A XERORADIOGRAPHIC STUDY OF THE DEVELOPING QUARTERHORSE FOREDIGIT AND METACARPOPHALANGEAL REGION FROM SIX TO TWELVE MONTHS OF AGE

The purpose of the project was to provide a reference for radiographic anatomy of the developing equine foredigit and metacarpophalangeal region. Using xeroradiographic techniques, both foredigits and metacarpophalangeal regions of six Quarter Horse foals were radiographed at 1 day of age and then at 2-week intervals until the foals were 6 weeks old. The foals were then radiographed at 4-week intervals until they were 12 months old. The period from birth to 6 months has been described in a previous report. This paper deals with the period from 6 to 12 months of age. Lateromedial and dorsopalmar xeroradiographs of each foredigit and metacarpophalangeal region and a dorsal 65° proximal-palmarodistal oblique view of the distal part of the digit were made at each examination. Foals were weighed and were measured at the withers immediately prior to each examination. Representative xeroradiographs were selected and appropriately labeled to demonstrate normal radiographic anatomy of these regions. Earliest radiographic visualization of distal epiphyseal ossification in metacarpal 2 and metacarpal 4 was extremely variable and ranged from 4 to 38 weeks. It was not possible to determine accurately the ages at which distal physes of the small metacarpal bones closed. In one foal, three of four of these physes were closed at 26 weeks, while in another foal, none had closed when last radiographed at 54 weeks. Radiographic closure of the proximal physis of the middle phalanx ranged from 18 to 30 weeks (mean = 26 weeks). Radiographic closure of the proximal physis of the proximal phalanx ranged from 22 to 38 weeks (mean = 30 weeks). Radiographic closure of the distal physis of metacarpal 3 ranged from 18 to 38 weeks (mean = 29 weeks).     

Encephalitis attributed to dactylariosis in Japanese quail chicks (Coturnix coturnix japonica)

Dactylaria gallopava was isolated from brain tissue of 1-to-3-week-old quail chicks. Successive batches demonstrated elevated (15-20%) mortality preceded by incoordination and lateral recumbency. Chicks exhibited cerebellar and cerebral encephalitis characterized by brown-red discoloration of affected brain tissue. Decontamination of setters and hatchers resulted in abrupt cessation of mortality in subsequent placements, implicating incubators as the source of infection.     

Prolonged Natural Deferment of Hatching in Killifish

The drying up of flooded lowlands stranded eggs of Fundulus confluentus, which were unhatched and viable after as much as 3 months' exposure. The eggs were found in the moist plant debris on the soil surface. When ovigerous sods were immersed in tap water, normal fish hatched within 15 to 30 minutes.     

Aboveground growth interactions of paired conifer seedlings in close proximity

Where belowground resources are relatively abundant, naturally established trees sometimes occur in very close proximity to one another. We conducted a two-year study to assess the aboveground interactions between Douglas-fir (Pseudotsuga menziesii), grand fir (Abies grandis) and noble fir (Abies procera) seedlings planted in closely spaced (stems 10 cm apart) conspecific and heterospecific pairs. Paired seedling growth also was compared to seedlings planted with no neighbor. Stem height growth was not affected by the presence of a neighbor seedling, although diameter growth was slightly reduced. Branch diameter growth and weight were reduced where seedling crowns overlapped; branch morphological data suggested that this was caused by shading rather than mechanical interactions. Light measurements showed the potential for significant shading, particularly by the relatively large, dense crowns of Douglas-fir. Heterospecific pairs including Douglas-fir demonstrated the competitive production principle in that their mean growth was greater than the average of conspecific pairs of both species. Neighbor seedling height significantly affected subject seedling growth; neighbor effects were similar whether the neighbor seedling was growing on the north or south side of the subject seedling. Light reflected from Douglas-fir crowns had a lower red: far-red ratio than that of noble fir, although there was no evidence of a phytochrome-mediated growth response to the neighbor seedling. While heterospecific seedling pairs showed reduced competition, we found no evidence of facilitation for seedlings growing in very close proximity.