Floating nurseries? Scyphozoan jellyfish, their food and their rich symbiotic fauna in a tropical estuary

Abstract

BackgroundThe anthropogenic modification of trophic pathways is seemingly prompting the increase of jellyfish populations at the expense of planktivorous fishes. However, gross generalizations are often made because the most basic aspects of trophic ecology and the diverse interactions of jellyfish with fishes remain poorly described. Here we inquire on the dynamics of food consumption of the medusoid stage of the scyphozoan jellyfish Stomolophus meleagris and characterize the traits and diversity of its symbiotic community.MethodsS. meleagris and their associated fauna were sampled in surface waters between November 2015 and April 2017 in Málaga Bay, an estuarine system at the Colombian Pacific. Stomach contents of medusae were examined and changes in prey composition and abundance over time analysed using a multivariate approach. The associated fauna was identified and the relationship between the size of medusae and the size those organisms tested using least-square fitting procedures.ResultsThe presence of S. meleagris medusa in surface waters was seasonal. The gut contents analysis revealed that algae, copepods and fish early life stages were the more abundant items, and PERMANOVA analysis showed that the diet differed within the seasons (P(perm) = 0.001) but not between seasons (P(perm) = 0.134). The majority of the collected medusae (50.4%) were associated with individuals of 11 symbiotic species, 95.3% of them fishes, 3.1% crustaceans and 1.6% molluscs. Therefore, this study reports 10 previously unknown associations. The bell diameter of S. meleagris was positively related to the body sizes of their symbionts. However, a stronger fit was observed when the size relationship between S. meleagris and the fish Hemicaranx zelotes was modelled.DiscussionThe occurrence of S. meleagris was highly seasonal, and the observed patterns of mean body size through the seasons suggested the arrival of adult medusae to the estuary from adjacent waters. The diet of S. meleagris in the study area showed differences with previous reports, chiefly because of the abundance of algae that are seemingly ingested but not digested. The low number of zooplanktonic items in gut contents suggest the contribution of alternative food sources not easily identifiable. The observed changes in the composition of food in the guts probably reflect seasonal changes in the availability of prey items. The regular pattern in the distribution of symbionts among medusae (a single symbiont per host) and the positive host-symbiont size relationship reflects antagonistic intraspecific and interspecific behaviour of the symbiont. This strongly suggest that medusa represent an “economically defendable resource” that potentially increases the survival and recruitment of the symbionts to the adult population. We argue that, if this outcome of the symbiotic association can be proven, scyphozoan jellyfish can be regarded as floating nurseries.

Planktonic associations between medusae (classes Scyphozoa and Hydrozoa) and epifaunal crustaceans

“…as hosts ( Berggren, 1994 ; Pagès, 2000 ; Hayashi, Sakagami & Toyoda, 2004 ; Towanda & Thuesen, 2006 ; Ohtsuka et al, 2010 ; Ohtsuka, Boxshall & Srinui, 2012 ; Boco & Metillo, 2018 ). The commercially harvested shrimp, Penaeus stylirostris (Stimpson, 1871), was found on Stomolophus meleangris ( Riascos et al, 2018 ). Notably, young Callinectes sapidus , the Chesapeake Blue Crab, was reported by Jachowski (1963) as regularly found on Chrysaora quinquecirrha (Desor, 1848) medusae without consuming them.…”

“…While research has expanded around services jellyfish provide ( Riascos et al, 2018 ), much of this research focuses on benefit and harm to vertebrates ( Brodeur, 1998 ; Cardona et al, 2012 ; Mir-Arguimbau, Sabatés & Tilves, 2019 ). However, the relationships between scyphomedusae, hydromedusae and other invertebrates are currently poorly characterized.…”

Table 1: Associations reported organized by host.

“…as hosts (Berggren, 1994;Pagès, 2000;Hayashi, Sakagami & Toyoda, 2004;Towanda & Thuesen, 2006;Ohtsuka et al, 2010;Ohtsuka, Boxshall & Srinui, 2012;Boco & Metillo, 2018). The commercially harvested shrimp, Penaeus stylirostris (Stimpson, 1871), was found on Stomolophus meleangris (Riascos et al, 2018). Notably, young Callinectes sapidus, the Chesapeake Blue Crab, was reported by Jachowski (1963) as regularly found on Chrysaora quinquecirrha (Desor, 1848) medusae without consuming them.…”

“…Additional regulation and management should be considered for jellyfish species known to harbor juveniles of commercially viable crustaceans. It is clear that many crustaceans, fish, and other organisms live in, upon and around medusae, thus indiscriminate efforts to remove or destroy blooms of endemic species are likely unwise (Tilves et al, 2018;Riascos et al, 2018).…”

Figure 1: Summary of Google Search Results.

“…as hosts (Berggren, 1994;Pagès, 2000;Hayashi, Sakagami & Toyoda, 2004;Towanda & Thuesen, 2006;Ohtsuka et al, 2010;Ohtsuka, Boxshall & Srinui, 2012;Boco & Metillo, 2018). The commercially harvested shrimp, Penaeus stylirostris (Stimpson, 1871), was found on Stomolophus meleangris (Riascos et al, 2018). Notably, young Callinectes sapidus, the Chesapeake Blue Crab, was reported by Jachowski (1963) as regularly found on Chrysaora quinquecirrha (Desor, 1848) medusae without consuming them.…”