On the Nature of the Neurotrophic Phenomenon in Urodele Limb Regeneration

The nervous control of regeneration of body parts in the urodeleamphibian and other animals has been one of the best model systemsfor the study of the neurotrophic phenomenon. In the past mostof these studies were experimental morphological, but recentlythe salient problems on the nature of the cellular responseto the neurotrophic agent and the nature of the nervous agentitself are also analyzed molecularly. The ensemble of studiesreviewed in the present work, which also show that the agentof the nerve is a peptide and defines aspects of its effecton molecular synthesis in regenerate cells, leads me to advancethe following theories. I propose that the neurotrophic agentaffects only the rate of ongoing events in the cell and notthe quality and kind of the events; that the events are alreadyindigenous to the responding cells; that alteration in therateof events, for example increasing the rate of molecular syntheses,yields an increased cell population which by its size and increasedcellular interactions has formative and differentiated capabilitieswhich do not exist in a smaller cell population; and finallythat the neurotrophic factor (NTF) is one of many "conversational"peptides including nervegrowth factor (NGF) and epidermal growthfactor (EGF) which function to alter the absolute rate of ongoingcellular events.     

Comparisons of abundance of coral-reef fish: Catch and effort surveys vs visual census

Abstract Catch per unit effort (CPUE) in fisheries science and visual counts in marine ecology are widely used to provide estimates of relative abundance. Concurrent use of these techniques therefore offers an opportunity for cross-validation. This study compares CPUE to underwater visual census (UVC) estimates of relative species abundance in a multispecies fishery: coral-reef fish in the Solomon Islands. Multivariate analyses showed large differences between CPUE and UVC estimates of abundance. The families Acanthuridae and Scandae tended to be the primary cause of differences between the techniques when the full assemblage offish was analysed. However, the relationship between CPUE and UVC did not improve when these families were excluded from the data set and the analyses repeated on families (Serranidae, Lutjamdae, Lethrinidae) caught by the predominant gear type, handlining. This result highlights the point that the choice and use of particular methods require careful consideration in conjunction with the nature of factors being investigated. Many problems of sampling are specific to particular methods and some investigations may benefit from a more pluralistic approach.     

The potential interplay of posture, digestive anatomy, density of ingesta and gravity in mammalian herbivores: why sloths do not rest upside down

1. The interaction between the density of ingesta and gravity observed in the digestive systems of ruminant herbivores should receive attention in other non‐ruminant herbivorous mammals. The resting postures adopted by non‐ruminants are of particular interest. 2. A new interpretation of established findings regarding the digestive tract of sloths illustrates that the interplay of posture, anatomy, the density of ingesta and gravity can provide a novel explanation of behavioural and morphological adaptations in herbivores, as the average particle size and dry‐matter content increases within their forestomach from its caudal towards its cranial portion. In sloths, this could be indicative of a stratification of ingesta occurring in the upright sitting posture adopted while resting, as opposed to their characteristic upside down posture when moving. 3. The sitting resting posture of sloths could therefore be an adaptation to exploit the tendency of the forestomach contents to stratify in order to pass larger, more difficult‐to‐digest particles faster from the fermentation chamber.     

Functional differentiation of African grazing ruminants: an example of specialized adaptations to very small changes in diet

We assess whether interspecific differences in craniodental morphology within a single ruminant feeding guild, the grazers, represent anatomical adaptations to subtle differences in diet. Differences in craniodental anatomy follow a distinct taxonomic pattern that is paralleled by dietary niche differentiation recorded in species' stable carbon (δ¹³C) and nitrogen isotope (δ¹⁵N) compositions, strongly supporting a hypothesis for functional divergence within the grazers. We propose that the evolutionary origin of grazers were multifold; at least two and up to four different types of grazing can be discerned within the 11 taxa studied here alone. However, correspondence between craniodental adaptations and isotopic differences across species are not found when only δ¹³C data are considered (i.e. morphological differences do not reflect varying proportions of C₃ browse to C₄ grass consumed). This implies that alternate anatomical adaptations to grazing are not related to differences between variable (part-time browsing) and obligate grazers, as previously predicted. Rather, anatomical differences correlate strongly with changes in δ¹⁵N, which we infer to reflect functional responses to changes in diet quality associated with the degree of feeding selectivity and short-, medium-, or tall-grass grazing.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 755–764.