Texas beckons.

Many Canadian medical families have been approached by US headhunters anxious to recruit family physicians to practise in the US. Lynne Sears Williams and her husband, Calgary family physician Jim Williams, went to Texas to see what opportunities awaited. In this article she describes the high and low points of recruitment efforts south of the border.     

alpha-melanocyte-stimulating hormone and habituation of prey-catching behavior in the Texas toad, Bufo speciosus.

We investigated dose-dependent effects of alpha-melanocyte-stimulating hormone (alpha-MSH) on habituation in the Texas toad, Bufo speciosus. Additionally, we determined changes in plasma and brain levels of alpha-MSH following peripheral administration of the peptide or following exposure to an ether stressor. The ability of alpha-MSH to facilitate acquisition of habituation was dose dependent. Plasma alpha-MSH concentrations were elevated within 5 min of dorsal lymph sac injection and remained elevated up to 600% over controls after 30 min. Administration of 50 microgram alpha-MSH had no effect on plasma corticosterone levels. Radiolabeled alpha-MSH was detected in cerebrospinal fluid microdialysates within minutes of peripheral injection. Concentrations of alpha-MSH in the telencephalon and preoptic area were significantly lowered after ether exposure, whereas levels in the optic tectum, thalamus/hypothalamus, brainstem, and plasma were unchanged. We conclude that alpha-MSH administered peripherally facilitates habituation in a dose-dependent fashion. Our results confirm that the effects of alpha-MSH are independent of corticosterone secretion. The peptide is cleared rapidly into the bloodstream and enters the cerebrospinal fluid after dorsal lymph sac injection. Neuronal alpha-MSH may help toads gather information about their environment when exposed to certain stressors.     

Genetics of house flies. Variability studies with North Dakota, Texas, and Florida populations.

Genetic data were used to compare the structure of native house fly populations collected in North Dakota, Texas, and Florida. Recombination studies with mutant markers on chromosomes 3 and 4 indicated a lack of inversion polymorphism among the three populations in those areas of the genetic map studied. Significant differences were observed among flies from the three regions with regard to the frequency of 1) females that produced only male progeny, and 2) male-determining 3rd chromosomes (IIIm chromosomes). However, the North Dakota and Texas flies were more similar to each other than to the Florida flies since populations from the two former areas possessed a low frequency of both male-producing females and IIIm chromosomes; in contrast, the Florida population was void of females that produced males only and a high percentage if not all Florida males appeared to possess the IIIm male-determining mechanism. Tests for recessive lethal 3rd chromosomes showed that there was no significant difference in the frequency of lethal factors recovered from the North Dakota and Texas flies; the presence of IIIm chromosomes in Florida males precluded the recovery of lethal factors from this population by the method employed. The data suggest that house fly strains to be employed in genetic control programs should 1) originate from target control areas to avoid possible behavioral differences existing among flies from different locales, 2) be initiated with as many flies as possible to provide a background for the maintenance of variability, and 3) be renewed periodically with field-collected material since the genotype may be capable of rapid reorganization in response to laboratory selection pressures.     

Unusual aetosaur armor from the Upper Triassic of West Texas,U.S.A.

We report two unusual aetosaur scutes from the Tecovas Member of the Dockum Formation, Chinle Group (upper Carnian) of Crosby County, Texas, U.S.A. Originally collected by University of Michigan expeditions in the 1920’s, these scutes cannot be assigned with certainty to any known species of aetosaurs known from the American Southwest. One of these scutes may be a cervical horn ofParatypothorax, and if so confirms the similarities of this aetosaur toDesmatosuchus in the possession of horned lateral spikes. The other is a paramedian scute of a new aetosaur taxon inadequately known at present to be assigned a formal name. These scutes indicate that aetosaurs were more diverse in the Chinle Group than currently known, but do not alter the robust Late Triassic biochronology based on aetosaurs.     

Palynology of the Dockum group (Upper Triassic), Texas,U.S.A.

A palynofloral assemblage is described from the Upper Triassic Dockum Group of Texas. Forty palynomorph species are recorded and these are correlated with European Upper Triassic assemblages. The Dockum Group assemblage is considered to be of late Karnian age.Two new genera, Tulesporites gen. nov., type species T. briscoensis sp. nov., and Daughertyspora gen. nov., type species D. chinleanus (Daugherty) comb. nov. have been erected; new species are Converrucosisporites matsenii sp. nov., Pyramidosporites traversei sp. nov., Callialasporites triassicus sp. nov., Plicatipollenites minutotriletus sp. nov., Triadispora dockumensis sp. nov., Bhardwajispora jansonii sp. nov., Protodiploxypinus americus sp. nov., P. ujhelyi sp. nov., Klausipollenites gouldii sp. nov., Pityosporites old-hamensis sp. nov., Abietineaepollenites bujakii sp. nov., Falcisporites oviformis sp. nov. and F. tecovasensis sp. nov.     

Larval Hannemania sp. infestations of Spea spp. in the Southern High Plains, Texas, USA

We describe a case history of larval Hannemania sp. (Acari: Trombiculidae) infestations in two spadefoot toads (Spea spp. Anura: Pelobatidae) captured from playa wetlands in the Southern High Plains, Texas. Hannemania sp. larvae were superficially attached to the skin, not encysted, and dermal changes were not observed. Gross field examinations revealed a presumed occurrence of Hannemania sp. in Spea spp. at four of 24 wetlands in 2003 and 2004. Although other species of amphibians were present (Ambystoma tigrinum mavortium, Bufo cognatus, Bufo debilis insidior, Pseudacris clarkii, Gastrophryne olivacea, Rana blairi, Scaphiopus couchii), investigators did not observe infestations in these species. Future research should focus on identifying this Hannemania to species level and determining if it influences Spea spp. survival.     

Morphological variation in intergrade pupfish populations from the Pecos River, Texas, U.S.A.

In the early 1980s, sheepshead minnow Cyprinodon variegates was introduced into the Pecos River, Texas, U.S.A. where it hybridized with the endemic Pecos pupfish C. pecosensis . By 1985, pupfish populations throughout approximately 300 km of the river consisted exclusively of individuals of hybrid origin (intergrades). There was significant ( P <0·05) geographic variation in most morphological characters; the general pattern of variation was of a bidirectional cline centred near Pecos, Texas. At that site, morphology of intergrade populations resembled mostly that of the introduced species. Upstream and downstream from Pecos, morphology shifted progressively toward that typical of the native form. Intergrade populations were morphologically intermediate to the parental forms, showed a rapid approach to random assortment of characters, and generally exhibited greater morphological variability than occurred in either parent species. These observations and the consistent lack of bimodality in frequency distributions of a morphological hybrid index support the contention that intergrade populations comprise panmictic admixtures of C. variegates and C. pecosensis .