Biochemical adaptations of the stout razor clam Tagelus plebeius to changes in oxygen availability: resilience in a changing world?

Climate change is producing sea level rise and deoxygenation of the ocean, altering estuaries and coastal areas. Changes in oxygen availability are expected to have consequences on the physiological fitness of intertidal species. In this work we analyze the coping response of the intertidal razor clam Tagelus plebeius (Lightfoot, 1786) to extreme environmental changes in oxygen concentration. Their biochemical responses to normoxia, hypoxia and hyperoxia transition at different intertidal level (low- high) were measured through an in situ transplant experiment. The high intertidal level negatively affected the analyzed T. plebeius populations´ traits. The differences in reactive oxygen species production, total oxyradical scavenger capacities and catalase activity also suggested more stressful conditions at the high level where long-term hypoxia periods occur. Both hypoxia and re-oxygenation provoked re-adjustments in the antioxidant responses and higher lipid oxidative damage (normoxia < hypoxia < re-oxygenation). The observed responses in transplanted clams at the opposite intertidal level suggested the potential acclimation of T. plebeius to cope with new environmental conditions. These findings are discussed within a global changing context where both increasing deoxygenation conditions and sea level rise are predicted to be exacerbated in the area driven by climate change challenges.

A new solitary, interstitial species of Loxosomatidae (Entoprocta) from the coast of Galicia (NW Spain), Loxosoma discoides n. sp.

A new solitary species of Loxosomatidae (Entoprocta), Loxosoma discoides n. sp., is described. The specimens were found in the intertidal level of two locations in the Galician (NW Spain) coast. This new species, with “table-tennis bat” appearance, is characterised by showing large lateral wings in the calyx, which confer the singular aspect. It is the first record of this genus at the coast of the Iberian Peninsula.

Spatial distribution and abundance of Hemigrapsus crenulatus (H. Milne Edwards, 1837) (Decapoda, Varunidae) in the Puerto Cisnes estuary (44°S, Aysen region, Chile)

Our knowledge on the status of Hemigrapsus crenulatus (H. Milne Edwards, 1837) populations along the Chilean coast is scarce. The aim of the present study was to quantitatively estimate the spatial distribution and abundance of Hemigrapsus crenulatus in the Puerto Cisnes estuary (44°S, Aysen region, Chilean Patagonia). The spatial distribution appeared to be aggregated, with 3.64 ± 7.99 ind/m2 as gross density, and 10.50 ± 10.62 ind/m2 as a potential ecological density, i.e., if the quadrants with zero individuals are not taken into consideration. The equation of the negative binomial distribution was: where: . The average density of Hemigrapsus crenulatus under stones is lower if all beach surfaces are considered. Its abundance or dominance on estuarine beaches probably would be due to the fact that this species is one of the crustaceans of the lower intertidal level that can survive under a wide range of salinity values.

Invasión de un poliqueto nativo en una isla del Pacífico Oriental Tropical

Fluctuations in population dynamics, like demographic expansions and invasions, are relatively common in ecosystems, and in certain cases may affect biodiversity and a suite of other ecological attributes. In this paper, we report the appearance and population explosion of the reef-building polychaete (Sabellariidae) Idanthyrsus cf. cretus in Gorgona Island (Eastern Tropical Pacific), describing some ecological characteristics (abundance and coverage). The survey was carried out in three study areas of Gorgona Island, located in the Colombian Pacific. Sampling was performed randomly at low, mid and high intertidal levels, in order to measure density and coverage. Density was measured randomly in three study areas at low, mid and high intertidal levels collecting samples (N=37) of 100 cm2 from the colony. Coverage was measured using random transects (N=21) per locality and intertidal levels (20 m length × 1 m width). A total of 1,904 I. cf. cretus were collected with a mean density of 73 ind./100 cm2. Coverage was statistically different between intertidal zones, with the highest values in the mid-intertidal level (11%). Differences in coverage of I. cf. cretus colonies among study areas are probably due to differing intertidal physical characteristics: the availability of adequate substrate and building materials in the study areas sediments, which in turn might affect abundance and colony size. Suitable substrate and construction material might have favored the rapid spreading and local invasion of this species.

Foraminíferos Bentônicos do Estuário de Cacha-Prego Ilha de Itaparica, Bahia, Brasil

The Cacha-Prego estuary is a spit built coastal feature of Holocene age located in the Itaparica Channel (Todos os Santos Bay, Bahia State) and does not present any river input, hence, any fresh water that flow into the estuary is associated with the seeping water table. The thalweg is under wide variations in salinity, characteristic of a mixohaline-euhaline environment. On the other hand, the upper intertidal areas showed salinity levels typical of euhaline environment. The benthic foraminifera assemblage is represented by 71 species, while the living microfauna is composed of 19 species. Most of the living species were found within mangrove swamps, at the upper intertidal level, which were not exposed to brackish low-tide flows. The foraminifera assemblage distribution in the Cacha-Prego estuary is heterogeneous and reflects different microhabitats. In spite of the importance of the allochthonous elements transported into the estuary by the prevailing flood tidal flows, the autochthonous elements, represented by common species typical of paralic environments, were dominant in the estuary.

