Lessons from the past: Evolutionary impacts of mass extinctions

Mass extinctions have played many evolutionary roles, involving differential survivorship or selectivity of taxa and traits, the disruption or preservation of evolutionary trends and ecosystem organization, and the promotion of taxonomic and morphological diversifications—often along unexpected trajectories—after the destruction or marginalization of once-dominant clades. The fossil record suggests that survivorship during mass extinctions is not strictly random, but it often fails to coincide with factors promoting survival during times of low extinction intensity. Although of very serious concern, present-day extinctions have not yet achieved the intensities seen in the Big Five mass extinctions of the geologic past, which each removed ≥50% of the subset of relatively abundant marine invertebrate genera. The best comparisons for predictive purposes therefore will involve factors such as differential extinction intensities among regions, clades, and functional groups, rules governing postextinction biotic interchanges and evolutionary dynamics, and analyses of the factors that cause taxa and evolutionary trends to continue unabated, to suffer setbacks but resume along the same trajectory, to survive only to fall into a marginal role or disappear (“dead clade walking”), or to undergo a burst of diversification. These issues need to be addressed in a spatially explicit framework, because the fossil record suggests regional differences in postextinction diversification dynamics and biotic interchanges. Postextinction diversifications lag far behind the initial taxonomic and morphological impoverishment and homogenization; they do not simply reoccupy vacated adaptive peaks, but explore opportunities as opened and constrained by intrinsic biotic factors and the ecological and evolutionary context of the radiation.

Life in the end-Permian dead zone

The fossil record of land plants is an obvious source of information on the dynamics of mass extinctions in the geological past. In conjunction with the end-Permian ecological crisis, ≈250 million years ago, palynological data from East Greenland reveal some unanticipated patterns. We document the significant time lag between terrestrial ecosystem collapse and selective extinction among characteristic Late Permian plants. Furthermore, ecological crisis resulted in an initial increase in plant diversity, instead of a decrease. Paradoxically, these floral patterns correspond to a “dead zone” in the end-Permian faunal record, characterized by a paucity of marine invertebrate megafossils. The time-delayed, end-Permian plant extinctions resemble modeled “extinction debt” responses of multispecies metapopulations to progressive habitat destruction.

Global change and climate-driven invasion of the Pacific oyster (Crassostrea gigas) along European coasts: a bioenergetics modelling approach

Aim The spread of non-indigenous species in marine ecosystems world-wide is one of today's most serious environmental concerns. Using mechanistic modelling, we investigated how global change relates to the invasion of European coasts by a non-native marine invertebrate, the Pacific oyster Crassostrea gigas. Location Bourgneuf Bay on the French Atlantic coast was considered as the northern boundary of C. gigas expansion at the time of its introduction to Europe in the 1970s. From this latitudinal reference, variations in the spatial distribution of the C. gigas reproductive niche were analysed along the north-western European coast from Gibraltar to Norway. Methods The effects of environmental variations on C. gigas physiology and phenology were studied using a bioenergetics model based on Dynamic Energy Budget theory. The model was forced with environmental time series including in situ phytoplankton data, and satellite data of sea surface temperature and suspended particulate matter concentration. Results Simulation outputs were successfully validated against in situ oyster growth data. In Bourgneuf Bay, the rise in seawater temperature and phytoplankton concentration has increased C. gigas reproductive effort and led to precocious spawning periods since the 1960s. At the European scale, seawater temperature increase caused a drastic northward shift (1400 km within 30 years) in the C. gigas reproductive niche and optimal thermal conditions for early life stage development. Main conclusions We demonstrated that the poleward expansion of the invasive species C. gigas is related to global warming and increase in phytoplankton abundance. The combination of mechanistic bioenergetics modelling with in situ and satellite environmental data is a valuable framework for ecosystem studies. It offers a generic approach to analyse historical geographical shifts and to predict the biogeographical changes expected to occur in a climate-changing world.

Inventaire des invertébrés marins de l'Indochine (1ʳᵉ liste)

A first list of the marine invertebrate species collected along the coast of Nhatrang (Vietnam) is presented.

