Relations between morphology, buoyancy and energetics of requiem sharks

Sharks have a distinctive shape that remained practically unchanged through hundreds of millions of years of evolution. Nonetheless, there are variations of this shape that vary between and within species. We attempt to explain these variations by examining the partial derivatives of the cost of transport of a generic shark with respect to buoyancy, span and chord of its pectoral fins, length, girth and body temperature. Our analysis predicts an intricate relation between these parameters, suggesting that ectothermic species residing in cooler temperatures must either have longer pectoral fins and/or be more buoyant in order to maintain swimming performance. It also suggests that, in general, the buoyancy must increase with size, and therefore, there must be ontogenetic changes within a species, with individuals getting more buoyant as they grow. Pelagic species seem to have near optimally sized fins (which minimize the cost of transport), but the majority of reef sharks could have reduced the cost of transport by increasing the size of their fins. The fact that they do not implies negative selection, probably owing to decreased manoeuvrability in confined spaces (e.g. foraging on a reef)

Digestive enzyme activities in the guts of bonnethead sharks (Sphyrna tiburo) provide insight into their digestive strategy and evidence for microbial digestion in their hindguts

Few investigations have studied digestive enzyme activities in the alimentary tracts of sharks to gain insight into how these organisms digest their meals. In this study, we examined the activity levels of proteases, carbohydrases, and lipase in the pancreas, and along the anterior intestine, spiral intestine, and colon of the bonnethead shark, Sphyrna tiburo. We then interpreted our data in the context of a rate-yield continuum to discern this shark's digestive strategy. Our data show anticipated decreasing patterns in the activities of pancreatic enzymes moving posteriorly along the gut, but also show mid spiral intestine peaks in aminopeptidase and lipase activities, which support the spiral intestine as the main site of absorption in bonnetheads. Interestingly, we observed spikes in the activity levels of N-acetyl-β-d-glucosaminidase and β-glucosidase in the bonnethead colon, and these chitin- and cellulose-degrading enzymes, respectively, are likely of microbial origin in this distal gut region. Taken in the context of intake and relatively long transit times of food through the gut, the colonic spikes in N-acetyl-β-d-glucosaminidase and β-glucosidase activities suggest that bonnetheads take a yield-maximizing strategy to the digestive process, with some reliance on microbial digestion in their hindguts. This is one of the first studies to examine digestive enzyme activities along the gut of any shark, and importantly, the data match with previous observations that sharks take an extended time to digest their meals (consistent with a yield-maximizing digestive strategy) and that the spiral intestine is the primary site of absorption in sharks.PostprintPeer reviewe

Gamification of Authoring Interactive E-Books for Children: The Q-Tales Ecosystem

The e-book industry is reshaping the norm of traditional book publishing and most publishing houses are concentrating their efforts in digital, in order to satisfy new market needs and capture significant market share. Currently, one of out of five e-books sold, are children-related and overall, the e-book industry is projected to be valued at $18.9 billion by 2018. Nevertheless, the increased market penetration of independent writers accompanied with continuous technological improvements leads to new challenges for the stakeholders involved, as a growing number of individuals with limited resources attempt to compete against traditional publishing houses. The Q-Tales ecosystem aims to support the community of creative professionals, experts and parents co-create new (or transform existing) children literature into high quality interactive e-books. At this new disruptive approach of self-publishing, the gamification paradigm was employed, creating game-like experiences, to motivate professionals participate in the process and adopt it. The present study focuses on the gamification aspect of Q-Tales as means to drive engagement with the entire ecosystem and promote its appropriate use, enhancing the overall goal of creating interactive children e- books. The gamification design of the Q-Tales distributed system for collaborative authoring of interactive e-books for children is presented and discussed as a case study of gamification of electronic services. More specifically, game elements, such as points, leaderboards, badges, missions and feedback were infused in the architectural units of the platform, in correspondence to the overall development of the Q-Tales Gamification Framework

Serum Lp(a) Lipoprotein Levels in Patients with Atherosclerotic Occlusive Disease of the Lower Extremities

