Spawning synchrony and aggregative behaviour of cold-water echinoderms during multi-species mass spawnings

Abstract

Although many marine invertebrates reproduce by releasing gametes into the water, major spawning events have rarely been observed for cold-water invertebrates. We documented mass spawnings by the sea star Asterias vulgaris and the ophiuroid Ophiopholis aculeata on 6 July 1996 and 2 July 1998, and by these 2 species plus a second ophiuroid Ophiura robusta and the sea urchin Strongylocentrotus droebachiensis on 3 July 2003. In each year, the abrupt spawning events coincided with the first major intrusion of warm surface water into a region normally dominated by cold upwelling. The behaviours of the ophiuroids and sea stars favoured fertilization success. First, they spawned from elevated surfaces, with the central disc raised, to increase suspension and mixing of gametes. Second, many individuals pseudocopulated, which involved crawling over one another in the case of the sea star, and individuals holding their central discs together in the case of the 2 ophiuroids. Models of fertilization success need to incorporate such behaviours to better understand fertilization in the sea.KEY WORDS: Ophiopholis aculeata · Ophiura robusta · Asterias vulgaris · Strongylocentrotus droebachiensis · Mass spawning · Behaviour · Pseudocopulation · External fertilization · Northern Gulf of St. Lawrence Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 361: [161][162][163][164][165][166][167][168] 2008 Japan (Kubota 1980) and for the palolo worm Eunice viridis in the Samoan Islands (Caspers 1984). Subsequently, multi-species mass spawnings have been documented for many sessile tropical species (corals, anemones and sponges) that spawn at a predictable time in coordination with environmental rhythms (Harrison et al. 1984, Babcock et al. 1992). In contrast, there are surprisingly few reports of major spawning events for temperate and cold-water invertebrates. The reports most clearly indicating synchronous spawning by large numbers of individuals are probably those of Minchin (1987Minchin ( , 1992, Breen & Adkins (1980), Sewell & Levitan (1992) and Hamel & Mercier (1996). The scarcity of such observations, due to their short duration and unpredictable timing, greatly limits our understanding of fertilization dynamics. In particular, we know little about how animals behave during major spawnings. Strong selective pressure to adopt behaviours that enhance fertilization success would be expected. Most reports of spawning behaviours are based on incidental spawnings of a few individuals.The aim of the present paper is 3-fold: (1) to report rare spawning events involving mass multi-species spawnings of cold-water echinoderms; (2) to consider environmental factors that potentially triggered these highly synchronized events; and (3) to describe behaviours during spawning, including rapid aggregation and pseudocopulation, which likely enhanced fertilization success. MATERIALS AND METHODSOur observations were made during the course of ecological studies of sea stars (Gaymer et al. 2001...

Spawning time of two shallow-water brittle stars

“…In fact, earlier sightings of brittle star spawning in subtidal habitats were mostly in the evenings (Hendler 1991, Hagman & Vize 2003. A recent investigation, however, reported 2 daytime spawning ophiuroids (Himmelman et al 2008). Our experiments showed that O. scolopendrina males could be induced to spawn regardless of whether it was day or night, as long as the tide was low (Fig.…”

“…The low tide is just one such condition we found for Ophiocoma scolopendrina. In other brittle stars, abrupt temperature changes have been implicated (Himmelman et al 2008). The results of our water-level experiment (Fig.…”

“…For example, histological studies of common Caribbean reef corals narrowed down their reproductive seasons to within 1 to 2 mo (Soong 1991), but the actual spawning of each species was observed to take place within a 1 h period (Van Veghel 1994). Direct observation in the field provides good evidence of natural spawning events, but systematic observation requires significant time and resources (see Harrison et al 1984, Himmelman et al 2008. Even in the intertidal zone, the most accessible marine environment, knowledge of a species' spawning times is often based on sporadic observations or indirect inferences from experiments (Marshall 2002, Pearson et al 2004.…”

Sea urchin fertilization in a warm, acidified and high pCO2 ocean across a range of sperm densities

“…This underscores the importance of in determining sperm to egg ratios for these tests as 11 highlighted elsewhere (Dinnel et al, 1987). Previous studies of fertilization in H. erythrogramma used 10 3 -10 5 sperm ml -1 to achieve fertilization rates > 60% (Evans (Himmelman et al, 2008;Pennington, 1985).…”

Brooding in Psolus patagonicus (Echinodermata: Holothuroidea) from Argentina, SW Atlantic Ocean

“…On this basis, it is reasonable to assume its reproductive cycle and brooding period are related to the seasonal abundance of phytoplankton. Environmental factors such as food availability synchronize reproductive events (Himmelman 1975;Tyler 1988;Gage and Tyler 1991;Smiley et al 1991;Himmelman et al 2008).…”