Diagnosis of vibriosis in the era of genomics: lessons from invertebrates

Global changes linked to increases in temperature and ocean acidification, but also to more direct anthropogenic influences such as aquaculture, have caused a worldwide increase in the reports of Vibrio-associated illnesses affecting humans and also animals such as shrimp and molluscs. Investigation of the emergence of Vibrio pathogenesis events requires the analysis of microbial evolution at the gene, genome and population levels, in order to identify genomic modifications linked to increased virulence, resistance and/or prevalence, or to recent host shift. From a more applied point of view, the elucidation of virulence mechanisms is a prerequisite to devising prophylactic methods to fight infectious agents. In comparison with human pathogens, fairly little is known about the requirements for virulence in vibrios pathogenic to animals. However, the advent of genome sequencing, especially next-generation technologies,the possibility of genetically manipulating most of the Vibrio strains, and the recent availability of standardised animals for experimental infections have now compensated for the considerable delay in advancement of the knowledge of non-model pathogens such as Vibrio and have led to new scientific questions.

Biodiversidad estacional del macrozoobentos mesolitoral de fondos blandos en la playa de Salaverry, La Libertad – Perú

La biodiversidad del macrozoobentos en el mesolitoral de la playa de Salaverry se determinó durante setiembre 2015 a marzo 2016. Se establecieron cuatro transectos (A, B, C y D) y se fijaron tres estaciones. Además se determinó la biodiversidad estacional a través de los índices de Shannon - Wiener (H'), Margalef (d'), Equidad de Pielou (J'), Simpson (λ) y de Similitud de Bray- Curtis. Las muestras fueron colectadas quincenalmente, utilizando un cilindro de Penchaszadeh de 0,028 m2. Asi también se tomaron datos de temperatura, salinidad y granulometría. Las especies se identificaron utilizando claves taxonómicas de invertebrados marinos. Se registraron especies de las clases Polychaeta, Nemertea, Gastropoda, Bivalvia y Malacostraca (Subphylum Crustacea). La biodiversidad del macrozoobentos para primavera fue de 2,51 bits/ind y para verano de 1,91 bits/ind con una riqueza de 22 especies.

Antibacterial marine bacterium deter luminous vibriosis in shrimp larvae

Inhibitory activity of a marine pigmented bacterium - Alteromonas sp. - isolated from Penaeus monodon Fabricius larva against pathogenic and environmental isolates of Vibrio harveyi was studied. All the isolates were inhibited to varying degrees by Alteromonas sp. in vitro. The antibacterial substance produced by the Alteromonas sp. was soluble in organic solvent and closely bound to the external surface of bacterial cells. The antibacterial Alteromonas sp., when allowed to colonize on shrimp larvae, suppressed the activity of V. harveyi M3 and reduced mortality of P. monodon larvae in vivo.

The Russell Cycle. An update and review of trends in zooplankton and fish larvae off Plymouth 1924-2009. Occasional Publication of the Marine Biological Association 24

Regular plankton sampling off Plymouth by the Marine Biological Association (MBA) has been carried out from the early 1900s. Much of the sample analysis and description of the results was carried out by Sir Frederick Russell and Professor Alan Southward (AJS), the latter having completed the organisation and transfer of the paper records to digital files. The current authors have transferred the main data files of AJS on zooplankton and fish larvae to the MBA long-term database (including various editing and checking against original analysis records and published data) together with adding the data for 2002-2009. In this report the updated time-series are reviewed in the context of earlier work, particularly with respect to the Russell Cycle. It is not intended as an exhaustive analysis. Brief details of the sampling and comments on data processing are given in an appendix.

Culture and Nutritional Enrichment of the Rotifer Brachionus Rotundiformis ( Tschugunoff ) for the Rearing of Marine Fin Fish and Shrimp Larvae

The present study is an attempt to standardize the environmental condition like pH, salinity and photoperiod, and also the feed for the maximum production of rotifers. Considering the deficiency of essential fatty acids in rotifers, enrichment experiments were carried out and fatty acids profile were analysed. Attempts were made to improve the production of clown fish (Amphiprion sebae) juveniles using enriched rotifers. Attempts were also made to rear various larval stages of Penaeus monodon with enriched rotifers as a substitute for Artemia nauplii.

