Scientists first discovered sponges can be carnivores less than 20 years ago. Most live in the deep ocean, which makes it difficult to fully understand their lifestyle.
The harp sponges collected by MBARI scientists mark the first time researchers observed the complete cycle of a carnivorous sponge's unique approach to sexual reproduction.
Most sponges release actively swimming sperm into the surrounding seawater, but it appears that all carnivorous sponges transfer sperm in condensed packages (spermatophores), the researchers report.
The swollen balls at the tip of the harp sponge's upright branches hold the sperm packets. The balls release the spermatophores into passing currents, and other nearby sponges capture the packets on fine filaments along their branches. The sperm then works its way from the packets into the host sponge to fertilize its eggs, according to the research scientists.
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