Temperature response in a shallow-water Mediterranean population of Caulerpa racemosa var. cylindracea (Caulerpales, Chlorophyta), and a possible strategy of season anticipation

Abstract

We studied growth and photosynthetic response of a shallow-water population of the invasive alga Caulerpa racemosa var. cylindracea off the Island of Ischia (Gulf of Naples, Italy). The effects of temperature on relative growth rate (RGR), light-saturated photosynthetic rate (Pmax), dark respiration rate (Rd) and optimal quantum yield (Fv/Fm) were assessed for thalli collected in two seasons (early winter and early summer). While temperatures higher than 22°C stressed early winter thalli, as reflected in the decrease in growth rates and optimal quantum yields, both increased with temperature in early summer plants. A difference between the two seasonal samples also occurred in the high-temperature sensitivity of respiration rates, which was enhanced in early winter plants. As changes in a number of the traits considered occur in advance of seasonal minima and maxima, C. racemosa var. cylindracea may behave as a season anticipator. The contribution of observed patterns to the colonization success of the alga is discussed.

Alien species along the Italian coasts: an overview

“…Factors involved in the colonization success of Caulerpa spp. were studied, including tolerance to sedimentation (Piazzi et al 2005), photo- (Raniello et al 2006) and thermal (Flagella et al 2008) acclimation, and allelopathy (Raniello et al 2007).…”

First record of <em>Caulerpa cylindracea</em> (Caulerpaceae, Chlorophyta) in Andalusia (Southern Spain)

“…lamourouxii are confined to the central and eastern part of the basin; the invasive species occurs also in colder waters. This behavior is additionally suggested by the relative growth rates of the invasive taxon during the winter period, which remains positive down to 10 °C in laboratory conditions (Flagella & al., 2008). The present report and that for Table 1; circles represent distinct ITS1-5.8S-ITS2 copies; circle size is proportional to the frequency of that copy; triangles indicate large substitutions denoted by the number; bars across lines connecting clone sequences indicate bp substitutions.…”

Absence of successful sexual reproduction of Caulerpa racemosa var. cylindracea in the Adriatic Sea

“…There is a general agreement that in the Mediterranean Sea Caulerpa racemosa reproduces both by fragmentation and sexually (Ruitton et al 2005a, b;Flagella et al 2008;Klein & Verlaque 2008;Vá zquez-Luis et al 2008;Baldacconi & Corriero 2009;Katsanevakis et al 2010a, b; and many others), although the entire lifecycle involving sexual reproduction has not been demonstrated. To date, the only published research on sexual reproduction of C. racemosa in the Mediterranean Sea was made on a population from the Aegean Sea in Greece (Panayotidis & Ž uljević 2001) where the process of gamete formation and release of C. racemosa was observed in situ and in laboratory conditions.…”