ISSN: 0001-5113 ACTA ADRIAT., UDC: 597.582.2 591.16:597.582.2(497.5 Trogir)(262.3) AADRAY 46 (1): 77 - 82, 2005 Original scientific paper Reproductive period and histological analysis of the painted comber, Serranus scriba (Linnaeus, 1758), in the Trogir Bay area (eastern mid-Adriatic) Barbara ZORICA, Gorenka SINOVČIĆ and Vanja ČIKEŠ KEČ Institute of Oceanography and Fisheries, P.O. Box 500, 21 000 Split, Croatia A total of 798 specimens of the painted comber, Serranus scriba (Linnaeus, 1758), were caught in Trogir Bay (eastern mid-Adriatic) from June 2001 to May 2002 and analyzed. Total length ranged 7.1-20.0 cm (mean 11.0±1.7 cm); body weight ranged 4.21-108.99 g (mean 18.59±10.248 g). Histological analysis of 242 specimens confirmed simultaneous hermaphroditism. The annual variation of gonadosomatic index indicates that S. scriba spawns from May to August. Descriptions based on microscopic examinations of ovarian and testicular tissues are given. Key words: Serranus scriba, simultaneous hermaphrodite, spawning season INTRODUCTION throughout the year, especially during the spring and summer. Fishing takes place early in the The painted comber, Serranus scriba morning. (Linnaeus, 1758), is a subtropical species, abundant The purposes of this study were to in the eastern Atlantic from the Bay of Biscay to acquire knowledge on gonad maturation using Mauritania (MAIGRET & LY, 1986), including the macroscopic and histological examination and Canary, Azores and Madeira Islands, and in the to determine the reproductive period of the Mediterranean and Black Sea (BAUCHOT, 1987). painted comber in the Adriatic Sea. It is generally found along continental shelves covered with Posidonia or Cymodocea beds, at a depth of 0.5-150 m. S. scriba is a simultaneous MATERIAL AND METHODS hermaphrodite (FISCHER & PETERSEN, 1987), with A total of 798 painted combers were caught as the possibility of self-fertilization (ATZ, 1965). It a by-product species by small coastal trawler (12 tends to spawn during spring and summer and is mm stretched mesh) in the Trogir Bay (eastern reproductively active for five months, depending mid-Adriatic; Fig. 1) from June 2001 to May on environmental conditions (THRESHER, 1984; 2002. SHAPIRO, 1987). Painted combers are mainly Total length was measured to the nearest 0.1 caught in the Adriatic Sea by small coastal trawl and trammel bottom nets as a by-catch species cm; total weight and gonad weight were measured to the nearest 0.01 g. The gonadosomatic index 78 ACTA ADRIATICA, 46(1): 77-82, 2005 Fig. 1. Location of Trogir Bay (GSI) was calculated for each fish and values eosin, and examined by microscope. Oocytes were averaged monthly. The GSI was calculated were classified according to morphology and as Wg x 100/W, where Wg is the weight of the the presence and position of lipid droplets, gonads and W is the wet weight of the fish. yolk vesicles, and granules (YAMAMOTO, 1956). Spermatogenic cells were classified according Gonads of 242 specimens caught during to GRIER (1981). the peak of the spawning period were taken for histological analysis. They were fixed in 4% formaldehyde solution, dehydrated in alcohol, RESULTS AND DISCUSSION and embedded in paraffin wax. Longitudinal Total length ranged 7.1-20.0 cm (mean or cross sections (10 µm) were made with 11.0±1.7 cm; mode 10.5 cm; Fig. 2). Body weight a microtome, stained with hematoxylin and ranged 4.21-108.99 g (mean 18.59±10.248 g). Fig. 2. Total length frequency of Serranus scriba caught in the Trogir Bay from June 2001 to May 2002 ZORICA, SINOVČIĆ & ČIKEŠ KEČ: Reproductive period and histological analysis of the painted comber in the Trogir Bay 79 Fig. 3. Monthly variation of the gonadosomatic index (GSI) of Serranus scriba from the Trogir Bay GSI values were low from September (0.99%) the anus. Each lobe was covered by smooth to March (0.65%; Fig. 3). They increased in muscle and connective tissue (tunica albuginea). April (1.50%) and May (2.37%), peaked in June Longitudinal and cross sections of the gonads (3.96%), and decreased in July (3.67%) and revealed that the dominant tissue was