Leptognathioides polita ( Hansen 1913 )

Bird, Graham J., 2014, Tanaidacea (Crustacea: Peracarida) of the North-east Atlantic: the genera Leptognathioides and Portaratrum of the ‘ Atlantic Margin’, Journal of Natural History 48 (29 - 30), pp. 1771-1815 : 1776-1777

Leptognathioides polita ( Hansen 1913)

Leptognathia polita: Hansen (1913) : 96 –99, plate IX figs 5a–f

Leptognathia polita: Just (1970) : 24

Non Leptognathia polita: Holdich and Bird (1985) : 444, Table 1, = Leptognathioides potens Bird and Holdich, 1984

Leptognathioides polita: Bird and Holdich (1984) : 292, figs 4–5

Diagnosis

Female: with pereonites all shorter than broad. Cheliped propodus without obvious step process on inferior margin, fixed finger with triangular tooth on incisive margin. Pleopod endopod with six distolateral setae, exopod lateral margin with proximal seta and nine distal setae. Uropod exopod one-segmented. Preparatory male: pleopod rami broader than in female, endopod with one distomedial and eight distolateral setae; exopod with proximolateral seta and distolateral fringe of ten setae.

Material examined [for morphometrics]

One non-ovigerous (non-ov.) ♀, two preparatory (prep.) ♂♂, AFEN 1998 Stn 54503#3; three non-ov. ♀♀, one prep. ♂, AFEN 1998 Stn 54518#1; one manca-II, AFEN 1998 Stn 54521#1/3; two non-ov. ♀♀, AFEN 1998 Stn 54549#2; one non-ov. ♀ (?), AFEN 1998 Stn 54552#1; three manca-II, one manca-III, four non-ov. ♀♀, one ov. ♀, one prep. ♂, AFEN 1998 Stn 54552#4; one non-ov. ♀, AFEN 1998 Stn 54553#2; one non-ov. ♀, AFEN 1998 Stn 54554#3; two non-ov. ♀♀, one prep. ♂, BIOFAR Stn 263; one prep. ♂, BIOFAR Stn 264; three manca-III, 102 non-ov. ♀♀, 13 post-ov. ♀♀, 50 prep. ♂♂, BIOFAR Stn 380; seven non-ov. ♀♀, five prep. ♂♂, BIOFAR Stn 381; one non-ov. ♀, BIOFAR Stn 417; one manca-III, two non-ov. ♀♀, BIOICE Stn 2021; one manca-III, five non-ov. ♀♀, one ov. ♀, BIOICE Stn 2023; one non-ov. ♀, BIOICE Stn 2024; one non-ov. ♀, BIOICE Stn 2025; three manca-III, 17 non-ov. ♀♀, one ov. ♀, two post-ov. ♀♀, five prep. ♂♂, BIOICE Stn 2030; one prep. ♂, BIOICE Stn 2362; three manca-II, four manca-III, 58 non-ov. ♀♀, three ov. ♀♀, 19 prep. ♂♂, BIOICE Stn 2673; one non-ov. ♀, BIOICE Stn 2947; one non-ov. ♀, one post-ov. ♀, two prep. ♂♂, one fragment, BIOICE Stn 3115; one manca-II, four non-ov. ♀♀, four prep. ♂♂, BIOICE Stn 3124; 97 non-ov. ♀♀, nine post-ov. ♀♀, nine prep. ♂♂, BIOICE Stn 3249; five non-ov. ♀♀, one ov. ♀, BIOICE Stn 10722 (data unknown, possible mislabelling) .

Distribution in main study area

Represented by 88 records from AFEN area: three from the West Shetland Slope 367–554 m , two from Faroe Bank Channel 862–1011 m, and 83 from the Faroe- Shetland Channel 602–1408 m . By 31 records from BIOFAR: seven from Faroe Plateau 225–497 m , four from the Faroe-Norway Rise 507–808 m, seven from the Faroe-Shetland Channel 509–1150 m, five from the Iceland-Faroes Rise (N, Faroes ) 503–804 m , four from the Iceland-Faroes Rise (S, Faroes ) 509–894 m , two from the Norwegian Basin 1022–1261 m, and one each from the Faroe Bank Channel and Wyville-Thomson Ridge at 1038 m and 732 m respectively. By 89 records from BIOICE: eleven from Denmark Strait 203–1012 m ; three from Greenland-Iceland Rise 213–231 m; nine from Iceland Shelf E, N, NE, NW and W 148–196 m ; 15 from Iceland Plateau 225–1008 m ; 21 from Iceland-Faroes Rise (N, Iceland) 215–996 m ; six from Iceland-Faroes Rise (S, Iceland) 350–550 m ; five from Irminger Basin 240–305 m; and 19 from Kolbeinsey Ridge 203– 905 m.

Overall depth range: 148–1408 m; overall temperature range –0.82°C to 6.5°C, almost evenly split between positive and negative temperatures (n = 84).

Distribution elsewhere

East Greenland, Jørgen Brønlund Fjord, 40–105 m ( Just 1970).

Remarks

Additional figures shown here supplement or correct some given by Bird and Holdich (1984), and include those for ‘preparatory males’. As they were omitted in that paper, the size ranges of the different life-stages are: manca-II 1.2–1.5 mm; manca-III 1.6– 2.1 mm; non-ovigerous female 1.8–3.9 mm; ovigerous female 2.7–3.5 mm; postovigerous female 2.6–3.7; preparatory male 2.5–3.4 mm.

The maxilliped structure ( Figure 1A ) is close to what was drawn by Bird and Holdich and very similar to that of new species described below, with the bases having an anterior projection over the endites and the latter each with a distal lobe on the oral-surface bearing a seta. Some individuals have seemingly bisegmented uropods ( Figure 1E ) but these are not well-defined as in the new species described below. The preparatory male is very similar in most respects to the female but has thicker antennules ( Figure 1C ) and more well-developed pleopods ( Figure 1D ).

This species is widespread and occasionally abundant in the shelf–bathyal zone of (largely) the cold-water region between Iceland and the Shetlands ( Figure 12 ) and is a good ‘marker’ for this water mass where it impinges on the Shetland and Faroe slopes within the Faroe-Shetland Channel (e.g. Bett 2000; Bird 2001). Here there is a rapid turnover between 500–600 m depth of the tanaidacean fauna, from one typical of the West European shelf and upper slope to one characteristic of the bathyal ‘cold water’ zone, in which L. polita is a significant contributor ( Bird 2001). Nevertheless, this species has a broad thermal tolerance and is one of the few tanaidaceans that apparently straddle the cold–warm water-mass interface. There is also evidence from this distribution of an association with the southern overspill of cold Norwegian Sea water across the Iceland-Faroe Rise. The type (and only) locality recorded by Hansen (1913) was Ingolf Stn 141, north of the Faroes, at 1242 m, with a temperature of –0.6°C. This corresponds to region ‘39, Norwegian Basin’ in Table 1. This species was not recorded by Bodil et al. (2011).

Figures

Figure 1. Leptognathioides polita. Female (BIOICE Stn 2673): (A) Maxilliped; (B) maxilla. Preparatory male (BIOICE Stn 2673): (C) habitus; (D) pleopod (all setae plumose); (E) uropod, lateral. Scale bar: 2 mm for (C), 0.25 mm for (A, B, D, E).

Figure 12. Distribution of Leptognathioides and Portaratrum species in Atlantic Margin studies. Small black filled circles indicate all tanaidacean records, large black filled circles L. polita, red filled circles L. biarticulata, and blue filled circles P. holdichi; red arrow indicates joint record of L. biarticulata and P. holdichi.