Postmortem metabolism of short-finned squid muscle (Illex illecebrosus)

Postmortem biochemical changes were examined in the mantle muscle of the short-finned squid (Illex illecebrosus) in relation to the physical events associated with rigor. Unlike mammalian muscle, the major muscle phosphagen is arginine phosphate rather than creatine phosphate. Arginine phosphate levels did not change dramatically during the progress of rigor development. ATP depletion was found to be closely related to glycogen depletion as is often observed in mammalian muscle. The postmortem accumulation of octopine was related to the initial muscle glycogen content at death but a significant lag in its production was observed. The postmortem conversion of glucose to glucose-6-phosphate appeared to be the rate-limiting step in the overall conversion of glycogen to octopine. The intermediates found in the postmortem catabolism of squid muscle ATP were ADP, AMP, IMP Ino and Hx. Unlike most vertebrate fishes, AMP was found to accumulate in squid before conversion to IMP whereas accumulations of IMP and Ino were less than those normally found in vertebrate muscle.     

A source of large axons for neurophysiology: the North Atlantic squid Illex illecebrosus.

A new axon preparation from the ommastrephid squid (Illex illecebrosusus (Lesueur)) is described. This squid is common in the Northwestern Atlantic and features a number of long, unbranched, and moderately large-diameter axons having no apparent 'twigging.' Although the diameters of these axons are somewhat smaller than those of 'giant' axons coming from some other species of squid, this axon preparation should be considered as an attractive alternative for neurobiologic research.     

Optical properties of a cephalopod eye (the short finned squid,Illex illecebrosus)

Summary The extent to which the cephalopod eye is optically similar to the teleost eye was determined by measuring refractive error, accommodative ability, spherical and chromatic aberrations, and refractive indices and radii of curvature of the ocular media. The squid eye is well corrected optically underwater although a tendency toward hyperopia exists. This may be due to the existence of chromatic aberration and the fact that an aquatic environment is somewhat limited to the blue end of the spectrum. Accommodation takes place by movement of the lens toward the retina in a manner similar to the teleost eye. However, the squid lens is not spherical but slightly flattened. The lens is overcorrected as far as spherical aberration is concerned. Thus peripheral light rays focus further from the lens than paraxial ones. The function of this unusual example of lens development is unknown.     

Climate change and temporal trends in body size: the case of rodents

A reduction in body size has been proposed as the third universal ecological response to global warming, after species distributional shifts and phenological changes. However, some recent studies raise doubts about the validity of this pattern, in particular for endotherms. Within this context, here we analyzed data on body mass (m_b) for 17 rodent species, covering (at least) the last six decades, together with data on temperature change and basal metabolic rate (BMR) for each species. We found that: 1) ten species (58.8%) showed no significant changes in m_b, while the remaining seven species (41.2%) decreased their size during the 20th century; 2) phylogenetic generalized linear mixed models indicate that there is a significant and negative effect of the year of collection on m_b; 3) the correlation coefficient between m_b and the year of collection (r_year) was not correlated with species mean m_b, species distributional range, the length of the time series, or the change in ambient temperature; and 4) the correlation between r_year and (residual) BMR was significant (and negative) only for species that do not use torpor. In summary, our results suggest that reductions in m_b are common among rodents, but we were unable to identify a clear cause behind these changes (e.g. some results support the energetic argument behind the Bergmann's rule but other do not). We concluded that with less than 0.5% of the extant (known) rodent species analyzed to date, we still are far from reaching a clear understanding of current patterns of variation in body size that are associated with global environmental change for this group.     

Active trends,passive trends,cope's rule and temporal scaling: New categorization of cladogenetic changes in body size

Regimes of cladogenetic change in body size recognized in the fossil record are related to the time scales over which they are observed. A new categorization of regimes of cladogenetic size change is proposed: this scheme includes seventeen types. In a random distribution, the pure, single‐cause regimes are rare (0.01 probability of appearance) while mixed regimes, resulting from the simultaneous operation of two or more causes are frequent (0.115 probability of appearance). Some regimes seem to be nonrandomly distributed.     

