Effect of β-carotene, β-echinenone, astaxanthin, vitamins A and E, and fucoxanthin on the biological defense of the sea urchin P. depressus has been investigated by Kawakami et al. (1998). The authors found the highest phagocytic index in group getting β-echinenone with feed. It is interesting that fucoxanthin (major carotenoid of brown seaweeds) does not accumulate in the gonads but have significant effect on phagocytic activity and quantity of ovulated eggs. Feeding experiments with Lytechinus variegatus have shown significance of dihydroxycarotenoids (lutein and zeaxanthin on development of eggs and the subsequent growth and a survival of larvae (George et al., 2001).

One of the important factors, which are crucial for accumulation and utilization carotenoids in organism of sea urchins, is sex and stage of gonad maturity. It is known, that the carotenoids content in males of sea urchins Dendraster excentrias and Strongylocentrotus franciscanus is higher than in females (Goodwin, 1984). For females and males of S. intermedius and S. nudus differences in carotenoids content during annual reproductive cycle exert influence on their gonad coloring (Borisovets et al., 2002, Zadorozhny et al., 2003). For these species, color grade of gonads according to market color scale is better for females than males (Kalinina et al., 2002). In addition, the certain interrelation between color and maturity of gonads was observed: improvement of color characteristics occurs in process of growth of gonads, both in females and males.

Consequently, all these data testify to activity and importance of carotenoid metabolism in a reproduction of sea urchins. In addition to β-carotene and echinenone, several carotenoids, not accumulating in gonads but present in significant amounts in natural food of sea urchins (lutein is primary xanthophyll of green algae (Goodwin, 1980), fucoxanthin – in brown seaweeds (Haugan & Liaaen-Jensen, 1994), zeaxanthin is typical for red algae (Carnicas et al., 1999)) may play an important role in processes of reproduction and biological defense of animals.

Effect of a Diet on Roe Color

Basis of a diet of sea urchins makes up of macrophytes, however under certain circumstances they also consume animal feed and detritus. Effect of various kinds of feed on color characteristics of gonads has been investigated in a number of studies. The majority of researchers agree in opinion, that gonadal index (relative mass of gonads) first of all depend on quantity of accessible food (Kawamura, 1973; Pearse, 1981; Brewin et al., 2000), its color and taste - from its quality (Hagen, 1996; Minor, Scheibing, 1997; Hoshikawa et al., 1998). However, among researchers there is no common opinion concerning specific composition of algae at which consumption sea urchins, in particular genus Strongylocentrotus, have the most preferable roe color. One authors consider brown seaweed as those, namely Laminaria (Levin, 1987; Hoshikawa et al., 1998; Krupnova & Pavlyuchkov 2000), others mention green algae (e.g. Ulva) (Smiths, 1946; Fuji, 1967), and the third consider red seaweed and even sea grasses (Yevseyeva, 1999). Some researchers suggest that the animals on mixed algae diet have the best color parameters of gonads (Lozano et al., 1995; Vadas et al., 2000).

For the sea urchins living at sublittoral – an area with high, as a rule, phytoproduction - the food availability is the second, after temperature, the factor of an environment having essential influence on their reproductive characteristics (Thompson, 1984; Pearse, 1981;

Introduction of carotenoids (or components with their high content) in a feed at artificial culture of some species - Evechinus chloroticus (Goebel and Barker, 1998), Strongylocentrotus droebachiensis (de Jong-Westman et al., 1995; Harvardsson et al., 1999; Pearce 2000; Robinson et al., 2002, Liyana-Pathirana et al., 2002), Psammechinus miliaris (McLaughlin and Kelly, 2001), Lytechinus variegatus (Plank et al., 2002), Paracentrotus lividus (Shpigel et al., 2005) have been carried out.

Goebel and Barker (1998) have shown that without carotenoids gonads become pale cream unsuitable for market. Astaxanthin addition to feed composition leads to improving the yellow-orange colors of gonads. Experimental group of the urchins supplemented astaxanthin as well as algal feed (Ulva latuca and Macrocystis pyrifera) showed the best results in terms of gonad color. Similar results have been obtained by Kelly et al. (2001): best color characteristics of gonads have been reached at feeding of sea urchins by feed mix used for rearing salmon, which containing astaxanthin and canthaxanthin. At the same time, astaxanthin is not typical pigment for sea urchins and degree of its accumulation remains not clear. It is known, though sea urchins are able to assimilate some astaxanthin but in much smaller quantities, than β-carotene (Tsushima et al, 1993b; Harvardsson et al., 1999).

Pearce has shown (2000), that rather high concentration of carotenoids is capable to improve gonad color in sea urchins. Such color improvement has been been attained by adding β-carotene in concentration of 200 mg/kg, and optimum concentration of the pigment is 250 mg/kg of a feed. At the same time, number of authors have found that carotenoid content in sea urchins decreases in the course of feeding experiments (Motnikar et al., 1997; Plank et al., 2002). Probably, it is caused by relatively low concentration of pigments in a feed.

Relationship between Roe Color and Carotenoid Content

It should be noted, that an objective estimation and comparison of organoleptic parameters, such as color, offers some difficulties. It is known, that color can be measured using reflecting spectrophotometers or colorimeters or visually with color atlases or special scales (Jadd & Wyszecki, 1975). In the studies devoted to research of color characteristics of sea urchin gonads instrumental (Agatsuma, 1998; Borisovets et al., 1999; Robinson et al., 2000; Robinson et al., 2002), and visual methods (Kalinina et al., 2000; Goebel and Barker, 1998; Pearce, 2000; Vadas et al, 2000; Pearce et al., 2002) were applied. At a visual estimation commercial scale with three grade (Kalinina el al., 2000; Sedova et al., 2000; Vadas et al, 2000), or more detailed one-dimensional scales with the bigger number of grades (Goebel and Barker, 1998; Vadas et al., 2000; Pearce et al., 2002) were used. As natural color of gonads varies in considerable limits major disadvantage of one-dimensional scales is their subjectivity - ambiguity and inaccuracy in description of color.

Another possibility is using three-dimensional color systems. Usually CIE L*a*b* (1976) system was used for evaluation color of sea urchin roe (Agatsuma 1998; Borisovets et al., 1999; Robinson et al., 2000, 2002). The data obtained in the CIE L*a*b* (1976) are convenient for the subsequent statistical analysis. Additionally, recalculation of L*a*b* color characteristics into Munsell’s system is possible. Along with the convenience in usage and