Georgina A. Rivera-Ingraham

Effect of Human Pressure on Population Size Structures of the Endangered Ferruginean Limpet: Toward Future Management Measures

Abstract Human predation has affected population size structures (in the sense of distribution of body size within particular populations), which has been used to track losses of larger and more fertile individuals from populations. In this sense, human exploitation can also decrease the reproductive output of invertebrate populations such as the endangered limpet Patella ferruginea. A total of 7077 individuals of this protected limpet were analysed among “Under custody” and “Without custody” sites, the strongest indication of human exploitation being the absence of a great number of larger limpets at “Without custody” sites. Likewise, recruitment was lower in “Without custody” than in “Under custody” sites, although the mean density was not affected. The presence of 4084 individuals inside the harbour area of Ceuta indicates the requirement of the involvement of harbour authorities and environmental agencies in a global conservation plan, establishing small fenced reserve areas in artificial breakwaters and natural substrates where dense populations are settled. These reserves could be useful as a focus for larval export via their previous rebalance of sex ratio.

The physiological response of the marine platyhelminth Macrostomum lignano to different environmental oxygen concentrations

SUMMARY The respiration rate of meiofauna is difficult to measure, and the response to variations in the environmental oxygen concentration has so far been mainly addressed through behavioral investigation. We investigated the effect of different oxygen concentrations on the physiology of the marine platyhelminth Macrostomum lignano. Respiration was measured using batches of 20 animals in a glass microtiter plate equipped with optical oxygen sensor spots. At higher oxygen saturations (>12 kPa), the animals showed a clear oxyconforming behavior. However, below this value, the flatworms kept respiration rates constant at 0.064±0.001 nmol O2 l−1 h−1 individual−1 down to 3 kPa PO2, and this rate was increased by 30% in animals that were reoxygenated after enduring a period of 1.5 h in anoxia. Physiological changes related to tissue oxygenation were assessed using live imaging techniques with different fluorophores in animals maintained in normoxic (21 kPa), hyperoxic (40 kPa) or near-anoxic (~0 kPa) conditions and subjected to anoxia–reoxygenation. The pH-sensitive dyes Ageladine-A and BCECF both indicated that pHi under near-anoxia increases by about 0.07–0.10 units. Mitochondrial membrane potential, Δψm, was higher in anoxic and hyperoxic than in normoxic conditions (JC1 dye data). Staining with ROS-sensitive dyes – DHE for detection of superoxide anion (O2•−) formation and C-H DFFDA for other ROS species aside from O2•− (H2O2, HOO• and ONOO) – showed increased ROS formation following anoxia–reoxygenation treatment. Animals exposed to hyperoxic, normoxic and anoxic treatments displayed no significant differences in O2•− formation, whereas mitochondrial ROS formation as detected by C-H2DFFDA was higher after hyperoxic exposure and lowest under near-anoxia conditions compared with the normoxic control group. Macrostomum lignano seems to be a species that is tolerant of a wide range of oxygen concentrations (being able to maintain aerobic metabolism from extremely low PO2 up to hyperoxic conditions), which is an essential prerequisite for successfully dealing with the drastic environmental oxygen variations that occur within intertidal sediments.

Updated global distribution of the threatened marine limpet Patella ferruginea (Gastropoda: Patellidae): an example of biodiversity loss in the Mediterranean

Patella ferruginea is the most threatened macroinvertebrate in the western Mediterranean, where it is at serious risk of extinction. There is little information on the status of the various populations and most data were published more than 25 years ago. This study provides updated information on the global status of this species, and implications for management and conservation, and tests the hypothesis that population structure can be influenced by collection by people and by the type of substrate. Fifty-five localities were surveyed in Corsica, Sardinia, Tuscany and Sicily, on the islands of Egadi and Pantelleria, and on the Zembra archipelago and Tunisian coasts. The species is extinct on mainland Italy and Sicily but isolated individuals can be found on Egadi and Pantelleria. Populations on Corsica and Sardinia have declined dramatically during the last 25 years. The population in the Zembra archipelago is well preserved, although more widely on Tunisian coasts the species is highly threatened. The information provided here, combined with information from the literature, indicates a strong decline and/or extinction of many populations throughout the western Mediterranean and the presence of healthy populations only in some locations along the north African coast. The species exhibits an increase in density and mean size in areas free of human pressure but the type of substrate (natural or artificial) has no strong influence.

