Valve orientation and functional morphology of the foramen of some siphonotretacean and acrotretacean brachiopods

It has recently been suggested that the foramen of siphonotretacean and acrotretacean brachiopods functioned as an exhalant siphon and that it was a feature of the dorsal valve. In representatives of these superfamilies the pedicle was considered to have emerged from between the valves. Re-examination of the evidence on which these arguments were based suggests that some of it is capable of more than one interpretation. The remainder, together with consideration of the mantle canal patterns, cemented mode of attachment, and comparative morphology of some discinaceans and siphonotretaceans, strongly supports the traditional view that the foramen of these forms was located in the ventral valve and that it served as a pedicle opening.     

Egg development of the stoneflies Siphonoperla burmeisteri(Chloroperlidae) and Dinocras cepùnalotes(Perlidae)

SUMMARY. 1. The duration of egg incubation ( Y ) in Dinocras cephalotes and Siphonoperla burmeisteri was related to constant temperatures from 4 to 24°C, by the regression equations Y=2382 T ^{− 1, 402}(r²=0.992, P<0.001) and y= 2683 T ^−1.667 ( r ²=0.994, P <0.001), respectively. No diapause was observed in either species.
2. Egg incubation in D. cephaloles was slow and took 784.9±92.7 (mean ± SD) degree days between 12 and 20°C. significantly more than in S. burmeisteri (445±76.17 degree days: t = 7.44. d.f.=13, P <0.001).
3. For D. cephalotes hatching occurred at temperatures between 12 and 24°C, and for S . burmeisteri between 8 and 20°C. The mean volume of the eggs of D. cephalotes was about 5 times greater than that of S. burmeisteri and the mean body lengths of the newly-hatched nymphs were 1.13 mm and 0.95 mm respectively.
4. This study shows that the freshwater fauna of northern Fennoscan- dia also contains species with warm stenotherm eggs. D. cephalotes. which is of a Mediterranean origin (Zwick, 1981a), may exist at the limit of its distribution in northern Fennoscandia.     

Temporal Organization in Avian Reproduction

Recent studies have demonstrated that biological rhythms haveimportant roles in avian reproduction. In the photoperiodicstimulation of the reproductive complex, there are two systemsinvolved in the interpretation of day length. One system isentrained by the photoperiod, probably by dawn. This entrainedsystem in turn entrains two light-sensitive phases which occurlater in the day. If the photoperi od is long enough, it ispresent during the sensitive phases when it can induce the productionof luteinzing hormone and follicle stimulating hormone. Theinterrenal gland appears to be a part of the entraining systeminasmuch as injections of corticosterone can set a sensitivephase when light can induce gonadal development. The annual cycle of photosensitivity and photorefractorinessappeals to be controlled by the temporal relations between thedaily rhythms of corticosterone and prolactin which change seasonally.When the hormonal relations of photosensitive and photorefractorybirds are simulated by injections of the hormones, the appropriateconditions (photosensitivity or photorefractonness) can be produced.Seasonal changes in the hormonal relations are not direct reflectionsof changes in the photoperiod; they depend on more complex physiologicalexperiences. The systems involved in egg laying and parental behavior mayalso have a temporal basis of biological rhythms. For example,the intensity of the pigeon cropsac response depends on thetime of daily injections of prolactin relative to those of corticosterone.It is apparent that the daily rhythm constitutes the basic structuialunit in the temporal organizationtion of avian reproduction.     

Electrophysiological and behavioural responses to lactic acid stimuli in larvae of Tenebrio molitor L. (Coleoptera: Tenebrionidae) and permeability of antennal sensilla

Abstract. Of the five types of antennal sensilla in larvae of Tenebrio molitor L., only the uniporous long pointed pegs and papillate plates are readily permeable to an aqueous solution of CoCl₂, which is generally indicative of a gustatory function. An electrophysiological investigation confirms the gustatory role of the papillate sensilla on the antenna, and it suggests that they are responsible for mediating the behaviour of larvae toward lactic acid stimuli. Larvae with ablated antennae do not aggregate as would normal animals in the presence of lactic acid stimuli. The uniporous long pointed pegs show no response to lactic acid or other aqueous stimuli.     

CONTINUING THE DEFINITION OF DEATH DEBATE: THE REPORT OF THE PRESIDENT'S COUNCIL ON BIOETHICS ON CONTROVERSIES IN THE DETERMINATION OF DEATH

The President's Council on Bioethics has recently released a report supportive of the continued use of brain death as a criterion for human death. The Council's conclusions were based on a conception of life that stressed external work as the fundamental marker of organismic life. With respect to human life, it is spontaneous respiration in particular that indicates an ability to interact with the external environment, and so indicates the presence of life. Conversely, irreversible apnoea marks an inability to carry out the necessary work of life, an inability which the Council considers an indicator of death. This conception has been conceived to circumvent criticisms of the previous model of loss of somatic integration, a model the Council admits that, in the presence of evidence of continuing functional integration in brain dead patients, was looking less than convincing. Nevertheless, by focusing on external work and ignoring the more essential work of integrative unity, the Council's conception of the nature of life is untenable, and of no assistance in supporting a relation of equivalence between the concepts of brain death and death. Consequently, the Council's conclusions do little to advance the definition of death debate, a potentially intractable debate that may necessitate the investigation of alternate ethical justifications for organ harvesting.