Thymallus ligericus, Persat & Weiss & Froufe & Secci-Petretto & Denys, 2019

Persat, Henri, Weiss, Steven, Froufe, Elsa, Secci-Petretto, Giulia & Denys, Gaël P. J., 2019, A third European species of grayling (Actinopterygii, Salmonidae), endemic to the Loire River basin (France), Thymallus ligericus n. sp., Cybium 43 (3), pp. 233-238 : 234-238

Thymallus ligericus n. sp.

( Figs 2-6 )

Material examined

Holotype. – MNHN 2018-0722 , 337 mm SL J, France: Loire drainage, Cantal Dept., Alagnon River at La Chapelle d’Alagnon: 45°6’ 21”N- 2°53’48”E, 9 Sep. 2016, Persat and FDAAPPMA15 coll.

Paratypes. – MNHN 2018-0723 , 327 mm SL ♀, collected together with the holotype ; MNHN 2018-0724 , 252 mm SL ♀, France: Loire drainage, Haute-Vienne Dept., Combade River at Masléon : 45°46’1”N- 1°33’16”E, 28 May 2015 , Persat and FDAAPPMA87 coll .; MNHN 2018-0725 , 252 mm SL ♀, Combade River at Masléon , same date, location, and collectors ; MNHN 2018-0726 , 290 mm SL ♀, Loire Dept., Lignon River at Boën-sur-Lignon : 45°45’6”N- 3°59’33”E, 29 May 2015, Persat, Juglaret and Buttazzoni coll. ; MNHN 2018-0727 , 278 mm SL ♀, Loire Dept., Lignon River at Boën-sur-Lignon : same date, location, and collectors ; MNHN 2018-0728 , 300 mm SL J, Puy-de-Dôme Dept., Dore River at Vertolaye : 48°38’11”N- 3°42’23”E, 29 May 2015, Persat, Juglaret and Buttazzoni coll. ; MNHN 2019-0266 , 284 mm SL J, Puy-de-Dôme Dept., Dore River at Vertolaye : same date, location, and collectors ; MNHN 2019-0267 , 269 mm SL ♀, Haute-Loire Dept., Loire River at Chadron : 44°58’7”N- 3°55’11”E, 22 Sep. 2016 , Persat and ONEMA43 coll .; UCBLZ – 2019.9. 1009, 304 mm SL J, Ardèche Dept., Allier River at Laveyrune : 44°37’54”N- 3°53’40’E, 22 Sep. 2016 , Persat , FDAAPPMA09, FDAAPPMA43 and FDAAPPMA48 coll .; UCBLZ – 2012.9. 1008, 405 mm SL ♀, Cantal Dept., Alagnon River at Ferrières-Saint-Mary: 45°10’41”N- 3°53’43”E, 27 Jun. 2016, Persat and Lesbre coll.

Diagnosis

Thymallus ligericus n. sp. differs from T. thymallus by a more elongated body ( Fig. 2 ), the presence of a pointed snout revealing a strait or convex snout profile ( Fig. 3A ) (vs. a concave profile for T. thymallus , Fig. 3B ), a more inferior mouth with a transversal aperture and a fleshier upper lip ( Fig. 4A ), a high number of black dots on the flanks (usually from more than 50 to several hundreds vs. less than 50 in the Rhône populations; Figs 2 , 5 ), a shorter head length (20.0-23.7% SL vs. 17.5-19.9% SL), smaller occipital and orbital depths of the head (respectively: 54.8-71.7% HL vs. 73.2-76.1% HL; 43.5-53.4% HL vs. 51.1-56.4% HL) and a shorter horizontal eye diameter (22.6-26.3% HL vs. 26.1- 31.7% HL).

Description

Morphometric measurements are given in table I. The holotype counts are given in brackets.

Thymallus ligericus n. sp. has an elongated body ( Fig 2 A-C) and a smaller head height ( Fig. 4 ). The throat is usually covered by small scales. It has a pointed snout giving a strait or convex snout profile ( Fig. 3A ). Its mouth is clearly inferior with a transversal aperture more resembling the nase Chondrostoma nasus (Linnaeus, 1758) ( Fig. 4A ). The upper lip is fleshy. The adipose fin is usually rounded. Concern- ing meristic data, this species has VII-VIII 14-15 dorsal fin rays (VII-14), I 14-16 pectoral fin rays (I-15), I 9-11 pelvic fin rays (I-10), IV-V(9-11) anal fin rays (V-11), 73 + 2 to 87 + 4 lateral scales (81 + 3), 8.5-9.5 transverse dorsal scales and 8.5-9.5 transverse pelvic scales. According to Knizhin (unpubl. data), who observed 7 specimens from the Loire catchment, this species has (15)18(19) pyloric caeca.

