Histomorphological study of ovarian atresia over the reproductive cycle of Octopus vulgaris from Galician waters (NW Spain)

Reproductive biology of the totoaba (Totoaba macdonaldi), an endangered species in the Gulf of California

The totoaba (Totoaba macdonaldi) is an emblematic species endemic to the Gulf of California, which has been protected since the mid-70 s by Mexican and international laws. For the present study, 153 totoaba individuals were collected from 2011 to 2014, on which gonad histology analyses were carried out. We identified six ovarian phases and eleven oocyte subphases in the gonad development of females; in males, four development phases were identified. The totoaba is an iteroparous species based on the number of breeding opportunities. According to the organization of the ovary and the presence of oocyte subphases, ovarian dynamics can be considered asynchronous, as demonstrated by the multimodal distribution of oocyte diameter. The totoaba is a batch spawner that releases oocytes over several months. The reproductive period spans from February to May, with a reproductive peak in March. Likewise, the gonadosomatic index showed that the reproductive activity of totoaba peaked in March and April. The female:male sex ratio, although variable throughout the sampling period, yielded an overall value of 0.89:1, with non-significant differences between the number of females and males (P > 0.05). The length at first sexual maturity (L50%) was 1 354 mm TL for females and 1 299 mm TL for males. The average fecundity was 2 662 626 (standard error, s.e., 1 021 124) oocytes, and the average relative fecundity was 99 (s.e. 22) oocytes g-1 (ovary-free). The mean and maximum oocyte diameter showed a positive and non-significant (P > 0.05) relationship with the mean sea surface temperature.

Gonadal Degeneration Is Mediated by Apoptotic Processes in the Semelparous Gray Side-Gilled Sea Slug Pleurobranchaea maculata

AbstractSpecies undergoing postreproductive death experience great changes in their reproductive organs, which are driven by numerous physiological processes. To assess whether apoptotic processes are involved in the dynamics of the reproductive organs of Pleurobranchaea maculata, the gonadal structure of this semelparous side-gilled sea slug was studied using light and scanning electron microscopy. Apoptotic cells at different gonadal developmental stages were detected by in situ TUNEL assay. Apoptosis was primarily focused on spermatogonia during gonadal cell proliferation, probably as a regulatory mechanism that maintains homeostasis in reproductive cells. Visible gonadal degeneration at the end of the reproductive period is accompanied by apoptosis of the basal lamina cells of the acini, suggesting that apoptotic processes are involved in the gonadal degeneration observed in P. maculata.

Biochemical Composition and Energy Strategy Along the Reproductive Cycle of Female Octopus vulgaris in Galician Waters (NW Spain)

The common octopus, Octopus vulgaris, has a short life cycle, growing rapidly to maturity, spawning once, and characterized by an asynchronic oocyte development and a synchronic ovulation dying after breeding. This species has a protein and amino acid metabolism and it is usually defined as an income breeder. However, most biochemical studies lack an examination of the whole reproductive cycle, in particular the spawning process. We here studied the biochemical changes and determined the energy strategy along reproduction in female O. vulgaris, and found that proteins were the main energy reserve, primarily located in the body muscle when sexually maturing and decreasing during breeding. Lipids were also an important source of energy in the ovary and digestive gland and decreased during breeding too. By contrast, glycogen had a minor contribution to the energy content and was the unique compound that increased in spawning and post-spawning females. Additionally, the most abundant fatty acids (FA) in all tissues were 16:0, 18:0, 20:1n9, 20:4n6 (ARA), 20:5n3 (EPA) and 22:6n3 (DHA), with a clear predominance of long-chain polyunsaturated FA. The FA profile of mature ovaries was compared with other life stages finding similitudes with eggs, hatchlings and juveniles but considerable differences with paralarvae which showed higher DHA/ARA and EPA/ARA ratios. Therefore, we found important biochemical changes along the reproductive cycle that determined the energetic signature in each tissue, though no significant energy trade-offs between tissues were found, suggesting that, on the one hand, female O. vulgaris obtained energy directly from food accumulated simultaneously in the somatic and reproductive tissues during sexual maturation. However, an energy reallocation from somatic to reproductive growth would occur once vitellogenesis has started, so that the rate at which body growths would decrease in favor of ovary growth. On the other hand, during breeding, a general decrease in the energy content occurred in all tissues, so that the ovary would be responsible for the spawning success, whereas muscle tissues and digestive gland would independently supply the energy needed for the body maintenance safeguarding the female survival needed for the maternal care.