Isolation and cloning of DNA from somatic tissue of soft corals (Cnidaria: Octocorallia)

A method is described for isolating high molecular weight DNA from somatic tissue of soft corals. The method avoids problems associated with the presence of nucleases, pigments and other secondary metabolites in soft corals. Tissue is frozen in liquid nitrogen, pulverized with a pestle and mortar, and the powder extracted with buffered sodium dodecyl sulphate at 4°C in the presence of phenol/chloroform. This technique has been applied toAlcyonium, Sinularia, Sarcophyton andLobophytum species. Repeated sequences have been cloned fromAlcyonium sp., and used to probe slot-blots of genomic DNA and Southern blots of restriction digests. Homologous repeated sequences were detected in threeAlcyonium sp., but not in threeSinularia sp., despite these genera being closely related.     

Ingestion-independent rates of ammonium excretion by the copepod Calanus pacificus

The relationship between food ingested and NH ₊ ⁴ excretion rate was investigated for female Calanus pacificus collected in August, 1982, from the San Juan Archipelago, Washington State, USA. The copepods were preconditioned to 6 densities of the diatom Thalassiosira weissflogii (0 to 10⁴ cells ml^–1) for 30 h before the experiment. The experiment was conducted with nutrients added in excess to maintain equal rates of NH ₊ ⁴ uptake by the diatoms at all densities. Although ingestion rates of C. pacificus varied from 0 to over 20% of body N d^–1 at the different food levels, excretion was a constant 6.6 nM NH ₊ ⁴ copepod^–1 h^–1 or about 10% of body N d^–1. This ingestion-excretion relationship, which is consistent with previous respiration and fecundity studies, suggests that the ecological dominance of C. pacificus only under conditions of high food abundance may be due to a dramatic increase in its growth efficiency as ingestion increases above the level supporting a constant metabolic rate. The maintenance of a constant level of metabolism during relatively short periods of low food abundance may be advantageous if it allows the copepod to exploit more effectively short-term variability in its food resulting from environmental heterogeneity or vertical migration.Contribution No. 1360 from the School of Oceanography, University of Washington, Seattle, Washington 98195, USA     

Chromosomal mosaicism confined to chorionic tissue

Chorionic villus samples from two healthy pregnant females were obtained for first trimester fetal diagnosis. The karyotypes were 46, XX/47, XX, +3 and 46, XX/47, XX, +15, respectively. In both cases fibroblast cultures after termination of pregnancy were shown to have normal karyotypes.     

Larval period and its influence on post-larval life history: comparison of lecithotrophy and facultative planktotrophy in the aeolid nudibranch Phestilla sibogae

The variable duration of the pelagic phase of metamorphically competent larvae of benthic marine invertebrates is set by an interaction between environmental factors and larval traits that together influence the chance that a larva will encounter and respond to a suitable settlement site. In the Hawaiian aeolid nudibranch Phestilla sibogae Bergh, an extended competent larval phase resulted in a cascade of negative effects on larval and post-larval life-history traits. When raised as fed (i.e., facultatively planktotrophic) larvae, an extended larval period resulted in lower larval survival, slightly lower metamorphic success, and delayed reproduction. When raised as unfed (i.e., lecithotrophic) larvae, an extended larval period resulted in lower larval and post-larval weights, survival, metamorphic success, and reproductive output, and also resulted in a longer juvenile period and delayed reproduction. The chance nature of locating a settlement site generally spreads these negative effects over all larvae of a cohort, and so balances the relative fitness of the genetic lineages within a population.     

Echolocation in two very small bats from Thailand Craseonycteris thonglongyai and Myotis siligorensis

Summary The echolocation and hunting behavior of two very small bats, Craseonycteris thonglongyai (Hill) and Myotis siligorensis (Horsfield), from Thailand, were investigated using multiflash photographs, video, and high-speed tape recordings with a microphone array that allowed determination of distance and direction to the bats. C. thonglongyai is the world's smallest mammal and M. siligorensis is only slightly larger. Both bats hunted insects in open areas. The search signals of C. thonglongyai were 3.5 ms long multiharmonic constant frequency (CF) signals with a prominent second harmonic at 73 kHz repeated at around 22 Hz. The band width (BW) of the short terminal frequency modulated (FM) sweep increased during the very short approach phase. In the final buzz the CF component disappeared, the duration decreased to 0.2 ms, and the repetition rate increased to 215 Hz (Figs. 2, 3, 4). There was no drop in frequency in the buzz. The video recordings of C. thonglongyai indicated that it seizes insects directly with the mouth (Fig. 1). M. siligorensis produced 5.4 ms long CF search signals at 66 kHz. The repetition rate was around 13 Hz. In the approach phase an initial broad band FM sweep was added. The buzz consisted of two phases, buzz I and buzz II. Buzz 11 was characterized by short cry durations (around 0.3 ms), a constant high repetition rate (185 Hz), a distinct drop in frequency, and a prominent second harmonic (Figs. 5, 6, 7). The drop in frequency, apparently typical of vespertilionid bats, has been explained by physiological limitations in sound production. However, C. thonglongyai produced very short signals at very high repetition rates without any frequency drop. The drop may be of adaptive value since it enables M. siligorensis to produce very short signals with high sweep rates. The drop moves the pronounced second harmonic into the frequency range of most interest to the bat (Fig. 7D). The sweep rate in this frequency range may now increase to twice the maximum rate that the vocal cords can produce directly. C. thonglongyai and M. siligorensis belong to different superfamilies, Emballonuroidea and Vespertilionoidea, respectively. In spite of their phylogenetic distance they produce strikingly similar search signals of narrow BW around 70 kHz with high source levels (100–115 dB peSPL peak equivalent sound pressure level). We argue that the signal resemblance is due to the similarity in size and hunting behavior of the two bats both hunting insects in open areas. High frequencies are heavily attenuated in air, but because of their small size the bats are restricted to hunting small insects which only reflect echoes at high frequencies. Thus, the emitted frequency is probably the lowest possible given the prey size. Hence, the two bats can only maximize the range of their sonar by decreasing the BW and emitting high intensities. Correspondence to: A. Surlykke     

A scanning electron microscope study of the mandibular morphology of boreal copepods

Morphological details of the mandibular blades of 11 species of copepods were examined with scanning electron microscopy. The micrographs improved our understanding of the complex toothed edge of the mandibular blade, which in turn aids in identification of the copepod prey of chaetognaths by gut-content analysis. Beklemishev's discovery of siliceous tooth crowns in calanoid copepods was confirmed for most of the species examined. Long, sharp projections on the crowns of herbivorous species, and the deep grooves into which they fit on the teeth of the opposite mandible, suggest a cracking rather than a grinding function for these teeth.