Snover and Hohn: Validation and interpretation of skeletal marks in Caretta caretta and Lepidochelys kempu 



685 



LK-7 and LK-8 were difficult to inter- 

 pret and in our initial assessment we 

 underestimated age by one year. In 

 both of these samples, the LAG rep- 

 resenting the end of the second GM 

 was very close to the outer edge of the 

 bone cross-section and was difficult 

 to differentiate from the edge. Hence 

 these samples were not counted in the 

 initial assessment. Because both of 

 these animals died in the fall, there 

 would have been a full growing sea- 

 son, and hence a growth zone, follow- 

 ing the completion of the second GM. 

 Both of these animals were recovered 

 dead in Cape Cod, Massachusetts, 

 during the fall of 1999 when record 

 numbers of cold-stunned sea turtles 

 stranded in that region. 



Humerus cross-sections from LK-9 

 through LK-13 (Fig. 3) showed poorly 

 defined annuli at the end of the first 

 GM — annuli similar to the poorly 

 defined annulus in LK-4 (Fig.2A). 

 Subsequent GMs in these humerus 

 cross-sections contained well-defined 

 LAGs. Without prior knowledge of 

 these animals' history we accurately 

 aged each of them from GM counts 

 and stranding date. Specimens LK-9 

 through LK-13 demonstrated clearly 

 that well-defined LAGs were depos- 

 ited at the end of year two and in 

 subsequent years, providing evidence 

 that any lines between the year-one 

 annulus and the year-two LAGs were 

 supplemental. 



Known-age loggerhead sea turtles 



The first known-age loggerhead sea 

 turtle, CC-1, was 29.4 years old. 

 Eleven LAGs were discernible around 

 the circumference of the bone cross- 

 section (Fig. 4A), although the LAGs 

 become too compressed on the lateral 

 edges of the bone to be differentiated; 

 hence counts were made on the ven- 

 tral and dorsal edges.! Fig. 4). Trac- 

 ing the LAGs from the lateral to the 

 ventral edge of the bone, we observed 

 that these LAGs at some point became 

 bifurcating and splitting LAGs and we 

 interpreted each branch as a separate 

 LAG. An additional nine LAGs can 

 still be seen within the resorption zone 

 in most areas of the bone (Fig. 4B). On 

 the dorsal side of the cross-section, at 

 least four less-distinct LAGs or annuli 

 could still be observed; these had been 



LAG-4 CAG"-3- 



E 

 GM-' 



Figure 1 



Image of a humerus cross-section from a headstart Kemp's ridley {Lepido- 

 chelys kempii, LK-1) sea turtle. GM-1 refers to growth mark one; LAG-2, 

 LAG-3, and LAG-4 refer to the lines of arrested growth ending growth marks 

 two, three, and four. Curved dashed lines highlight GM-1 and the LAG. 

 Black bar represents 1 mm in length. This specimen was 5.0 years old. 



Annulus ending 

 GM-1 



B 



/? 



Supplementa 



lines 



Annulus ending 

 GM-1 



Figure 2 



Images of humeri cross-sections of two coded-wire-tagged Kemp's ridley 

 sea turtles (L. kempii). GM-1 refers to growth mark one. Black bar repre- 

 sents 1 mm for both images. (A) Specimen LK-4 was 1.27 years old. (B) 

 Specimen LK-6 was 1.72 years old. 



