Fine structural description of the lateral ocellus of Craterostigmus tasmanianus Pocock, 1902 (Chilopoda: Craterostigmomorpha) and phylogenetic considerations

The lateral lens eye of adult Craterostigmus tasmanianus Pocock, 1902 (a centipede from Australia and New Zealand) was examined by light and electron microscopy. An elliptical, bipartite eye is located frontolaterally on either side of the head. The nearly circular posterior part of the eye is characterized by a plano-convex cornea, whereas no corneal elevation is visible in the crescentic anterior part. The so-called lateral ocellus appears cup-shaped in longitudinal section and includes a flattened corneal lens comprising a homogeneous and pigmentless epithelium of cornea-secreting cells. The retinula consists of two kinds of photoreceptive cells. The distribution of the distal retinula cells is highly irregular. Variable numbers of cells are grouped together in multilayered, thread-like unions extending from the ventral and dorsal margins into the center of the eye. Around their knob-like or bilobed apices the distal retinula cells give rise to fused polymorphic rhabdomeres. Both everse and inverse cells occur in the distal retinula. Smaller, club-shaped proximal retinula cells are present in the second (limited to the peripheral region) and proximal third of the eye, where they are arranged in dual cell units. In its apical region each unit produces a small, unidirectional rhabdom of interdigitating microvilli. All retinula cells are surrounded by numerous sheath cells. A thin basal lamina covers the whole eye cup, which, together with the distal part of the optic nerve, is wrapped by external pigment cells filled with granules of varying osmiophily. The eye of C. tasmanianus seemingly displays very high complexity compared to many other hitherto studied euarthropod eyes. Besides the complex arrangement of the entire retinula, the presence of a bipartite eye cup, intraocellar exocrine glands, inverse retinula cells, distal retinula cells with bilobed apices, separated pairs of proximal retinula cells, medio-retinal axon bundles, and the formation of a vertically partitioned, antler-like distal rhabdom represent apomorphies of the craterostigmomorph eye. These characters therefore collectively underline the separate position of the Craterostigmomorpha among pleurostigmophoran centipedes. The remaining retinal features of C. tasmanianus agree with those known from other chilopod eyes and, thus, may be considered plesiomorphies. Characters like the unicorneal eye cup, sheath cells, and proximal rhabdomeres with interdigitating microvilli were already present in the ground pattern of the Pleurostigmophora. Other retinal features were developed in the ancestral lineage of the Phylactometria (e.g., large elliptical eyes, external pigment cells, polygonal sculpturations on the corneal surface). The homology of all chilopod eyes (including Notostigmophora) is based principally on the possession of a dual type retinula.     

Regulation of the Pleuronectes americanus Na+/H+ exchanger by osmotic shrinkage, β-adrenergic stimuli, and inhibition of Ser/Thr protein phosphatases

The ubiquitous Na⁺/H⁺ exchanger NHE1 is regulated by protein phosphorylation events, but the mechanisms involved are incompletely understood. We recently cloned NHE1 from the red blood cells of the winter flounder, Pleuronectes americanus (paNHE1), and demonstrated its activation by osmotic cell shrinkage, β-adrenergic stimuli, and the Ser/Thr protein phosphatase PP1 and PP2A inhibitor calyculin A (CLA) (Pedersen et al. [2003] Am. J. Physiol. 284, C1561–C1576). Here, we investigate the mechanisms involved in paNHE1 activation by these stimuli. Osmotic shrinkage and CLA were only partially additive in their effects on paNHE1 activity, and CLA-mediated paNHE1 activation was inhibited by osmotic cell swelling. Activation by the β-adrenergic agonist isoproterenol (IP) was fully additive to activation by osmotic shrinkage or CLA. IP-mediated, but neither shrinkage-nor CLA-mediated paNHE1 activation were associated with an increase in cellular cyclic adenosine monophosphate (cAMP) level. IP-mediated activation was partially blocked by the protein kinase A (PKA) inhibitor H89 (10μM), wherease shrinkage- and CLA-mediated activation were unaffected. All three stimuli activated paNHE1 in a manner unaffected by inhibitors of protein kinase C (calphostin C, 5 μM) and protein kinase G (KT5823, 10 μM) as well as of myosin light chain kinase (ML-7, 10 μM). IP-mediated, but not shrinkage-mediated, paNHE1 activation was associated with an increase in serine phosphorylation of the paNHE1 protein. It is suggested that paNHE1 activation by osmotic shrinkage and by PP1/PP2A inhibition involves partially convergent signaling pathways, whereas activation of paNHE1 by β-adrenergic stimuli is mediated by a separate pathway.     

