Individual Variation in the Covering Behaviour of the Shallow Water Sea Urchin Paracentrotus lividus

Abstract. A number of recent field‐based studies have investigated the possible functions of covering behaviour in a range of echinoid species. Some of these have found important relationships between covering behaviour and environmental factors, such as light (in particular, ultra‐violet light) and covering item availability. However, these studies have often shown considerable within‐species variation, thus making covering functionality both within and between species difficult to interpret. The present study experimentally investigates individual variability in covering behaviour characteristics of the sea urchin Paracentrotus lividus (Lamarck). Data were collected bimonthly over a 1‐year period at Lough Hyne, Ireland, by observing P. lividus in outdoor aquaria. Significant variations in covering behaviour characteristics were observed as a function of individual size and mobility but not as a function of sex. A significant relationship between water temperature, mobility and covering behaviour was also found and is hypothesized to have implications for grazing activity in P. lividus. In contrast to previous field studies of P. lividus at Lough Hyne, no summer ‘peak’ in the proportion of individuals covering was observed. However, there was a significant relationship between local solar radiation and ‘time to first cover’. Overall, these data highlight (i) the ecological significance of individual variation in P. lividus covering behaviour and (ii) the importance of investigating multiple factors as potential determinants of echinoid covering behaviour.     

Patterns of Activity of the Sea Urchin Paracentrotus lividus in the Bay of Port-Cros (Var, France, Mediterranean)

Abstract. Tagged individuals of the sea urchin Paracentrotus lividus followed in Port Cros Island showed mostly nocturnal movements, with individual peaks of activity which were not coordinated for the population during the night period. The straight line distance travelled in 24 h has a mean value of 49 cm, with a range of 0 to 240 cm. Neither sea urchin size nor depth affect activity. The urchins living on rocky substrate moved significantly more than those on seagrass beds. From one day to another, the distance travelled by the population of urchins varies significantly; this is not related to season. The activity is negatively correlated with the mean wind speed; during a period of turbulence lasting several hours, movement was significantly oriented to the deep. Periods of inactivity of 1 or 2 days were observed; they are not coordinated for the individuals followed, and the relation between feeding and movement is not clear. Urchins seem to stay in a quite small area, at least for some months.     

Seasonal Variation in the Covering ­Behaviour of the Echinoid Paracentrotus lividus (Lamarck)

Abstract. Covering behaviour is displayed by several regular echinoid species but its functional significance has yet to be quantified. Some of the most popular theories have interpreted this behaviour as an adaptive response to avoid over-exposure to light and/or as an anti-predator strategy. Since both predation pressure and light intensity may be seasonal as well as diurnal in nature, the aim of the present study was to quantitatively examine, in situ , the potential seasonality of covering behaviour in the purple sea urchin, Paracentrotus lividus (Lamarck). Data were collected over a one-year period at Lough Hyne, Co. Cork in Ireland. A peak in covering activity was observed over the summer months. Predator density and light intensity (sunlight hours) were also shown to vary seasonally at Lough Hyne. Covering behaviour in P. lividus , as in other echinoids, may be a response to a number of simultaneously interacting factors. At Lough Hyne, however, light intensity and covering item availability appear to be particularly important factors.     

Seasonal Changes in Gonad Index,Biochemical Composition and Heavy Metal Determination of Sea Urchin Paracentrotus lividus Gonads from the South Coast of Morocco

Ocean Science Journal - Seasonal variations of the gonad index (GI), the biochemical composition, and the concentration of heavy metals in the gonads of the sea urchin, Paracentrotus lividus...     

Movement patterns of the sea urchin Paracentrotus lividus in a marine reserve and an unprotected area in the NW Mediterranean

Sea urchins can alter the composition and dynamics of algal communities by grazing. Changes in their displacement capability can influence their grazing and thus their effect on algal communities. The daily and monthly movement of Paracentrotus lividus inside and outside a marine reserve in the NW Mediterranean Sea was studied in order to determine the role of predation in sea urchin movements and its potential grazing impacts. During the 3‐month study, the total distance travelled by sea urchins ranged from 71.8 to 673.6 cm (mean = 379.2 cm, SD = 221.3). Home ranges (distances from the initial position) were between 50 and 302 cm (mean = 150.7 cm, SD = 99.4). Movements were not directional but random, with a mean of 150 cm around the initial position. The activity of Paracentrotus lividus was significantly higher at night than during daylight. Total displacement at the end of the experiment was significantly higher in the unprotected area than in the reserve, as was the home range. The linear distance travelled in a 24‐h period ranged between 6 and 220 cm with a mean home range of 51 cm. These results agree with those of other authors, and allow us to rule out major migratory processes of sea urchin populations in this area. Nevertheless, these results underline the role of predatory fishes in reducing herbivory pressure by trophic cascades, reinforcing the evidence that sea urchin escape behaviour may be an important factor in structuring algal communities.     

