The life cycle of Hydrozoans typically comprises two phases: the polyp, either solitary or colonial, with generally a benthic habitat, and the medusa which lives in the plankton. In its typical metagenetic cycle, the medusa is budded from the polyp, which is the product of sexual reproduction of medusae. However, several alternative reproduction patterns have also been described. In particular some species are able to perform a regressive transformation of the medusae that transform themselves into polyps bypassing sexual reproduction. In a species with alternative morphs switched by the environment, the more labile is the correlation between environmental factors acting on the genetic switch and the factors to which the resulting form is adapted, the more hazardous will be the development of either body form. However, we can explain the evolutionary advantage offered by reversion between morphs of these plastic species living in shallow water unpredictable environments: should produced medusae be released in the "wrong" environment, they would still have a chance of survival under another form.
Bioconstructions such as coralligenous outcrops and maërl beds are typical Mediterranean underwater seascapes. Fine-scale knowledge on the distribution of these sensitive habitats is crucial for their effective management and conservation. In the present study, a thorough review of existing spatial datasets showing the distribution of coralligenous and maërl habitats across the Mediterranean Sea was undertaken, highlighting current gaps in knowledge. Predictive modelling was then carried out, based on environmental predictors, to produce the first continuous maps of these two habitats across the entire basin. These predicted occurrence maps for coralligenous outcrops and maërl beds provide critical information about where the two habitats are most likely to occur. The collated occurrence data and derived distribution model outputs can help addressing the challenge of developing basin-wide spatial plans and to guide cost-effective future surveys and monitoring efforts towards areas that are presently poorly-sampled.
Abstract The Mediterranean red coral, Corallium rubrum (L.), has been a valuable economic resource for more than 2000 years. The Sicily Channel and surrounding areas are one of the most famous red coral fishing grounds of the whole region, hosting the deepest ever found living colonies and large sub-fossil red coral deposits; the so-called Sciacca banks are a unique location in the whole Mediterranean Sea. In this paper, a morphometric description of this sub-fossil population is presented for the first time from studies of colonies in the collection of several coral factories from Torre del Greco (Naples), with radiocarbon age estimations and growth rate evaluations. From the results of this study, after several thousand years Sciacca red coral colonies maintained the organic matrix structure with evident annual discontinuities, allowing estimations of the annual growth rate (about 0.3 mm/year) and the average population age (about 33.5 years). These resulting data are similar to the values determined for deep-dwelling living red coral populations. The radiocarbon dating evidenced a range of ages, from 8300 to 40 years before 1950 CE, mostly falling between 2700 and 3900 YBP, suggesting that colonies accumulated over a wide span of time. In view of the tectonically active nature of the area, several catastrophic events affected these ancient populations, maintaining them in a persistent state of early-stage, structurally similar to the those in current over-exploited areas.
Three species belonging to the genus Zanclea : Zanclea divergens , Zanclea tipis , sp. nov. and Zanclea exposita , sp. nov. have been described as epizoic of bryozoan from the coral reef of the Bunaken Marine Park (Sulawesi Sea, Indonesia). The record of Z. divergens is the second after its description from Papua New Guinea. Zanclea tipis is characterized by a polymorphic colony and a medusa with very extended exumbrellar pouches. Zanclea exposita shows a naked hydrorhiza creeping on the surface of the bryozoan skeleton. An evolutionary trend among the Zancleidae, from species epibionts of algae and bivalve shells with the hydrorhiza covered by perisarc to species symbiotic with bryozoan with a naked hydrorhiza, is discussed.
