1 exopod 1 width of endpod. Male pleopod 1 exopod terminally and medially equipped with setae. Male pleopod 1 endopod, groove opening 60% of length, and groove opening with row of small scales and four stout small setae on proximal lobe. Male pleopod 1 endopod with 19 distal and nine lateral setae.

Plp2 ( Fig. 15 ) very similar to Plp1, but with much shorter sympod, about 0.3 as long as rami, with three medial coupling setae. Appendix masculina 1.1 length of endopod, acute, small denticles on distal part.

Plp3 ( Fig. 14 ) with very short sympod (0.1 length of endopod and exopod), as following pleopods; endopod with four medial and three lateral plumose setae, exopod bare.

Plp 4 ( Fig. 14 ) endopod with two plumose setae.

Urp ( Fig. 14 ) endopod 0.6 length of exopod. Uropod endopod with two distal setae.

Female paratype ( Figs 16–19 ) (differences to holotype male) of 9 mm length: Dorsolateral spines present on 1–3, of cauliflower shape; female with long spines on pereonite 1, almost as long as supraocular ones, frontally curved ( Fig. 16 ). Pereonites, pleonites and pleotelson of female with very similar pattern of spination if compared with male, but cauliflower-like spines are generally slightly more pronounced. Four erect marginal coxal spines present on pereonite 1. Margins of coxae 2 and 3 with anteriorly and posteriorly directed spines in female only. No coxal spine on pereonite 1 of either sex; one spine on coxa 2 of female, coxae 3–4 with cauliflower-like elevations on female, 5–7 only with tubercles in both sexes. Pleon spination of female with submedial and lateral cauliflower-like setae. Position of most posterior lateral spines 70% of pleotelson length in female. Antennular flagellum of female broken off. Antennal flagellum ( Fig. 17 ) of four articles. Maxilliped ( Fig. 17 ) with long, oval epipod, endite with six spine-like setulated setae, medially with another five simple setae, no coupling hooks present. Pereopods 2–4 ( Fig. 18 ) and 5–7 ( Fig. 19 ), ornamentation with tubercles and denticulate spines in both sexes, but more prominent in female. On ischium-carpus tubercles on pereopods 2–4 in female. Marginal setae of P2–3 dactylus in female only. Pereopod 4 dactylus with few setae in female, none in male. Pleopod 2 ( Fig. 20 ) without appendix masculina. Endopodite of uropod ( Fig. 20 ) with three setae.

Remarks: F. sandwichi can easily be distinguished from all other species of Fissarcturus by its typical ornamentation of the dorsum. It is characterized by a strongly frontally bent supraocular spine, equipped with some tubercular-like pegs (females with another second pair of cephalic spines which are only slightly shorter). All other species of Fissarcturus possess more spines on additional pereonites, except for F. patagonicus (Ohlin, 1901) and F. granulosus (Nordenstam, 1933) , which are characterized by minute supraocular spines. Moreover, the dorsum of F. sandwichi is covered with flat, cauliflower-like

Figures

Figure 11. Fissarcturus sandwichi sp. nov. Male holotype, dorsal and lateral views.

Figure 12. Fissarcturus sandwichi sp. nov. Male holotype, antennula, antenna, left mandible, maxillula, maxilla, maxilliped.

Figure 13. Fissarcturus sandwichi sp. nov. Male holotype, pereopods 1–3, 6.

Figure 14. Fissarcturus sandwichi sp. nov. Male holotype, pereopods 4–5, 7, pleopods 3–4, uropod.

Figure 15. Fissarcturus sandwichi sp. nov. Male holotype, pleopods 1–2.

Figure 16. Fissarcturus sandwichi sp. nov. Female paratype, lateral view.

Figure 17. Fissarcturus sandwichi sp. nov. Female paratype, antennula, antenna, maxillula, maxilla, maxilliped.

Figure 18. Fissarcturus sandwichi sp. nov. Female paratype, pereopods 2–4.

Figure 19. Fissarcturus sandwichi sp. nov. Female paratype, pereopods 1, 5–7, pleopod 1.

Figure 20. Fissarcturus sandwichi sp. nov. Female paratype, pleopods 2–4, uropod.