Natatolana borealis ( Liljeborg, 1851 )

Keable, Stephen J., 2006, Taxonomic Revision of Natatolana (Crustacea: Isopoda: Cirolanidae), Records of the Australian Museum 58 (2), pp. 133-244 : 157

Natatolana borealis ( Liljeborg, 1851)

Synonymy in Keable & Bruce, 1997: 659, figs. 1–4.

Type material. Syntypes: deposition of the original material was not indicated, 333, 5? ♀♀ in the Zoological Museum , Lund University, Sweden , probably represent at least part of the original type series examined by Liljeborg (Keable & Bruce, 1997). All examined. Type locality: Kristiansund [as Christiansund, c. 63°23'N 7°45'E] and Bergen [c. 60°23'N 5°20'E], Norway .

Material examined. Listed by Keable & Bruce (1997).

Diagnosis. Interocular furrow: moderately developed, distinct but not extending across the cephalon. Frontal lamina: lateral margins straight, parallel. Antenna: c. 0.4× as long as body, reaching to posterior of pereonite 4. Coxal plates: furrows variously developed, faint and incomplete on coxae 2 and 3 only. Pleonite 4: apex forming a broad acute point. Pleotelson: broad, length 0.96× basal width; anterodorsal depression absent; anterolateral margins convex; posterolateral margins convex; apex not produced, lateral margins converging smoothly to a point; with 6–8 RS. Pereopod 2: propodus with 4–6 RS on palm (4 large and 2 small). Pereopod 3: propodus with 3 RS on palm. Pereopod 7: basis broad, width 0.57× length; distance between anterior margin and medial carina less than between posterior margin and medial carina; posterior margin with setae along entire length. Penes: absent. Pleopod 2 appendix masculina: just shorter than endopod, 0.87× length of endopod; margins straight or bent slightly medially; slender; apex not at angle to adjacent margins, with lateral projection forming a Y-shape with acute apex. Uropods: exopod slightly shorter than endopod, 0.87× the length of the endopod.

Variation. In smaller males (e.g., 22 mm) the appendix masculina is shorter (e.g., 0.81× endopod) and the Y shaped process on the appendix masculina apex may be absent or only partially developed (Keable & Bruce, 1997).

Size. Adults to c. 33 mm.

Remarks. Keable & Bruce (1997) redescribe Natatolana borealis and discuss its identification and character variation. This species can be readily recognized by the shape and setation of the uropods and pleotelson, and by the distinctive shape of the appendix masculina of adult males.

The material of Natatolana borealis reported from South Africa by Kensley (1975, 1978) is not N. borealis . Kensley (1975) noted the South African specimens have coxae with sinuate posterior margins, and a small notch at posteroventral corner where an acute coxal point is produced. Kensley suggested that this was a variation that may be due to the immaturity of the specimens. This does not seem to be the case, juvenile Natatolana usually resemble the adult very closely in these features (personal observation) and the coxae of smaller specimens identified by Keable & Bruce (1997), as N. borealis , are similar to those of the adults. Also, one of the specimens reported by Kensley (1975) (SAM A-13556) has an apparently fully developed basis of pereopod 7 attached to the body and can therefore be considered to have reached adult size. A unusual feature of the South African specimens is that the carpus of pereopods 4–5 [figured as pereopod 6 by Kensley (1975)] is greatly elongated (c. 2 times as long as the merus and 1.5 times as long as the propodus). This is a unique character within Natatolana and indicates that these specimens represent an undescribed species. Unfortunately, the material is not in good enough condition to describe.

Distribution and ecology. Disjunct North Atlantic records—primarily recorded from northeastern Atlantic coasts between 70° and 10°N, westwards to about 22°W but also recorded from off South Carolina, USA (Keable & Bruce, 1997; Johansen & Brattegard, 1998). At depths of 5–1478 m with the depth range varying with locality (Keable & Bruce, 1997; Johansen & Brattegard, 1998).

Natatolana borealis is well documented as a scavenger, feeding on dead and dying fish (Keable & Bruce, 1997). Ecological and physiological studies reporting this species, subsequent to those summarized by Keable & Bruce (1997), include Johansen (1999, 2000a, 2000b), Johansen & Brattegard (1998), Kaïm-Malka (1997), Kaïm-Malka et al. (1998), Bozzano & Sarda (2002) and Castro et al. (2005).