Estimating elephant densities from wells and droppings in dried out riverbeds

In this paper, we present a new method for estimating elephant densities by counting elephant wells and dung boli within dry seasonal flooding rivers. A combination of aerial and ground counts of elephant wells and dung boli in the Ewaso Ngiro River were related to elephant numbers, obtained from an on‐going monitoring program of individually identified elephants in Samburu and Buffalo Spring National Reserves, Kenya. The total number of elephant observations was highly correlated with both densities of wells and dung boli at a spatial resolution of 4‐km river‐section. This indicates that both wells and droppings can be used for estimating relative densities at such spatial resolution. The method can be used as a quick and reliable way of estimating relative elephant densities in semiarid regions but is sensitive to differences in the time when different parts of the river dry out and will be unreliable in areas with secondary un‐censused water sources. A short 4‐week period between the river dry out and the count is recommended, because of an error induced by a level of well reuse and the difficulties in counting areas of high well densities from the air.     

Saltatory search in a lateral line predator

The dwarf scorpionfish Scorpaena papillosa detected the hydrodynamic signals produced by prey with the mechanosensory lateral line. This species displayed a pause and move search pattern that is consistent with a saltatory search. The pause phase of the search cycle was probably used to detect prey because pauses often ended early in order to initiate an approach at prey and prey were detected throughout the search space. The move phase of the search cycle repositioned the fish so that it moved approximately a third of the reactive distance. Move distance was found to be the most important factor in gaining novel search space. Turning was shown to be relatively unimportant in gaining novel search space with a high frequency of low turn angles made by the fish. The dwarf scorpionfish, however, exhibited a spiralling or looping pattern over a search path exhibiting a turn bias towards either the left or right. The dwarf scorpionfish adopted a search behaviour that is consistent with a saltatory search and efficient for lateral line predation.     

Ultrastructure de l'organe Ampullaire de Gymnotus carapo (Gymnotidae); Origine et Nature des Mucopolysaccharides

Résumé Les organes sensoriels cutanés de type ampullaire, spécifiques du système de la ligne latérale chez Gymnotus carapo, sont étudiés ici sous leur aspect morphologique et histochimique. Cellules sensorielles et cellules accessoires constituent un épithélium simple tapissant l'ampoule. Innervée par une seule fibre se terminant par un énorme bouton terminal, chaque cellule sensorielle a une surface libre importante, en contact avec les substances muqueuses qui remplissent l'ampoule et le canal intraépidermique. Les cellules accessoires de l'epithélium sensoriel et les cellules de la paroi du canal sont secrétrices des mucopolysaccharides neutres du canal.

---

Ultrastructure of the ampullary organ of Gymnotus carapo (Gymnotidae) nature and origin of its polysaccharids

Summary The specific cutaneous organs of the lateral line system in Gymnotus carapo have been observed by morphological and histochemical methods.The ampullary epithelium is constituted by a layer of sensory and accessory cells. Each sensory cell is innervated by one fiber ending with a large terminal bud. The sensory cells have also an important free surface in contact with the mucoïd substances which fill up the ampullae and the intraepidermic canal.The accessory cells of the ampullary epithelium and the cells of the canal's wall produce the canal's neutral mucopolysaccharids.

Ce travail a été réalisé avec l'aide de la Direction de Recherches et Moyens d'Essais, accordée au Dr. T. Szabo (Contrat n 659-594).     

Ontogenetic changes in spot configuration (numbers,circularity, size and asymmetry) and lateral line in Neurergus microspilotus (Caudata: Salamandridae)

Coloration in three of four species of the genus Neurergus including N. microspilotus is characterized by the presence of yellow spots on a dark skin, but there is no available information about changes in spot configuration, speed of development and degree of association between melanophore‐free region and the lateral line. In this study, spot numbers, spot circularity, spot size and spot asymmetry were studied during larval to adult growth in N. microspilotus during July 2012 to June 2015. The mean numbers of spots increased during the late larval stage till postmetamorphic period from 13.33 ± 3.77 to 22.53 ± 4.09 and reached 42.62 ± 4.06 in adults. At the same time, the extent of spots gradually decreased in size from 5.80 ± 1.00 to 3.57 ± 0.97 mm² and reached 3.55 ± 1.42 mm² in adults, but the spot circularity increased from 0.48 ± 0.23 to 0.78 ± 0.49 and reached 0.80 ± 0.15 in adults. In adults, the numbers, circularity, size and asymmetry of spots remain stable with little but non‐significant changes during the study period. Histological study shows that formation of a melanophore‐free region correlates with the development of the lateral line receptors. This study demonstrates that the effects of lateral line on chromatophores persist through middle larval stages but diminish as metamorphosis completes.     

