4 R.H.M. Eertman 
Table 1. Interspecific relationships between the investigated species taken into account the revised classification as 
reviewed by Haszprunar (1988) and Bieler (1992). 
CLASS SUBCLASS ORDER SUPERFAMILY ` FAMILY SUBFAMILY | GENUS SPECIES 
Gastropoda Prosobranchia, Patellogastropoda  Patelloidea Acmaeidae Patelloida __P. mimula 
Neritimorpha — Neritoidea Neritidae Nerita __N. chameleon 
Vetigastropoda — — Trochoidea Trochidae Austrocochlea — A. constricta 
Caenogastropoda __Littorinoidea Littorinidae ` Littorininae. Littorina . .L. articulata 
Lacuninae __Bembicium ` B.auratum 
Cerithioidea Planaxidae Planaxis __P. sulcatus 
| Muricoidea Muricidae Morula —M. marginalba 
In the present study the ctenidia of a number of common gastropods from Moreton Bay were 
investigated with SEM and LM. The purpose of selecting a range of gastropods was to test, for the 
first time, the level of difference in gill ultrastructure between major taxa (e.g. clades such as 
Patellogastropoda (Patelloida mimula), Neritimorpha (Nerita chameleon) and Vetigastropoda 
(Austrocochlea constricta) versus the more 'advanced' Caenogastropoda, including representatives 
of the families Muricidae (Morula marginalba), Planaxidae (Planaxis sulcatus) and Littorinidae. By 
examining two local species of the caenogastropod family Littorinidae (a world-wide and well 
defined group), results could be compared at the intergeneric level (Littoraria articulata versus 
Bembicium auratum) and also viewed in relation to the various niches occupied by littorinids within 
the study area. The results will be discussed in the context of the systematics of the species involved 
(Table 1), taking into account the latest reorganisation of the *prosobranch' classification as reviewed 
by Haszprunar (1988) and Bieler (1992). 
Materials and methods 
Animals: АП investigated species were collected during low tide at Wellington Point on the western 
shore of Moreton Bay, South-East Queensland, where they inhabit the intertidal zone on rocky 
shores and jetty piles (Eertman and Hailstone, 1988). The animals were transferred to the laboratory, 
where they were held in 10 | aquariums filled with seawater taken from the collection site. The water 
was continuously aerated and maintained at a constant temperature of 22 "C. The animals were 
allowed to acclimatize to laboratory conditions for at least 48 hours before the gills were removed. 
Scanning Electron Microscopy: The shell of a species was carefully cracked with a vice, and then the 
animal removed. The gills were excised and rinsed in freshly filtered seawater, before being left in 
16 % glycerol for 1 hour to remove the bulk of mucous deposits (Mariscal et al., 1978). The gills 
were then sonicated (Unosonics sonicator) for one or two periods of 30 seconds in freshly prepared 
16 % glycerol to remove any remaining mucous. After a further rinse in fresh seawater, the gills 
were fixed for 2 hours in 3 % glutaraldehyde, prepared with 0.1 M phosphate buffer (osmotically 
adjusted with 5 % sucrose, to prevent tissue damage caused by osmotic shock). As mucous particles 
sometimes remained attached to the surface of the gill filaments, the gills were sonicated for an 
additional period of 30 seconds in 5 96 (v/v) NH,OH after fixation. After a final rinse in 0.1 M 
phosphate buffer, the tissue was dehydrated in a graded series of ethanols and critical point dried 
after two changes of amyl acetate. The gills were gold-coated in a SPI sputter coater and examined 
using a Philips SEM 505. 
Transmission Electron Microscopy: The gills were fixed for 2 hours in 3 96 glutaraldehyde, prepared 
with 0.1 M phosphate buffer (with 5 % sucrose added). After a rinse in phosphate buffer, they were 
postfixed for 80 minutes in phosphate buffered 1 % osmium tetroxide. Subsequently the gills were 
