Francesco Zaccanti

Unite research with what citizens do for fun: “recreational monitoring” of marine biodiversity

Institutes often lack funds and manpower to perform large-scale biodiversity monitoring. Citizens can be involved, contributing to the collection of data, thus decreasing costs. Underwater research requires specialist skills and SCUBA certification, and it can be difficult to involve volunteers. The aim of this study was to involve large numbers of recreational divers in marine biodiversity monitoring for increasing the environmental education of the public and collecting data on the status of marine biodiversity. Here we show that thousands of recreational divers can be enrolled in a short time. Using specially formulated questionnaires, nonspecialist volunteers reported the presence of 61 marine taxa encountered during recreational dives, performed as regular sport dives. Validation trials were carried out to assess the accuracy and consistency of volunteer-recorded data, and these were compared to reference data collected by an experienced researcher. In the majority of trials (76%) volunteers performed with an accuracy and consistency of 50-80%, comparable to the performance of conservation volunteer divers on precise transects in other projects. The recruitment of recreational divers involved the main diving and tour operators in Italy, a popular scientific magazine, and mass media. During the four-year study, 3825 divers completed 18757 questionnaires, corresponding to 13539 diving hours. The volunteer-sightings-based index showed that in the monitored area the biodiversity status did not change significantly within the project time scale, but there was a significant negative correlation with latitude, suggesting improved quality in the southernmost areas. This trend could be related to the presence of stressors in the northern areas and has been supported by investigations performed by the Italian Ministry of the Environment. The greatest limitation with using volunteers to collect data was the uneven spatial distribution of samples. The benefits were the considerable amounts of data collected over short time periods and at low costs. The successful development of citizen-based monitoring programs requires open-mindedness in the academic community; advantages of citizen involvement in research are not only adding large data sets to the ecological knowledge base but also aiding in the environmental education of the public.

Growth and population dynamics model of the Mediterranean solitary coral Balanophyllia europaea (Scleractinia, Dendrophylliidae)

Complex life history processes of corals, such as fission, fusion, and partial mortality of colonies, that decouple coral age from size, are rare or clearly detectable in corals that produce distinct colonial or solitary forms. In some of these corals, individual age may be determined from size, and standard age-based growth and population dynamics models may be applied. We determined population size and structure and measured growth rates of Balanophyllia europaea individuals at Calafuria in the eastern Ligurian Sea. We then applied demographic models to these data. Growth rate decreased with increasing coral size. The age–size curve derived from field measurements of growth rates fits that obtained from the computerized tomography analysis of skeletal growth bands. The frequency of individuals in each age class decreased exponentially with age, indicating a population in a steady state. The survival curve showed a turnover time of 3.6 years and a maximum life span of 20 years. This is nearly three times the turnover time and maximum life span recorded for Balanophyllia elegans living off the western coasts of North America, the only congeneric species whose population dynamics has been studied. The Beverton and Holt population model may be useful for comparative analyses of demographic traits and for resource management of solitary or compact, upright growth forms that rarely fragment. This paper completes the description of the main life-strategy characteristics of the Mediterranean endemic coral B. europaea, together with our previous studies on the reproductive biology of this species. This constitutes a major advance in the understanding of the biology and ecology of Mediterranean scleractinian corals, and represents the most complete description of a coral from this geographic area to date that we are aware of.

Environmental implications of skeletal micro-density and porosity variation in two scleractinian corals

The correlations between skeletal parameters (bulk density, micro-density and porosity), coral age and sea surface temperature were assessed along a latitudinal gradient in the zooxanthellate coral Balanophyllia europaea and in the azooxanthellate coral Leptopsammia pruvoti. In both coral species, the variation of bulk density was more influenced by the variation of porosity than of micro-density. With increasing polyp age, B. europaea formed denser and less porous skeletons while L. pruvoti showed the opposite trend, becoming less dense and more porous. B. europaea skeletons were generally less porous (more dense) than those of L. pruvoti, probably as a consequence of the different habitats colonized by the two species. Increasing temperature had a negative impact on the zooxanthellate species, leading to an increase of porosity. In contrast, micro-density increased with temperature in the azooxanthellate species. It is hypothesized that the increase in porosity with increasing temperatures observed in B. europaea could depend on an attenuation of calcification due to an inhibition of the photosynthetic process at elevated temperatures, while the azooxanthellate species appears more resistant to variations of temperature, highlighting possible differences in the sensitivity/tolerance of these two coral species to temperature changes in face of global climate change.

