Occurrence of 2-Aminobutanoic Acid in the Incubation Medium of Mixed Rumen Ciliate Protozoa1

An unknown, ninhydrin-positive substance detected on paper chromatograms of the endogenous metabolites of mixed rumen ciliate protozoa was isolated and purified by column chromatography with ‘Dowex’ 50-X8 resin and identified as 2-aminobutanoic acid (α-amino-n-butyric acid) on the basis of elementary analysis, mass spectrometry, paper chromatography, infrared spectrometry, and melting point.     

Effect of Bicuculline on the GABA Receptor of the Crayfish Neuromuscular Junction

SINCE it was reported that bicuculline is a specific antagonist of γ-aminobutyric acid (GABA)^1–3, much attention has been paid to the action of this alkaloid on cortical neurones^4–6. Thus it seemed worthwhile to test the mode of action of bicuculline on the inhibitory neuromuscular junction of the crayfish, where the action of GABA has been well documented^7,8.     

How to recognize in situ fossil cephalopods: evidence from experiments with modern Nautilus

Field and flume experiments with modern Nautilus pompilius establish two prerequisites to recognize in situ preservation of fossil cephalopod shells (soft parts were within body chamber in situ at the time of fossilization): occurrence of the upper jaw within the body chamber and the position of jaws within the body chamber. Morphology of shells and jaws in modern and fossil nautiloids is so similar that these prerequisites can be applied for fossil nautiloids and provide implications for ammonoids. The upper jaws of Nautilus start to move at a water velocity of > 0.2 m/s, when the shells are reoriented with the aperture downstream; jaws are therefore unlikely to be secondarily deposited near the shell aperture by bottom currents. The lower jaws, moved at the velocity of > 0.1 m/s, can be deposited around the shell aperture by weak current (0.1–0.2 m/s in velocity), but never enter the inside of body chamber. Neither jaw is likely to be separately and selectively displaced from the inside of the body chamber through scavenging of the soft parts by burrowing infaunal animals. An upper jaw preserved inside the body chamber, together with a lower jaw, is thus a reliable indicator of in situ preservation; a sole lower jaw preserved around the shell aperture is likely to be secondarily deposited. Sedimentary structures inferring rapid burial events and jaw size are useful as additional evidence. Smaller jaws were more likely to be displaced from the body chamber by scavenging by infaunal animals after in situ burial, so that smaller jaws preserved within the body chamber suggest less scavenging. These findings are crucial to interpreting the taphonomic history and palaeo-ecology of fossil cephalopods.     

Experimental fragmentation patterns of modern Nautilus shells and the implications for fossil cephalopod taphonomy

Shells of modern Nautilus pompilius from the Philippines were experimentally fragmented designed to mimic: (1) transport with sediment; (2) sediment loading; and (3) collision during floating. The breaking patterns by other mechanisms (predation and implosion by hydrostatic pressure) documented in the literature were also considered. The breaking patterns produced by various mechanisms are distinct and can therefore be differentiated. The results allow identification of the distinct mechanisms responsible for specific fragmentation not only in modern Nautilus but also in fossil cephalopods. This is a new approach for the more complete recognition of post-mortem transport of fossil cephalopods and their early taphonomic history, and contributes to our understanding of their palaeobiogeography and palaeoecology.     

Growth Factors of Bacterial Origin for the Culture of the Rumen Oligotrich Protozoon, Entodinium caudatum

Attempts were made to develop an artificial medium suitable for axenic culture of Entodinium caudatum. Agnotobiotic cultures of the protozoon were established as stock cultures for testing the suitability of various growth media. A cell-free extract of mixed bacteria isolated from the rumen was shown to contain one or more growth factors for the protozoon when supplied with activated charcoal as a carrier. The medium (CYSE medium), which supported the growth of the protozoon in the presence of 50 μg/ml each of penicillin and chloramphenicol, consisted of activated charcoal (20 mg), heat-treated yeast (Y) (80 mg), 13%β-sitosterol-coated rice starch (S) (120 mg), and cell-free extract of rumen bacteria (1 ml) in 40 ml buffer solution. When culturing the protozoon, the CYSE medium was supplemented daily with 20 mg each of Y and S and half of the medium was replaced with fresh medium once every 5 d. The possible use of this method to establish an axenic culture of E. caudatum is discussed.     