Colouration in life

In adults, overall body colour is usually darker than that of the Rhone or Rhine T. thymallus , but this might depend on the substrate. They can take on a blue metallic sheen in the darkest individuals. The sides are highly spotted by usually more than 50 and up to hundreds of black dots (270 in the holotype) ( Figs 2 A-C, 5), sometimes extending up to the head, with the exception of the uppermost section of the Alli- er River where the population is less spotted. In some populations, dots might be coalescent forming a kind of short horizontal lines. The lateral large faint wine-red patch in the centre of the side above the pectoral fins, common in many European populations, is often not visible when present because of the dark background colour of the body. Paired and anal fins have a rather dark green-brown colour. The pectoral fin does not develop the patchy colouration pattern usually visible in the largest T. thymallus of the Rhine and sometimes Rhone catchments. Caudal fin is dark-greenish, sometimes turning to dark purple, with a blue iridescent shine in large individuals. The large dorsal fin of the adults, especially in the males, is a bit less extended and less coloured than in the Rhône or Rhine populations of T. thymallus . The fin rays are contrastingly lighter than the inter ray membrane. The outer margin of the dorsal fin is often underlined by a thin pink line ( Fig. 6 ). Towards the posterior part of the dorsal fin, the edge line takes a brown colour that extends more and deeper between the last dorsal fin rays. A checked pattern of alterna- tively dark grey and brown-reddish blotches covers most of the surface of the fin. This checked pattern is completed on its outer and posterior part by an alignment of increasingly clear blotches showing the same blue iridescent shine as the caudal fin. For large individuals, this blue colour part of the dorsal fin is visible from the riverbank.

Colouration in preservation

Fixed in formalin, then preserved in 70° ethanol, most of the colours, except the black dots, turn to grey. The checked pattern and colours of the dorsal fin, as well as the faint wine-red become faded but persist, for at least several years.

Etymology

Ligericus is a Latin adjective meaning “from the Loire drainage”.

Vernacular name

Loire grayling (English), Ombre d’Auvergne,, Ombre de la Loire (French).

Distribution and habitat

The Loire grayling lives in medium to large foothill, canyon and plateau rivers of the mountainous part of the Loire catchment, i.e. in the Upper Vienne, Upper Loire and Upper

Allier districts, where it cohabits with brown trout Salmo trutta Linnaeus, 1758 , and Atlantic salmon Salmo salar Linnaeus, 1758 , in the Allier branch. It is able to colonise rather small rivers with mean discharges of ca. 1 m 3 /s when protected from overfishing. It is able to swallow and digest caddisfly larvae with their gravel cases, a common prey in the Loire catchment ( Persat, 1976). Only one known population, from the Besbre River, seems to have been driven to extinction, but all populations are potentially threatened by climatic change as droughts result in exceedingly high temperatures and too low water velocities. Up to now, stocking attempts appear to regularly fail in sustaining local native populations ( Persat et al., 2016), suggesting that wild stocks are more competitive than introduced ones. However, some Loire grayling populations have been successfully introduced elsewhere, such as in the Corrèze River of the Dordogne catchment, based on stocks reared at the Puy-de-Dôme federal fish farm of Besse-en-Chandesse (M. Mestas, pers. comm.).

