Stability of unique pattern of lateral line system of Baikal stone sculpin (Paracottus knerii, Cottidae) after colonization by this species of Yenisei River system

Abstract

The study of the lateral line system in the stone sculpin Paracottus knerii (Dybowski, 1874) from Lake Baikal revealed pattern uniqueness and species specificity. This is demonstrated in autonomy of the supraorbital, infraorbital, and preoperculo-mandibular sensory canals, as well as in the presence of gaps inside them. The pattern of the lateral line differs significantly from that in the species of the genus Cottus Linnaeus, 1758, which is illustrated by the example of Cottus sibiricus Warpachowski, 1889. In this particular species, all sensory canals, except for the preoperculo-mandibular canal, are connected as a single system. The C. sibiricus pattern of the system is significantly different from the Baikal P. knerii. As a whole, in the individuals of P. knerii from the Yenisei River System, the Baikal pattern of the lateral line system is retained, containing autonomous sensory canals. Comparative analysis of transformations of the lateral line system in the Baikal and Yenisei stone sculpins showed that the transformations go in different directions. In the Baikal form, there is an increase in the number of gaps in the infraorbital sensory canal and the occipital commissure. This leads to an increase in the autonomy of separate segments of the sensory canal. On the contrary, in the Yenisei form P. knerii, number of breaks inside the sensory canals decreases, while preserving their autonomy. In Yenisei fishes (unlike the Baikal ones), the supraorbital canal does not have gaps in most cases, its pre- and post-coronal parts are interconnected. The supraorbital canals of the left and right sides do not connect in the form of a letter “V”, they are interconnected by a narrow coronal commissure, as is in species of the genus Cottus. The trunk canal (CLL) in most river sculpins is longer than in Baikal individuals. In the caudal part, the CLL has several autonomous segments, which is not found in Baikal fish.