ovarian; August (1.82%). Consequently, the reproductive testicular tissue was restricted to the anterior period for this species in this environment is region and positioned ventrolaterally (Fig. 4). May to August. Oocytes of different development stages Microscopic examination confirmed that were simultaneously present within the ovarian ovarian and testicular tissues of S. scriba gonads lamellae, which were radially oriented towards matured at the same time. Ovarian tissue was the lumen. This type of ovary is known as yellowish while testicular tissue was white. The asynchronous (MARZA, 1938). Oocytes of the ovotestis was formed of two fairly cylindrical so-called “second growth” (ZANUY & CARRILLO, lobes of similar size that joined at the level of 1973) or “vitellogenesis” (FEBVRE et al., 1975) Fig. 4. (a) Longitudinal and (b) cross sections of Serranus scriba gonads (40x). OT = ovarian tissue; TT = testicular tissue 80 ACTA ADRIATICA, 46(1): 77-82, 2005 Fig. 5. Serranus scriba oocytes (40x). A = primary growth phase; B = yolk vesicle formation; E = early vitellogenesis; H = hydrated oocyte; L = late vitellogenesis; n = nucleus; o = oil droplet; y = yolk granules; zr = zona radiata phase were most numerous. Three stages of type of oocyte is called a “hydrated oocyte” oocytes were identified during this phase (Fig. (HUNTER & MACEWICZ, 1985) and spawning 5): (a) yolk vesicle formation - yolk vesicles begins with its formation (HUNTER et al., 1986). appeared in the cytoplasm of oocyte cells and A smaller number of primary-growth oocytes rounded up the nucleus. Later, the number were noticed, together with the second growth and size of yolk vesicles increased and lipid oocytes, in all histological sections. The primary- inclusions began to accumulate in the cytoplasm. growth oocytes represent oocyte reserves for the The zona radiata and follicular layer became next reproductive season. visible; (b) vitellogenesis - the yolk vesicles were The testes were organized inside the lobules. larger in number and size; some had fused. Yolk Testicular tissue extended upwards and towards granules, which appeared first in the periphery the central lumen of the gonad. The lobules con- of the cytoplasm, increased in size and number, sisted of many seminiferous tubules containing dispersing throughout the cytoplasm; (c) ripe cysts. Each cyst was formed of spermatogenic - several oil droplets fused together, forming a cells in the same stage of spermatogenesis and large droplet that migrated towards the animal bounded by a thin layer of connective tissue. pole together with the nucleus. The nucleus was In accordance with the terminology of GRIER not always visible due to disintegration of the (1981), the following cells were observed (Fig. nuclear membrane and dispersion of its contents 6): (a) spermatogonia - globular cells positioned into the cytoplasm. The yolk granules fused, at the periphery of the seminiferous tubules, forming a continuous mass of fluid yolk. This usually forming cysts; (b) spermatocytes - oval Fig. 6. Testicular tissue of Serranus scriba (40x). S = spermatogonia; SP = spermatocytes; ST = spermatids ZORICA, SINOVČIĆ & ČIKEŠ KEČ: Reproductive period and histological analysis of the painted comber in the Trogir Bay 81 cells smaller than spermatogonia; (c) spermatid The histological characteristics of S. scriba cells with a large and rounded nucleus; (d) sper- agree with those of other Serranus species (GARCÍA-DÍAZ et al., 1999; 2002). Nevertheless, matozoa - spermatid cells rejected into the cyst further detailed histological analysis of the S. cavity as spermatogenesis neared its end. They scriba gonad is required to obtain a more continued to develop as spermatozoa. detailed spawning pattern of this species. REFERENCES ATZ, J.W. 1965. Hermaphroditic Fish. Science, GRIER, H.J. 1981. Cellular organization of the 150: 789-797. testis and spermatogenesis in fishes. Amer. BAUCHOT, M.L. 1987. Serranidae. In: W. Fischer, Zool., 21: 345-357. M.L. Bauchot, M. Schneider (Editors). HUNTER, J.R. & B.J. MACEWICZ. 1985. 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