NOTE Ebert and Southon: Confirmation of longevity for Strongy/ocentrotus franascanus with '""carbon 



917 



2.5 



3.0 



Figure 1 



Jaw growth increments, AJ, for tagged red sea urchins iStrongylocen- 

 trotus franciscanus) from northern California, Oregon, and Washing- 

 ton; fitted Hne is the Tanaka function (Tanaka, 1982, 1988; Ebert et 

 al., 1999) v/ithf= 10.95650 ±0.35064 SElstandard error), d = 0.04937 

 ±0.01664, and a = 8.63029 ±0. 16659; M is approximately 1 year for all 

 samples; (A) entire data set; n = 1582; (B) restricted scale to show just 



jaws larger than 2.0 cm and degree of scatter; n = 336; conversion to 



1 981 7 

 body diameter, D, from jaw length, J, is D =4.8951J ; therefore 



jaw lengths of 2.0 and 2.7 cm would have expected test diameters of 



11.9 and 17.9 cm, respectively. 



E-G are similar to changes shown in coral samples from 

 the Galapagos (Guilderson and Schrag, 1998) and may in- 

 dicate that '■^C levels in surface waters in regions of strong 

 upwelling were still rising when sea urchin were collected 

 in 1992. The conclusion is that '''C analysis supports the 

 age estimates based on tetracycline tagging and use of the 

 Tanaka function: large red sea urchins are old and may 

 have ages of 100 years or more 



Discussion 



The largest reported red sea urchins, with body diam- 

 eters over 19 cm, are from British Columbia, Canada, 

 (Bureau, 1996) and with estimated jaw lengths of about 

 2.8 cm would be expected to be around 200 years old (Fig. 

 2A), Age estimates of lOO-i- years far exceed estimates of 

 life span for other sea urchins (Table 1) based on growth 

 lines in ossicles. Natural growth lines, however, tend to 

 underestimate ages of old individuals because very small 

 increments will have alternations of dark and light areas 

 that are difficult or impossible to resolve and hence counts 

 underestimate age (Ebert, 1988). For example, the maxi- 

 mum age estimate for Strongylocentrotus droebachiensis, 

 the commercial species of the U.S. east coast, is 25 years 

 by counts of growth lines (Robinson and Maclntyre, 1997) 

 but at least twice this if tagging and size structure (Russell 

 et al., 1998) are used. Similarly, tagging and size structure 



of Evechinus chloroticus (Lamare and Mladenov, 2000) 

 have indicated survival rates similar to S. franciscanus 

 but the maximum number of growth lines reported was 

 only 10 (Dix, 1972). Survival rate, however, is not a fixed 

 parameter for a species and there is local variation, as well 

 as geographic patterns, evident in the survival rate for S. 

 franciscanus (Ebert et al. 1999). 



Estimates of annual survival rates based on growth pa- 

 rameters and mean size for red sea urchins from southern 

 California to Alaska (Ebert et al., 1999) indicate that very 

 old individuals would not be expected in southern Califor- 

 nia where few individuals attain ages of 50 years. At more 

 northern locations, the probability of long life increases 

 (Fig. 4) and ages of lOO-i- are expected, particularly in 

 Washington and Alaska. The mechanism causing the lati- 

 tudinal pattern are unclear. Latitudinal differences in sur- 

 vival may be due to increased disease outbreaks associated 

 with higher temperatures in the south (Ebert et al. 1999) or 

 the presence of more predator species in the south (Tegner, 

 2001). Physiological senescence related to temperature is 

 unlikely because there is no pattern to growth differences 

 associated with latitude (Ebert et al., 1999) and no evidence 

 for physiological decline in relative gonad size in the south 

 (Tegner and Levin, 1983) or north (Kramer and Nordin, 

 1975). The largest individuals continue to develop gonad 

 masses in accord with the same allometric relationships 

 as smaller individuals. It is reasonable to conclude that 

 senescence does not occur in red sea urchins. 