Behavioral responses of maned wolves (Chrysocyon brachyurus, Canidae) to different categories of environmental enrichment stimuli and their implications for successful reintroduction

The maned wolf (Chrysocyon brachyurus, Illiger, 1815, Canidae) is a threatened species that inhabits the cerrados of Brazil, Argentina, Peru, Bolivia, Paraguay, and Uruguay. Captive maned wolves could be potentially used in reintroduction programs for species conservation; however, it is necessary that their behavior and cognitive abilities are conserved. Environmental enrichment is a tool used to stimulate captive animals and maintain a natural behavioral repertoire. To compare the variation of captive maned wolves' behavioral responses to environmental enrichment, we studied three maned wolves held by Belo Horizonte Zoo, Brazil. Foraging, interspecific, and intraspecific stimuli were offered to the animals and their responses were compared with a baseline and postenrichment treatments. The test was used to help in choosing which one of the three individuals would participate in a reintroduction project. The results showed that stimuli type did influence the animal's responses, and that individually wolves responded differently to foraging, interspecific, and intraspecific enrichment items (P80.05 for some behaviors in each enrichment category). The individual's personality seemed to influence their behavioral responses, with animals showing bold and shy responses, and this trait should be considered during decision makings for reintroduction.     

Restoration of tensile strength in bark samples of Ficus benjamina due to coagulation of latex during fast self-healing of fissures

Background and Aims

The functions of plant latex have been discussed for a long time. Today, many studies support a defence mechanism as being its main function. A role as a self-healing mechanism was never attributed to the coagulation of latex. In this study we quantified the contribution of the coagulation of Ficus benjamina (weeping fig) latex to a restoration of the mechanical properties of the bark after external lesions.

Methods

Tensile tests of F. benjamina bark were conducted either immediately after injury or at various latency times after injury.

Key Results

A significant increase in the tensile strength of bark samples until 30 min after injury was found, and this effect could be attributed to the coagulation of plant latex alone. The tensile strength remains nearly constant until several hours or days after injury. Then, very probably due to other mechanisms such as cell growth and cell proliferation, the tensile strength begins to increase slightly again.

Conclusions

The coagulation of latex seals lesions and serves as a quick and effective pre-step of subsequent, more effective, long-lasting self-healing mechanisms such as cell growth and proliferation. Thus, a fast self-healing effect can be included in the list of functions of plant latex.     

Male parenting and response to infant stimuli in the common marmoset (Callithrix jacchus)

Callithrix jacchus infants are raised in complex family environments where most members participate in rearing the young. Many studies examining male parental behavior have focused on the carrying of infants with observations made within the family context. However, interference from family members can make it difficult to assess the father's motivation to care for infants. Our goals were to develop a testing paradigm for determining an individual's response to infant stimuli separate from family influences, compare a male's motivation to respond to an infant stimulus outside the family with his paternal behavior within the family, to compare responses to infant stimuli of parentally experienced versus inexperienced males and finally to develop a reproducible and standardized method of testing male responsiveness to infant stimulus that could serve to evaluate hormonal manipulations. Fifteen experienced common marmoset fathers were evaluated using three different measures of parental behavior: (1) instantaneous scan sampling, (2) continuous focal sampling in the family, and (3) continuous focal sampling of males presented with four infant stimuli: familiar and unfamiliar infants, familiar and unfamiliar infant vocalizations. Six parentally inexperienced males (non-fathers) served as controls. Males that carried the most in the family were typically the same males that responded most to the infant vocalization tests. Experienced fathers did not differ in their latency to enter the stimulus cage for any of the four infant stimuli response tests while inexperienced males took significantly longer to enter the stimulus cage. In addition, fathers expressed a greater frequency of infant-directed behavior than did the inexperienced males during the unfamiliar infant and unfamiliar vocalization tests. These studies show that experienced male marmosets are highly motivated to interact with infant stimuli and that there is interindividual variability in response to infant vocalizations. Testing males outside of the family allows for a clear assessment of male's interest in infant stimuli in both parentally experienced fathers and inexperienced males.     