Stylasterids belong to one of the few calcifying hydroid families that are commonly found in shallow tropical coral reefs.Although these corals are accurately described from a taxonomic point of view, information about their ecology is scarce.Distichopora violacea is one of the most common stylasterids of the Indo-Pacific region; however, no information is yet available on its distribution and abundance.To fill this gap data we gathered data during three scientific expeditions on four Maldivian atolls.In each atoll investigations were carried out at three depths, both in the ocean and in the lagoon reef, to examine differences in colony density and distribution.Distichopora violacea was observed in all the studied atolls; however, its distribution and density were not homogeneous among them.This species was more abundant in the ocean reefs than in the lagoon ones, suggesting a strong influence of water movement.Moreover, we found a high variability in colony density in the eastern ocean reefs that was tentatively attributed to a different topography of the reef: colonies were more abundant on the gentle slopes of Malè atolls than on the steep reefs of Felidhoo.Oceanographic features, mainly due to the seasonal monsoons, are likely to interact with the biological requirements of the species in determining the observed asymmetrical geographical distribution.The present investigation provides new insights on the stylasterid D. violacea and, for the first time, quantitative data on its distribution and density that can be useful for conservation and management of this CITES regulated species.
In the Mediterranean, at the end of the 19thcentury, dolphins were identified as pest species for their disruptive actions during some fishing phases. Numerous fishermen organizations asked for permission to hunt dolphins, and the killing of a dolphin was often institutionally favoured by several national laws. We provide a picture of the systematic culling campaigns for dolphins in Italy up to the absolute prohibition of capture, analysing the governmental measures implemented against dolphins, the official number of individuals killed and their value (in Italian liras) in 11 Italian Maritime Compartments from 1927 to 1937. Officially, over 6,700 dolphins were killed in 10 years along the Italian coast and rewards distributed for about 360,160 Italian liras, which, at the current exchange rate, correspond to 355,000 euros, for a contribute of about 52 euros for each dolphin. Considering that the meat was consumed both at the family level or sold, mainly as salted and dried meat, the dolphin hunting could be considered a profitable activity in those years for the fishermen. Due to the scarce information available on the size of the dolphin populations around the Italian coast, it is difficult to estimate the impact of the bounty fishing on the Italian populations during the studied period. Nevertheless,it is possible to hypothesizethat it could have affected all the local recruitment, producing an effect on the local population far from being negligible.
Abstract Healthy specimens of the Mediterranean Petrosia ficiformis har bour endocellular cyanobacteria (Aphanocapsa feldmanni) caus ing a violet pigmentation of the sponge. Necrosis in P. ficiformis can be easily detected by the occurrence of white patches scat tered over the surface. Necrotic specimens were examined along the Gallinara Island coasts (Western Ligurian Sea), in coincidence with environmental stress (heavy rainfall, land run‐off, high sea‐water temperature). The appearance of white patches is due to the gradual sloughing of the pinacodermal covering, as evidenced by scanning electron microscopic observations. Sloughing leads to progressive tissue degeneration in the deeper parts. Histologi‐cal sections showed that, concomitantly with the loss of the su perficial layer, internal sponge tissues degenerate and the sponge body becomes exposed to the invasion of ciliates. Spicule bun dles of the skeletal network separate damaged tissues from the healthy ones, thereby slowing down spread of necrosis and en abling successful recovery.
The skeleton of most Porifera species consists of siliceous spicules that, after the sponge death, persist for a long time in the sediment. The reduced suspension occurring within the meadows of the seagrass Posidonia oceanica makes these habitats a stable deposit for sponge spicules. Spicules trapped into the network of rhizomes progressively buried, named “matte”, represent a sedimentary sequence interpretable on a temporal scale. By means of a vertical corer we collected samples of sediment at 0.5, 1, 1.5 and 2 m depth along the matte profile in order to quantify the amount of biogenic silica used to assess past dynamics of the sponge community in four P. oceanica meadows of the Ligurian sea. The content in biogenic silica was determined by spectrophotometric analysis of the sediments. While at Prelo Bay the values are constant in the core sample, a general decreasing trend with depth was observed in the meadows of Punta Pedale, while in the site of Punta Manara the major amount of silica was found deeper in the matte. The temporal variations of sponge abundance were probably due to historical anthropogenic factors. In the meadow of Bergeggi, BSi concentrations, significantly lower compared to all other sites, were likely caused from inputs from the close Savona harbor and strong bottom currents avoiding spicule deposition.
