Abstract
The importance of mucus produced by jellyfish species remains as understudied as their feeding behavior. Here, we study medusae under captivity, ascertain the role of mucus, and describe its feeding behavior. Between February and March 2019, live adult cannonball jellyfish, Stomolophus sp. 2, were collected in Las Guásimas Bay (Gulf of California, Mexico) and were offered fish eggs, mollusk “D” larvae, or Artemia nauplii in 4-day trials. Descriptions of feeding structures were provided for S. sp. 2. Digitata adhere food and scapulets fragment them, which, driven by water flow, pass via transport channels to the esophagus and the gastrovascular chamber where food is digested. Due to stress by handling, medusae produced mucus and water, lost feeding structures, and decreased in size. Based on our observations and a thorough literature review, we conclude that the production of mucus in S. sp. 2 plays several roles, facilitating capture and packing of prey, acting as a defense mechanism, and facilitating sexual reproduction; the latter improves the likelihood of a population persisting in the long run, because fertilized oocytes in mucus transform to planulae, settle, and transform into asexually reproducing polyps. Polyps live longer than the other life stages and are more resistant to adverse environmental conditions than the medusoid sexual stage.
Highlights
Worldwide, the number of studies on medusae species are increasing due to their massive irruptions occurring in several places [1,2]
For medusae fed Artemia nauplii, we found food (Figure 2B,C) in oral arms and scapulets covered with mucus (Figure 3)
During the transport of food items, we observed digitata covering the base of the inner oral arms throughout the mouth; it was here where we found food items conglomerated and adhered (Figure 2B,C)
Summary
The number of studies on medusae species are increasing due to their massive irruptions occurring in several places [1,2] These events are attributed to factors such as overfishing of their competitors, natural predators [1,2,3,4], eutrophication of coastal waters [5], global ocean sprawl in artificial structures [6,7], alterations in flow of rivers [8,9], and climate change [10,11,12,13,14]. Jellyfish aggregations play important roles in marine ecosystems; during blooms, they can exhaust local plankton communities and impact wider trophic webs [15,16,17] Most cnidarian medusa, such as scyphozoan (jellyfish) and cubozoan (box jellies) species, reproduce sexually and asexually. Finger-like projections (digitate) [30] are observed in these structures; they paralyze prey [28] to retain food particles [31] and carry them through the pores [28,30]
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