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Biological Evidence 2013, Vol.3, No.2, 4-11
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5
on the plates brought to one scale. Captions to images contain the following information about specimen
illustrated: sampling sight, sex (f: female; m: male; (?): sex unknown); age (years); shell height in mm.
Photo slide
(
http://bio.sophiapublisher.com/article_picture.php?article_id=536&type=be
)
As for
R. venosa
, obviously, the Blue Bay population can be divided into two fundamentally different groups
based on the color patterns’ character: 1. with dark color of the spiral ribs from light brown to black (D-line), 2.
with almost white spiral patterns, contrasting with the background color to varying degrees (W-line). We consider
the color as character, and color variants as its state. Character is controlled by a gene, and the character states, by
its alleles. The W-line and D-line allelomorphs background color can range from very dark to very light, which
indicates that the background color and pattern are controlled by different genes. Based on the frequency of
occurrence, we can conclude that the D-line specimens are correlated to a dominant allele and W-line, correlated
to the recessive one. This could apply not only to the gene that determines the color of the spiral patterns, but also
to the shell outer surface background. Despite the fact that the color of the background and the color of the spiral
patterns (lines and stripes) are regulated by different genes, they primarily "work" in a similar mode. This is
realized in the benefit connection of melanistic specimens with dominant (A) D-line alleles, and albinistic - with
recessive (a) W-line allele.
Our studies allow asserting that typical form of the native range predominates in most populations of the Black
Sea area (Photo 3). Among the Blue Bay population, more than 50% of individuals are the typical form, which
represent the dominant (A) allele (Photo 4~6), another 25% are intermediate phenotype (Photo 7). Recessive (a)
allele is responsible for the coloration of the spiral ridges, which was less than 25% of the total population (Photo
8). In other populations of the Black Sea, such individuals may be less or absent. Nevertheless, such individuals
are present in most populations (Photo 9, 10). At present one specific dwarf population consisting only albinistic
specimens was found in Azov Sea (Photo 1). The largest specimen (32.8 mm) of this population is shown on
Photo 9 B. The finding of albinist dwarf population in the Sea of Azov suggests that a certain type of dwarfism
associated with recessive color allele. In the Black Sea populations albinists generally were found among dwarf
specimens, which also confirms the suggestion above.
The earlier albinism phenogenesis studies (Wright, 1916) shows that the basis of allelic changes are continuous
gradation of the same morphogenetic factor (for example, the amount of matter or the reaction rate), operating
with a threshold effect. Now our present research may serve as a confirmation of these conclusions.
All varieties of
R. venosa
shell outer part coloration and patterns are produced by two different genes, each of
which has two (A, a) alleles.
Annotation for photos:
Photo
1
:
Rapana venosa
sampling sites (white stars): 1, Romanian coast; 2, northwestern Black Sea shelf; 3, Mezhvodnoye Bank; 4,
Donuzlav region; 5, Sevastopol vicinity (Blue Bay, Lermontov Cap); 6, Laspee Bay; 7, Karadag mountains coast; 8, Kerch Strait
region; 9, South Azov offshore
Photo
2
: The Author is ready to rapana sampling on Blue Bay shore, Sevastopol vicinity, Crimea.