Determinants of territory size of the dusky gregory

To test the effect of food abundance and intruder pressure as determinants of territory size, the dusky gregory Stegastes nigricans were used as subjects on a coral reef in southern Taiwan during November to December 2000. Adults were used as intruders to provoke aggressiveness in a conspecific territory owner. The owner's maximum distance of attack (MDA) was used to delineate the territory size. While the owner of a territory appeared to defend a single boundary against different conspecifics, size variations among territories were evident. The effect of an intruder's identity on territory‐size regulation was not clear because for each territory examined, the MDA was found to be neither linked to the body size of the intruder nor to the amount of algae in the intruder's territory. Moreover, no significant differences were found between the MDAs that the owner maintained against neighbours and non‐neighbours even though, when conspecifics intruded in pairs, the probability was significantly higher for the first attack to be launched on a neighbour than on a non‐neighbour. Also when a neighbour and a non‐neighbour appeared simultaneously near the territory, the bite rate against the neighbour was also significantly higher. An inverse relationship between the amount of algae in the defended territory and the MDA of the owner indicates that food abundance might account for variations among territories. By contrast, territory size was not linked to the body size of the owner.     

Determinants of the size of aphid–parasitoid assemblages

Abstract:  Aphid parasitoids have to cope with a range of different life-history features of their hosts in terms of size at maturity, abundance, ant-attendance, host specificity, host alternation and many more. Their hosts often show large fluctuations in numbers during a season or in different habitats and the plants they live on strongly shape their performance. Plant characteristics (i.e. life form, ecological strategy, light exposure , nutrient provision, habitat type) also affects the environment of aphids and their associated parasitoids. Using data restricted to Central European aphids and their primary parasitoids, effort is directed to identifying significant ecological variables, which might influence the diversity of parasitoid assemblages in aphids. Most parasitoid species were reported from the Aphidini and Macrosiphini. Aphids, which are very abundant, host-alternating, polyphagous and live on grasses appear to support larger parasitoid assemblages than those which are less abundant, non-host-alternating, mono- or oligophagous and feed on trees or herbs. Obligate myrmecophiles support fewer parasitoids than facultative myrmecophiles. Different degrees of mobility, the production of wax wool and alate adults did not have significant effects on parasitoid numbers. Discriminant function analysis using different degrees of ant attendance as dependant variable indicated that aphid specific characters and the number of primary parasitoids contributed most to the separation of the groups. Plant specific characters seem to contribute little to the development of different degrees of myrmecophily and parasitization patterns.     

Evolutionary trends in body size of parasitic flatworms

Evolutionary trends in body size have been identified within several lineages, but not all have followed Cope's rule, which states that average body size within a taxon tends to increase over time. In organisms such as parasites, space constraints may have shaped the evolution of body sizes, favouring small-bodied taxa capable of exploiting new niches. Here, the average adult body sizes of families in three groups of parasitic flatworms, the Digenea and two clades of Monogenea (Monopisthocotylea and Polyopisthocotylea), are related to their clade rank. Clade rank reflects the number of branching events, and thus the total path length, between an extant family and the root of the phylogenetic tree. Among families of Digenea, all of which are endoparasites of vertebrates, there was no trend in body size evolution. In contrast, the Monopisthocotylea and Polyopisthocotylea, which are (with the exception of Polystomatidae and Sphyranuridae) ectoparasites of fish, revealed significant negative relationships between family body size and clade rank, suggesting an evolutionary trend of decreasing size. In addition, an analysis of body size distributions in monogenean families also provides support, albeit weak, for this trend. From an ancestor parasitic on the skin of fishes, monogeneans have diversified by colonizing other microhabitats on their hosts, including such space-limited sites as the gaps between secondary gill lamellae. Using a conservative likelihood ratio test, however, a random walk, or null model of evolution could not be discarded in favour of the directional trends mentioned above. Nevertheless, these results suggest that body size has taken different evolutionary paths in endo- and ectoparasitic flatworms.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 181–189.     

