Chemical Defenses of Cryptic and Aposematic Gastropterid Molluscs Feeding on their Host Sponge Dysidea granulosa

Abstract

Numerous opisthobranchs are known to sequester chemical defenses from their prey and use them for their own defense. Information on feeding biology is critical for understanding the ecology and evolution of molluscs, yet information on feeding biology is still scarce for many groups. Gastropterid molluscs are often found on sponges, but there is controversy as to whether they are true sponge feeders. On Guam, we found the gastropterids Sagaminopteron nigropunctatum and S. psychedelicum on the sponge Dysidea granulosa. They seem to rely on contrasting defense strategies as S. psychedelicum has vivid colors, consistent with the warning coloration found in many chemically defended opisthobranchs, whereas S. nigropunctatum is highly cryptic on the sponge. S. nigropunctatum is avoided by the pufferfish Canthigaster solandri in aquarium assays. We analyzed the secondary metabolites of the two species and found that both share polybrominated diphenyl ethers (BDEs) with their host sponge D. granulosa. S. psychedelicum and S. nigropunctatum sequester the major BDE in the sponge and accumulate it in the mantle at approximately the same concentration as in the sponge (4.03 and 2.37%, respectively), and concentrate it in their parapodia at over twice the sponge concentration (7.97 and 10.10%, respectively). We also detected trace amounts in the mucus secretion of S. psychedelicum, and quantified significant amounts in the mucus (1.84%) and egg masses (2.22%) of S. nigropunctatum. Despite contrasting color patterns displayed by the two gastropterid species, they seem to share a similar

Detecting arthropod intraguild predation in the field

“…Fournier et al 2006;Moser et al 2008), although thus far no antibodies have been developed for coccinellid intraguild prey. In GC-MS, distinctive prey chemicals or suites of chemicals are isolated from the predator in order to identify diet components (Knutsen and Vogt 1985;Becerro et al 2006). Because ladybirds possess taxonomically-specific defensive alkaloids (Daloze et al 1995), GC-MS of prey alkaloids in predator bodies is particularly appropriate for studying IGP of other ladybird species by H. axyridis (Hautier et al 2008;Sloggett et al 2009;Sloggett et al 2011) and to date are used in the only two published field studies on the ecological impact of H. axyridis (Hautier et al 2008;Hautier et al 2011).…”

Endobacteria in the tentacles of selected cnidarian species and in the cerata of their nudibranch predators

“…The sesquiterpenes proved to be toxic to certain shrimps (Yasman et al 2003). Becerro et al (2006) reported that the tropical nudibranch species Sagaminopteron nigropunctatum and S. psychedelicum feeding on the sponge Dysidea granulosa sequester polybrominated diphenyl ethers (BDEs) in their mantle material and parapodia. BDEs seem to be feeding deterrents to the pufferfish Canthigaster solandris.…”

The Sequestration of Oxy-Polybrominated Diphenyl Ethers in the Nudibranchs Miamira magnifica and Miamira miamirana

“…The same metabolite was present at twice the concentration in the parapodia of S. psychedelicum (7.97%) and S. nigropunctatum (10.10%). In the mucus of S. psychedelicum , 2 was detected in trace amounts; whereas in the mucus (1.84%) and egg masses (2.22%) of S. nigropunctatum , the level of 2 was quite significant [9]. …”

“…OH- and OMe-PBDEs have been typically reported from sponges of the genus Lamellodysidea [1], Dysidea [2,3] and Phyllospongia [4,5,6] and occasionally from molluscs [7,8,9]. The bioaccumulation of OMe-PBDEs at ppm levels has also been reported in marine mammals, suggesting the persistent nature of these compounds in the environment [10].…”