Growth and Demography of the Solitary Scleractinian Coral Leptopsammia pruvoti along a Sea Surface Temperature Gradient in the Mediterranean Sea

The demographic traits of the solitary azooxanthellate scleractinian Leptopsammia pruvoti were determined in six populations on a sea surface temperature (SST) gradient along the western Italian coasts. This is the first investigation of the growth and demography characteristics of an azooxanthellate scleractinian along a natural SST gradient. Growth rate was homogeneous across all populations, which spanned 7 degrees of latitude. Population age structures differed between populations, but none of the considered demographic parameters correlated with SST, indicating possible effects of local environmental conditions. Compared to another Mediterranean solitary scleractinian, Balanophyllia europaea, zooxanthellate and whose growth, demography and calcification have been studied in the same sites, L. pruvoti seems more tolerant to temperature increase. The higher tolerance of L. pruvoti, relative to B. europaea, may rely on the absence of symbionts, and thus the lack of an inhibition of host physiological processes by the heat-stressed zooxanthellae. However, the comparison between the two species must be taken cautiously, due to the likely temperature differences between the two sampling depths. Increasing research effort on determining the effects of temperature on the poorly studied azooxanthellate scleractinians may shed light on the possible species assemblage shifts that are likely to occur during the current century as a consequence of global climatic change.

Accelerated female differentiation of the gonad by inhibition of steroidogenesis in amphibia

Larvae of toad (Bufo bufo) and frog (Rana dalmatina) were treated with 17 β C (androsten-3 one 17 β-carbossilic acid) at early stages of development in order to inhibit the activity of 5-α-reductase and to reduce the level of dehydrotestosterone, die active form of the male hormone. The effects of drug treatment on larval ovarian differentiation were analyzed at different stages in the rostral portion of the gonad of Bufo (Bidders organ, a rudimentary ovary) and at early stages of metamorphosis in the female gonads of Rana. The Bidders organ of experimental Bufo larvae were characterized by a considerable increase in volume and an anticipated differentiation of germ cells. In fact, oocytes of these specimens were present at earlier stages and increased in size at a faster rate than controls. The gonads of female larvae of Rana showed a much higher number of oocytes, which were also considerably larger in size. As a working hypothesis, we suggest that cells present in the larval androgenic component of the gonad may synthesize small amounts of dehydrotestosterone acting locally by diffusion upon the gynogenic component destined to produce an ovary. This hormone would inhibit ovarian development in genetic males and would regulate the time table of differentiation in genetic females. Hence the exuberant ovarian development in specimens with an induced lower level of dehydrotestosterone.

The effects of aromatase and 5 alpha-reductase inhibitors, antiandrogen, and sex steroids on Bidder's organs development and gonadal differentiation in Bufo bufo tadpoles.

Embryos of toads (Bufo bufo) were treated with aromatase (4-OHA) and 5 alpha-reductase (17 beta C) inhibitors, antiandrogen (CPA), estradiol-17 beta, testosterone, and 5 alpha-dihydrotestosterone in order to study the role played by sex steroids in the development and sex differentiation of gonads. Test compounds were administered to tadpoles in water and morphometric and cytometric analyses were carried out on histological sections of the cephalic Bidders organ (a rudimentary ovary) and of the gonadal region. In Bidders organs, the number and size of oogonia and oocytes were modified by the treatments. However, the female commitment of the Bidders organ occurs independently from steroid treatments that lead to an acceleration or slackening of the processes of proliferation and differentiation of oogonia. 4-OHA and androgens caused various degrees of inhibition of ovarian differentiation, with gonads maintaining an undifferentiated condition. Estrogen provoked a shift of the sex ratio towards the female sex, yet slackened gonadal growth. 17 beta C accelerated ovarian differentiation in females while CPA enhanced gonadal differentiation in both sexes by promoting the germ and somatic cell proliferation. We suggest that sex hormones may have a local regulatory role in gonadal differentiation during early developmental stages. Furthermore, the strong tendency of Bidderian germ cells to develop in the oogenetic way regardless of sex genotype and steroid treatments, and the quantitative sex differences found in the control Bidders organs and gonads, suggest that other factors (such as intracellular mechanisms) may be involved in the initial steps of the process of germ cell differentiation.

Gains and losses of coral skeletal porosity changes with ocean acidification acclimation

Ocean acidification is predicted to impact ecosystems reliant on calcifying organisms, potentially reducing the socioeconomic benefits these habitats provide. Here we investigate the acclimation potential of stony corals living along a pH gradient caused by a Mediterranean CO2 vent that serves as a natural long-term experimental setting. We show that in response to reduced skeletal mineralization at lower pH, corals increase their skeletal macroporosity (features >10 μm) in order to maintain constant linear extension rate, an important criterion for reproductive output. At the nanoscale, the coral skeletons structural features are not altered. However, higher skeletal porosity, and reduced bulk density and stiffness may contribute to reduce population density and increase damage susceptibility under low pH conditions. Based on these observations, the almost universally employed measure of coral biomineralization, the rate of linear extension, might not be a reliable metric for assessing coral health and resilience in a warming and acidifying ocean.

