Journal of Experimental Marine Biology and Ecology 256 2001 85–97
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Longevity determines sizes of an adult intertidal barnacle
,1
C.J. Jeffery , A.J. Underwood
Centre for Research on Ecological Impacts of Coastal Cities and Institute of Marine Ecology ,
Marine Ecology Laboratories , A11, University of Sydney, Sydney, NSW 2006, Australia
Received 25 May 2000; received in revised form 16 October 2000; accepted 17 October 2000
Abstract
The small honeycomb barnacle Chamaesipho tasmanica Foster and Anderson often forms continuous sheets covering the substratum at mid-shore levels of sheltered rocky shores but also
occurs in sparse distributions on exposed shores, and on higher levels of sheltered shores, in south-eastern Australia. Larger barnacles are generally found in more exposed and higher areas.
Effects of each site on ultimate sizes of barnacles were therefore examined by measuring growth of barnacles of the same cohort at sheltered and exposed shores from the end of 1989 to the end of
1992. Because Chamaesipho varied in size among sites, and because size was not necessarily representative of age, three growth models were proposed to explain this size differential. While
rates of growth and periods of growth did not differ, differences in longevity were found to influence size so that larger barnacles survived longer and were more abundant on the more
exposed shores. In fact, when barnacles were aged, it was found that a greater proportion of older barnacles
. 3 years of age occupied these exposed areas. It seems that site-specific characteris- tics influenced longevity in some places so that larger Chamaesipho continued to predominate in
these areas. Crown copyright
2001 Published by Elsevier Science B.V. All rights reserved.
Keywords : Australia; Barnacle; Chamaesipho; Growth; Longevity; Models
1. Introduction
Environmental cues influence growth of barnacles Crisp, 1960; Bertness, 1989; Bertness et al., 1991; Shkedy et al., 1995; Calcagno et al., 1997. Rates of growth in
barnacles will vary under differing conditions of wave-exposure Bertness, 1989;
Corresponding author. Tel.: 161-2-9385-1825; fax: 161-2-9662-7995.
E-mail address : c.jefferyunsw.edu.au C.J. Jeffery.
1
Present address: Centre for Marine and Coastal Studies, University of New South Wales, Sydney, NSW 2052, Australia.
0022-0981 01 – see front matter Crown copyright
2001 Published by Elsevier Science B.V. All rights
reserved. P I I : S 0 0 2 2 - 0 9 8 1 0 0 0 0 3 0 7 - 5
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.J. Jeffery, A.J. Underwood J. Exp. Mar. Biol. Ecol. 256 2001 85 –97
Bertness et al., 1991; Shkedy et al., 1995 and will also vary in species of barnacles where adjoining walls fuse Connell, 1961; Luckens, 1975; Hui and Moyse, 1987.
Bertness et al. 1991 recorded greater growth in Semibalanus balanoides in low tidal areas where barnacles were dense and where water velocity and wave-exposure were
large, rather than in upper habitats or those with smaller wave-exposure or velocities. Crisp 1960 also found an association between increased current flow and growth of
barnacles. Increased growth of Semibalanus in exposed habitats Hatton and Fischer- Piette, 1932; Moore, 1934, 1935 can also be linked to reduced algal cover in these areas
Barnes, 1955. Similarly, Luckens 1970 found that the barnacle Chamaesipho brunnea in New Zealand grew faster when submerged for longer periods but rates of
growth were density-dependent. That is, the more dense populations in the upper range of distribution of this species had slower rates of growth than sparse populations lower
on the shore. In addition, Shkedy et al. 1995 showed that growth of Balanus amphitrite was fastest on upper levels with greatest exposure, rather than on middle and lower
levels of the shore where barnacles were more dense.
Considerable variation in distribution and abundance of populations of the small honeycomb barnacle Chamaesipho tasmanica exists from place to place at the Cape
Banks Scientific Marine Research Area Sydney, Australia; small patches of larger barnacles often inhabit exposed areas, and higher levels of sheltered shores, whereas
large numbers of smaller barnacles carpet the mid-littoral substratum on sheltered shores. It may be, therefore, that larger barnacles are generally found on these upper and
more exposed shores because growth is fastest here. Apart from faster growth, adults may be of different sizes in different areas because they grow for longer periods or
because they survive longer in some areas. Three models were therefore proposed to explain the differences in size of adult Chamaesipho in different sites at Cape Banks.
The first model is that barnacles may grow faster at some sites — therefore finishing growth at a larger size in these areas. It was predicted that, if the same cohort of
barnacles were measured from juvenile
, 1 mm to adult sizes, rate of growth of these juveniles in different areas should be correlated with the sizes of adults in these areas.
The second model proposed that barnacles grow at the same rate, but have longer periods of growth in some areas. It was predicted that, if juveniles from the same cohort
were measured from settlement, the periods during which barnacles in different areas grew should be correlated with sizes of adults in these areas. The third model is that
barnacles keep growing, but live longer at some sites. Therefore, if juveniles from the same cohort were measured there should be a correlation between longevity of these
juveniles and size of adults. Greater longevity will be recorded in areas where barnacles are relatively large.
2. Materials and methods
