Abstract
Multiannual delayed gametophyte cultures can stay vegetative for years, while also having the ability to grow. This study aims to investigate whether male and female multiannual delayed gametophyte strains of the species Saccharina latissima and Alaria esculenta grow at different rates in culture. We furthermore assessed how changing sex ratios can affect the reproductive yields of these cultures. The results indicate that the reproductive yield of cultures declines with decreasing male:female ratios, a correlation that becomes especially apparent at higher culture densities for both species. Female gametophyte densities in particular affected the observed reproductive yield of the cultures, with S. latissima cultures showing a clear reproductive optimum (sporophytes·mL−1) at 0.013 mg·mL−1 DW female gametophyte biomass, while the reproductive success of A. esculenta peaked at a density of 0.025 mg·mL−1 DW of female gametophyte biomass, after which the reproductive yield started to decline in both species. The results show that the sex ratio of a gametophyte culture is an important biotic life cycle control, with higher amounts of female gametophyte biomass halting gametophyte reproduction. Understanding how these changing sex ratios in gametophyte cultures affect reproduction is especially important in the aquaculture of kelp, where reliable preforming cultures are key to long-term success.
Highlights
Interest in using delayed gametophytes as seed stock for large scale aquaculture of brown seaweeds is growing globally
The male:female sex ratio had a significant effect on the reproductive success of S. latissima gametophytes (WELCH ANOVA, F4,55 = 7.6, p < 0.05; Table S2)
The male:female sex ratio had a significant effect on the reproductive success of A. esculenta gametophytes (WELCH ANOVA, F4,57 = 7.5, p < 0.05; Table S3)
Summary
Interest in using delayed gametophytes as seed stock for large scale aquaculture of brown seaweeds is growing globally. The advantages of using delayed cultures are well understood [1]: (i) they can be kept healthy for prolonged periods of time [2,3,4], (ii) they can be successfully cryopreserved [5] and (iii) gametophyte cultures can be cloned [6]. In order to use these delayed gametophytes for large-scale aquaculture, we first need a detailed understanding of the controlled growth and reproduction of larger volumes of these delayed gametophyte cultures [10]. This is especially important for multiannual delayed (MAD) gametophytes, which are gametophytes that delayed their sexual reproduction by more than a year, thereby transgressing seasonally induced reproduction [11]. The first culture type is created from large amounts of extracted zoospores [12], 4.0/)
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