Morales-Ávila, J.R., J.R., Palomares-García & R.J., Saldierna-Martínez (2023). The interplay between Microsetella norvegica (Harpacticoida, Ectinosomatidae) and Pleurobrachia bachei (Ctenophora:Pleurobrachiidae) reveals novel trophic interactions. Elsevier (Eds.), Regional Studies in Marine Science. 61: 102869. DOI: 10.1016/j.rsma.2023.102869.
José Raúl Morales-Ávila 1, José Ricardo Palomares-García 2 y Ricardo Javier Saldierna-Martínez 3
Despite the wide geographic distribution of Microsetella norvegica little is known regarding its
interspecies interactions. In this work, we provide the first description of the interaction between
the harpacticoid copepod M. norvegica and the ctenophore Pleurobrachia bachei in the southeastern
Gulf of California. M. norvegica exhibited two remarkable trophic strategies during the period of this
study. A parasitic strategy is proposed since M. norvegica undergoes ontogenetic changes from egg to
late-copepodite in the mesoglea of the ctenophore. In contrast, adult females exhibited a short-time
interaction with the ctenophore, consistent with a micropredation trophic strategy. Females occurred
inside the ctenophore in three stages of maturity: lacking egg-sac (presumably fertilized), ovigerous,
and with egg-sacs just detached from the female genital segment. This suggests that females enter into
the ctenophore’s mesoglea to release egg-sacs, and then leave the host to continue a free life where
mating occurs. Accordingly, we propose that M. norvegica is able to exhibit a protelean life history
in which larvae are parasitic, but adults are free living. Copepods invaded all stages of ctenophores
(i.e. from larval to adult stage = 15.1 mm in sagittal diameter) with low prevalence, ranging from
0.01 to 0.4% and intensity between 1 to 3 adult females. In contrast, developmental stages from
egg to copepodites reached up to 18 individuals per host. Density of M. norvegica was relatively
high attaining up to 29.2 ind. 100 m-3. Positive correlation between abundance of ctenophores and
copepods (r2 = 0.6, p < 0.05) suggests a synchronization of the interaction. Abundances were highest
during the coldest season at shallow sampling stations with oligotrophic water characterized by low
levels of chlorophyll-a, and moderate oxygenated waters
Palabras clave: trophic interactions; Parasitism; Micropredation; Protelean life cycle; southeastern Gulf of California
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