Osmoregulation in elephant fish, CALLORHYNCHUS MILLII (HOLOCEPHALI)

Osmoregulatory mechanisms in holocephalan fishes are unknown except that they conduct urea-based osmoregulation as in elasmobranchs. We, therefore, examined changes in plasma parameters of elephant fish, Callorhynchus millii, after gradual transfer to concentrated (120%) or diluted (80%) seawater (SW). In control fish, plasma Na and urea concentrations were about 300mM and 450mM, respectively. These values were equivalent to those of sharks and rays, but the plasma urea concentration of elephant fish was considerably higher than that reported for chimaeras, another holocephalan. After transfer to 120% SW, the plasma Na concentration markedly increased, while a conspicuous decrease in plasmaurea concentration was observed following transfer to 80% SW. In elephant fish, we could not find a discrete rectal gland. Instead, approximately 10 tubular structures were located in the wall of post-valvular intestine. Each tubular structure was composed of a putative salt-secreting component consisting of a single-layered columnar epithelium, which was stained with anti-Na+,K±ATPase serum. It is most likely that the tubular structures in the posterior intestine represent a primitive form of the rectal gland in elephant fish. In addition, we have identified two C-type natriuretic peptides (CNPs) from the heart and brain of elephant fish, which may contribute to the control of NaCl excretion from the rectal gland of elephant fish as it does in elasmobranchs.

Implementing elements of Schon's reflective practitioner in an undergraduate public relations program

While the internship unit in a public relations degree is often viewed as the foremost area of experiential learning it can fail to deliver significant learning outcomes for student and teacher. This paper explores the use of other activity-based learning (ABL) methods as implemented in the Deakin University public relations undergraduate degree. The paper applies Donald Schon's concept of the reflective practitioner to learning undertaken in an internship unit and compares this application to two other units where ABL is used and the focus is on creating a client-professional relationship. For the purpose of this paper information was analysed using the 2006 on-campus cohort only. The cohort was further refined to include those students who successfully completed the degree of BA in public relations. Student internship evaluation forms and unit records were viewed to gain statistical information.