Patterns of spatial genetic structuring in the endangered limpet Patella ferruginea: implications for the conservation of a Mediterranean endemic

Patella ferruginea Gmelin, 1791 is an endangered marine gastropod endemic to the Western Mediterranean. Its range is restricted to the Sardinian-Corsican region (SCR), North Africa, a few scattered sites in Southern Spain, and Sicily. Inter-simple sequence repeat (ISSR) markers and three different mitochondrial DNA (mtDNA) regions, Cytochrome c Oxidase subunit I, 12S (small-subunit ribosomal RNA gene) and 16S (large-subunit ribosomal RNA gene), were used to investigate the presence of genetic population structuring. The mtDNA sequences showed very low levels of genetic differentiation. Conversely, ISSRs showed the presence of two main genetic groups, corresponding to Spain, North Africa and Sicily and the SCR. The SCR was further split into two subgroups. The ISSR results suggest that, on a regional scale, the genetic structure of P. ferruginea is mainly determined by the restriction of gene flow by dispersal barriers. On a more local scale human harvesting may play a crucial role in population structuring by increasing the effect of genetic drift.

Seasonal activity and foraging behaviour of the endangered limpet Patella ferruginea

Patellid limpets are herbivorous gastropod molluscs found on temperate rocky shores where they are often the dominant grazers. An analysis of their behavioural traits is crucial for an understanding of the dynamics of intertidal communities. Patella ferruginea, endemic to the Mediterranean, is the most endangered marine macro-invertebrate on the Western Mediterranean rocky shores and it is, currently, under serious risk of extinction. However, little is known about the biology of the species. Individuals forage almost exclusively during high tide through all seasons and types of tide. The species has not been significantly influenced by tides, whereas the season, their size and the day/night cycle do influencing their behaviour. Small individuals show significantly shorter foraging excursions and less extension of their foraging areas than do larger ones. The geometry of their foraging paths shows a very low incidence of trail following that could be a mechanism to avoid passing over previously grazed areas.

Osmoregulation, bioenergetics and oxidative stress in coastal marine invertebrates: raising the questions for future research

ABSTRACT Osmoregulation is by no means an energetically cheap process, and its costs have been extensively quantified in terms of respiration and aerobic metabolism. Common products of mitochondrial activity are reactive oxygen and nitrogen species, which may cause oxidative stress by degrading key cell components, while playing essential roles in cell homeostasis. Given the delicate equilibrium between pro- and antioxidants in fueling acclimation responses, the need for a thorough understanding of the relationship between salinity-induced oxidative stress and osmoregulation arises as an important issue, especially in the context of global changes and anthropogenic impacts on coastal habitats. This is especially urgent for intertidal/estuarine organisms, which may be subject to drastic salinity and habitat changes, leading to redox imbalance. How do osmoregulation strategies determine energy expenditure, and how do these processes affect organisms in terms of oxidative stress? What mechanisms are used to cope with salinity-induced oxidative stress? This Commentary aims to highlight the main gaps in our knowledge, covering all levels of organization. From an energy-redox perspective, we discuss the link between environmental salinity changes and physiological responses at different levels of biological organization. Future studies should seek to provide a detailed understanding of the relationship between osmoregulatory strategies and redox metabolism, thereby informing conservation physiologists and allowing them to tackle the new challenges imposed by global climate change. Summary: From an energy-redox perspective, changes in environmental salinity induce a wide diversity of responses in marine invertebrates. Characterization of mitochondrial function may allow disentangling evolutionary adaptations to different marine environments

POPULATION DYNAMICS AND VIABILITY ANALYSIS FOR THE CRITICALLY ENDANGERED FERRUGINEAN LIMPET

ABSTRACT The current study deals with the critically endangered limpet Patella ferruginea (Gastropoda: Patellidae) endemic to the western Mediterranean. The species has been in decline since the early 20th century and is currently restricted to certain locations on the Iberian Peninsula, Corsica, Sardinia, and the North African coasts of Morocco, Algeria, and Tunisia. Its large size and conspicuous shell often makes the species a target of human collection. We describe the results of temporal monitoring conducted on one of the remaining most important P. ferruginea populations in North Africa, and provide quantitative data on growth rates, natural mortality, and harvesting rates. The maximum collection rates were recorded during the summer months, when fishermen most attend the beach. This type of mortality mostly affected medium and large individuals, and increased natural mortality rates up to 37%. All results and previously available data were implemented for population viability analysis. We determined that the species is clearly overexploited in the study area, and may face local extinction within the next 20 y if harvesting activities are not controlled. Even though more precise predictions could be obtained by using a longer time series, our study is the first attempt to model the future viability of the species, and indicates the urgent need of establishing efficient protection measures.

