Vafidis D et al. (2020), Population Density, Size Structure, and Reprodu...

ECB-ART-49647

Animals (Basel) 2020 Aug 26;109:. doi: 10.3390/ani10091506.

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Population Density, Size Structure, and Reproductive Cycle of the Comestible Sea Urchin Sphaerechinus granularis (Echinodermata: Echinoidea) in the Pagasitikos Gulf (Aegean Sea).

Vafidis D , Antoniadou C , Ioannidi V .

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Sphaerechinus granularis is a common grazer that lives in various sublittoral habitats, displaying typical covering behavior; i.e., putts shell-fragments, pebbles, and algae on its test. It is an edible species of increasing commercial importance due to the depletion of the common urchin's, Paracentrotus lividus, stocks. Its biology, however, is not adequately studied over its distributional range. The present study examines population density, size structure, and reproductive biology of S. granularis in the Aegean Sea. Samplings were made with SCUBA-diving (8-10 m) and included: (i) visual census along transects to estimate density, and (ii) random collection of specimens at monthly intervals to assess biometry and gametogenesis. Population density had moderate values that almost doubled when inputted to Distance software. S. granularis had larger dimensions in the sheltered site; size-structures were unimodal (65-70 mm and 70-75 mm, in exposed and sheltered site, respectively). An annual reproductive cycle was evident, according to GSI and gonads' histology, with a clear spawning peak in early spring. This pattern conforms to previous reports from the Atlantic, but precedes those from the Mediterranean (reproduction in summer). The provided baseline knowledge on the biology of S. granularis is important for the viable management of its developing fishery.

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References [+] :

Carey, Sea urchins in a high-CO2 world: partitioned effects of body size, ocean warming and acidification on metabolic rate. 2016, Pubmed, Echinobase

	Figure 1. Covering behavior of the sea urchin Sphaerechinus granularis: underwater photography of a specimen in station 2, S2 (photo from Dr. Alexios Lolas).
	Figure 2. Map of the study area indicating the location of sampling stations (S1 and S2).
	Figure 3. Mean size (test diameter Dt and height Ht in mm) and biomass (total weight tW in g) ± Fisher LSD of the sea urchin Sphaerechinus granularis in S1 and S2 sampling stations of Pagasitikos Gulf.
	Figure 4. Size frequency histogram (Dt in mm) of the sea urchin Sphaerechinus granularin in S1 and S2 sampling stations of Pagasitikos Gulf.
	Figure 5. Temporal trend of the mean gonad-somatic index GSI ± Fisher LSD of Sphaerechinus granularis at the two sampling stations (S1, S2) in Pagasitikos Gulf.
	Figure 6. Histology of ovaries of Sphaerechinus granularis. NP = nutritive phagocytes, Og = oogenesis, RO = relict oocytes, PO = previtellogenic oocytes, O = oocytes, OW = ovarian wall, GE = germinal epithelium, N = nucleus, Stage I = recovery, Stage II = growing, Stage III= premature, Stage IV = mature, Stage V = pre-spent, Stage VI = spent.
	Figure 7. Histology of testes (right) of Sphaerechinus granularis. NP = nutritive phagocytes, L = lumen, Sc = spermatocytes, St = spermatids, GE = germinal epithethelium, TW = teste wall, RS = relict spermatozoa (stages are defined as in Figure 6).
	Figure 8. Temporal trend of the relative frequency of each gonadal developmental stage of female and male Sphaerechinus granularis individuals at the two sampling stations (S1, S2) in Pagasitikos Gulf (I = recovery, II = growing, III= premature, IV = mature, V = pre-spent, VI = spent).