915 



Red sea urchins (Strongylocentrotus franciscanus) 

 can live over 100 years: confirmation with 

 A-bomb carbon 



Thomas A. Ebert 



Department of Zoology 



Oregon State University 



Corvallis, Oregon 97331-2914 



E mail address eberttfn'sciences oregonstate edu 



John R. Southon 



Center for Accelerator Mass Spectrometry 

 Lawrence Livermore National Laboratory 

 Livermore, California 94551-9900 



Red sea urchins (Strongylocentrotus 

 franciscanus) along the west coast of 

 North America, like most large sea 

 urchins in temperate waters world- 

 wide, are the focus of a commercially 

 important fishery. In a review of bio- 

 logical data for purposes of fishery 

 management, the life span of red sea 

 urchins was suggested to be 7-10 

 years (Sloan, 1986) and they have 

 been included with much shorter-lived 

 species for illustrating complex popula- 

 tion dynamics (Hastings and Higgins, 

 1994). Recent work with tetracycline 

 and calcein tagging (Ebert, 1998; Ebert 

 et al., 1999), however, has shown that 

 individuals continue to grow through- 

 out life, although at a very slow rate, 

 and large individuals are estimated to 

 be in excess of 100 years old. A poten- 

 tial problem with the studies using 

 tetracycline and calcein is that one- 

 year time intervals were used between 

 tagging and recapture and therefore it 

 is possible that occasionally there may 

 have been very good years for growth 

 that were missed. If occasional growth 

 spurts occurred, largest sizes would 

 have been attained in much less than 

 100 years. The potential problem of 

 missed good years for growth could be 

 resolved with a marker that captures 

 a longer period of time. The accuracy 

 of age estimates has consequences 

 for resource management where size 

 limits may need adjustment in order to 

 protect older individuals (Hilborn and 



Walters, 1992; Congdon et al., 1994; 

 Ebert, 1998). There is also the need to 

 understand the evolution of life histo- 

 ries of species where long life tends to 

 be an indicator of uncertainty in indi- 

 vidual reproductive success (Murphy, 

 1968; Roff 1992; Stearns, 1992). 



Enhanced radiocarbon in the oceans 

 due to atmospheric testing of nuclear 

 weapons that began in the 1950s (Ny- 

 dal and Lovseth, 1983; Broecker et 

 al., 1985, Duffy et al., 1995) provides 

 a permanent marker in carbonate- 

 based skeletal elements that are not 

 reworked by resorption and deposition 

 during growth and hence has a long 

 time period between mark and recov- 

 ery. The enhanced radiocarbon marker 

 has been used in various studies to 

 validate the periodic (usually annual) 

 nature of growth zones in fish (Kalish, 

 1993, 1995; Campana, 1997; Campana 

 et al., 2002) and invertebrates (Tureki- 

 an et al., 1982; Witbaard et al.. 1994; 

 Peck and Brey, 1996) where validation 

 by chemical tags such as tetracycline 

 has been impractical. Red sea urchins 

 lack interpretable growth zones (Breen 

 and Adkins, 1976) and therefore there 

 is no natural feature to serve as a cross 

 check for studies using chemical tags. 

 In the present study we present a test 

 and confirmation of age in red sea 

 urchins estimated from tetracycline 

 tagging using an enhanced ^*C signal 

 in the ocean from nuclear weapons 

 testing. 



Materials and methods 



Red sea urchins were tagged with tet- 

 racycline from 1989 to 1992 in northern 

 California, Oregon, and Washington 

 and collected after time intervals of 

 approximately one year (details pre- 

 sented in Ebert et al., 1999). It is not 

 possible to determine whether a live 

 sea urchin has a tetracycline mark 

 and therefore large collections had 

 to be made. Skeletal elements were 

 cleaned with sodium hypochlorite 

 bleach to remove all organic material 

 not bound in the calcite of the skeleton, 

 and then skeletal ossicles were exam- 

 ined by using UV illumination to detect 

 the tetracycline marks, which fluoresce 

 yellow. Growth increments were mea- 

 sured in jaws of Aristotle's lantern of 

 1582 tagged-recovered red sea urchins 

 and used to estimate growth parame- 

 ters. Jaw ossicles, the demipyramids of 

 Aristotle's lantern, are internal skeletal 

 elements that grow around all surfaces 

 but not equally in all directions so that 

 a change in jaw length, AJ , is mostly 

 at the end closest to the esophagus 

 and there is little growth closest to the 

 mouth, the labial end, where the teeth 

 extend from the jaw. 



The Tanaka function (Eq. 1) was used 

 to describe growth (Tanaka, 1982, 1988) 

 because it can model data that show an 

 initial lag, an exponential phase with a 

 maximum, and can include continuing 

 growth throughout life. This function 

 is described in greater detail else- 

 where (Tanaka, 1982, 1988; Ebert et 

 al., 1999). The usual formulation of the 

 Tanaka model is zisize as a function of 

 size at time t and At is assumed to be 

 fixed for all individuals in the sample, 

 usually at zit = 1 year (Tanaka, 1982, 

 1988; Ebert, 1998; Ebert et al., 1999) 

 and not included explicitly in the equa- 

 tion. In the present study we estimated 

 the amount of jaw that would have to 

 be removed to represent the time span 

 from the time of collection in the 1990s 

 with relatively high i*C levels to the 

 time before atmospheric testing of 

 atomic bombs (relatively low '■'O and 



Manuscript approved for publication 

 10 July 200.3 by Scientific Editor. 



Manuscript received 13 July 2003 at 

 NMFS Scientific Publications Office. 



Fish. Bull. 101(4):915-922 (2003). 