Osmoregulation and salinity-induced oxidative stress: is oxidative adaptation determined by gill function?

ABSTRACT Osmoregulating decapods such as the Mediterranean green crab Carcinus aestuarii possess two groups of spatially segregated gills: anterior gills serve mainly respiratory purposes, while posterior gills contain osmoregulatory structures. The co-existence of similar tissues serving different functions allows the study of differential adaptation, in terms of free radical metabolism, upon salinity change. Crabs were immersed for 2 weeks in seawater (SW, 37 ppt), diluted SW (dSW, 10 ppt) and concentrated SW (cSW, 45 ppt). Exposure to dSW was the most challenging condition, elevating respiration rates of whole animals and free radical formation in hemolymph (assessed fluorometrically using C-H2DFFDA). Further analyses considered anterior and posterior gills separately, and the results showed that posterior gills are the main tissues fueling osmoregulatory-related processes because their respiration rates in dSW were 3.2-fold higher than those of anterior gills, and this was accompanied by an increase in mitochondrial density (citrate synthase activity) and increased levels of reactive oxygen species (ROS) formation (1.4-fold greater, measured through electron paramagnetic resonance). Paradoxically, these posterior gills showed undisturbed caspase 3/7 activity, used here as a marker for apoptosis. This may only be due to the high antioxidant protection that posterior gills benefit from [superoxide dismutase (SOD) in posterior gills was over 6 times higher than in anterior gills]. In conclusion, osmoregulating posterior gills are better adapted to dSW exposure than respiratory anterior gills because they are capable of controlling the deleterious effects of the ROS production resulting from this salinity-induced stress. Summary: Gill tissues with different functions (respiratory/osmoregulatory) differentially produce reactive oxygen species and are differently adapted to deal with oxidative stress.

Antioxidant Defenses and Trace Metal Bioaccumulation Capacity of Cymbula nigra (Gastropoda: Patellidae)

The present study deals with the effect of trace metals on the endangered limpet Cymbula nigra. The Bay of Algeciras (Strait of Gibraltar) was used as the study site. Important industrial activity takes place in the area, including frequent oil spills. However, it is home to important populations of C. nigra. The objective of this work was to determine if these animals were being affected at a subcellular level by the pollutants present in their environment and to analyze the trace metal concentrations in the animal’s soft tissues. To determine the effects of water quality on the antioxidant activity and concentrations through field experimentation, a total of six sites were selected in Algeciras Bay, three located in the inner areas (environmentally degraded sites with higher levels of pollutants) and three in the outermost areas of the Bay. Stress associated to reactive oxygen species formation was assessed on digestive glands and gills as the enzymatic antioxidant activity of catalase (CAT), superoxide dismutase (SOD), and glutathione S-transferase (GST) and as the concentrations of lipid-soluble (α-tocopherol and β-carotene) and the water-soluble antioxidants (reduced and oxidized glutathione (GSH and GSSG)). Gills and digestive glands of those animals located in the inner areas of Algeciras Bay showed higher CAT activity values than those located in the outer areas. As a general pattern, we observed higher antioxidant activities and concentrations in digestive glands that in gills, suggesting the possibility that pollutants are mainly being incorporated by limpets through the food. As a general rule, larger animals showed greater concentrations of these compounds. Iron, zinc, and manganese, in this order, were present in the tissues at the highest concentrations. Chromium and manganese were found in significantly higher concentrations in those animals collected from the inner areas of the Bay. Through the present study, we provide the first data regarding the antioxidant defense levels and metal accumulation capacity of this species, and we reinforce the idea that this endangered species may be, in fact, relatively tolerant to degraded environments.

Ecological considerations and niche differentiation between juvenile and adult black limpets ( Cymbula nigra )

The endangered patellid limpet Cymbula nigra is present in the extreme western Mediterranean, yet the species has rarely been the subject of study in this region. The aim of the present research is to describe the ecology, distribution and population structure of the species in an area of the Mediterranean coast of North Africa (Ceuta). Results indicate that the species prevails in waters that have an important Atlantic influence. Furthermore, different shell morphologies are distinguished, and in consequence, a statistical analysis is carried out based on morphometric data. Based on maximum shell length, height/length coefficients and shell morphology, a total of three significantly different morphologies are described. Furthermore, considering physical parameters such as height over seawater level and average substratum inclination, juveniles resulted to be clearly segregated from the two other groups. Additionally, no differences were found regarding the topography of the substrate used by juvenile and adult individuals, although the colonized surfaces are significantly smoother than those where Patella ferruginea is present.