Morphological and mtDNA sequence studies on three crucian carps (Carassius: Cyprinidae) including a new stock from the Ob River system, Kazakhstan

Three morphologically and genetically distinct forms of the genus Carassius were collected from the Ob River system, Kazakhstan, Central Asia; Carassius carassius, Carassius gibelio gibelio and an unknown stock tentatively referred to as Carassius gibelio sub-species M. The last mentioned had 33-41 gill rakers, being intermediate between the other two forms (23-27 in C. carassius and 44-49 in C. g. gibelio), and five scales in the upper transverse series, less than in the others. It also had a relatively larger erythrocyte suggesting triploidy and an mtDNA haplotype distinct from all other known crucian carps. Comparative mtDNA phylogenetic analysis suggested that C. gibelio gibelio in the Ob River system was introduced from China and the Amur River, the same possibly being true for European C. gibelio gibelio based on published haplotypes. C. gibelio sub-species M is thought to be more widely distributed in central Asia, probably extending as far west as European Russia.

Visual pigments and the photic environment: the cottoid fish of Lake Baikal

The endemic cottoid fish of Lake Baikal in Eastern Siberia offer a singular opportunity for examining within a number of closely related species, the relationships of visual pigments, photoreceptor complements and depth within a deep freshwater environment. The lake, the deepest (1600 m) and one of the largest and most ancient in the world, is unique in that the oxygen levels at the bottom are only reduced to about 80% of the surface levels. We have studied, by light microscopy, microspectrophotometry and visual pigment extraction, the retinas from 17 species of Baikal cottoids that live at different depths within the lake. Generally the retinas contain, in addition to rods, large green-sensitive double cones and small blue-sensitive single cones: surprisingly for freshwater fish, the visual pigments are based on Vitamin A1. The lambda max of both rods and cones are displaced to shorter wavelengths with increasing depth. Surface species have cones with lambda max at about 546, 525 and 450 nm and rods at 523 nm, deeper living species retain cones, but with lambda max shifting towards 500 and 425 nm and with rods at 480 nm, whereas the deepest living fish possess only rods (lambda max 480-500 nm). These data clearly show a correlation between photoreceptor complement, visual pigment lambda max and depth, but question the hypothesis that there is a correlation of pigment lambda max with water colour since, in contrast to oceanic waters, the maximum transmission of Baikal water is between 550 and 600 nm.

Comparative study of two protein-coding regions of mitochondrial DNA from three endemic sculpins (Cottoidei) of Lake Baikal

Two protein-coding regions (cytochrome b, ATPase 8, and part of ATPase 6) from mitochondrial DNA of Cottus kessleri, Cottocomephorus grewingki, and Cottocomephorus inermis--Baikalian endemic sculpins--were amplified via polymerase chain reaction, and sequenced. Two novel primers--L8352 (5'-TAAAGATTGGTGAC TCCCAACCACC) and H8773 (5'-GTAGGGAGT AAGCCCAATATGTT)--were used for the latter region. Phylogenies suggested by sequence divergence of the genes of ATPases appeared to be different from those computed from data for cytochrome b. The time of species branching was estimated as 1-2 million years (Myr) on the basis of merged sequences. Hence, members of the Baikalian cottoid species flock are much more distant from each other than members of the cichlid fish flocks of the great lakes of Africa (0.2 Myr). Topology of the phylogenetic tree does not contradict the relationships derived from morphological data. However, genetic distances suggest that C. grewingki and C. inermis are not sister species, contrary to general belief.