Temporal trends in the impact factor of European versus USA biomedical journals

Background

The impact factors of biomedical journals tend to rise over time. We sought to assess the trend in the impact factor, during the past decade, of journals published on behalf of United States (US) and European scientific societies, in four select biomedical subject categories (Biology, Cell Biology, Critical Care Medicine, and Infectious Diseases).

Methods

We identified all journals included in the above-mentioned subject categories of Thomson Reuters Journal Citation Reports® for the years 1999, 2002, 2005, and 2008. We selected those that were published on behalf of US or European scientific societies, as documented in journal websites.

Results

We included 167 journals (35 in the subject category of Biology, 79 in Cell Biology, 27 in Critical Care Medicine, and 26 in Infectious Diseases). Between 1999 and 2008, the percentage increase in the impact factor of the European journals was higher than for the US journals (73.7±110.0% compared with 39.7±70.0%, p = 0.049). Regarding specific subject categories, the percentage change in the factor of the European journals tended to be higher than the respective US journals for Cell Biology (61.7% versus 16.3%), Critical Care Medicine (212.4% versus 65.4%), Infectious Diseases (88.3% versus 48.7%), whereas the opposite was observed for journals in Biology (41.0% versus 62.5%).

Conclusion

Journals published on behalf of European scientific societies, in select biomedical fields, may tend to close the “gap” in impact factor compared with those of US societies.

What''s Already Known About This Topic?

The impact factors of biomedical journals tend to rise through years. The leading positions in productivity in biomedical research are held by developed countries, including those from North America and Western Europe.

What Does This Article Add?

The journals from European biomedical scientific societies tended, over the past decade, to increase their impact factor more than the respective US journals.     

Fish mouth dimensions and size selectivity in a Portuguese longline fishery

The relationship between fish total length (TL) and mouth size in six species was investigated in light of the implications for the modelling of size selectivity of hooks. Significant non-linear relationships were found in three species, suggesting that optimal size at capture is not a linear function of hook size. These results strongly support the choices made in modelling skew-normal selectivity with optimal size at capture as a function of hook size.     

Determinants of territory size in the pomacentrid reef fish,Parma victoriae

Summary Factors governing the size of territories defended by the pomacentrid reef fish, Parma victoriae, were investigated, prompted by contradictory predictions in the literature concerning the effects of food supply and competitors. Observations were carried out over the non-breeding period (March–October) on a medium density population in which territories were partially contiguous. The territory size of adult fish varied between 3 and 26 m², and was inversely correlated with local densities of conspecifics. The same range in territory size was found for both males and females, which did not differ in the time they spent on territory defence and foraging activities. No correlation existed between territory size and the abundance of algal food, body size, age or time spent on territory defence. Also, there was little variation in territory size over time, despite seasonal changes in the abundance of food algae.Experimental reduction of food supplies on isolated territories of males and females had no effect on territory size. In a higher density habitat an experiment was carried out in which population density and food abundance were simultaneously manipulated. This showed that territory size was primarily determined by intraspecific interactions, as territories exhibited considerable increases in size upon removal of neighbours. No changes in the size of defended areas resulted from either artificial increases or decreases of food levels. There were also no changes in the time spent on defence of territories, foraging time or feeding rates associated with food manipulations or territory expansion, which suggested that food was not a limited resource. This conflicted with current theories proposed to explain territory defence and expansion. It is hypothesized that intraspecific interactions constrain territory size well below the optimum in terms of the abundance of preferred food algal species.     