Invertebrate larval dynamics in seasonally closed estuaries

Estuarine benthic assemblages are often numerically dominated by polychaetes. The limits of these populations are determined by larval, and probably to a lesser extent adult movement. A previous study (Newton 1996), indicated that planktonic polychaete larvae were very abundant over the summer months in the Hopkins River; however, the identification and source of these larvae was not known. Defining the extent of a population, and therefore the likelihood of that population recovering following a perturbation, is crucial for effective estuarine management. This study investigated both the likely source of the larvae, (i.e. estuarine or marine) and the extent of larval dispersal within and between estuaries by addressing the following questions: Which taxa produced the planktonic larvae? Are these taxa resident estuarine species? Are the larvae of different taxa evenly distributed within the estuary or do physicochemical parameters or other factors influence their abundance? Are the same larvae found in other estuaries along the coast? and Is there exchange of these larval taxa with the marine environment and other estuaries? Larvae were identified and described by culturing commonly occurring planktonic larvae until adult characteristics appeared. The spionids, Carazziella victoriensis and Prionospio Tatura, numerically dominated the plankton in the Hopkins and the spionid, Orthoprionospio cirriformia was recorded from the Hopkins, Curdies and Gellibrand estuaries. Two spionids, Carazziella sp. and Polydora sp. were identified from tidal waters. Mouth status and physicochemical conditions (salinity, temperature and dissolved oxygen) were monitored in each estuary. Whereas the Merri and Gellibrand estuaries were predominantly stratified over the sampling period, the Curdies was more often well mixed and the Hopkins varied from well mixed to stratified. The duration of mouth opening and hence the opportunity for larval exchange also varied in each estuary. The Merri River was closed for 13.5% of days over the study period, the Gellibrand River for 18.4%, the Hopkins River for 49% and the Curdies River for 71.0%. The distributions of larvae at spatial scales of metres, 100s of metres and kilometres were investigated within a single estuary. While the same larvae, C. victoriensis, P. Tatura and bivalve larvae, were found along the length of the Hopkins estuary the abundances varied at different spatial scales suggesting different processes were influencing the distribution of P. Tatura larvae, and C. victoriensis and bivalve larvae. The distribution of larvae between several estuaries was investigated by monitoring meroplankton at two sites at the mouth of each of the four estuaries approximately monthly (except for winter months). Different meroplanktonic assemblages were found to distinguish each estuary. Further, C. victoriensis and P. Tatura larvae were only recorded in the Hopkins but larvae of the spionid, Orthoprionopio cirriformia were detected in the Hopkins, Curdies and Gellibrand estuaries. The extent of larval exchange with other estuaries and the marine environment was determined by monitoring tidal waters. Settlement trays were also deployed to determine if larvae were moving into estuaries and settling but not recruiting. P. tatura larvae were not detected in the tidal waters of any estuary and while C. victoriensis and O. cirriformia were found in both flood and ebb tides there was no evidence of movement of theses taxa to other estuaries. Larvae of the spionids, Carazziella sp. and Polydora sp., were found in tidal waters of each estuary but were rarely detected in the plankton within the estuaries. Neither species was found as an adult in background cores from any estuary, nor with the exception of a few individuals in the Merri, were they detected in settlement trays in any estuary. I conclude that the source of the larvae of C. victoriensis, P. Tatura and O. cirriformia is estuarine and while C. victoriensis, and O. cirriformia move in and outh of the source estuary in tidal waters there was no evidence for movement to other estuaries. The spionids, Carazziella sp. and Polydora sp were considered to be marine and while they moved in and out of estuaries in tidal waters they did not usually settle in the estuaries. The results of this study are a crucial first step in the development of ecological models to better understand dispersal in seasonally closed estuaries that are typical of southern Australia. This study emphasises the unique physicochemical characteristics and biological assemblages within these estuaries and the need for estuarine management to reflect these differences.