In Vitro Production of Lysine from 2,2'-Diaminopimelic Acid by Rumen Protozoa

Rumen protozoa can produce lysine from free 2,2'-diaminopimelic acid (DAP). However, the quantitative importance of this transformation has been disputed; lysine contents of protozoal incubation supernatants reported by Onodera & Kandatsu [12] and Masson & Ling [9] show a 26-fold difference. The in vitro experimental methods of both groups were compared to determine the causes of this difference. Lysine production was proportional to DAP concentration. Results with rumen protozoa from sheep or goats were similar. The incubation medium and deproteinizing procedure of the Welsh group gave a two-fold increase in lysine production compared with Japanese protocols. Omissions of rice starch from protozoal incubations slightly increased lysine production, whereas omissions of antibacterial agents resulted in varying, yet relatively small changes. The greatest cause of the difference was the number of rumen protozoa incubated. When this factor was taken into account, the difference in the maximum rates of lysine production between the Welsh and Japanese groups was only three-fold, namely 4.5 versus 15.0 nmol lysine/10⁵ protozoa/h. Adding other amino acids to the incubations suggested that DAP uptake by rumen protozoa may occur via transport system ASC. The importance of DAP metabolism by protozoa as a source of lysine for ruminant host animals is discussed.     

Intraspecific variation of hatchling size in Late Cretaceous ammonoids from Hokkaido,Japan: implication for planktic duration at early ontogenetic stage

Tajika, A. & Wani, R. 2011: Intraspecific variation of hatchling size in Late Cretaceous ammonoids from Hokkaido, Japan: implication for planktic duration at early ontogenetic stage. Lethaia, Vol. 44, pp. 287–298. Intraspecific variations of the early shell dimensions (ammonitella and protoconch diameters) of two Late Cretaceous (earliest Campanian) ammonoid species (Gaudryceras tenuiliratum and Hypophylloceras subramosum) from the Haboro and Ikushumbetsu areas, Hokkaido, Japan, show no significant difference between these areas that are approximately 110 km apart. The geographic distributions of G. tenuiliratum and H. subramosum are supposed to be mainly controlled by the flotation and transportation during the embryonic stage within floating egg masses and/or post‐embryonic stage because of their small hatchling sizes (1.18–1.46 mm in diameter for G. tenuiliratum, and 0.91–1.13 mm in diameter for H. subramosum), suggesting these two ammonite species at the embryonic and/or post‐embryonic stages were transported at least 110 km. Postulating that the velocity of palaeocurrent around the Haboro and Ikushumbetsu areas during the Cretaceous Period was 0.25 m/s, similar to those in the modern ocean current flowing off the eastern Pacific coast of Hokkaido, the egg masses and/or hatchlings of G. tenuiliratum and H. subramosum were buoyant and transported more than 5 days. The preliminary comparison of hatchling size through time suggests that the hatching sizes of H. subramosum in Hokkaido increased slightly from the Middle Turonian until the earliest Campanian (during about 7 Myr). □ammonoid, hatchling, paleoecology, variation, Cretaceous.     

Formation of 2-Aminobutanoic Acid from Threonine and Methionine by Mixed Rumen Ciliate Protozoa

Precursors of 2-aminobutanoic acid (2-ABA), found in the incubation medium of mixed rumen ciliate protozoa, were examined with washed or starved bacteria-free ciliates. Threonine and methionine strongly stimulated the formation of 2-ABA. Formation of 2-ABA by direct conversion of threonine and dethiomethylation of methionine was confirmed by radiotracer experiments with [U-¹⁴C]L-threonine and [carboxyl-¹⁴C] and [methyl-¹⁴C]L-methionine.     

Occurrence and density of Halobates micans (Hemiptera: Gerridae) in the eastern South Indian Ocean

Two species of ocean skaters, Halobates germanus and Halobates micans, live in the tropical and subtropical waters of the Indian Ocean. From December 1992 to December 1993, Halobates was intensively sampled in the easternmost region of the South Indian Ocean (13–18.5°S, 114–121E°), from which there have been a small number of records of Halobates. No H. germanus was caught, but a total of 1190 H. micans were collected, with densities estimated at 13 900–28 100 individuals/km². This suggests that H. micans lives in the study area at high densities comparable to those in the Atlantic and the Pacific Oceans. We also discuss the possible effects of ocean currents and winds on the geographic distributions of the two Halobates species in the eastern South Indian Ocean.