Flexibility in reproductive attributes may facilitate the invasive capacity of the Mediterranean fanworm, Sabella spallanzanii (Gmelin)

Abstract

Context The Mediterranean fanworm arrived as a non-indigenous species in parts of Australasia, where it has established and then rapidly spread from the initial points of arrival, despite marked differences in environmental conditions compared from its natal habitat in the Mediterranean Sea. Aims To better understand the invasive capacity of this species in New Zealand. Methods Maturation, reproductive cycle, and gametogenesis were investigated, with a focus on female gamete development, for a population in Auckland, and the results were compared with those of previous studies in the Mediterranean Sea and Australia. Key results Egg sizes in female fanworms were highly variable throughout the year; however, a reduced presence of larger eggs was observed from August to November, which could indicate spawning. This Auckland fanworm population also appeared to have a female-skewed sex ratio compared with previous studies where a 1:1 sex ratio was observed. Fanworm maturation was reached at ~6 cm in length, compared with 15 cm in natal populations. Fanworms with body size smaller than 5 cm were not mature and did not produce mature gametes, in contrast to an Australian fanworm population. Conclusions The observed Mediterranean fanworm population in New Zealand demonstrates reproductive flexibility and high fecundity, contributing to its invasive capacity. Implications The reproductive biology of a species is important in determining its invasive capacity, and may also be flexible between populations, with implications for effective biosecurity management strategies.