Little has been reported concerning circulus arteriosus cerebri in adult rats. A study of rats' brains perfused with latex and fixed in formalin revealed the general configuration of a circular type pattern of the major ccrebral arteries in which all vessels were patent. N o major vessel was "string-like" and no circles were incomplete. Certain morphological features not described previously were observed. Included among the more significant of these were: (1) the asymmetrical origin of the posterior cerebral artery Pound to occur in more than half of the animals; ( 2 ) the presence of cleft-like buttonhole formations along the anterior cerebral artery o f one or both sides, a feature that was practically species characteristic; ( 3 ) the occasional presence of an anterior communicating artery supplemental to the commonly occurring side to side fusion of the two anterior cerebral arteries. Two animals, possessing two anterior communicating arteries connecting otherwise unfused anterior cerebral arteries, were exceptional; ( 4 ) an olfactory artery to the nasal cavity branched prominently from the anterior cerebral artery in all animals.Before exiting from the cranial cavity through the dorsomedial cribriforrn foramen, the olfactory artery gave origin to a laterally dirccted ramus, the central cribriform artery, that passed through the central cribriform foramen into the nasal cavity.The usefulness served by rats for investigational purposes can not be overstated; yet significant gaps exist in the descriptive anatomy of this animal.The monograph by Howell ('26), the ambitious work of Greene ( ' 3 5 ) and the impressive assemblage of anatomical essays by Farris and Griffith ('49) have collated collectively a tremendous amount of information on the rat. Yet, none of these gives more than meager information at best relative to the major encephalic vessels of the rat. Both Greene ('35) and Farris and Griffith ('49) were satisfied in accepting as identical with the rat and i n substituting for it, Adachi's ('28) description of the circle of Willis of humans, a somewhat unsatisfactory procedure for the presentation of rat morphology. Howell ('26) ignored completely any reference to the circle of Willis.Moffat's ('62) meticulous study clarified much concerning the early embryology of the arteries of the brain of the rat, and this author contributed greatly towards a fundamental understanding of basic concepts relative to the development of specific encephalic vessels (Moffat, '57, '61, 'Bla).

Marine crabs inhabit shallow coastal/estuarine habitats particularly sensitive to climate change, and yet we know very little about the diversity of their responses to environmental change. We report the effects of a rarely studied, but increasingly prevalent, combination of environmental factors, that of near-future pCO2 (~1000 µatm) and a physiologically relevant 20% reduction in salinity. We focused on two crab species with differing abilities to cope with natural salinity change, and revealed via physiological and molecular studies that salinity had an overriding effect on ion exchange in the osmoregulating shore crab, Carcinus maenas. This species was unaffected by elevated CO2, and was able to hyper-osmoregulate and maintain haemolymph pH homeostasis for at least one year. By contrast, the commercially important edible crab, Cancer pagurus, an osmoconformer, had limited ion-transporting capacities, which were unresponsive to dilute seawater. Elevated CO2 disrupted haemolymph pH homeostasis, but there was some respite in dilute seawater due to a salinity-induced metabolic alkalosis (increase in HCO3− at constant pCO2). Ultimately, Cancer pagurus was poorly equipped to compensate for change, and exposures were limited to 9 months. Failure to understand the full spectrum of species-related vulnerabilities could lead to erroneous predictions of the impacts of a changing marine climate.

No abstract

No abstract

No abstract