Methods for the Induction of Reproduction in a Tropical Species of Filamentous Ulva

Abstract

The green seaweed Ulva is a major fouling organism but also an edible aquaculture product in Asia. This study quantified for the first time the effect of key factors on the reproduction of a tropical species of filamentous Ulva (Ulva sp. 3). The controlled timing of release of swarmers (motile reproductive bodies) was achieved when experiments were initiated in the early afternoon by exposing the thalli to a temperature shock (4°C) for 10 min and subsequently placing them into autoclaved filtered seawater under a 12 h light: 12 h dark photoperiod at 25°C. The release of swarmers then peaked two days after initiation. In contrast, segmentation, dehydration, salinity or time of initiation of experiments had no effect of any magnitude on reproduction. The released swarmers were predominantly biflagellate (95%), negatively phototactic and germinated without complementary gametes. This indicates that Ulva sp. 3 has a simple asexual life history dominated by biflagellate zoids.

Regulation of gametogenesis and zoosporogenesis in Ulva linza (Chlorophyta): comparison with Ulva mutabilis and potential for laboratory culture

“…In nature, the induction of sporulation might be triggered by segmentation as potentially observed by Gao et al (2010) during green tides. Certainly sporulation events also occur even without fragmentation, whenever the SIs are either not produced or perceived in Ulva ’s life cycle ( Stratmann et al, 1996 ), which might explain the underlying mechanism of sporulation events reported in a recent study with a tropical Ulva species ( Carl et al, 2014 ).…”

Reproductive output and productivity of filamentous tropical Ulva over time

“…DNA barcoding was used to assign species names to samples from F 2 and F 3 of each collection (Lawton et al 2013;Carl et al 2014b) (see Supplementary Material; Online Resource 5). All samples were identified as Ulva sp.…”

“…Subsequently, the samples were gently washed three times with filtered seawater (FSW; 0.2 μm and UV sterilised) to remove debris, epiphytes and invertebrates. Approximately 100 filaments were collected to induce the formation and release of swarmers (collective term for reproductive bodies, including gametes, zoospores, zoids) using a temperature shock at 4°C for 10 min (Carl et al 2014b), and the filaments were subsequently cut using a blender (Carl et al 2014a). The release of swarmers ( Fig.…”

“…This will also allow artificial seeding that is independent from the harvest of biomass. The seedstock culture can be maintained in the laboratory which allows for the control of environmental factors, in particular light, to ensure optimal conditions for the controlled production of seedlings (Carl et al 2014b). Previous studies have demonstrated a direct effect of light on the reproduction of Ulva with a general decrease in reproduction with decreasing light intensities (Han et al 2003;Kalita and Tytlianov 2003;Lüning et al 2008;Kalita and Titlyanov 2011).…”

“…Our results further demonstrate that under culture, Ulva sp. 3 has a simple asexual life history via negatively phototactic zoids (Carl et al 2014b) with released swarmers being predominantly biflagellate over all generations. In general, the life history of Ulva is either characterised by an asexual-only life history or an alternation between sexual and asexual reproduction from one generation to the next (Fletcher 1989;Hiraoka et al 2003bHiraoka et al , 2011.…”