Testes morphology and reproductive aspects of male Brazilian codling ( Urophycis brasiliensis Kaup 1858)

Summary The very first data on male ‘brótola’ Urophycis brasiliensis(Phycidae, Gadiformes) are presented here. Apart from the description of the macroscopic and microscopic morphology of the testes, preliminary results are given with respect to reproductive aspects of the males caught off the Uruguayan coast. In Uruguay, the gadiforms are represented by two species of commercial interest: the hake Merluccius hubbsi being theprincipal fishing resource, and Brazilian codling Urophycisbrasiliensis locally called ‘brótola’, one of the most important coastal resources of the artisanal fisheries (Anon. 1991). Although the latter species is common in coastal waters of the Atlantic between 23° and 40° S, little information is available. Between 1993 and 1996, a comprehensive 3‐year study dedicated to aspects of the biology and fisheries of U. brasiliensis in Uruguayan waters was carried out. A manuscript on reproductive aspects of the females has been submitted for publication (Acuña et al. 2000). In the present paper, first results on the gonadal morphology of the males are given. Vladikov (1972) compared the testes of different gadids, including another species of the genus, Urophycis chuss . However, to date no related information has been published on U. brasiliensis , likely also due to the fact that males are much less frequent than females in nearshore captures. Samples (N = 58) of shallow captures (< 20 m) of ‘brótola’ were obtained from artisanal fishermen in the two most important fishing ports in Uruguay: Piriápolis (34° S 55° W) and LaPaloma (34° S 54° W) (Acuña et al. 2000). Additional samples (N = 21) of deeper captures (up to 53 m) were obtained on spring and summer cruises of the research vessel ‘Aldebarán’ (INAPE; National Fisheries Institute). In the field, total length and weight were recorded to the nearest cm and g, respectively ( Table 1). Fish size ranged from 23–60 cm and 113–2400 g, respectively. Following dissection, the fish were sexed, and in most cases (N = 69) testes were weighed to the nearest 0.01 g. Gonads were extracted and fixed in 10% buffered formalin until the histological analysis. In the laboratory, ten testes were cut at different levels (cephalic, medium and caudal) to determine possible longitudinal differences in the spermatogenesis. Twenty samples were analyzed histologically to identify testicular structures and to diagnosethe gonad maturity stage. Each piece was dehydrated, embeddedin paraffin, cut to 7 µm thickness and finally stained with Mayer'shaematoxilin and eosin (Ganter and Jollès 1970). The gonado‐somatic index (GSI) was calculated and compared in bothshallow and deeper capture areas in spring and summer. 1 Total length (cm) and weight (g) of male U. brasiliensis captured by the artisanal fishery and from RV ‘Aldebarán’. Mean values ± standard deviation are presentedMacroscopically, the male gonad of U. brasiliensis ( Fig. 1) is easily distinguishable from the ovaries, allowing a rapid and unmistakable sex identification in the field. Two testes of dissimilar length are found below the swimbladder. They can be seen as two whitish ribbons presenting a smooth surface and several irregular lobes, similar to U. chuss testes (Vladykov 1972). Their macroscopic structure corresponds to type IIIa of the classification presented by Vladykov (1972). The lobes are larger in the cephalic portion than in the caudal portion, and fused to the vas deferens that longitudinally crosses both testes. In the caudal region, they are fused and open to the urogenital orifice. 1Macroscopic view of the U. brasiliensis testes, corresponding to an individual of 31 cm. Note the dissimilar length and irregular lobes in the two testes. Numbers indicate centimeters Histologically, the ‘brótola’ testes correspond to the lobular type described by Billard (1986) with anastomosing tubules ( Fig. 2). All along the testes, similar spermatogenesis was observed. They can also be defined as the unrestricted spermato‐gonial type of Grier (1981), the most common testes type in fish species, where it is possible to find spermatogenesis along the entire length of the tubule. In the caudal region, an area is found without spermatogenetic epithelium but with a greater concentration of spermatozoa ready to be evacuated. 2Histological section of U. brasiliensis testes. Z = spermatozoa; CC = spermatocyte cyst; TC = spermatid cyst; ZC = spermatozoa cyst; L = lumen of a spermatogenic tubule. Scale bar = 100 µm Males were significantly less represented in the captures than were females (P < 0.05), making up only 3% of the total catch (N = 2500). Wenner (1983) and Gallardo‐Cabello (1986) showed sex segregation in two other species of the same family ( Phycis phycis, P. blennoides ). At the same time, Eklund and Targett (1990) observed different sex proportions in captures of U. regia (spotted hake) and U. chuss (red hake). However, this effect was explained by selectivity of the capturing gear. Mean total length of males showed significant differences (P < 0.05) between shallow (34.8 cm) and deeper (29.3 cm) captures. The segregation by size might be explained by intraespecific competition (Sedberry and Musick 1978) which, in combination with the selectivity of the fisheries, would result in a higher proportion of females in the samples. Captures revealed a significant size difference between males (this paper) and females (Acuña et al. 2000), reaching mean lengths of 33.6 cm and 44.0 cm, respectively. The size of all individuals exceeds the one proposed as the mean size of maturity (23 cm) for U. brasiliensis males caught off Southern Brazil (M. Haimovici, pers. comm.). Due to the scarce representation of the males in the samples, it was not possible to study the spatial and temporal variation of testicular maturation. At any rate, mainly stages of mid‐ and late recrudescence, partially spent and one post‐spawn were identified. At a mean length of 32.6 cm, signs of testes recrudescence ( Table 2) were observed. 2 Mean total length (cm) of U. brasiliensis males for each maturity stage diagnosed histologically (mid/late recrudescence; partially spent and post‐spawn) ± standard deviationTesticular GSI ranged between 0.04 and 2.80. In deeper captures, mean GSI was significantly higher, indicating a greater maturation activity during spring and summer. This may suggest that reproductive events of U. brasiliensis take place outside the artisanal fishing areas, as proposed for females of the species by Vizziano et al. (1993) and Acuña et al. (2000).