REPRODUCTIVE STRATEGY OF DOSINIA PONDEROSA (GRAY, 1838) (VENERIDAE) IN PUERTO LIBERTAD, SONORA, MEXICO CARLOS A. AGUILAR-CRUZ, 1 ABRIL K. ROMO-PIN ˜ ERA, 1 * FRANCISCO J. FERN ´ ANDEZ-RIVERA MELO, 2 CARMEN RODR ´ IGUEZ-JARAMILLO 3 AND EMELIO BARJAU-GONZ ´ ALEZ 1 1 Departamento Acad ´ emico de Ciencias Marinas y Costeras, Universidad Aut ´ onoma de Baja California Sur, Carretera al Sur Km 5.5, La Paz, BCS 23080, M ´ exico; 2 Comunidad y Biodiversidad, A.C. Isla del Peruano 215, Lomas de Miramar, Guaymas, Sonora 85448, M ´ exico; 3 Laboratorio de Histolog ´ ıa e Histoqu ´ ımica, Centro de Investigaciones Biol ´ ogicas del Noroeste, La Paz, BCS 23090, M ´ exico ABSTRACT The reproductive strategy of Dosinia ponderosa at a site of the eastern coast of the Gulf of California, Puerto Libertad, Sonora is reported. Samples of visceral mass were taken from 30 clams that were collected monthly from March 2015 to March 2016, and the length and weight of the tissue without shell of each organism were recorded. Through histological analysis, the gonadal index were calculated, and the reproductive stages of the ponderous dosinia were determined. Six oocyte substages and five gonadal development stages for females and five for males are described. The sex ratio was 1:1, and no undifferentiated specimens were found. The sexual maturity phase was observed throughout the year, with two reproductive peaks in June–July and October–November. No correlation was observed between the reproductive activity and temperature or primary productivity. KEY WORDS: clam, Dosinia ponderosa, reproductive biology, bivalvia, Veneridae, gonadal development INTRODUCTION Molluscs are an important food resource in Mexico, repre- senting 6% of the fishery production and 9% of the national aquaculture production (CONAPESCA 2017). Clam pop- ulations in the Gulf of California are in states of maximum exploitation or overfishing, whereas in the central Mexican Pacific, the same resource is collapsed (Arregu´ın-S´anchez & Arcos-Huitr´on 2011). The ponderous dosinia Dosinia ponder- osa (Gray, 1838) is an exploited resource whose fishing grounds in southern Mexico are already depleted, and of which there is no recent diagnosis within the Gulf of California. Studying the reproductive cycle is essential for establishing a spawning time, particularly in commercially important marine species. It is the starting point for studies of recruitment, age, and growth that provide the basic information for its manage- ment (Clemente & Ingole 2009). The ponderous dosinia is a little studied species in the Mexican Pacific; they are gonochoric organisms, with a proportion of sexes of 1:1 and without rec- ords of undifferentiated specimens (Baqueiro-C´ardenas & Aldana-Aranda 2000), where it has been suggested that its re- productive event may be related to periods of increasing tem- perature (Baqueiro & Stuardo 1977, Arreola-Hern´andez 1997, Baqueiro-C´ardenas & Aldana-Aranda 2000) or not (Garc´ıa- Dom´ınguez 2002). On the West Coast of the Gulf of California in Bah´ıa Con- cepci´on, its reproductive activity was from May to November (Arreola-Hern´andez 1997) and in September and October (Garc´ıa-Dom´ınguez 2002), whereas in Zihuatanejo, on the West Coast of the Mexican Pacific, its reproductive activity was from March to November, almost all year-round, with reproductive peaks from September to November (Baqueiro-C´ardenas & Aldana-Aranda 2003). There is no history of reproduction of this species on the East Coast of the Gulf of California. In Mexico, reproduction studies have been a support for fisheries management, being this information useful for estab- lishing fishery closures, minimum sizes, and harvesting areas (DOF 2018). As a basic principle, the establishment of these tools should be based on scientific research aimed at repro- ductive biology and individual growth of species, allowing for stable stocks to be maintained, in addition to including the empirical knowledge of producers (Seijo et al. 1997, Fern ´andez- Rivera Melo et al. 2018). Nevertheless, information on repro- ductive studies for bivalves in specific areas is very scarce, which has forced decision-makers to use studies of geographical re- gions with characteristics very different from the specific areas where the resource is used. Knowing the basic biological pa- rameters of Dosinia ponderosa is essential as a basic tool for decision-making in fisheries management. MATERIALS AND METHODS A total of 30 specimens of Dosinia ponderosa were collected monthly from March 2015 to March 2016, by means of free and semiautonomous diving in Puerto Libertad, Sonora (Fig. 1), at a depth between 5 and 20 m. The specimens were fixed with a solution of formalin 10% in seawater. The shell length (SL) of each specimen was recorded with a vernier caliper precision of ±0.1 mm and the wet weight of the tissue without shell (WS) with a digital balance of ±0.1 g of precision. A portion of visceral mass was histologically processed by dehydration in gradual changes of ethanol of 70%–100% concentration, rinsed with limonene and paraffin inclusion, and slides were prepared with 5 mm thick sections and dyed with GillÕs hematoxylin–eosin-phloxine. Histological preparations were observed and photographed through a compound micro- scope (Olympus BX41 with a digital camera Nikon DS-Ri1). The sex of each organism was determined. The observed sex ratio was tested with an expected one of 1:1 (Zar 2010). For the description of the substages of the oocytes and the stages of *Corresponding author. E-mail: akromo@uabcs.mx DOI: 10.2983/035.039.0302 Journal of Shellfish Research, Vol. 39, No. 3, 511–518, 2020. 511