AbstractObjective to evaluate the association between Lp(a) lipoprotein levels, other serum lipids and the presence of lower limb atherosclerotic occlusive disease. Materials and methods angiographic findings in 36 patients were related to serum Lp(a). Total cholesterol, triglycerides, LDL-cholesterol, HDL-cholesterol and Lp(a) levels were compared with those of 73 age- and sex-matched healthy controls. Results atheromatous lesions were localised in the femoropopliteal (≈60%) and aortoiliac (≈40%) segments. The number of stenosed arteries was ≥2 and the range of stenosis severity was between 40% and 100%. There was a significant increase in serum Lp(a) (p= 0.000001) and a decrease in serum HDL (p= 0.000009) levels in patients compared to controls. No difference was observed in total cholesterol, LDL-cholesterol or triglyceride. However, the ratio of total cholesterol/HDL-cholesterol was significantly higher (p= 0.005) in patients. Conclusion a dyslipidaemic serum profile, characterised by increased Lp(a) levels and decreased HDL-cholesterol levels, is associated with atherosclerotic occlusive disease of the lower extremities

The Response of Gastric pH and Motility to Fasting and Feeding in Free Swimming Blacktip Reef Sharks, Carcharhinus melanopterus

In many fish and reptiles, gastric digestion is responsible for the complete breakdown of prey items into semi-liquid chyme. The responses of the stomach to feeding and to periods of fasting are, however, unknown for many lower vertebrates. We inserted data loggers into the stomachs of free-swimming captive adult blacktip reef sharks (Carcharhinus melanopterus) to quantify gastric pH, motility and temperature during fasting and following ingestion of food. Gastric acid secretion was continuous, even during long periods of fasting, with a mean pH of 1.66 ± 0.40 (± 1 SD) when the stomach was empty. Stomach contractions were greater following meals of mackerel than for those of squid. Gastric motility following feeding on mackerel, was positively influenced by ambient temperature, and followed a quadratic relationship with meal size, with maximum motility occurring after meals of 0.8–1.0% body weight. Diel changes in gastric motility were apparent, and were most likely caused by diel changes in ambient temperature. Gastric digestion in blacktip reef sharks is affected by both biotic and abiotic variables. We hypothesize that behavioral strategies adopted by sharks in the field may be an attempt to optimize digestion by selecting for appropriate environmental conditions

Spin Content of the Quantum Soliton

The classical soliton solution, quantized by means of suitable translational and rotational collective coordinates, is embedded into the one-particle irreductible representation of the Poincare group corresponding to a definite spin. It is shown, that within the conventional quasiclassical expansion such embedding leads to a set of nontrivial consistency conditions imposed on the classical solution. The validity of these relations is considered for a number of soliton models in 2+1- and 3+1-dimensions.Comment: 10 pages, Standard LaTe

Etmopterus lailae Sp Nov., a New Lanternshark (Squaliformes: Etmopteridae) from the Northwestern Hawaiian Islands

A new species of lanternshark, Etmopterus lailae (Squaliformes: Etmopteridae), is described from the Northwestern Hawaiian Islands, in the central North Pacific Ocean. The new species resembles other members of the “Etmopterus lucifer” clade in having linear rows of dermal denticles, and most closely resembles E. lucifer from Japan. The new species occurs along insular slopes around seamounts at depths between 314–384 m. It can be distinguished from other members of the E. lucifer clade by a combination of characteristics, including a longer anterior flank marking branch, arrangement of dermal denticles on the ventral snout surface and body, flank and caudal markings, and meristic counts including number of spiral valve turns, and precaudal vertebrate. A key to species of the Etmopterus lucifer-clade is included

Multiyear social stability and social information use in reef sharks with diel fission–fusion dynamics

Animals across vertebrate taxa form social communities and often exist as fission–fusion groups. Central place foragers (CPF) may form groups from which they will predictably disperse to forage, either individually or in smaller groups, before returning to fuse with the larger group. However, the function and stability of social associations in predatory fish acting as CPFs is unknown, as individuals do not need to return to a shelter yet show fidelity to core areas. Using dynamic social networks generated from acoustic tracking data, we document spatially structured sociality in CPF grey reef sharks at a Pacific Ocean atoll. We show that sharks form stable social groups over multiyear periods, with some dyadic associations consistent for up to 4 years. Groups primarily formed during the day, increasing in size throughout the morning before sharks dispersed from the reef at night. Our simulations suggest that multiple individuals sharing a central place and using social information while foraging (i.e. local enhancement) will outperform non-CPF social foragers. We show multiyear social stability in sharks and suggest that social foraging with information transfer could provide a generalizable mechanism for the emergence of sociality with group central place foraging