Curtis Lawrence A
Biol Bull. 1985 Oct;169(2):377-390. doi: 10.2307/1541489.
The estuarine neogastropod, Ilyanassa obsoleta, was studied to determine the influence of sex and trematode parasites on the well-known tendency of this snail to aggregate on carrion. Fifteen experimental arenas (1 x 5 m) were delimited on the Cape Henlopen sandflat in Delaware Bay between July 1982 and November 1983. Snails (n = 2111) were examined by dissection. Frequencies of snails in specific categories of sex and parasitism in the arenas were determined before carrion was made available (expected frequencies), and these frequencies were compared with frequencies of the same categories among snails responding to carrion (observed frequencies). Experiments were categorized for analyses into breeding and nonbreeding temporal groups based upon the presence/absence of females with egg cases. Sexual condition alone affected carrion response. Uninfected females in reproductive condition tended to respond more frequently than predicted by controls (positive response) both during and after reproductive season, or else responded as predicted (neutral response). During breeding season males tended to show a neutral response and afterward to respond less frequently than expected (negative response). Parasite influence on carrion response was not detected until after the breeding season, at which time it was pronounced. Both sexes showed a positive response when infected with Lepocreadium setiferoides. Zoogonus rubellus and Gynaecotyla adunca infections produced negative responses in females but neutral responses in males. Austrobilharzia variglandis was inhibitory to females and probably to males as well. Himasthla quissetensis infections seemed not to affect response of either sex. Multiple infections were relatively frequent (9% of snails examined) and also influenced carrion response.
对河口新腹足类动物伊利亚那萨螺（Ilyanassa obsoleta）进行了研究，以确定性别和吸虫寄生虫对这种蜗牛聚集在腐肉上这一众所周知的习性的影响。1982年7月至1983年11月期间，在特拉华湾的亨洛彭角沙滩上划定了15个实验区域（1×5米）。通过解剖检查了2111只蜗牛。在提供腐肉之前确定实验区域内特定性别和寄生虫类别蜗牛的频率（预期频率），并将这些频率与对腐肉有反应的蜗牛中相同类别的频率（观察频率）进行比较。根据有无带卵囊的雌性，将实验分为繁殖期和非繁殖期两个时间组进行分析。仅性状况就影响对腐肉的反应。处于生殖状态的未感染雌性在生殖季节期间和之后往往比对照组预测的反应更频繁（阳性反应），或者反应与预测一致（中性反应）。在繁殖季节，雄性往往表现出中性反应，之后反应频率低于预期（阴性反应）。直到繁殖季节之后才检测到寄生虫对腐肉反应的影响，此时这种影响很明显。感染了刺鳞 Lepocreadium setiferoides 的雌雄两性都表现出阳性反应。感染红腺 Zoogonus rubellus 和钩腺 Gynaecotyla adunca 会使雌性产生阴性反应，但雄性产生中性反应。多腺 Austrobilharzia variglandis 对雌性有抑制作用，可能对雄性也有抑制作用。感染魁氏 Himasthla quissetensis 似乎不影响任何性别的反应。多重感染相对频繁（占检查蜗牛的9%），也影响对腐肉的反应。
