Natatolana rossi (Miers, 1876)

Keable, Stephen J., 2006, Taxonomic Revision of Natatolana (Crustacea: Isopoda: Cirolanidae), Records of the Australian Museum 58 (2), pp. 133-244 : 218-221

Natatolana rossi (Miers, 1876)

Figs. 41–42

Cirolana rossi Miers, 1876a: 228 .– 1876b: 109. pl. 3, fig. 3.– Hutton, 1879: 340.– Filhol, 1885: 453, 499.– Hansen, 1890: 355.–Thomson & Chilton, 1886: 154.– Chilton, 1909: 606, 651.– Nierstrasz, 1917: 91, pl. 13, figs. 11–17.–1931: 158.– Stephensen, 1927: 361.– Hurley, 1961: 267.– Kussakin, 1967: 223.– Ellis, 1981: 123.

Natatolana rossi .– Bruce, 1981: 958.– 1986: 53, 93, 97, 222.– Brusca et al., 1995: 82.

Cirolana hirtipes .– Filhol, 1885: 455, 499, pl. 53 fig. 6.– Nierstrasz, 1931: 158.– Hurley, 1961: 267 [mis-identification, not N. hirtipes ( Milne Edwards, 1840) ].

Not Cirolana rossi .– Hale, 1952: 24 [mis-identification = N. matong Bruce, 1986 ].

Type material. Lectotype: designated here, 3, 18 mm, BMNH 1844 :3 . Paralectotypes: all BMNH, 2, 1843: 70; 6, 1844: 3; 1, 1848: 80; 2, 1856: 33. Details as per the list of Ellis (1981) except the material presented by Lieut. A. Smith has the label: “Rendezvous Cove, Auckland Island, ‘Erebus’—Antarctic Expedition” and has registration number: 1843:70, not 1856:33. All examined. Type locality: originally New Zealand , [c. 40°S 175°E] and Auckland Islands , New Zealand , [50°35'S 166°E], now restricted to Auckland Islands , New Zealand .

Material examined. New Zealand: 4, NMNZ Cr 9199, west of Rangitikei River mouth, 40°16'S 174°58.5'E, 75 m, RV Acheron , 2 Mar. 1976 ; 1, NMNZ Cr 9197, between West Entry Point and Duffers Reef , Pelorus South , 40°57.5'S 174°01.5'E, 29 m, RV Acheron , 5 Mar. 1976 ; 4, NMNZ Cr 9201, south of Mana Island , 41°10'S 177°43'E, 37–53 m, 21 Oct. 1969 ; many, QM W10261, Tasman Bay , 41°17.55'S 173°16.97'E, trap, 14 m, 2 May 1971 , NIWA stn K179(4); 36, NMNZ Cr 4997, Kaikoura , [42°23'S 173°41'E], feeding on crayfish bodies in hagfish trap, Jul. 1987 ; 20, NMNZ 4998 , Kaikoura , baited trap, 10 Sep. 1974 . 10, NMNZ 9200 , North Otago, on Squalus acanthus , 27–33 m, J. Graham, Oct. 1961 ; 10, NMNZ Cr 4999, Auckland Island , [50°35'S 166°E], in crab pots, 55 m, L.D. Ritchie, 11 Feb. 1970 .

Diagnosis. Eyes: well developed; elongate, length c. 2× height. Interocular furrow: well developed, extending across the cephalon; produced medially. Frontal lamina: lateral margins straight, narrowing anteriorly, or medially constricted. Antenna: c. 0.35–0.5× as long as body, reaching to between the posterior of pereonite 3 and pereonite 4. Coxal plates: furrows strongly developed, on all coxae. Pleonite 4: apex forming a broad acute point, or slightly rounded. Pleotelson: broad, length 0.8× basal width; anterodorsal depression absent; anterolateral margins almost straight and angling posteriorly toward the midline, or convex; posterolateral margins straight, markedly angled to anterolateral margins and meeting at an acute angle or convex; apex not produced, lateral margins converging smoothly to a point; with 10–16 RS. Pereopod 2: propodus with 3 RS on palm. Pereopod 3: propodus with 2 RS on palm. Pereopod 7: basis broad, width 0.64× length; distance between anterior margin and medial carina less than between posterior margin and medial carina; posterior margin with setae completely absent along entire length. Penes: absent. Pleopod 2 appendix masculina: extending subequal with tip of endopod, 0.96× length of endopod; margins very slightly curved laterally; slender; apex not at angle to adjacent margins, bluntly rounded. Uropods: exopod subequal to endopod, 0.94× the length of the endopod.