Effect of codend mesh size increases on the size selectivity of commercial species in a small mesh bottom trawl fishery

The effects of increasing codend mesh size from 11.6 to 25 and 28.7 mm (inside stretched mesh) on the selectivity of greater lizardfish (Saurida tumbil), squid (Loligo sp.), and penaeid shrimp caught by an inshore otter trawling fishery at Nha Trang City, Vietnam were assessed. The proportion of escaping trash fish from the studied codends was also examined. In general, the lengths at 50% retention (L₅₀) of the studied species increased with increasing codend mesh size. L₅₀ values of greater lizardfish for the 25 and 28.7 mm codends were 109.4 and 145.9 mm, respectively. The 11.6, 25, and 28.7 mm codends selected shrimp at L₅₀s of 8.33, 11.86, and 13.92 mm, respectively, and squid (mantle lengths) at 13.1, 36.1, and 41.9 mm, respectively. The mean proportions of escaping trash fish were 0.06, 0.68, and 0.85 for the three codends, respectively. A minimum mesh size of 25 mm is a good compromise between management goals and fishery demands.     

Spatial and temporal trends of global pollination benefit

Pollination is a well-studied and at the same time a threatened ecosystem service. A significant part of global crop production depends on or profits from pollination by animals. Using detailed information on global crop yields of 60 pollination dependent or profiting crops, we provide a map of global pollination benefits on a 5' by 5' latitude-longitude grid. The current spatial pattern of pollination benefits is only partly correlated with climate variables and the distribution of cropland. The resulting map of pollination benefits identifies hot spots of pollination benefits at sufficient detail to guide political decisions on where to protect pollination services by investing in structural diversity of land use. Additionally, we investigated the vulnerability of the national economies with respect to potential decline of pollination services as the portion of the (agricultural) economy depending on pollination benefits. While the general dependency of the agricultural economy on pollination seems to be stable from 1993 until 2009, we see increases in producer prices for pollination dependent crops, which we interpret as an early warning signal for a conflict between pollination service and other land uses at the global scale. Our spatially explicit analysis of global pollination benefit points to hot spots for the generation of pollination benefits and can serve as a base for further planning of land use, protection sites and agricultural policies for maintaining pollination services.     

A null model of temporal trends in biological invasion records

Biological invasions are a growing aspect of global biodiversity change. In many regions, introduced species richness increases supralinearly over time. This does not, however, necessarily indicate increasing introduction rates or invasion success. We develop a simple null model to identify the expected trend in invasion records over time. For constant introduction rates and success, the expected trend is exponentially increasing. Model extensions with varying introduction rate and success can also generate exponential distributions. We then analyse temporal trends in aquatic, marine and terrestrial invasion records. Most data sets support an exponential distribution (15/16) and the null invasion model (12/16). Thus, our model shows that no change in introduction rate or success need be invoked to explain the majority of observed trends. Further, an exponential trend does not necessarily indicate increasing invasion success or 'invasional meltdown', and a saturating trend does not necessarily indicate decreasing success or biotic resistance.     

Environmental and scale-dependent evolutionary trends in the body size of crustaceans

The ecological and physiological significance of body size is well recognized. However, key macroevolutionary questions regarding the dependency of body size trends on the taxonomic scale of analysis and the role of environment in controlling long-term evolution of body size are largely unknown. Here, we evaluate these issues for decapod crustaceans, a group that diversified in the Mesozoic. A compilation of body size data for 792 brachyuran crab and lobster species reveals that their maximum, mean and median body size increased, but no increase in minimum size was observed. This increase is not expressed within lineages, but is rather a product of the appearance and/or diversification of new clades of larger, primarily burrowing to shelter-seeking decapods. This argues against directional selective pressures within lineages. Rather, the trend is a macroevolutionary consequence of species sorting: preferential origination of new decapod clades with intrinsically larger body sizes. Furthermore, body size evolution appears to have been habitat-controlled. In the Cretaceous, reef-associated crabs became markedly smaller than those in other habitats, a pattern that persists today. The long-term increase in body size of crabs and lobsters, coupled with their increased diversity and abundance, suggests that their ecological impact may have increased over evolutionary time.