Consumption rates of the periwinkle Littorina obtusata on the brown seaweed Ascophyllum nodosum

Anti-herbivory defenses support persistence of seaweeds. Little is known, however, about temporal dynamics in the induction of grazer-deterrent seaweed traits. In two induction experiments, consumption rates of the periwinkle Littorina obtusata (L.) on the brown seaweed Ascophyllum nodosum (L.) Le Jolis were measured in 3-d intervals. Changes in palatability of directly grazed A. nodosum were tested every 3 d with feeding assays using fresh and reconstituted seaweed pieces. Likewise, assays with fresh A. nodosum assessed changes in seaweed palatability in response to water-borne cues from nearby grazed conspecifics. Consumption rates of L. obtusata varied significantly during the 27-d induction phase of each experiment. Direct grazing by L. obtusata lowered palatability of fresh and reconstituted A. nodosum pieces to conspecific grazers after 15 d as well as after 6 and 12 d, respectively. After 12, 18, and 24 d, fresh A. nodosum located downstream of L. obtusata-grazed conspecifics was significantly less palatable than A. nodosum located downstream of ungrazed conspecifics. Changes in L. obtusata consumption rates and A. nodosum palatability during both induction experiments suggest temporal variation of grazer-deterrent responses, which may complicate experimental detection of inducible anti-herbivory defenses.

抗植食性防御是海藻维持种群存续的核心策略。然而，学界对植食者诱导型海藻防御性状的时间动态仍缺乏深入认知。本研究通过两组诱导实验，以每3天一次的频率测定了钝顶滨螺（Littorina obtusata (L.)）对褐藻泡叶藻（Ascophyllum nodosum (L.) Le Jolis）的摄食率。
研究通过两种平行方式检测被直接啃食的泡叶藻适口性变化：每3天使用新鲜与重构的海藻组织块开展摄食测定；同理，利用新鲜泡叶藻，通过评估其对邻近被啃食同种个体释放的水源性信号的响应，分析海藻适口性的动态变化。
在两组实验的27天诱导期内，钝顶滨螺的摄食率均存在显著波动。直接被滨螺啃食的泡叶藻，其新鲜组织块的适口性在15天后显著降低，而重构组织块的适口性则分别在6天和12天后下降，均削弱了对同种滨螺的取食吸引力。在处理第12、18、24天时，处于钝顶滨螺啃食同种个体下游的新鲜泡叶藻，其适口性显著低于处于未被啃食同种个体下游的泡叶藻。
两组诱导实验中钝顶滨螺摄食率与泡叶藻适口性的变化规律，均表明植食者诱导型抗植食防御响应存在时间异质性，这一特性可能为诱导型抗植食防御的实验检测带来额外复杂度。