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Marine parasites are an important but often neglected component of ecosystems. This is particularly true for cnidarian parasites and their life cycles; few evidences of trophic transmission of trematodes from jellyfish to fish have been reported. This context inspired our idea of investigating one of the most complex and diffused jellyfish in the Mediterranean Sea, Rhizostoma pulmo. This work is the first attempt to study Trematoda parasites in Adriatic scyphomedusae. The goals are to 1) determine prevalence and intensity of metacercariae in Rhizostoma pulmo, 2) identify the species involved through morphological and molecular analysis, 3) test whether infection parameters change in different body parts and in relation to jellyfish size. While waiting for molecular results, all parasites morphologically investigated potentially belonged to the genus Opechona. The total number of parasites varied between 18.7 ± 6.7 parasite per individual in 0-2 cm diameter jellyfish up to 510.2 ± 136.4 parasites in larger ones. The 100% of infected individuals suggests that R. pulmo is a true host of digenetic trematodes, at least for this Opechona sp., and therefore important for their life cycle in the region. This also supports the theory that fish predate on Rhizostoma p., since trophic interactions are necessary for this genus to complete their cycles. Parasitology may be another way to investigate fish-jellyfish predation, integrating methods like gut contents and stable isotopes analysis. Further aspects should be investigated such as the characterization of parasites life cycle, the differences between the scyphozoan species and the potential role of blooms as elevators for parasites towards the fish compartment.

Il presente studio si propone di approfondire la biologia ed il ciclo riproduttivo del gobione italiano (Gobio benacensis), specie endemica a corologia cisalpina inclusa nella categoria “Endangered” (EN) della lista rossa IUCN, con l’intento di fornire informazioni utili a redigere corretti piani gestionali volti alla conservazione della specie. Le indagini sono state condotte in un corso d’acqua del Bacino del Fiume Isonzo (Torrente Reca, Nordest Italia) ed hanno riguardato 86 esemplari catturati nell’aprile 2016 al fine di definirne la consistenza e la struttura della popolazione e 77 esemplari, catturati mensilmente e bimestralmente tra aprile 2016 e febbraio 2017, per la definizione del ciclo riproduttivo. Le curve di regressione del peso sulla lunghezza totale per i maschi (W=0,1253TL2,8770) e per le femmine (W=0,1555TL2,7554), confrontate mediante ANCOVA, non hanno denunciato differenze significative. I valori medi ± deviazione standard dell’indice gonadosomatico GSI per i maschi sono compresi tra 0,61±0,49 e 1,75±0,58, mentre per le femmine tra 1,02±0,88 e 14,15±2,80. L’indice epatosomatico HSI ha denunciato range compresi tra 0,05±0,02 e 2,68±1,26 e tra 0,25±0,19 e 1,75±0,58 rispettivamente per i maschi e per le femmine. Le analisi istologiche di ovari e testicoli, analizzati per la prima volta nella specie, hanno permesso di identificare gli stadi di maturazione, che unitamente all’analisi del GSI indicano che la specie depone le uova a più riprese durante il periodo riproduttivo compreso tra aprile e giugno. Nei maschi è stata, tuttavia, evidenziata una prolungata attività riproduttiva che si protrae fino al mese di agosto.

The aim of the present work is to study the biology and the reproductive cycle of the Italian gudgeon Gobio benacensis, which is included as “endangered” (EN) in the IUCN Redlist, due to the endangered status, information could be useful for the correct management of the species and for the scheduling of focused conservation plans. Analyses were carried out within a watercourse included in the Isonzo River Basin (Reca Stream, Northeast Italy) and regarded 86 specimen collected during April 2016 in order to assess population consistence and structure, and 77 specimens collected monthly and bimonthly between April 2016 and February 2017 to investigate the reproductive cycle. Regression between total length (TL) and body weight (W) obtained for males (W=0,1253TL2,8770) 54 2 and females (W=0,1555TL2,7554) were analyzed using the ANCOVA and did not show significant differences. Mean values of the gonadosomatic index (GSI) ranged from 0,61±0,49 and 1,75±0,58 for males and from 1,02±0,88 and 14,15±2,80 for females. Hepatosomatic index (HIS) showed ranges between 0,05±0,02 and 2,68±1,26 for males and between 0,25±0,19 e 1,75±0,58 for females. Analyses of ovaries and testicles, firstly performed for this species, allowed to identify maturation stages. The results show that G. benacensis females repeatedly spawn during the reproductive period between April and June and that males prolonged reproductive activity until August.

Descrizione tassonomica delle specie di Scyphozoa presenti nei mari italiani

The investigation of jellyfish gastrovascular systems mainly focused on stain injections and dissections, negatively affected by thickness and opacity of the mesoglea. Therefore, descriptions are incomplete and data about tridimensional structures are scarce. In this work, morphological and functional anatomy of the gastrovascular system of Rhizostoma pulmo (Macri 1778) was investigated in detail with innovative techniques: resin endocasts and 3D X-ray computed microtomography. The gastrovascular system consists of a series of branching canals ending with numerous openings within the frilled margins of the oral arms. Canals presented a peculiar double hemi-canal structure with a medial adhesion area which separates centrifugal and centripetal flows. The inward flow involves only the “mouth” openings on the internal wing of the oral arm and relative hemi-canals, while the outward flow involves only the two outermost wings’ hemi-canals and relative “anal” openings on the external oral arm. The openings differentiation recalls the functional characteristics of a through-gut apparatus. We cannot define the gastrovascular system in Rhizostoma pulmo as a traditional through-gut, rather an example of adaptive convergence, that partially invalidates the paradigm of a single oral opening with both the uptake and excrete function.