SOMERTON: LIFE HISTORY OF DEEP-SEA KING CRAB 



centrations at the depth inhabited by L. couesi 

 reduce the ability of females to aerate clutches 

 larger than some fixed size. 



One consequence of an asymptotic form to the 

 fecundity and size relationship is that the repro- 

 ductive effort, or the proportion of the total energy 

 intake devoted to reproduction, must decrease 

 over some part of the reproductive lifespan of 

 L. couesi. Theory predicts and many animals 

 display an increase in reproductive effort with age 

 (Pianka and Parker 1975). Since fecundity ap- 

 pears to be fairly constant over approximately 

 one-half of the mature size range of L. couesi, 

 reproductive effort could increase only if either 

 egg size increased with age or growth ceased. 

 Individual dried egg weight, however, does not 

 increase with crab size (P = 0.15), and the lack of 

 wear and accumulation of epifauna on the exo- 

 skeleton suggests that molting, and presumably 

 growth, continues throughout the life of females. 



Egg Size 



Lithodes couesi eggs in a late stage of develop- 

 ment have a mean length of 2.3 mm (SD = 0.076, 

 N — 33). This size is quite similar to previous 

 estimates of mean or median egg size reported for 

 other species in the genus Lithodes — L. antarc- 

 tica, 2.2 mm (Guzman and Campodonico 1972); L. 

 aequispina, 2.1 mm (Hiramoto and Sato 1970) — 

 but roughly twice the egg size reported for species 

 in the genus Paralithodes — P. camtschatica , 

 1.0 mm (Haynes 1968); P. platypus, 1.2 mm 

 (Sasakawal975). 



The larger size oi Lithodes spp. eggs compared 

 with Paralithodes spp. eggs conforms to a theory 

 of egg size and pattern of larvae development first 

 discussed by Thorson (1950), which proposes that 

 benthic invertebrates generally have large eggs 

 and lecithotrophic larvae in high latitudes or 

 in deep water, but have small eggs and plank- 

 totrophic larvae in other areas. At great depths or 

 at high latitudes water temperatures are low and 

 larval development is protracted. Species may 

 compensate for slow larval development by pro- 

 ducing larger and more yolky eggs, which in turn 

 result in larger larvae with greater energy re- 

 serves. These larval features may be necessary to 

 allow the larvae either to migrate to the surface, to 

 capture a broader array of food items, or to forgo 

 feeding entirely. Stage 1 zoeae of L. couesi have 

 conspicuously more yolk than P. camtschatica 

 larvae in the same stage of development (J. 



Bowerman ), but it is unclear whether or not 

 these larvae migrate to the surface. Unusually 

 large eggs have been previously reported for 

 abyssal shrimp (Zarenkov 1965) and abyssal crabs 

 (Garth and Haig 1971). 



Parasites 



Of the 674 female L. couesi examined, 5 were 

 parasitized by the rhizocephalan, Briarosaccus 

 callosus. All five females were >90 mm and, on 

 the basis of size alone, should have been mature, 

 but none were carrying eggs and all had unusually 

 small pleopods compared with uninfected crabs of 

 similar size. Thus, similar to other species of crabs 

 (Barnes 1974), L. couesi females are apparently 

 castrated by B. callosus. One male L. couesi was 

 also observed with the parasite; however, the 

 abdomens of males were not routinely examined 

 and other parasitized males could have been 

 missed. Briarosaccus callosus has been previously 

 reported as a parasite of L. couesi (Boschma 1970). 



Adaptations for Life on the Upper Slope 



Lithodes couesi is conspicuously different in 

 appearance (Figure 7) from the shallow-water 

 king crabs, P. camtschatica and P. platypus, 

 because of three features: 1) bright red, 2) inflated 

 branchial chambers, 3) elongated legs. All of these 

 features are apparently adaptations for living in 

 deeper water. 



The red coloration of deepwater crustaceans has 

 long been a subject for speculation, but the general 

 consensus is that within some range of depth, red 

 is cryptic due to the rapid attenuation of red light 

 originating from the surface and the low in situ 

 production of red light from bioluminescence 

 (Marshall 1954). At depths greater than this 

 range, the ambient light is too weak for visual 

 predators and crustaceans are often white or 

 transparent (Zenkevich and Birstein 1956); at 

 depths shallower than this range, red may be 

 too conspicuous to visual predators and the red 

 cartenoid pigments are often complexed with 

 proteins to produce blue, green, and brown pig- 

 ments (Goodwin 1960). 



Crabs living on the continental slope have 

 branchial chambers which are more inflated than 



"J. Bowerman, Fishery Biologist, Northwest and Alaska 

 Fisheries Center Kodiak Laboratory, National Marine Fish- 

 eries Service, NOAA, RO. Box 1638, Kodiak, AK 99615, pers. 

 commun. June 1980. 



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