Lateral line scale types and review of their taxonomic distribution

The trunk canal of fishes is contained within a series of lateral line (LL) scales. To categorise LL scale structural types, and determine their distribution, an analysis of original data was undertaken using light and scanning electron microscopy in combination with a literature survey from over 1,000 species representative of most orders of bony fishes. Our categorisation of LL scales is based on the relationship between the tube, or ossified trunk canal segment, and associated scale. Tubular‐Scalar LL scales consist of a distinguishable tube and elasmoid scale in scale pockets. Four types occur only in species with elasmoid scales. Integrated LL scales do not develop in scale pockets, and their tube is enclosed or extended by a non‐elasmoid scale or spines. Integrated 1 and 2 LL scales co‐occur with ganoid and calcidermoid scales, and Integrated 3 LL scales occur when common scales are absent or elasmoid. Tubular LL scales are tubes only, occurring mainly in scaleless species or with calcidermoid and elasmoid scales. Non‐Tubular LL scales are composed only of a scale, co‐occurring mainly with cycloid scales. There is consistency of LL scale type in many orders, families and genera and the presence of different types within taxa can be meaningful.     

Tadpole-like Conformations of Huntingtin Exon 1 Are Characterized by Conformational Heterogeneity that Persists regardless of Polyglutamine Length

Soluble huntingtin exon 1 (Httex1) with expanded polyglutamine (polyQ) engenders neurotoxicity in Huntington's disease. To uncover the physical basis of this toxicity, we performed structural studies of soluble Httex1 for wild-type and mutant polyQ lengths. Nuclear magnetic resonance experiments show evidence for conformational rigidity across the polyQ region. In contrast, hydrogen–deuterium exchange shows absence of backbone amide protection, suggesting negligible persistence of hydrogen bonds. The seemingly conflicting results are explained by all-atom simulations, which show that Httex1 adopts tadpole-like structures with a globular head encompassing the N-terminal amphipathic and polyQ regions and the tail encompassing the C-terminal proline-rich region. The surface area of the globular domain increases monotonically with polyQ length. This stimulates sharp increases in gain-of-function interactions in cells for expanded polyQ, and one of these interactions is with the stress-granule protein Fus. Our results highlight plausible connections between Httex1 structure and routes to neurotoxicity.     

Phylogenetic distribution of regeneration and asexual reproduction in Annelida: regeneration is ancestral and fission evolves in regenerative clades

Regeneration, the ability to replace lost body structures, and agametic asexual reproduction, such as fission and budding, are post‐embryonic developmental capabilities widely distributed yet highly variable across animals. Regeneration capabilities vary dramatically both within and across phyla, but the evolution of regeneration ability has rarely been reconstructed in an explicitly phylogenetic context. Agametic reproduction appears strongly associated with high regenerative abilities, and there are also extensive developmental similarities between these two processes, suggesting that the two are evolutionarily related. However, the directionality leading to this relationship remains unclear: while it has been proposed that regeneration precedes asexual reproduction, the reverse hypothesis has also been put forward. Here, we use phylogenetically explicit methods to reconstruct broad patterns of regeneration evolution and formally test these hypotheses about the evolution of fission in the phylum Annelida (segmented worms). We compiled from the literature a large dataset of information on anterior regeneration, posterior regeneration, and fission abilities for 401 species and mapped this information onto a phylogenetic tree based on recent molecular studies. We used Markovian maximum likelihood and Bayesian MCMC methods to evaluate different models for the evolution of regeneration and fission and to estimate the likelihood of each of these traits being present at each node of the tree. Our results strongly support anterior and posterior regeneration ability being present at the basal node of the annelid tree and being lost 18 and 5 times, respectively, but never regained. By contrast, the ability to fission is reconstructed as being absent at the basal node and being gained at least 19 times, with several possible losses. Models assuming independent evolution of regeneration and fission yield significantly lower likelihoods. Our findings suggest that anterior and posterior regeneration are ancestral for Annelida and are consistent with the hypothesis that regenerative ability is required to evolve fission.