第一遍没读懂,"In order to withstand tidal currents, juvenile horseshoe crabs frequently burrow in the sand. Such burrowing discourages barnacles from clinging to their shells.”
奇怪现象:Such burrowing discourages barnacles from clinging to their shells即一般juvenile horseshoe crabs 会附着 barnacles 。但是, juvenile horseshoe crabs are found not to have significant barnacle populations, even though they seldom burrow(这排除BURROW使它们没有附着barnacle的原因)。所以你要找另外原因解释 found not to have significant barnacle 。E的意思为 juvenile horseshoe crabs ( Until they are fully grown指在他们长大前)一年有几次脱旧壳,长新壳。所以上面的barnacle都给脱掉了,当然没发现 barnacle 。