ARMETTA and STEVENS: BIOLOGY OF THE HAIR CRAB 



100m 



58°N 



80 



— ' — 



160 

 1 I 



173°W 



170' 



167' 



164' 



16r 



Figure 10. — Locations and densities of Erimacrus isenbeckii larvae collected in the southeastern Bering Sea, 

 1976-81. Locations where no larvae were found are omitted. With permission, from Armstrong et al. 1983 (see text 

 footnote 4). 



strong et al. 1984^M. Highest concentrations (over 

 20,000 larvae/100 m^ at one station) were found 

 in waters 40-80 m deep, within about 24 km of St. 

 Paul Island. Very few larvae were found near St. 

 George Island. 



Reproduction 



The gonopore plugs found in female hair crab 

 collected by NMFS resembled those described by 

 Yoshida ( 1940) as having a "distal end that swells 

 into an irregular form outside the aperture" and 

 were of male origin (Morado^^). The proximal tip 

 of the plug extends to the spermatheca, as noted 



iiArmstrong, D. A., J. L. Armstrong, G. Jensen, R. Palacios, 

 and G. Williams. 1984. Distribution, abundance, and biology 

 of blue king and Korean hair crabs around the Pribilof Is- 

 lands. Interim Rep. OCSEAP/OMPA contract No. 83-ABC- 

 00066. Office of Marine Pollution Assessment, Alaska Office 

 RD/MPF24, P.O. Box 1808, Juneau, AK 99802. 



12J. F. Morado, Fisheries Research Biologist, Northwest and 

 Alaska Fisheries Center. National Marine Fisheries Service, 

 NOAA, 7600 Sand Point Way N.E.. Seattle, WA 98115, pers. 

 commun. May 1982. 



also by both Yoshida and Hirano (1935). The flex- 

 ible, swollen membrane (Fig. 8c) that closed the 

 aperture of some females is apparently not an 

 exogenous plug, but a part of the female crab's 

 body. The purpose of gonopore plugs is not known, 

 but Hirano (1935) has conjectured that they serve 

 to prevent copulation with other males during the 

 period between the completion of copulation and 

 spawning. They may also prevent degradation of 

 the sperm from contact with seawater. Hartnoll 

 (1969) reported that similar plugs have been ob- 

 served in Cancer irroratus, C. pagurus, Cal- 

 linectes sapidus, and Carcinus maenas and sur- 

 mised that they prevent loss of sperm from female 

 crabs which mated while still soft, or that they 

 are a vestigial remnant of a hard sperm-case ap- 

 plied externally by more primitive ancestral 

 brachyurans. 



The following sequence of events is suggested 

 by the observed associations between shell condi- 

 tion of female crabs and the presence or absence 

 of gonopore plugs. After mating, the plugs loosen 

 and slough off, either by mechanical abrasion 

 (Yoshida 1940) or by dissolution from within as 



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