Effects of global warming on reproduction and potential dispersal of Mediterranean Cnidarians

Multiple reproduction forms in the polyps of the cannonball jellyfish Stomolophus sp. 2: Probable life-cycle reversal

The jellyfish genera Stomolophus spp. is one of the most abundant in the Pacific Ocean, yet it has not been thoroughly studied. Until recently, research has been developed and directed to its knowledge because of the economic interest in its exploitation. The genus Stomolophus in the Pacific Ocean is composed of five species (S. agaricus, S. chunii, S. collaris, S. fritillaria, and S. meleagris), and Stomolophus sp. 2 has been recently reported in the central part of the Gulf of California. Therefore, this study aimed to describe in vivo the different developmental stages of Stomolophus sp. 2 life cycle. As a result, multiple polyp reproduction forms were described, such as polyp-stolon formation, polydisc strobilation with more than 20 ephyrae formed by each strobila, and polyp formation directly from juvenile ephyra. In the degenerating phase, the polyps turned into cysts induced by stress conditions, such as changes in temperature, oxygen, and food availability. The life cycle of Stomolophus sp. 2 can be distinguished from that of S. meleagris by showing various asexual reproduction mechanisms and polydisc-like strobilation. The formation of polyps directly from the ectoderm of degenerating juvenile medusae suggests the possibility of a reversion cycle. Because of the different life cycles between S. meleagris and S. sp. 2, in addition to their morphological and genetic differences, this study proposes that Stomolophus sp. 2 should be considered a new species and suggests the name Stomolophus yaquilli, in reference to the indigenous community that lives in the species distribution area.

Reproductive cycle and gonadal output of the Lessepsian jellyfish Cassiopea andromeda in NW Sicily (Central Mediterranean Sea)

Knowledge of the reproductive strategy is a key prerequisite to predict population dynamics and potential invasiveness of both native and non-indigenous outbreak-forming species. In 2014 the Lessepsian upside-down jellyfish Cassiopea andromeda reached the harbor of Palermo (NW Sicily, Thyrrenian Sea), to date its established westernmost outpost in the Mediterranean Sea. To predict C. andromeda reproductive success in its novel habitat, gonad histology was carried out to record the number and size of mature and immature oocytes. Both male and female simultaneously presented gametes at all stages of development suggesting an asynchronous, yet apparently continuous, reproduction strategy. Indeed, oogenesis was observed throughout the year from pre-vitellogenic, vitellogenetic, and late-vitellogenetic to mature oocytes suggesting multiple reproductive events, as known in other Mediterranean Rhizostomeae. Oocytes were found from May to December, with two seasonal peaks of abundance (late spring = 392 and autumn = 272), suggesting imminent spawning events. Further, jellyfish size varied significantly throughout the year, with maximum diameter (up to 24 cm) in summer, and minimum diameter (6 cm) in winter. Small-sized jellyfish in winter belong to the new cohort, most probably arising from intense summer strobilation of polyps. Late spring fertilization, planula development, and metamorphosis, followed by polyp strobilation in the summer months, may explain the late appearance of a new jellyfish cohort, likely coincident with that recorded throughout winter.

Seasonal trends of the polyp expansion and nutritional condition of Alcyonium acaule (Octocorallia, Alcyonacea)

The ecological physiology of anthozoans, as well as their resistance to stressors, are strongly influenced by environmental factors and the availability of resources. The energy budget of anthozoans can vary seasonally in order to find an equilibrium between the available resources and respiration, polyp activity, growth, and reproduction processes. The variation in the biochemical composition of the animal tissues in these organisms results from a combination of the productivity processes of the water column coupled with the reproductive effort and potential starvation periods of the anthozoans. Here, the seasonal variation in the polyp activity of a slow-growing passive suspension feeder, the octocoral Alcyonium acaule, as well as their carbohydrate, protein and lipid contents, was investigated in a warm temperate environment using in-situ observations and biochemical analyses. Polyp activity exhibited a significant variability that was moderately dependent on season, while an aestivation phenomenon in A. acaule (i.e., a resting period in which the anthozoan is not capable of any polyp activity) during the warmer months is clearly observed. Carbohydrate concentrations in the coral species showed a significant increase in the late winter and spring seasons, and the lipid content increased during the spring. A higher abundance of lipids and carbohydrates coincided with a higher primary productivity in the water column, as well as with the octocoral reproduction period. In late autumn, there was a depletion of these biomolecules, with protein levels exhibiting great variability across sampling times. Complex alterations driven by climate change could affect the energy fluxes that depend on the dead or alive particles that are intercepted by marine animal forests. The obtained findings show a food shortage in late summer and autumn of the benthic suspension feeder A. acaule through the integrative descriptors of the ecophysiology of these anthozoans. This research contributes to the knowledge of energy storage capabilities in benthic suspension feeders in general, highlighting the importance of understanding the limits of resistance to starvation periods through these indicators.

Weak biodiversity connectivity in the European network of no-take marine protected areas

The need for international cooperation in marine resource management and conservation has been reflected in the increasing number of agreements aiming for effective and well-connected networks of Marine Protected Areas (MPAs). However, the extent to which individual MPAs are connected remains mostly unknown. Here, we use a biophysical model tuned with empirical data on species dispersal ecology to predict connectivity of a vast spectrum of biodiversity in the European network of marine reserves (i.e., no-take MPAs). Our results highlight the correlation between empirical propagule duration data and connectivity potential and show weak network connectivity and strong isolation for major ecological groups, resulting from the lack of direct connectivity corridors between reserves over vast regions. The particularly high isolation predicted for ecosystem structuring species (e.g., corals, sponges, macroalgae and seagrass) might potentially undermine biodiversity conservation efforts if local retention is insufficient and unmanaged populations are at risk. Isolation might also be problematic for populations' persistence in the light of climate change and expected species range shifts. Our findings provide novel insights for management directives, highlighting the location of regions requiring additional marine reserves to function as stepping-stone connectivity corridors.