Additional descriptive characters. Based on a topotype, male, 36 mm, NMNZ Cr.4999. Body: length c. 2.7× width. Colour yellow or salmon-pink in alcohol. Chromatophores absent. Eyes: with 18 ommatidia in horizontal diameter; with 8 ommatidia in vertical diameter; rectangular; colour tan in alcohol. Frontal lamina: length c. 4.2× basal width; apex expanded, anterior margin angled. Antennule: peduncular article 1 longer than article 2; article 2 with 1 large pappose seta; article 3 short, subequal to article 1. Flagellum 16-articulate. Antenna: peduncular article 4 with 1 patch of 6 SS on posterolateral margin, 2 SS distomedially, 3 PS and 1 penicillate setae at anterodistal angle; article 5 with 2 pappose at posterodistal angle, 3 SS at anterodistal angle. Flagellum 34-articulate. Mandible: setal row with 19 RS. Maxillule: medial lobe with 3 large robust pappose setae; lateral lobe with 13 RS on distal surface. Maxilla: lateral lobe with 12 SS; medial lobe with c. 12 SS and 23 PS; middle lobe with 26 SS. Maxilliped: endite with 5 coupling hooks, 1 SS and 12 PS. Pereon: ornamentation consists of 1 strongly developed furrow on lateral margin of pereonite 1 and 1 short, medial furrow on lateral margins of 4–7; pereonites 1 and 5 subequal in length and longest, pereonites 4, 6–7 subequal and longer than 2–3 which are subequal. Coxae: pereonite 1 and coxae 2–3 with rounded posteroventral corners, coxae 4–7 with increasingly produced, broad, acute posteroventral corners. Pleonite 2: dorsal posterolateral margin subequal with ventral posterolateral margin. Pereopod 7: basis anterior margin convex; medial carina with PS along entire length; posterior margin convex. Ischium anterior margin with SS; posterior margin with 4 RS (and 8 submarginally), PS present. Merus posterior margin with 5 RS (and 6 submarginally), SS present. Carpus posterior margin with 6 RS (and 2 submarginally), SS present. Propodus subequal to carpus; posterior margin with 6 RS, SS present. Pleopod 2 appendix masculina: arising sub-basally. Pleopods 1–5: exopod suture feebly developed (sutures present at margins but not medially) on pleopods 3–5; endopod PS on most of margins of pleopods 1–4, only a few setae on pleopod 5. Uropods: endopod lanceolate; medial margin convex, with 5 RS, PS along entire length; apex with 2 RS; lateral margin slightly convex, with 5 RS, PS on distal three-quarters. Exopod medial margin convex, with 3 RS, PS on distal threequarters; apex acute, with 2 RS; lateral margin convex, with 8 RS, PS along entire length.

Variation. There is considerable variation in the number of robust setae on the pleotelson and uropods of individuals within all samples examined. There are also some differences between samples; specimens in BMNH 1856 :33 ( New Zealand), QM W10261 (Tasman Bay), NMNZ Cr 9197, 9199, 9200 and 9201 ( Pelorus South , Rangitikei River , Otago, Mana Island , respectively), tend to have a greater number of robust setae on the pleotelson and uropods than specimens in other samples. A comparison (below) of 10 specimens from each of the samples NMNZ Cr 4999 (Auckland Island ) and 9200 (Otago) indicates this, figures for Cr 9200 are in square brackets. Pleotelson : 11 (20%), 12 (60%), 13 (20%), [14 (100%)]. Endopod , medial: 5 (30%), 6 (60%) [20%], [7 (80%)], 8 (10%); lateral: 4 (20%), 5 (40%), 6 (40%) [60%], [7 (30%)], [8 (10%)]. Exopod , medial: 3 (20%), 4 (80%) [10%], [5 (70%)], [6 (20%)]; lateral: 8 (30%), 10 (10%) [20%], 11 (50%) [40%], [12 (40%)]. Because the ranges tend to overlap and no other consistent feature (such as the variation in pleotelson shape as noted in the diagnosis and below) could be found to correlate with these variations, and separate the specimens in these samples, it was concluded that a single variable species is represented. The full variation in setal counts is as follows; pleotelson 10–16, uropod endopod medial margin 5–8, lateral margin 4–8, uropod exopod medial margin 3–6, lateral margin 8–12 .

