A biofilm micro-community dominated by the diatom Campylodiscus neofastuosus (Surirellales) binds detritus used as food source for rare brittle stars endemic to two Bahamian caves
2025
Steinitz-Kannan,Miriam | Carpenter,Jerry | Nienaber,Mark A.
The rare endemic brittle star Amphicutis stygobita (Echinodermata: Ophiuroidea: Amphilepididae) is found in Bernier Cave on San Salvador Island in The Bahamas. We report here on the diatom-rich detritus on which the brittle star feeds. The detritus contains a microbial biofilm dominated by a large diatom Campylodiscus neofastuosus Ruck & Nakov that thrives in the cave’s brackish water. The biofilm diatoms and bacteria produce sticky, carbohydrate-rich, extracellular polymeric substances (EPS) that add to the detritus’ nutritional value and help give the detritus a consistency for A. stygobita to pull it into its mouth. Of particular interest is that Campylodiscus neofastuosus has distinct cell wall features that make efficient use of the limited light in the cave. It appears these morphological adaptations might focus light onto the chloroplasts increasing light capture. Furthermore, large, dark, and highly lobed chloroplasts serve as an additional low-light adaptation. This is a rare instance where efficient photosynthetic activity by diatoms produces a complex biofilm that feeds an endemic cave species population.
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