Reproductive Seasonality of the Antarctic Sea Pen <i>Malacobelemnon daytoni</i> (Octocorallia, Pennatulacea, Kophobelemnidae)

The pennatulid Malacobelemnon daytoni is one of the dominant species in Potter Cove, Antarctica. Its abundance and range of distribution have increased in recent years probably related to climate change mediated alterations of environmental factors. This work is the second part of a study dealing on the reproductive ecology of Malacobelemnon daytoni, and aims to assess its reproductive seasonality over a two-year period. Sampling was carried out every month during 2009–2010 and samples were examined by histological analysis. Gametogenesis exhibited a seasonal pattern evidenced by the maturity stage index (MSI) and the number of mature oocytes and cysts throughout the year. Immature oocytes and spermatocytes were present year-round, but maturation was seasonal and it seems that more than one spawning per year was possible. These spawnings could be more linked with suspended particulate matter (SPM) (probably available via resuspension events) than with primary production pulses. This idea reinforces the hypothesis that winter time is not so stressful, in energy terms, in Potter Cove, which seems to depend on energy sources other than local phytoplankton production. There was not a strong inter-annual variability between the reproductive characteristics analyzed in 2009 and 2010; the only variable different was the size of oocytes (higher in 2009), suggesting different energy availability in each year, related with a higher concentration of SPM in 2009 (although it was not significant). Malacobelemnon daytoni could be the first reported Antarctic suspension feeder species that presents a reproductive cycle with more than a spawning event per year. This strategy would help to explain the success of this species in the Potter Cove ecosystem and in high ice-impacted areas.海笔类（Pennatulid）物种戴氏软海笔（Malacobelemnon daytoni）是南极波特湾（Potter Cove）的优势物种之一。近年来其种群丰度与分布范围均有所扩张，这一现象或与气候变化介导的环境因子改变相关。本研究为戴氏软海笔繁殖生态学系列研究的第二部分，旨在通过两年的观测周期评估其繁殖季节节律。研究于2009至2010年间每月开展采样，并通过组织学分析对样本进行检测。配子发生呈现出显著的季节节律，这一特征可通过成熟阶段指数（Maturity Stage Index, MSI）以及全年成熟卵母细胞与包囊的数量变化得以证实。未成熟卵母细胞与精母细胞全年均可被检出，但配子成熟过程具有季节特异性，且该物种每年或可发生多次产卵事件。此类产卵事件与悬浮颗粒物（Suspended Particulate Matter, SPM）的关联性或强于与初级生产脉冲的关联性，而该类颗粒物或可通过再悬浮事件获得补充。该观点进一步佐证了如下假说：就能量收支而言，波特湾的冬季并未面临过高的能量胁迫，其生态系统的能量来源或并非仅依赖于本地浮游植物生产。2009年与2010年的繁殖特征未呈现出显著的年际差异，仅卵母细胞尺寸存在明显区别（2009年的卵母细胞尺寸更大），这表明两年间的能量可利用性存在差异，而该差异或与2009年更高的悬浮颗粒物浓度相关（尽管该相关性未达到显著性水平）。戴氏软海笔或为首个被报道的、每年可发生多次产卵事件的南极悬浮食性物种。该繁殖策略或可解释该物种在波特湾生态系统以及高冰覆影响区域的种群优势地位。