BIOACOUSTIC PUBLICATIONS, 1988

ABSTRACT

We examined vocalisations of a solitary subterranean rodent, the Silvery Mole-rat Heliophobius argenteocinereus (Bathyergidae). Seven true vocalisations and one mechanical vocalisation were identified. The main frequencies of the analysed sounds (0.34–13.17 kHz) match to a great extent the frequency range suitable for transmission in underground burrows. Due to the narrow frequency range of vocalisations, motivation is predominantly expressed by the rate of tonality rather than by frequency changes. The vocal repertoire of the Silvery Mole-rat perfectly matches to Morton's MS rules, i.e. that low-frequency and harsh vocalisations indicate hostility whereas high tonal calls signalise appeasement or fear. In comparison with social species, this solitary bathyergid produces fewer calls. It lacks contact and alarm calls, but has a rich repertoire of mating calls (mating ends with duet vocalization of male and female). Acoustic signals seem to play a major role in lowering natural aggressiveness during the mating period.     

Contents Volume 14, 1988

Summary

Within the unpaired testis, spermatogonia, spermatocytes, spermatids and spermatozoa were found. In early spermatids, mitochondria take perinuclear positions and centrioles a diplosomal arrangement. Rootlet-like striated differentiations occur in slightly more advanced stages. Then a conical cytoplasmic projection develops, supported by a single row of closely spaced microtubules. At this stage of maturation, giant Golgi stacks occur within the cytoplasm of the cytophore which is rich in different elongate structures and oval dense bodies. With progressive differentiation, the nucleus elongates and its chromatin condenses into twisted lamellae. Two centrioles, which change their diplosomal configuration and come to lie in line to each other, and rootlet-like structures remain near the tip of the median cytoplasmic outgrowth. Mitochondria start to fuse into a single long cylindrical mitochondrial rod extending beside the lengthening nucleus. Bone-shaped rods, smaller dense sticks and dense bodies migrate into the outgrowth. Spermatozoa are totally ensheathed by cortical microtubules. These tubules show different arrangements along the cell body. The thread-like nucleus extends along the cell, the first quarter excepted, whereas the single mitochondrion extends over two thirds of the cell. Two strings with linearly arranged oval dense bodies run in the median to post-median cell segment; four rows of bone-shaped rods and two rows of smaller electron-dense sticks extend from the frontal end up to the beginning of the last third of the cell. All the different longitudinal cords run in the gaps between 4 sets of microtubules. Ciliary axonemes or lateral bristles were not observed. The present findings substantiate the hypotheses, that spermatozoa in the Macrostomida are aciliate and that Myozona takes an isolated position within the Macrostomidae. The occurrence of two centrioles, which come to lie in line to each other and which stay in the tip of the cytoplasmic outgrowth in spermatids, may indicate that biciliate spermatozoa are characteristic for the Rhabditophora (= Macrostomorpha+Trepaxonemata) and not an evolutionary novelty of the Trepaxonemata.     

Numbering of atoms in myo-inositol. Recommendations 1988. Nomenclature Committee of the International Union of Biochemistry.

A relaxation of previous recommendations on the numbering of the atoms of myo-inositol is suggested, so that substituents are not necessarily numbered so that the smallest possible locant is used. This allows an alternative designation to be used, when authors wish, to bring out structural relationships.     

Hydrographical observations west of the Banc d'Arguin,Mauritania, in May 1988

The present paper discusses the distribution of hydrographical parameters in Mauritanian waters between 19° 20 N and 20° 40 N. Data were collected during the first leg of the Dutch Mauritania Expedition in May 1988 with the R/V TYRO and comprise measurements of water temperature (T), salinity (S) and dissolved oxygen contents (O₂) in the area off the Banc d'Arguin. The time of investigation fell in the transitional period between the cold and warm season, which in this area is characterised by a peak in the trade wind speed and progressive heating of waters. Wind speed and sea surface temperature distribution in May 1988 were close to the seasonal averages which suggests that the observed hydrographical conditions were normal for this period as well. The highest spatial variability of T, S and O₂ was found near the southern end of the Banc d'Arguin, where the combined effect of coastal upwelling and seasonal heating made the thermocline upper limit rise towards the surface and upwelling waters reach the shallowest parts of the shelf. In the northern part of the study area upwelling phenomena were observed in the subsurface layers below 50 m depth; upwelling water did not reach beyond the outer edge of the shelf. The analysis of the TS diagram showed that water masses in the upper 300 m layer were mainly composed of South Atlantic Central Water with an admixture of warm, low-salinity surface water of Guinean origin. Traces of North Atlantic Central Water were found in the subsurface layer and at the deepest levels of measurements. Almost no traces of warm, saline water originating from the shallow Banc d'Arguin were registered during the survey.