Point-Snouted Whitefish

description

Description. General appearance is shown in Figure 10. Morphological and meristic characters of both sexes can be found in Tables 9, 12, and Suppl. material 1: Tables S 6, S 7 and first- and second-best ratios for both sexes combined can be found in Table 10. The description is valid for both sexes. Shape: Only slightly deep bodied with greatest body depth anterior of the dorsal fin. Dorsal and ventral profile equally arched such that both the dorsal profile from the tip of snout to the anterior origin of dorsal fin and the ventral profile from the interorbital area to the pelvic fin origin are moderately convex. Head long. Mouth (i. e., width of upper and lower jaw) is thick, moderately long and often sub-terminal and only rarely terminal. Rostral plate is mostly wider than deep, not strongly pronounced and the tip of the snout is often pointy in the sagittal plane. Eye-socket thick and triangular (i. e., sickle-shaped). Pectoral fin moderately tapered. Anterior unbranched ray of the erected dorsal fin has an approx. 40 - 60 ° angle to body axis and from the middle to the end of the ray it is moderately bent posteriorly. Caudal peduncle stout and moderately long. Caudal fin forked

A taxonomic revision of the whitefish of lakes Brienz and Thun, Switzerland, with descriptions of four new species (Teleostei, Coregonidae)

diagnosis

Diagnosis. Coregonus acrinasus is a medium-sized whitefish with moderate pigmentation of all fins and body; dark greenish blue colour on the flanks above the lateral line; moderate to many pigmented small dots on the scales; tip of the snout pointy; long head; small eye with a thick and triangular shaped eye socket; many and moderately long gill rakers.

A taxonomic revision of the whitefish of lakes Brienz and Thun, Switzerland, with descriptions of four new species (Teleostei, Coregonidae)

distribution

Distribution and notes on biology. Coregonus acrinasus is found in Lake Thun (46 ° 40 ' N, 7 ° 46 ' E). Based on isotopic signatures C. acrinasus most likely feeds on a mix of benthic prey and zooplankton (Selz 2008; Hudson 2011; Ingram et al. 2012) and based on the size-at-age data C. acrinasus must have a rather fast growth rate (Suppl. material 1: Figures S 4 - S 6). The gill raker number and length of C. acrinasus (many gill rakers and moderately long gill rakers) suggests, based on the functional properties of the number of gill rakers on feeding on different prey items (Lundsgaard-Hansen et al. 2013; Roesch et al. 2013), that C. acrinasus feeds more on zooplankton and less on benthic prey, but this assumption needs to be verified in the future with stomach content analyses. The relative species abundances in the pelagic and benthic habitat from a habitat-stratified random sampling of Lake Thun (mid-October 2013: Vonlanthen et al. 2015) also points to this. Coregonus acrinasus occupies only the shallow waters of the benthic habitat (15 m; N = 1) and the moderately deep pelagic waters (approx. 10 - 35 m; N = 9) (Doenz et al. 2018). However, the habitat-stratified sampling needs

A taxonomic revision of the whitefish of lakes Brienz and Thun, Switzerland, with descriptions of four new species (Teleostei, Coregonidae)

etymology

Etymology. The name C. acrinasus is a combination of the ablative case of the Latin adjective acer resulting in acri, which means pointed and the noun nasus for nose. The name acrinasus refers to a phenotypic feature of this species, which often has a pointed snout when viewed in the sagittal plane.

A taxonomic revision of the whitefish of lakes Brienz and Thun, Switzerland, with descriptions of four new species (Teleostei, Coregonidae)