Ultrastructural,Sensory and Functional Anatomy of the Northern Elephant Seal (Mirounga angustirostris) Facial Vibrissae

Vibrissae (whiskers) play a key role in underwater orientation in foraging phocids through vibrotactile sensation processing. Our aim was to evaluate the structure of northern elephant seal (NES) vibrissae by means of light (LM) and transmission electron microscopy (TEM), in order to elucidate their function. Vibrissal follicles were processed using standardized laboratory methods and LM/TEM techniques. Individual follicular axonal numbers were counted and axonal diameter measured and averaged. NES have mystacial, rhinal, supraorbital and labial vibrissae. The vibrissal follicles are histologically subdivided into a ring, upper and lower cavernous sinuses (LCS). Each vibrissa is innervated by the deep vibrissal nerve. The average number of axons per large mystacial vibrissa is 1804 (±123), rhinal 985 (±241), supraorbital 1,064 (±204) and 374 (±65) in labial vibrissa. The entire vibrissal system carries an estimated 148 573 axons, and mystacial vibrissae alone have 125 323 axons. Axonal conduction velocity for each vibrissal type is 55.26 m/s for labial, 56.58 m/s for rhinal and 35.88 m/s for mystacial vibrissae. TEM and LM revealed a plethora of mechanoreceptors within the vibrissal follicles: Merkel cell‐neurite complexes, lanceolate and pilo‐Ruffini end organs. A vast number of sensory axons projecting from the entire vibrissal system indicate that the vibrissal sensory area takes up a large proportion of phocids’ somatosensory cortex. In conclusion, NES has highly sensitive and finely tuned vibrotactile vibrissal sense organs.     

Conversion of conifer plantations to native hardwoods: influences of overstory and fertilization on artificial regeneration

Forest tree species in the eastern US such as American chestnut (Castanea dentata (Marsh.) Borkh) and oaks (Quercus spp.) have been negatively impacted by forest changes over the past century. Many mature, introduced pine (Pinus spp.) plantations exist in the Midwest US following establishment 50–60 years ago yet have little economic and ecological value. As oak and chestnut have similar site preferences to pines, these stands may be ideal sites for hardwood restoration plantings. We sought to determine optimal management strategies for converting pine plantations by manipulating their canopies. We underplanted hybrid American chestnut and northern red oak (Quercus rubra L.) seedlings into three canopy treatments (control, shelterwood, clearcut) and included an open field treatment. For each of two growing seasons, 0, 30, or 60 g 19N–6P–12K of controlled-release fertilizer (CRF) were also applied to seedlings. Soil chemical parameters and leaf nutrients were analyzed throughout the study. Chestnut and oak seedlings had significantly greater height after two growing seasons in the clearcut and shelterwood than the control and open field, and chestnut had significantly greater diameter as well. Chestnut height and RCD growth were threefold that of oak after two growing seasons. In general, fertilization increased seedling growth more in the clearcut and open field than shelterwood and control for both species. Soils had significantly higher pH, K, and S in the open field than in pine stands. Results suggest that pine plantations may serve as target sites for restoration of these hardwood species. Shelterwoods and clearcuts are both favorable conversion options for oak and chestnut, and addition of CRF may augment further growth increase, especially in open environments.     

Effects of Forest Clearance and Cultivation on Bulk Density Variations and Relationships with Texture and Organic Matter in Tephra Soils of Mount Kupe (Cameroon)

Tephra soils around mount Kupe harbor forests which have in the past 30 to 40 years been subject to degradation giving way to continuous cultivation which have the tendency to reduce the yield potentials of the soils. This study was conducted to evaluate the state of degradation following the long periods of cultivation to assist put in place more sustainable management practices. Soil samples from six profiles developed from pyroclastic materials (tephra) of Quaternary age, three from cultivated farms and three from adjacent virgin forests were studied to establish the relationships that exist between bulk density (BD) and organic carbon (OC) content and between BD and particle size. Variations of BD and OC within profiles are erratic. Soil texture is dominated by sand (64.8–81.9%), followed by clay (11.6–32.2%) and then silt (0.8–11.9%). The relationships between BD, OC, and texture indicated that BD correlates negatively with clay (r = ?0.68, p < 0.01) and OC (r = ?0.15, p < 0.01) contents but inversely with sand (r = 0.43, p < 0.05) and silt (r = 0.33, p < 0.05) contents. Relationships between these properties were better observed in virgin forests than in cultivated farmlands indicating that virgin forest systems are more stable (equilibrium is maintained since they do not incur anthropic perturbations). The high and significantly similar OM contents in both systems indicate that farming practices in the study area are sustainable and need to be maintained since they conserve OM. Results of this study will contribute to management of similar soils in tropical environments.     

Monitoring the spore dynamics of Aphanomyces astaci in the ambient water of latent carrier crayfish

The specialized crayfish parasite Aphanomyces astaci causes the devastating crayfish plague in European crayfish. Even though A. astaci sporulation has been thoroughly studied under pure culture conditions, little is known about the sporulation dynamic from its live host. Our purpose was to investigate the A. astaci spore dynamic in its native parasite-host relationship by monitoring the sporulation from carrier crayfish into the ambient water using agent specific qPCR. American signal crayfish (Pacifastacus leniusculus) with known positive carrier status were housed individually and communally in two experimental set-ups using multiple replicates and different temperatures. Water samples were collected weekly, and spore numbers were quantified. We demonstrate here that live latent carrier crayfish continuously released a moderate number of A. astaci spores (~2700 spores per crayfish/week) in the absence of death and moulting events. In contrast, a pronounced sporulation increase was seen already one week prior to death in moribund crayfish, suggesting a crayfish plague-like condition developing in weakened or stressed individuals. Significantly more spores were produced at 18°C compared to 4°C, while a negative correlation was detected between spore numbers and temperatures rising from 17 to 23°C. This study is the first attempt to quantify the spore release from carrier crayfish on the basis of qPCR applied on water samples, and demonstrate that the approach successfully unravel A. astaci sporulation patterns. The results emphasize that carrier crayfish pose a constant infection risk to highly susceptible crayfish species regardless of crayfish life cycle state.     

Comparison of the DIFCO and Patoc 1 slide antigens in the screening of leptospirosis

A comparison of the Patoc 1 slide agglutination (SAT) and DIFCO slide agglutination test for the screening of leptospirosis in man, cattle and coypu (Myocastor coypus Molina) is reported. The economic costs, convenience and availability of the antigens for the tests are analysed. It is recommended that slide agglutination methods alone are not sufficient for the routine diagnosis of leptospirosis.