Behavioral thermoregulation by Ammocoete larvae of the sea lamprey (Petromyzon marinus) in an electronic shuttlebox

Ammocoete larvae of the sea lamprey Petromyzon marinus, a member of the primitive vertebrate class Agnatha, were tested for thermoregulatory behavior in an electronic shuttlebox (ichthyotron). The final preferendum derived from pooled data for 24 individually tested ammocoetes was characterized by a mean of 13.6 ± 0.17 (s.e.m.)°C, a mode and median of 140°C, and a range of voluntarily occupied temperatures from 10–19°C over a 3-day period.     

Synthesis of a cytosine nucleoside of 2-amino-2-deoxy-beta-D-xylofuranose.

1-(2-Amino-2-deoxy-beta-D-xylofuranosyl)cytosine (13) was synthesized by three routes: (a) coupling of 2-deoxy-3,5-di-O-p-nitrobenzoyl-2-(trifluoroacetamido)-D-xylofuranosyl chloride (5) with 2,4-dimethoxypyrimidine and subsequent treatment with methanolic ammonia, (b) coupling of 5 with 4-N-acetyl-2-O,4-N-bis(trimethylsilyl)cytosine followed by treatment with methanolic ammonia, and (c) thiation of 1-[3,5-di-O-acetyl-2-deoxy-2-(trifluoroacetamido)-beta-D-xylofuranosyl]uracil (6) by treatment with phosphorus pentasulfide in pyridine followed by amination of the resulting 4-thionucleoside 12 with metanolic ammonia. The best yield was obtained via route (a).     

Appearance of lymphocyte surface markers and functional responses in neonatal and young rabbit spleens

We examined spleen cells from newborn to 1-month-old rabbits for easily detectable surface immunoglobulin, complement receptors, and for in vitro proliferative responsiveness to anti-immunoglobulin antisera and several mitogens. From birth through the first month of life about 15% of the cells from rabbit spleens had easily detectable surface immunoglobulin while about 45% had C3 receptors. In adults as many as 77% of the spleen cells had easily detectable surface Ig but the proportion with C3 receptors remained about 45%. The proliferative response to anti-allotype antisera was present at birth, and was at adult levels by 1 month of age. The proliferative response to pokeweed mitogen was low when cells were obtained during the first week of life but was comparable in magnitude to the response of adult cells by 2 weeks of age. In vitro responsiveness to concanavalin A was present at low levels at birth and increased sharply during the first week. We did not observe significant stimulation of spleen cells from neonatal to 4-week-old rabbits by lipopolysaccharide from Salmonella typhosa. Our data suggest that lymphocyte surface markers and functional responses appear asynchronously in spleen cells of developing rabbits.     

Studies on plasma membranes. XXIII. Hormone-like action of concanavalin A on liver plasma membranes: inhibition of (Na+-K+)ATPase.

Concanavalin A inhibits the (Na+-K+)-ATPase activity of isolated rat-liver plasma membranes, while leaving the Mg2+-ATPase unaffected. Glucagon and cyclic AMP act supplementary to the lectin in the inhibition. The lectin effect is counteracted by insulin and L-epinephrine, and is completely abolished by the beta-adrenergic blocking agent propranolol. Results are discussed on the basis of the known interactions of concanavalin A with plasma membrane components, including its hormone-like action.     

A new method for determination of elastolytic activity using (14C) labeled elastin and its application to leukocytic elastase.

A new, highly sensitive and specific assay for elastolytic activity is described which employs insoluble elastin randomly labeled with [¹⁴C]. The substrate was prepared by labeling amino groups of the protein in vitro with [¹⁴C] methyl groups by reductive alkylation. The substrate was used to quantitate elastolytic activity from human leukocytes and to compare leukocytic elastase with pancreatic elastase. Purified human leukocytic elastase was approximately one-fourth as active as pancreatic elastase. Similar difference between leukocytic elastase and pancreatic elastase activities was found when the enzymes were tested against succinyl-L-alanyl-L-alanyl-L-alanine-p-nitroanilide, but not when t-BOC-L-alanine-p-nitrophenyl ester was used.     