The length of the antenna also varies, on some specimens it reaches to the posterior of pereonite 4 and is 0.5× the length of the body, while in the material described and the lectotype selected here (see below) it reaches to the posterior of pereonite 3 and is c. 0.35× the length of the body. The number of flagella articles in the antennae also ranges from 26–36. Furthermore, in some specimens the anterolateral and posterolateral margins of the pleotelson are relatively straight compared to the material illustrated here. In the material examined the number of coupling hooks on the maxilliped endites ranged from two to five. Smaller specimens have fewer articles in the antennular and antennal flagella, and fewer coupling hooks on the maxilliped endite.

The lectotype has 11 robust setae on the pleotelson, six on the uropod endopod medial margin, 6 on the uropod endopod lateral margin, four on the uropod exopod medial margin and 12 on the uropod exopod lateral margin. In the lectotype the antennae extend to just beyond pereonite 3 and the posterolateral margins of the pleotelson are only slightly convex and distinctly angled to the anterolateral margins, which are relatively straight.

Size. Lengths of 25 mm, 26 mm and 21 mm have previously been recorded ( Miers, 1876a, b; Nierstrasz, 1917; Kussakin, 1967). In the material examined here adults ranged from 18 mm up to 36 mm.

Remarks. Because of the large number of syntypes and the variation among them, a male (BMNH 1844:3, Auckland Is., Antarctic Expedition, Presented by Capt. James Clarke Ross) is selected here as a lectotype for Natatolana rossi to avoid future taxonomic confusion when identifying this species. The remaining type specimens become paralectotypes. A topotype that has been closely compared to the types is illustrated here, and used for the description of characters additional to the diagnosis, because the type specimens are fragile and are damaged so that they lack many setae.

Natatolana rossi is extremely similar to N. hirtipes in most features, as noted by Chilton (1909). Miers (1876a) distinguished N. rossi from N. hirtipes because Milne Edwards (1840) described the length of the cephalon of that species to be equal to the width. This description is incorrect, however, consistent differences between N. rossi and N. hirtipes include a medially produced interocular furrow (smoothly convex in N. hirtipes ), a convex anterior margin to the eye (angled in N. hirtipes ), a concave ventral margin to the cephalon (convex in N. hirtipes ) and a slightly more sinuate anterior margin of the basis of pereopod 7 in N. hirtipes . Large males of N. hirtipes may develop indistinct tubercles on the dorsal surface of pereonite 2, these are not apparent in material identified as N. rossi .

Natatolana rossi is also extremely similar to N. matong . The development of the interocular and coxal furrows does not reliably separate the two species as suggested by Bruce (1986). The shape of pleonite 4 is, however, consistently different between the two species, N. rossi having a more sinuate posterodorsal margin.

Distribution and ecology. New Zealand and southern Pacific Ocean south of New Zealand. In depths to 260 m ( Kussakin, 1967). Marsden (1999) has measured the feeding rate, oxygen consumption and effects of aerial exposure for this species, concluding it is a predator/scavenger capable of long periods of fasting.

Figures

Fig. 41. Natatolana rossi, topotype male, NMNZ Cr 4999. Scales = 0.5 mm. CEa = cephalon lateral view.

Fig. 42. Natatolana rossi, topotype male, NMNZ Cr 4999. Scales = 1.0 mm.