Reproductive strategy of Brachidontes rodriguezii (Bivalvia: Mytiloida) in the South-western Atlantic Ocean

Abstract

This study consisted in the characterization of reproductive aspects such as oocytes morphology, temporal variation in size and frequency of oocytes and the reproductive cycle of the mussel Brachidontes rodriguezii. This species dominates the rocky intertidal coast of Buenos Aires province, Argentine and is a prey item of several exploited species; however, due to the introduction of piers and seawalls, as a consequence of anthropogenic activities, the species also inhabits sandy coasts. Mussels were collected from May 2011 to May 2013. Gonad tissue samples were processed according to standard histological procedures. Four gonadal development stages were described for males and females. According to the significant decrease in the frequency of mature oocytes, the spawning events were detected between February and May. However, some evacuation events were recorded in June–July. This study reports the first record of two modalities of hermaphrodites in this species; individuals with male and female gonads and individuals with both types of gametes within a gonad.

Reproductive aspects of Brachidontes rodriguezii in the high intertidal; extreme environmental effects

“…In terms of the size of oocytes, the mean area of previtellogenic oocytes did not differ during the study period, mean size was around 130 mµ 2 and previous results in Villa Gesell showed similar values with mean areas ranging between 30-400 mµ 2 , reaching in October 2012 the highest mean value of the entire period (260.92 mµ 2 ) (Torroglosa & Giménez, 2019a). The same for the early vitellogenic oocytes showed a significant increased in size reaching maximum values in austral winter (~550 mµ 2 ), while in the lower level, early vitellogenic oocytes reached the highest mean value of the entire period (691.16 mµ 2 ) by November 2012 in austral spring (Torroglosa & Giménez, 2019a). Finally, for the vitellogenic oocytes, in this study record an increase in oocyte size reaching the maximum mean value 1354.70 mµ 2 by October 2012 while in the lower level vitellogenic oocytes area reached the highest mean value (1623.63 mµ 2 ) by December 2011 (Torroglosa & Giménez, 2019a).…”

“…The stress conditions increase in the higher intertidal zone as consequence of tides, organisms spend less time feeding and the longer exposure to aerial conditions leads to desiccation (Petes et al 2008;Helmuth et al 2011). Previous studies carried out in the same area revealed some reproductive features of B. rodriguezii in the low intertidal (Torroglosa & Giménez, 2019a) and a differential growth probably due to tides (Torroglosa & Giménez, 2019b).…”

“…The sections were stained with haematoxylin and eosin. Four gonad development stages (GDS) -developing, mature, spawning and post-spawning -were assigned following Torroglosa and Giménez (2019a) to describe the reproductive cycle. To establish the reproductive season (spawning event) the size and frequency of vitellogenic oocytes were analysed monthly.…”

“…These aerial conditions include high temperature and desiccation, along with a lower food supply (Connell, 1972); as long as mussels are exposed to the marine condition, food intake rises and the effect of high temperature decreases (Petes et al 2008). Previous studies carried out in the same area revealed some reproductive features of B. rodriguezii in the low level of intertidal (Torroglosa & Giménez, 2019a) and given the differential exposure to aerial conditions reported for the study area (Torroglosa & Giménez, 2019b) and the probable effects of exposure to high temperature, the objective of this study were to describe reproductive features of males and females of B. rodriguezii in the high intertidal level on the coast of Buenos Aires Province, Argentina. We predicted that under conditions of high-stress mussels would exhibit some trade off in reproductive aspects like shifts in the reproductive cycle or the size of gametes leading to a successful reproductive strategy under extreme environmental conditions.…”

Reproductive aspects and energy allocation compromise to aerial exposure in the intertidal mussel Brachidontes rodriguezii. A case study at two tidal levels

“…Different reproductive patterns were found here on B. rodriguezii's females from the two tidal levels studied. According to Torroglosa and Giménez (2019b), once adulthood is achieved individuals are at least potentially capable of spawning year-round. However, females at long air exposure (having more energy density, but less energy condition index) showed only one marked spawning episode in Summer at highest sea water temperature, while those of the lower level presented two more pronounced spawning events, in Spring and Autumn.…”