山东田横岛海域长牡蛎性腺发育及生化成分周年变化

为了阐明青岛近海长牡蛎(Crassostrea gigas)性腺发育周期及生化成分周年变化,于2019年4月—2020年3月,对青岛田横岛海区长牡蛎的性腺发育周期、生化成分(糖原、脂肪、蛋白质)的周年变化与环境因子(温度、盐度、叶绿素a)关系进行研究。研究显示,调查区长牡蛎性腺发育周期分为两个阶段:休止期(10—12月)和配子发生期(1—9月)。少部分长牡蛎配子发生于温度较低的1月(5.4℃),随着温度升高配子逐渐发育成熟,在6月温度较高(20℃)和叶绿素a浓度较大(1.67μg·L^-1)情况下,配子进入排放期。在配子发生期间,随着配子的成熟,条件指数和卵径在5月达到最大值,在配子排放后降低。生化成分含量为:在冬末春初浮游植物繁殖期间糖原含量储存在长牡蛎各组织中,随着性腺发育,各组织的糖原含量逐渐下降,为配子发育提供能量,这表明贮藏在各组织的糖原是配子发生期间的主要能源物质;性腺-内脏团的脂肪和蛋白质含量随着卵径增加呈上升趋势,产卵后其含量显著下降,表明脂肪和蛋白质与配子发育密切相关。研究结果表明,田横岛海域长牡蛎配子的发育方式为保守种模式。     

The Boreholes of the Sea Urchin Genus Echinometra (Echinodermata: Echinoidea: Echinometridae) as a Microhabitat in Tropical South America*

Abstract. Members of the genus Echinometru (Echinoideu: Echinometridue) inhabit hard substrata in shallow waters where they live in self-excavated dwellings. Boring by Echinometru spp. causes a secondary structure of the surface, thus forming additional microhabitats. In this study the effects of boring activities of Echinometru lucunter (L.) along the Caribbean coast of Colombia and of Echinometra vunbrunri A. Agassu in the Colombian Pacific is examined. Several species inhabit the boreholes occupied by these urchins. The associates live underneath the echinoid on the bottom of the borehole, where they find shelter from exposure and predators. The co-inhabitants of E. lucunter include the porcellanid Clusroroechus vunderhorsri (Schmitt ), the recently described brit-tlestar Ophiorhrix synoecim (Schoppe ), and the clingfish Acyrrus rubiginosus (Poey ). The species co-occumng with E. vunbrunti include the porcellanid crab Clusroroechus gorgonensis Werding amp; Haig and the clingfish Arcos decoris Briggs . With the exception of A. decoris, all of these species are obligatorily associated with the Echinomerra host.     

Seasonal variation of a molluscan assemblage living in a Caulerpa prolifera meadow within the inner Bay of Cádiz (SW Spain)

The molluscan macrofauna living in shallow muddy bottoms with the green algae Caulerpa prolifera was studied monthly between February 1994 and January 1996 in the inner Bay of Cádiz (SW Spain). The molluscan assemblage followed a similar pattern over the 2 years, displaying seasonal trends in species richness, abundance and structure. During the autumn and winter months, a decrease in abundance, species richness and diversity and an increase in evenness occurred. During the spring and summer months, the molluscan assemblage was characterised by an increase in species richness, abundance and diversity. These seasonal trends were supported statistically by the presence of significantly different groupings of seasonal samples in multivariate analyses.Despite human impacts in the bay (e.g. aquaculture activities, sewage), the presence of repetitive seasonal trends, based on the qualitative and quantitative data, indicates the stability of the molluscan assemblage over 2 years. Benthic characteristics from the inner Bay of Cádiz, such as shallow soft bottoms with the presence of macrophytes and current dynamics, seem to be key factors influencing the composition and seasonality of this molluscan assemblage.     

