Survive or swim: different relationships between migration potential and larval size in three sympatric Mediterranean octocorals

Abstract

Knowledge about migration potential is key to forecasting species distributions in changing environments. For many marine benthic invertebrates, migration happens during reproduction because of larval dispersal. The present study aims to test whether larval size can be used as a surrogate for migration potential arising from larval longevity, competence, sinking, or swimming behavior. The hypothesis was tested using larvae of three sympatric gorgonian species that release brooded lecithotrophic larvae in the same season: Paramuricea clavata, Corallium rubrum and Eunicella singularis. Despite different fecundities and larval sizes, the median larval longevity was similar among the three species. Free-fall speed increased with larval size. Nevertheless, the only net sinkers were the P. clavata larvae, as swimming was more common than free fall in the other two species with larger larvae. For the other two species, swimming activity frequency decreased as larval size increased. Interestingly, maximum larval longevity was lowest for the most active but intermediately sized larvae. Larval size did not covary consistently with any larval traits of the three species when considered individually. We thus advise not using larval size as a surrogate for migration potential in distribution models. The three species exemplified that different mechanisms, i.e., swimming activity or larval longevity, resulting from a trade-off in the use of energy reserves can facilitate migration, regardless of life history strategy.

Estimations of free fatty acid (FFA) as a reliable proxy for larval performance in Mediterranean octocoral species

“…Therefore, based on FFA content, we would expect C. rubrum larvae to be highly mobile, whereas P. clavata quite passive, and E. singularis larval motility high and highly variable. Measurements of larval swimming activity frequency (i.e., percentage of time during which active swimming or crawling behavior is displayed by larvae) (sensu Guizien et al, 2020) for the three species are in accordance with the values of FFA content measured, with 77% activity for C. rubrum (Martínez -Quintana et al, 2015), 5% for P. clavata and 20-90% for E. singularis (Guizien et al, 2020). Therefore, energy consumption may be a good proxy to estimate coral larvae swimming activity frequency.…”

Artificial reefs geographical location matters more than shape, age and depth for sessile invertebrate colonization in the Gulf of Lion (NorthWestern Mediterranean Sea)

“…Dispersion distance is generally correlated with PLD, thus a species with a long PLD is supposed to colonize habitats further away than species with a shorter PLD (Shanks, 2009). In this study, the five species were chosen among different phyla known for their contrasting planktonic durations, swimming abilities and larval dispersal periods, although these larval traits are only known accurately for E. singularis (Guizien et al, 2020;Zelli et al, 2020). P. fascialis and H. papillosa, the two species with short PLD (<24h and <12h, respectively) colonized ARs located close to the natural habitat where they are present (<4.8 km and <10 km, respectively).…”

“…Like most gorgonians, E. singularis releases lecithotrophic larvae in early summer (June to August). Even though larval competency period can reach up to 2 months (Guizien et al, 2020;Zelli et al, 2020), PLDs ranging from 7 to 14 days best explained gene flow among E. singularis natural populations dwelling in the fragmented rocky habitat of the GoL (Padron et al, 2018). E. singularis life span can reach 25-30 years with sexual maturity before 6 years (Gori et al, 2007;Weinberg and Weinberg, 1979).…”

Artificial reefs geographical location matters more than shape, age and depth for sessile invertebrate colonization in the Gulf of Lion (NorthWestern Mediterranean Sea)

“…Like most gorgonians, E. singularis releases lecithotrophic larvae in early summer (June to August). Even though larval competency period can reach up to 2 months (Guizien et al, 2020; Zelli et al, 2020), PLDs ranging from 7 to 14 days best explain gene flow among E. singularis natural populations dwelling in the fragmented rocky habitat of the GoL (Padron et al 2018). E. singularis life span can reach 25-30 years with sexual maturity before 6 years (Gori et al, 2007; Weinberg and Weinberg, 1979) (Weinberg and Weinberg 1979, Gori et al 2007).…”