Sources of fish in the ephemeral western iishana region of the Cuvelai–Etosha Basin in Angola and Namibia

The triangle between the Kavango and Kunene rivers is drained by the Cuvelai, an ephemeral and deltaic drainage system covering more than 100 000 km². In good rainfall years, the area becomes populated by fish communities dominated by five species migrating southward towards the endorheic Etosha Pan, the basin’s terminal sump. When water dries up, fish subsequently die-off and their sudden appearance in rainy years has captivated scientists for decades. The current study was prompted by hitherto untapped indigenous knowledge through narratives of opportunistic fish harvesting of migrating fish at temporary connections between the Kunene River and the Cuvelai- Etosha Basin. A reconnaissance fish survey in 2017 was complemented by digital satellite images and elevation data analyses. Results support the presence of at least three major ephemeral fish migration routes. The dominant fish genera migrating upstream in Kunene tributaries comprise Enteromius, Oreochromis and Clarias, all eurytopic and known to undertake upstream, lateral and downstream migrations on floodplains. Although other notable fish refugia in the Cuvelai–Etosha Basin are yet to be identified, there is a necessity for the protection and management of these migration routes in tandem with studies on the nature and extent of this inter-basin fish migration under climate change and variability.     

Decomposition in situ of the sublittoral Antarctic macroalgaDesmarestia anceps Montagne

 Large amounts of detached Antarctic macroalgae accumulate in hollows of the seabed, where decomposition rates of the detached macroalgae are expected to be low, caused by lack of contact of the major part of the macroalgae with the sediment. To determine decomposition rates in Antarctic waters, untreated and pre-killed Desmarestia anceps fronds contained in nylon net bags were studied for 10 months under natural conditions in Factory Cove, Signy Island. Physical decomposition was shown to be more important than microbial decomposition. A weight loss of 40% occurred in untreated material within 313 days, while pre-killed material almost all disappeared within 90 days. Despite the weight loss, changes in chlorophyll a content were negligible during the experiment. Changes in the C:N ratio and tissue N indicated low rates of microbial decomposition. Therefore, it was concluded that weight loss was mainly caused by fragmentation, and particles disappearing from the nets accounted for most of the loss of original tissue. It remains unknown as to how long nutrients stay in Antarctic macroalgal litter before they become available to the system. Received: 16 March 1995/Accepted: 18 June 1995     

Seasonal waves of asthma: A possible botanical cause

The seasonal incidence of asthma and of shoot-growth in eucalypts in four Australian capital cities (Brisbane, Sydney, Adelaide and Melbourne) are compared. The incidence of asthma appears to be closely correlated with the initial stages of the seasonal flushes in shoot-growth of eucalypts, when rapid cell-division occurs. A spring to early summer growth flush invariably occurs in all capitals when the mean monthly temperature rises above 16–18°C; it is initiated progressively later with increasing latitude firstly in Brisbane, then in Sydney, then Adelaide and finally Melbourne. Although the correlation between asthma and eucalypt shoot-growth is high, there is not necessarily a cause-and-effect relationship. Volatile compounds evaporated from young and old leaves are probably not responsible, but the fine faecal pellets from the numerous small larvae and adult insects which attack the young eucalypt shoots may produce possible asthma-allergens. The concentration of these allergens in the atmosphere is reduced by heavy rainfall and by off-shore winds, and may accumulate during periods when temperature inversions occur at low levels in the atmosphere (e.g. during autumn in Brisbane).Supported by a grant from the Asthma Foundation of Queensland.     

The molecular organization of the beta-globin complex of the deer mouse, Peromyscus maniculatus

Recombinant DNA clones have been isolated that contain 80 kb of the beta-globin complex from the deer mouse, Peromyscus maniculatus. Comparisons of this complex with that from the laboratory mouse, Mus domesticus (with an order 5'-Hbby, Hbb-bhO, Hbb-bhl, Hbb-bh2, Hbb-bh3, Hbb-bl, Hbb-b2 3') highlight organizational trends in the beta-globin complex since the two species diverged. Unlike other mammals studied thus far, the deer mouse possesses three adult genes. Partial sequence analysis indicates that each of the three adult genes is intact and hence may be functional. Hybridization of one of the two Mus pseudogenes, Hbb-bh3, to genomic blots from Peromyscus reveals that it has a homologous counterpart in Peromyscus. Homologous genes to the two gamma-like Mus genes, Hbb-bhO and Hbb-bhl, are also found in Peromyscus. The strong hybridization between the Hbb-bhl genes and significant nucleotide similarity between the Hbb-bhO genes suggest that both pairs are important for the ontogeny of these mice although no known product has been identified for the Hbb-bhO genes. The presence of Hbb-bhO and Hbb-bhl in Peromyscus suggests that the duplication that created this related gene set occurred before the two lineages diverged. A single gene for Hbb-y has been isolated from Peromyscus. The adult region in Peromyscus has undergone significant divergence from the same region in Mus, having three rather than two adult genes, the acquisition of at least 15 kb of extra DNA relative to Mus, and possibly the loss of the Hbb-bh2 pseudogene. The nonadult region of the complex, in contrast, contains the same set of genes apparently distributed over the same amount of DNA as in the Mus beta- globin complex. This observation suggests that the embryonic region of the complex is more evolutionarily stable than the adult region.      

Unusual cytological patterns in microsporogenesis in a cultivar of Fuchsia

Summary Multiple and multipolar spindles are a generalized feature of microsporogenesis in a cultivar of Fuchsia. Only the first meiotic division occurs and gives rise to sporads with nine microspores. Variation in chromosomal complements of the microspores is illustrated by pollen polymorphism. Since some of these pollen grains are able to germinate, the possible breeding value of this super-reductional type of division is questionable. Hypotheses concerning this phenomenon found in the literature are discussed in the light of our results.     

Chorda tympani proper nerve responses to intra-arterial and surface stimulation of the tongue in rhesus monkey and rat

The effect of intra-arterial injection of the proteins monellin,thaumatin and miraculin on the activity of the chorda tympaniproper nerve were recorded in the rhesus monkey (Macaca mulatto)and the rat (Sprague–Dawley). The substances were injectedinto the blood stream to the lingual artery. It was found thatmonellin and thaumatin elicited a response only in the monkeyand not in the rat. Acetylated thaumatin, a tasteless substance,gave no increase of the nerve activity. Miraculin had no effectin either species. NaCl, sucrose and citric acid injected intra-arteriallygave a response in both species. It is concluded that the responsesto intra-arterial injections were caused by stimulation of thetaste buds and not nerve fibers. The results suggest there aretaste receptors also on the parts of the taste cells not facingthe oral cavity. The finding that there was no cross-adaptationbetween intra-arterial and oral application supports this conclusion.