The Influences of Environment, Mating Habitat, and Predation on Evolution of Pinniped Lactation Strategies

Seals have adapted their social systems and lactation strategies to marine environments that include open and ice-covered oceans, high and low productivity, extremes in seasonality, and ocean- and terrestrial-type predators. Different explanations for the variation in pinniped lactation systems have been proposed but tests of alternative hypotheses have not sufficiently accounted for phylogeny and body size. After controlling for this variation, I predicted that environment, mating habitat, and predation would yield a fuller explanation. Lactation traits, duration, pup growth rate, and fat content were significantly influenced by both body size and phylogeny, which together explained 20–69% of the variation. After controlling for this variation, initial results did not support the environment hypothesis, as no differences in lactation traits were found between species living in polar (≥60°N) versus equatorial (<60°N) environments. In contrast, seals that nurse in areas of Arctic sea ice contending with ice-hunting predators, such as polar bears, had relatively short lactation compared to species living in the Antarctic and more equatorial regions. Also, the availability of predator-free islands for terrestrial mating and parturition was related to a harem mating system, increased sexual size dimorphism (SSD), and slow juvenile growth rates, less fat in milk, and longer lactation. Using structural equation modeling, latitude and size of harems provided independent explanations for all three lactation traits. Thus, use of islands in ice-free waters, predation in Arctic ice-covered waters, and more milk fat in high-latitude seals together provided adequate explanations for the evolution of lactation diversity among pinnipeds.     

Concepts and analysis of mass extinction with the late Ordovician event as an example

Twelve groups of fossils, including graptolites, brachiopods, nautiloids, trilobites, corals, crinoids, bryozoans, conodonts, ostracods, gastropods, chitinozoans, and acritarchs expired in different but substantial magnitude and global extent during the late Caradoc to latest Ashgill. It indicates a multiple‐episodic mass extinction containing the possible Prologue (late Caradoc), Climax episode (Rawtheyan) and Epilogue (late Hirnantian). The main causes of this mass extinction are recognized as a global sea‐level lowering in the climax and remarkable rapid rise at the final, and global cooling. The Chinese data, especially from the South China Paleoplate, are evaluated first. They are significant for explaining this global bioevent.     

Pockmarks enhance deep‐sea benthic biodiversity: a case study in the western Mediterranean Sea

Aim Pockmarks are craters on the sea floor formed by sub‐sea‐floor fluid expulsions, which occur world‐wide at all ocean depths. These habitats potentially host a highly specialized fauna that can exploit the hydrocarbons released. Pockmarks at relatively shallow depths can be easily destroyed by human activities, such as bottom trawling. In the present study, we investigated the combined effects of sea‐floor heterogeneity, rate of fluid emission and trophic conditions of different pockmarks on the biodiversity of the deep‐sea assemblages. Location Continental slope of the Gulf of Lions, western Mediterranean Sea, at water depths from 265 to 434 m. Methods We investigated the biodiversity associated with sea‐floor pockmarks that are both inactive and that have active gas emissions. Control sites were selected on the sea floor outside the influence of the gas seepage, both within and outside the pockmark fields. We examined the combined effects of: (i) sea‐floor heterogeneity; (ii) variable levels of fluid (gas) emissions; and (iii) trophic characteristics of the meiofaunal assemblage structure and nematode diversity. Results Sediments within the pockmark fields had lower meiofaunal abundance and biomass when compared with the surrounding sediments that were not influenced by the gas seepage. Although several higher taxa were absent in the pockmarks (e.g. Turbellaria, Tardigrada, Cumacea, Isopoda, Tanaidacea, Nemertina and Priapulida, which were present in the control areas), the richness of the nematode species within all of these pockmarks was very high. About 25% of the total species encountered in the deep‐sea sediments of the investigated areas was exclusively associated with these pockmarks. Main conclusions We conclude that both active and inactive pockmarks provide significant contributions to the regional (gamma) diversity of the continental slope in the western Mediterranean Sea, and thus the protection of these special and fragile habitats is highly relevant to the conservation of deep‐sea biodiversity.