龙须岛浪蚀花岗岩潮间带大型底栖藻类群落的季节变化模式

采用样方法对龙须岛浪蚀花岗岩潮间带进行了2年的生态学调查。龙须岛浪蚀花岗岩潮间带大型底栖藻类群落的种类组成存在着明显的季节变化 ,群落中最高和较高的藻类物种数量出现在4～8月 ,而最低值出现在10月份。在所有季节中红藻类群种类最为丰富 ,其次是褐藻 ,绿藻最少。群落中生物量的季节变化序列如下 :8月>10月>6月>12月>4月>2月。群落的生物量和各藻类类群的生物量的季节变化与龙须岛潮间带的海水温度变化相吻合 ,只有红藻类群的生物量在8月份略有下降。群落中大型底栖藻类的区系成分和优势种群存在着显著的季节波动或更替。总体来看 ,龙须岛浪蚀花岗岩潮间带大型底栖藻类群落的区系成分以暖温带成分为主 ,其次为冷水性成分、暖水性成分、温带成分和亚寒带成分。大型底栖藻类群落的物种丰富度指数季节变化序列依次为 :4月>6月>8月>2月>12月>10月 ,物种多样性为 :4月>6月>8月>2月>10月>12月 ,均匀度指数为 :4月>10月>2月>6月>8月>12月。龙须岛浪蚀花岗岩潮间带大型底栖藻类群落的季节变化可划分为3个季相 :“肠浒苔、珊瑚藻、石莼为优势种的冬、春季藻类群丛”、“鼠尾藻、石莼、珊瑚藻为优势种的夏季藻类群丛”和“石莼、叉枝藻、鼠尾藻为优势种的秋季藻类群丛”。潮间带海水的温度的季节变化是导致     

The Effect of Temporal Changes and Environmental Trophic Condition on the Isotopic Composition (ω13C and ω15N) of Atherina boyeri (Risso, 1810) and Gobius niger (L., 1758) in a Mediterranean Coastal Lagoon (Lake of Sabaudia): Implications for Food Web Structure

Abstract. ω¹³C and ω¹⁵N of organic matter sources and consumers were employed to analyse trophic differentiation between a benthic consumer, Gobius niger (L., 1758) (Pisces, Osteichthyes), and a pelagic consumer, Atherina boyeri (Risso, 1810) (Pisces, Osteichthyes) in a Mediterranean coastal lagoon (Lake of Sabaudia) in winter and summer 1999. Trophic differences between the two species throughout the two sampling periods were related to the environmental trophic condition (i. e. nutrient and phytopigment concentrations). Although these two fish have different habitats, they both exploited benthic organisms, above all in summer. When the nutrient and phytopigment concentrations were higher (summer), the most abundant benthic organisms were the main food sources for both species. In winter A. boyeri apparently shifted its feeding preferences to include zooplankton, confirming its opportunistic feeding strategy. Par-ticulate organic matter and algae seemed to play the main trophic role in the food web structure. Benthic invertebrates used both sources, while zooplankton seemed to rely exclusively on the particulate fraction. The overlapping and very depleted signatures of sedimentary and particulate organic matter highlights a strong link between sediments and water column, rarely observed in other aquatic ecosystems using stable isotopes. Such a finding further substantiates the importance of particulate organic matter as a food source in the study area.     

青岛湾潮间带活体底栖有孔虫Ammonia aomoriensis (Asano,1951)壳体δ18O值的季节变化

近岸浅水底栖有孔虫是陆架海区古环境重建的重要手段,但是至今对其活体的研究非常缺乏。2014年6月至2015年5月对青岛湾潮间带活体底栖有孔虫Ammonia aomoriensis进行了连续12个月的采样,用虎红染色以确认活体。对壳径范围在200~550μm的活体壳体,以每增加50μm壳径为一组,进行δ18O测试。结果显示,A.aomoriensis壳体δ18O的月平均值的季节变化趋势与温度和盐度一致,与温度反相关,与盐度正相关,即青岛湾A.aomoriensis壳体δ18O值受温度和海水δ18O的影响,其壳体δ18O值表现出了很好的季节性波动。但是A.aomoriensis壳体δ18O的变化滞后于所测温度和盐度约2个月,其记录的是虫体在生长周期内在真实钙化温度下分馏所得的δ18O值。