Reaction times and force production during escape behavior of a calanoid copepod, Undinula vulgaris

Effective escape behavior contributes to the success of copepods in planktonic communities. The kinematics of escape were studied in tethered Undinulavulgaris (Calanoida) by analyzing the timing and magnitude of their power strokes to a precisely controlled, sudden mechanical perturbation in the surrounding water. Copepods responded with rapid swims to water velocities of 36 to 86 μm s⁻¹. Reaction times were under 2.5 ms following stimulus onset. The time course of force exerted was complex, but reproducible from stimulus to stimulus. Multiple power strokes (“kicks”) were frequently observed in response to single stimuli. Time intervals of 5 ms were observed between the end of one escape kick and the beginning of the next. U. vulgaris developed maximum forces of 40 to over 100 dynes (dyn) during a rapid swim. The behavioral reaction times and intervals between multiple responses observed in this calanoid are among the shortest reported in aquatic invertebrates. Received: 25 November 1997 / Accepted: 8 October 1998     

Organic residue decomposition: The minicontainer-system a multifunctional tool in decomposition studies

The Minicontainer-test, first described by Eisenbeis (1993), was designed to study the kinetics of organic residue decomposition at a microsite level. It is derived from the litterbag technique and consists of polyethylene minicontainers (volume about 1.5 cm³) filled with a test substrate (litter, straw, cellulose, etc.). The minicontainers (MCs) are closed at either end with plastic gauze discs of variable mesh size (e.g. 20 μm, 250 μm, 500 μm or 2 mm). A definite number of such units are inserted into PVC-bars, which can be implanted into the soil horizontally or vertically, or be exposed on the soil surface horizontally. The bars are very stable and can be exposed in different environments for months to years. If required, the bars can be removed temporarily and stored, e.g. during soil cultivation. Should fresh litter be used, two phases of decomposition can be distinguished: a fast initial phase, which can be mainly related to the effect of leaching, and a second slow phase depending mainly on the activity of soil organisms and litter quality. Several questions can be addressed to investigations using MCs, e.g. 1) parts of the soil fauna which are involved in decomposition (nematodes, microarthropods, and smaller specimens of the macrofauna, e.g. enchytraeidae, diplopods and dipteran larvae) can be extracted from the litter substrate using a miniscale high gradient extractor, 2) the organic mass loss of litter can be determined, 3) microbial biomass (C_mic, N_mic) can be assessed by fumigation extraction and 4) microbial activity (respiration) in the test substrate can also be assessed by use of standardised methods. Compared to litterbag studies, the larger number of small replicate units improves the statistical evaluation. Until today the Minicontainer-test has been applied in forestry and agriculture, e.g. studying the effects of liming, soil restoration and the application of insecticides, e.g. Diflubenzuron (Dimilin) and Btk (Bacillus thuringiensis var.kurstaki).     

A possible prenatal evaluation of renal function by amino acid analysis on fetal urine

Intrauterine treatment of 4 fetuses with urethral obstruction was attempted in the third trimester of pregnancy. The fetuses displayed varying sonographic findings including pyelectasis, caliectasis, hydroureter, bladder dilatation, ascites, hydrops, missing kidneys and oligohydramnios. Ultrasonically guided aspiration from the dilated structures was carried out to relieve pressure on the kidney parenchyme and to collect fluid samples for diagnostic purposes. Amino acid concentrations in the fetal urine showed a pattern similar to plasma in 2 fetuses, a pattern almost like urine in 1 fetus and an intermediate pattern in the 4th fetus. Only the fetus with normal amino acid concentrations in the urine survived: the other 3 died in uremia shortly after birth. In 3 cases cells from the aspirated urine were cultured and used for chromosome analysis. The cell cultures grew fast and karyotyping was possible within 1 week. In 2 fetuses an intrauterine catheter was inserted to drain the kidney permanently into the amniotic cavity. In the first case the catheter was displaced to the fetal abdomen after some days of successful drainage. In the second case the catheter tore the placenta, and the child had to be delivered immediately.     

Environmental information stored in otoliths: insights from stable isotopes

The present study compares the stable oxygen-and carbon-isotope ratios (¹⁸0:¹⁶O;¹³C:¹²C) in the otoliths of Atlantic cod,Gadus morhua, with those expected at equilibrium with seawater. Otoliths from juveniles reared for a 3 mo period under controlled conditions indicate that otoliths are formed in isotopic disequilibrium with seawater. This is probably due to positive metabolic fractionating of the heavier isotopes. This vital effect remains constant over the temperature range studied here (9 to 16°C) but may differ among other species. Our data indicate that the concentration of¹⁸O in calcium carbonate is inversely related to temperature and is described as ¹⁸O_a – _w – 3.79 – 0.200(T°C). The¹³C:¹²C ratios of otoliths and body tissues are related to the carbon ratio in the food source, although we found that the¹³C concentration is considerably higher in the otoliths relative te, the body tissues and the diet.