Comparative material

Thymallus thymallus (Linnaeus, 1758) : BMNH

1979.6.22.191-192, 2 specimens, England: Thames drainage, Lambourn River at Lambourn, 1976 , Bellamy coll.; BMNH 1979.6.22.226-238, 4, Kennet River , 1973 , Bellamy coll.; BMNH 2018.9 .4.14, 1, River Holme at Lockwood, Huddersfield, 15 Sep. 2017 , Beer coll.; MNHN 1959-0546 , 1 , France: Rhône drainage at Nant-de-Sion, Spillmann coll.; MNHN B-2478, 2, Rhône drainage , de Candolle coll.; MNHN B-2479, 1, Rhône drainage , Blanchard coll.; MNHN B-2480, 3, Rhône drainage, Dept. Isère at Saint-Laurent-du-Pont , Galbert coll.; UCBLZ – 2012.9.1012, 2, Rhône drainage, Ain River at Crotenay, 11 Jun. 2014 , Persat and FDAAPPMA39 coll.; UCBLZ – 2012.9.1013, 1, Rhône drainage, Ain River at Marigny, 19 Jul. 2016 , Persat and FDAAPPMA39 coll.; UCBLZ – 2012.9.1014, 1, Rhône drainage, Bourne River at Saint Thomas en Royans, 19 Oct. 2010 , Persat and Mallet coll.; ZSM-Pis-032234/537416/389004, 1, Germany: Danube drainage, Inn River at Wasserburg, below dam, downriver to “Am Griess”, 48.058N 12.220E, 10 Nov. 2004 ; ZSM- Pis-036238/541401/392989, 1, Elbe drainage, Sächsische Saale stream North of Förbau, East of Münchberg, 50.212N 11.917E, 26 Sep. 2007 .

Acknowledgements. – This study was supported by the CNRS, the MNHN and the AFB and funded by the partnership MNHN-AFB 2016-2018. We are grateful to the Fishing Authorities, mainly the former CSP-ONEMA, the FDAAPPMA of Loire, Haute-Loire, Ardèche, Lozère, Cantal, Haute-Vienne and Puy de Dôme departments, and the Environment Ministry, which physically or finan- cially supported our investigations during so many years. We also thank the fish curators of the NHM, MNHN, UCBLZ and ZSB for providing pictures of specimens of their collections. Our particular thanks go to Pierre Grès, Stéphane Nicolas, Vincent Peyronnet, Valérie Prouha, Romain Max, François Desmolles, Stéphanie Charlat, Lucien Jonard, Marc Mestas, Thierry Millot, Henri Buttazzoni, Grégoire Juglaret, Hervé Brun and Julien Lesbre. Finally, we are very grateful to Agnès Dettai for correcting the manuscript.

Figures

Figure 2. – Specimens of Thymallus spp. in lateral view. Holotype of Thymallus ligericus n. sp. MNHN 2018- 0722, 337 mm SL J, Alagnon River at La Chapelle d’Alagnon, 9 Sep. 2016, Persat and FDAAPPMA15 coll., in live (A) and after preservation (B); Paratype of Thymallus ligericus n. sp. MNHN 2019-0267 (C), 269 mm SL ♀, Loire River at Chadron, 22 Sep. 2016, Persat and ONEMA43 coll; UCBLZ – 2012.9.1011 (D), 292 mm TL, Rhône drainage, Ain River at Crotenay, 10 Jun. 2014, Persat and FDAAPPMA39 coll.

Figure 3. – Head profiles of Thymallus spp. A: Paratype of Thymallus ligericus n. sp. MNHN 2018-0728, 300 mm SL J, Dore River at Vertolaye, 29 May 2015, Persat, Juglaret and Buttazzoni coll.; B: Thymallus thymallus UCBLZ – 2012.9.1010, 376 mm TL, Rhône drainage, Ain River at Crotenay, 10 Jun. 2014, Persat and FDAAPPMA39 coll.

Figure 4. – Mouth in ventral view of Thymallus spp. A: Holotype of Thymallus ligericus n. sp. MNHN 2018-0722, 337 mm SL J, Alagnon River at La Chapelle d’Alagnon, 9 Sep. 2016, Persat and FDAAPPMA15 coll.; B: Thymallus thymallus UCBLZ 2012.9.1010, 376 mm TL, Rhône drainage, Ain River at Crotenay, 10 Jun. 2014, Persat and FDAAPPMA39 coll.

Figure 5. – Average dot numbers on each scale row on the flank for populations of Thymallus ligericus n. sp. from the Upper Ance (47 specimens), Lower Ance (7 specimens) and Lignon Rivers (16 specimens) in the Loire drainage as well as for Thymallus thymallus populations from the Ain (176 specimens) and Loue rivers (35 specimens) in the Rhône drainage.

Figure 6. – Dorsal fin on a live paratype of Thymallus ligericus n. sp. MNHN 2018-0726, 290 mm SL ♀, Lignon River at Boën-sur- Lignon, 29 May 2015, Persat, Juglaret and Buttazzoni coll.