Simulation of fracture healing incorporating mechanoregulation of tissue differentiation and dispersal/proliferation of cells

Modelling the course of healing of a long bone subjected to loading has been the subject of several investigations. These have succeeded in predicting the differentiation of tissues in the callus in response to a static mechanical load and the diffusion of biological factors. In this paper an approach is presented which includes both mechanoregulation of tissue differentiation and the diffusion and proliferation of cell populations (mesenchymal stem cells, fibroblasts, chondrocytes, and osteoblasts). This is achieved in a three-dimensional poroelastic finite element model which, being poroelastic, can model the effect of the frequency of dynamic loading. Given the number of parameters involved in the simulation, a parameter variation study is reported, and final parameters are selected based on comparison with an in vivo experiment. The model predicts that asymmetric loading creates an asymmetric distribution of tissues in the callus, but only for high bending moments. Furthermore the frequency of loading is predicted to have an effect. In conclusion, a numerical algorithm is presented incorporating both mechanoregulation and evolution of cell populations, and it proves capable of predicting realistic difference in bone healing in a 3D fracture callus.     

Visual Sensation of an Ethological Stimulus, the Agonistic Display of Betta splendens, Revealed using Multi-Unit Recordings from Optic Tectum

We made multi-unit recordings from the optic tectum of Betta splendens while they viewed the agonistic display of conspecifics. Movement of displaying animals evoked brisk, arrhythmic bursting in tectal units. Particularly high frequency spike bursts coincided with the onset of full display, a behavioral element known to be of ethological significance. These results show that it is possible to obtain informative electrophysiological recordings from optic tectum using behaving conspecifics as stimuli. More frequent use of natural stimuli can be expected to contribute to a greater understanding of the link between the neural substrates of vision and visually guided behavior.     

Sperm competition selects for increased testes mass in Australian frogs

Game theory predicts that investment in spermatogenesis will increase with the risk and intensity of sperm competition. Widespread support for this prediction has come from comparative studies of internal fertilizing species reporting positive associations between testes mass and the probability that females mate with more than one male. Data for external fertilizers have generated conflicting results. We investigated how risk of sperm competition affects testes size in two families of Australian frogs: the Myobatrachidae and the Hylidae. We also examined effects of clutch size, egg size and oviposition location as alternative factors that might influence sperm production. Species were ranked according to probability of group spawning, and hence risk of sperm competition. Controlling for body size and phylogenetic relationships, we demonstrated that within the Myobatrachidae, the risk of sperm competition explained a significant amount of variation in testes mass. Oviposition location had a weak influence, with species ovipositing into foam having smaller testes. No significant effects of clutch size or egg size were detected. In hylids, the relationship between testes mass and risk of sperm competition was positive but not significant, again with no predictable effects related to egg size or number. These data provide an important test of sperm competition theory for externally fertilizing taxa.     

Features of Temporal Differentiation of the Chum Salmon Oncorhynchus ketaof the Anadyr Bay Region at Different Abundance Levels

The temporal heterogeneity of chum salmon stock of the Anadyr Bay region was investigated on the basis of a set of discrete external morphological features and fluctuating asymmetry level of some meristic structures. Differentiation of Anadyr Bay chum salmon during the spawning run was found to be associated with the abundance level of spawning stock in a particular year. Sharply pronounced temporal heterogeneity, based on the investigated characteristics, in the area near the river mouth can be considered as an indicator of the subsequent deficiency of spawners on the spawning grounds of rivers in the Anadyr Bay region.     

Role of Olfactory and Visual Cues in the Attraction/Repulsion Responses to Conspecifics by Gregarious and Solitarious Desert Locusts

Desert locusts [Schistocerca gregaria Forskål (Orthoptera, Acrididae)] change phase in response to population density: solitarious insects avoid one another, but when crowded they change to the gregarious phase and aggregate. The attraction/repulsion responses of gregarious and solitarious locusts maintain phase differences in locust populations. Despite considerable research, the cues for aggregation are poorly understood; moreover, the repulsion response of solitarious locusts has not previously been investigated. This study analyzes the role of visual and olfactory stimuli in triggering these different responses to conspecifics. Isolation-reared insects were repelled by both olfactory and visual stimuli from other locusts. Crowd-reared insects were attracted by the combination of olfactory and visual cues. In addition, olfactory stimuli affected other behaviors in both phases, and behavioral differences between isolation- and crowd-reared locusts were clear even in the absence of conspecifics. The sensory and neurological mechanisms underlying these responses are not well understood and will form the basis for neurobiological investigations of locust phase.