Bentho-pelagic distribution of early stages of softshell clams (Mya arenaria) in tidally contrasted regimes

We examined the settlement and recruitment of the softshell clam (Mya arenaria L., 1758) in two tidally contrasted regimes in eastern Canada. The Bay of Fundy (strong tides) and the Northumberland Strait (weak tides) were used to describe the distribution of planktonic larvae and early settlers. These distributions were compared with those of juvenile and adult forms observed in the same intertidal habitats. Results showed that the abundances of planktonic stages were the same at all tidal levels except in one site of the Bay of Fundy. Early settlers varied according to a site × intertidal level interaction. Juveniles and adults also varied according to a similar interaction, most being in the upper intertidal level. Simple linear regressions demonstrated that no relationship exists between the number of planktonic larvae and the number of early settlers. The only significant relationship observed was the one between the number of juveniles (1–5 mm size class) and the number of adults in one of the Northumberland Strait sites. Our results show, through the high spatial resolution and wide range of spatial scales covered by the study, that the dominant regional tidal regime does not have an effect on the distribution of the softshell clam. Local hydrodynamic effects appear to drive the intertidal distribution of the softshell clam life-cycle stages.

New observations on Loxosomella tonsoria, with notes on distribution and host specificity of the genus

Loxosomella tonsoria (Entoprocta: Loxosomatidae) was found associated with the polynoid polychaete Lepidonotus clava collected among the algae and debris scraped from the intertidal level at the rocky shore of Limens (Pontevedra, Spain). New features are added to the original description, together with the first description of its buds. Host specificity of the genus and distribution of this species are discussed.

Periwinkle (Gastropoda: Littorinidae) habitat selection and its impact upon microalgal populations

The present study examines habitat selection and grazing pressure of the periwinkle Nodilittorina lineolata (Gmelin, 1791) on the rocky shore of Arraial do Cabo, RJ, Brazil (lat. 23°S, long. 43°W). Transfer experiments suggest that periwinkles actively select the mid intertidal, where the cirripede Chthamalus bisinuatus Pilsbry is the dominant sessile invertebrate. We also conducted a caging experiment in the middle intertidal, manipulating grazers and light, to assess the impact of grazing upon microalgal density. Grazing pressure significantly reduced microalgal abundance at the mid-intertidal level, suggesting that food availability plays an important role in the habitat selection of periwinkles on the studied shore.

The role of pre-recruitment processes in the maintenance of a barnacle (Chthamalus challengeri Hoek) patch on an intertidal pebble shore in Japan

To understand the role of pre-recruitment processes (supply of larvae and recruitment) in the maintenance of an intertidal barnacle (Chthamalus challengeri Hoek) patch, the availability of cyprid larvae and the recruitment on natural pebble substrata was monitored on the Magarisaki pebble shore (Amakusa, Kyushu, Japan) during 1995 and 1996. Also, a hypothesis that predation and/or bulldozing by mobile intertidal mollusks during the post-recruitment period could be an important factor in mortality of these barnacles was tested. The collapse of the adult population and the consequent disappearance of the patch were observed by the middle of 1995. The larval availability was low (<FONT FACE="Symbol">@</FONT> 6 cyprid larvae/100 l), as was the recruitment (<FONT FACE="Symbol">@</FONT> 30 recruits/25 cm²). The recruits experienced high mortality, preventing them becoming adults able to maintain the patch. In 1996, a similar pattern of availability of the cyprid larvae, and even lower recruitment occurring only at the upper intertidal level was observed. A mobile mollusks exclusion experiment failed to detect any significant differences among the treatments, supporting the null hypothesis that the observed pattern of distribution was not caused by predation by mobile mollusks. There is my suggestion that the low availability of larvae and the low level of recruitment caused the non-maintenance of the patch.

Ecology and Distribution of Two Sympatric, Closely Related Sponge Species, Halichondria Panicea (Pallas, 1766) and H. Bowerbanki Burton, 1930 (Porifera, Demospongiae), with Remarks on their Speciation

North Atlantic coastal waters harbour two closely related sympatric sponges belonging to the genus Halichondria, viz. H. panicea and H. bowerbanki. From the study of their littoral and sublittoral microdistribution and ecology in the Oosterschelde area ( = Eastern Scheldt, S.W. part of The Netherlands) it is concluded that both occupy largely similar niches, although it was found that H. panicea is better equipped to endure exposure to air since it occurs up to a higher intertidal level than H. bowerbanki, while the latter is better equipped to withstand siltation. Other environmental factors as depth, light, current velocity and salinity affect the distribution and behaviour of both species similarly. From these observations it can be inferred, that speciation from a parent species cannot have been sympatrically through ecological segregation of individuals. The possibilities of geographical isolation of populations of a parent species on both sides of the Atlantic Ocean during past glacial periods resulting in an originally American species (H . bowerbanki) and an originally European species (H. panicea) are discussed.