On the reproduction of the simultaneous hermaphrodite Paroriza prouhoi (Holothuroidea: Synallactidae) in the Porcupine Abyssal Plain, north-east Atlantic

Long-term studies in the abyssal north-east Atlantic (1989–2005) have revealed large-scale changes in the benthic ecosystem and especially in some megafaunal invertebrate taxa over the period 1996–2002, termed the ‘Amperima Event’. Holothurians dominated the megafaunal samples. Temporal patterns in the abundance of holothurians showed a wide spectrum of responses, possibly related to the feeding and reproductive characteristics of the various species. One of the holothurians, the synallactid Paroriza prouhoi, is a simultaneous hermaphrodite, providing a distinct comparison with dioecious reproductive patterns more typical of deep-sea holothurian species. The reproductive biology and abundance/biomass patterns of P. prouhoi were investigated over the period 1989–2005. Paroriza prouhoi produces oocytes with a maximum diameter of ~370 µm. It has asynchronous patterns of gametogenesis both at the individual and population levels. Mean oocyte diameter and the ratio between previtellogenic and vitellogenic oocytes showed no significant differences between the periods prior to and after the Amperima Event. There were no significant differences in abundance or biomass over the time series. We conclude that the energy investment into gamete production by this hermaphrodite did not change over the 16 years examined. It is hypothesized that the feeding characteristics of P. prouhoi lead to a slow, steady and consistent production of gametes despite large-scale changes in organic matter supply to the seabed evident at the time series locality.