Gonochorism and planula brooding in the Mediterranean endemic orange coral Astroides calycularis (Scleractinia: Dendrophylliidae). Morphological aspects of gametogenesis and ontogenesis

Abstract Information on reproduction in temperate scleractinian corals is notably scant. Astroides calycularis is an azooxanthellate coral that inhabits the South-Western Mediterranean Sea, in shaded habitats from 0 to 50 m depth. Recently, it has been observed along the coast of the Adriatic Sea. This study is the first in-depth investigation of A. calycularis reproductive biology. Observations from the nineteenth century described A. calycularis as hermaphroditic; in contrast, we demonstrated gonochorism (male and female colonies) and brooding (planula releasing) as the reproductive mode, consistent with other members of the family Dendrophylliidae. Undifferentiated germ cells arose in the gastrodermis and subsequently migrated to the mesoglea, where they completed gametogenesis. During spermatogenesis, spermary diameter increased from 20 to 940 µm. During oogenesis, a conspicuous presence of lipid vesicles of exogenous origin (phagocytes) was observed in the ooplasma. As oogenesis progressed, the synthesis of yolk gradually reduced the nucleus to cytoplasm ratio. In the final stages of oogenesis, the nucleus migrated to the extreme periphery of the oocyte adhering to the oolemma, and became indented. Nuclear migration and shape change may facilitate fertilization and determine the future embryonic axis. During oogenesis, the oocyte diameter increased from 25 to 1590 µm. Embryogenesis took place in the coelenteron. Formation of a blastocoel was not observed, and development proceeded via stereoblastulae with superficial cleavage. Gastrulation took place by delamination. Embryo diameter ranged from 550 to 1140 µm. Released larvae (length 1700 to 2000 µm) were observed in the field during summer, along the benthos.

Colony and polyp biometry and size structure in the orange coral Astroides calycularis (Scleractinia: Dendrophylliidae)

Abstract Coral polyps inside a colony may differ in reproductive activity and ecological function even while sharing the same genetic identity. Although polyps are the basic units of coral colonies, their size, biometry and size structure have rarely been studied. This study investigated, for the first time, colony and polyp biometric relationships and intra-colony polyp population size structure in the Mediterranean endemic Astroides calycularis (Pallas, 1766). Biometric parameters for 160 colonies and 4162 polyps were measured with consideration of polyp position inside the colony (central or peripheral). The positive allometric relationship between polyp width and length, resulting in a progressively circular oral disc as polyp size increases, may relate to the low-sedimentation characteristics of the habitat of this species. The smaller size of peripheral polyps compared to central ones suggests that polyp budding occurs preferentially at the outskirts of the colonies, possibly increasing the competitive advantage for space utilization. Larger colonies had polyps with smaller size than small and medium colonies, due to an over-representation of the size class containing polyp size at sexual maturity. It is proposed that large colonies may invest energy in increasing polyp size up to the size at sexual maturity, rather than increasing the size of already mature polyps.

Redox-Based Flagging of the Global Network of Oxidative Stress Greatly Promotes Longevity

Despite more than 50 years of investigations into the free radical theory, the direct role of oxidative stress (OS) in aging and age-related diseases remains unproven. Little progress in identifying antioxidant drugs promoting longevity has been made, likely due to selectivity toward one or few radical species, variable efficacy in vivo, inherent pro-oxidant behavior of such drugs, or lack of synergism with metabolic redox homeostasis. Silencing the wide range of reactive free radicals has a great impact on OS-linked outcomes and age-related disorders. Here we show that an innovative, redox-active, multi-radical-scavenger catalytic drug delays the age-associated decline in physiological processes and markedly prolongs the mean lifespan of the adult freshwater annelids Aeolosoma viride by 170%. This unprecedented extension is associated with a decreased OS status. Consistently, treatment of annelids increases their natural resistance to oxygen-derived damage without affecting mitochondrial respiration or reproductive activity. Conversely, the superoxide dismutase (SOD)-mimetic EUK 134 that we selected as a positive control led to an increase in lifespan of ~50%, the same increase previously observed in nematodes. Our results show that reduction of the global network of OS has a profound impact on aging, prompting the development of a possible redox-based therapeutic intervention to counteract the progression of aging.