Rees (1959) from rearing experiments in the labo- 

 ratory. Larval development lasts 28 days and 

 normally encompasses at least six zoeal stages. 

 Rees also described the megalops stage which re- 

 sembles the adult in shape. 



Wharton found megalops in large numbers in 

 sand washed by waves. This stage swims with 

 the abdomen extended, whereas young adults 

 swim with the abdomen flexed. Megalops and 

 young adults were found to be distributed evenly 

 in the wave-washed zone rather than in colonies 

 as are adults. Wharton traced development of the 

 pleopods of females from the truly swimming 

 appendages of the megalops to the uniramous non- 

 swimming pleopods of adults. Adult males lack 

 pleopods. 



The average carapace length of young adidt 

 females increased from 3 mm. in early summer to 

 8 mm. the following May, and by August had in- 

 creased to 18 mm. (maximum, 26 mm.). Whar- 

 ton thought that females have one reproductive 

 period in summer at an age of about 1 year, then 

 live a short time longer and die at an age of about 

 1 year and 3 months. Williams (1947), studying 

 size- frequency distributions, thought that they 

 live to be 2 years of age, and Edwards and Irving 

 (1943) stated that at Woods Hole females live 

 27 months, males 25. Since large females (to 21 

 mm.) can be taken in winter, the latter estimates 

 are more likely correct, and Wharton's 26-mm. 

 female was probably 2 years old. 



Small males appear about the same time as 

 females. Sexually mature at very small sizes (car- 

 apace length, 3 mm.) they seek out and attach 

 themselves to year-old females. As many as seven 

 small males were found on a single large female, 

 and Wharton judged that they remain attached 

 for long periods : 



The attachment of the small males to the large females 

 is achieved by various methods. These semiparasitic 

 mates have been found in the gill chambers, clamped be- 

 tween the coxae of the thoracic appendages, attached to 

 egg masses, clamped by means of their telson to the 

 ovigerous hairs of the pleopods, and some seen to roam 

 about on the ventral surface of the larger females. A few 

 males seemed to be attached by means of the spermato- 

 phores which are extruded from the basal segment of the 

 fifth leg ; however, these may have been merely depositing 

 the spermatophores. 



By winter, the males are free living, and by the 

 following June attain a size of about 7 mm. (max- 



imum, 10 mm.). Wharton thought that these die 

 in July after a possible second mating period. 



It was estimated that growth of large females 

 from early June to late August may be as much as 

 0.08 mm. per day. However, both Wharton (1942) 

 and Williams (1947) noticed that there is con- 

 siderable annual fluctuation in size at the same 

 locality, and Williams further stated that there 

 is considerable variation in size between localities 

 in the same year. 



The beautiful adaptations of this species for 

 life in the shifting sand of the surf zone were 

 treated by Wharton, and the anatomical speciali- 

 zations were exhaustively discussed by Snodgrass 

 (1952). Adults can swim by means of the uropods, 

 but they are primarily adapted for burrowing 

 backward into wet sand. This is accomplished by 

 rotating the uropods in unison, throwing sand 

 dorsally, moving the second, third, and fourth 

 legs laterally and posteriorly in unison, and by 

 pushing the first legs alternately laterally and 

 anteriorly. Once the animal is buried, the fringed 

 antennae are allowed to lie on the sand extended 

 anterolaterally to strain the receding water of 

 waves. Stomach contents consist of small par- 

 ticulate matter, but the exact method of trans- 

 fer of food from the antennae to the mouth is 

 unknown. 



Emerita talpoida moves up and down the beach 

 with the tide, following shallow waves toward the 

 water or moving up the beach with deep waves. 

 Jones (1936) compared the habits of E. emerita 

 to those of E. talpoida and devised a clever 

 method of marking animals with string for the 

 purpose of tracing their movements on the beach. 



Edwards and Irving (1943) studied the influ- 

 ence of temperature and season on oxygen con- 

 sumption in E. talpoida at Woods Hole. They 

 found that oxygen consumption of winter animals 

 at 12° C. is about the same as that of the smallest 

 summer animals at 17° C; consumption of winter 

 animals at 3° C. is about the same as that of sum- 

 mer animals at 13° C. They concluded that E. 

 talpoida from the Woods Hole area becomes ad- 

 justed to seasonal changes in temperature in such 

 a manner that rate of metabolism in winter is 

 kept at a level comparable to that in summer. This 

 explains why growth is imiform throughout the 

 year, though the animals live in 6 to 12 feet of 

 water in winter rather than in the surf. The 

 method of feeding in winter was not discussed. 



MARINE DECAPOD CRUSTACEANS OF THE CAROLENTAS 



141 



