Federico Betti

Contribution to the understanding of seasonal cycle of Aurelia aurita (Cnidaria: Scyphozoa) scyphopolyps in the northern Adriatic Sea

Natural populations of Aurelia aurita scyphopolyps, settled on a wreck in the northern Adriatic Sea, were monitored for 22 months in order to study their seasonal cycle. The trend of Aurelia polyps is strongly dependent on water temperature with a peak of abundance in summer and low densities in winter. The strobilation process occurs only once a year, during the cold season, and the estimated number of released ephyrae is 780,000–2,600,000/m 2 . The species has been recorded only on the iron wreck while it is completely lacking from the close rocky cliff of Conero Promontory, suggesting that the increase of underwater structures of anthropogenic origin could be related to the increases of jellyfish biomass.

Temporal variations in growth and reproduction of Tedania anhelans and Chondrosia reniformis in the North Adriatic Sea

Most works concerning growth and reproduction of Mediterranean sponges have been performed in the oligotrophic western Mediterranean while little is known about sponge dynamics in the North-western Adriatic Sea, a basin characterized by low winter temperature and eutrophy. In order to deepen our understanding of sponges in the North Adriatic Sea and verify how its peculiar trophic and physical conditions affect sponge life cycles, temporal trend of sponge cover (%) and reproductive timing of Chondrosia reniformis and Tedania (Tedania) anhelans were studied over a 1-year period looking for a possible relation with variations of temperature or food availability. In C. reniformis, although little variations of sponge cover were evidenced around the year, the number of individuals and their size increase during spring. Asexual reproduction, via drop-like propagules, mainly occurs in spring and summer, while sexual reproduction is characterized by a maximum number of oocytes in August. T. anhelans progressively grows from spring to summer and develops propagules on its surface that reach their maximum size in July. In autumn, the sponge undergoes a process of progressive shrinkage and almost disappears in winter when temperature reaches 7–8°C. Larvae occur during summer. In the North Adriatic Sea sponges have larger sizes, higher density and a wider period of oocytes production compared with the same species from the Mediterranean Sea, suggesting these differences could be due to high food availability characterizing the eutrophic Adriatic basin. On the contrary, the sharp water temperature variations and the very low winter temperature, 5–6°C lower than what has been reported for the Mediterranean Sea, regulate temporal variations in abundance and cause the disappearance of thermophile species during winter.

Long-term life cycle and massive blooms of the intertidal hydroid Paracoryne huvei in the North-western Mediterranean Sea

ABSTRACT Paracoryne huvei is a rare encrusting hydrozoan living in the intertidal zone of the North-western Mediterranean Sea, from the Catalan coast to the Ligurian Sea. In 2014, a large bloom of P. huvei was recorded along the cliffs of the Marine Protected Area ‘Isola di Bergeggi’ (Ligurian Sea). The species has shown densities related to important biomass values never previously recorded (wet weight as high as 1600 g m−2), creating a continuous belt up to 1 m wide from February to April. At an increasing distance from the promontory, the species decreased in abundance, assuming a spotted aspect comparable to the colonies recorded by earlier researchers. In the Bergeggi area, the species has exhibited an almost complete cover of the lower intertidal zone, and for the first time it was recorded in the infralittoral and upper intertidal zone and in tide pools, demonstrating a wider range of habitat than had previously been observed. The life cycle appeared significantly shorter than cycles reported in earlier literature, and this phenomenon has been compared with similar observations from other shallow water hydrozoans in the same area. The abundance of the species was continually monitored in 2015–2016 to help assess the inter-annual variations in relation to temperature and rainfall trends and, indirectly, to competition with other species. Finally, a comparison of the 59 years of scattered data of occurrence in the literature has shown P. huvei to be a strict stenothermal species, reported only in winters characterized by average temperatures.

Ultrastructural evidence of a fungus-sponge association in the Ligurian Sea: a case study of Clathrina coriacea (Porifera: Calcarea)

Abstract Consecutive underwater observations carried out in shallow waters of Pontetto (Ligurian Sea) from June to the end of November 2013 revealed the presence of purple areas on the white surface of the asconoid calcareous sponge Clathina coriacea. Histological and ultrastructural investigations performed on the purple areas of the sponge showed the occurrence of a network of hyphae of an indeterminate fungus permeating the sponge tissues and presumably responsible for the unusual colour of the sponge. The hyphae, varying in size and morphology according to their location in the sponge body, are visible on the outermost sponge surface and, after crossing the mesohyl, penetrate inwards into the choanodermal layer, being mainly located along the apical border of the choanocytes. The occurrence of undamaged flagella and microvillar fringes, which are the organelles characterising the choanocyte cells, is consistent with a normal functionality of the sponge tissues, notwithstanding the presence of the fungal hyphae. The fungus develops only in summer because it disappears concomitantly with the approach of autumn. This feature is coherent with the consideration that the sponge acts as a suitable substrate for the developing fungus, which, in turn, does not interfere with the sponge filter-feeding activity.