HAYNES: EARLY ZOEAL STAGES OF LITHODID CRABS 



DISTINCTION BETWEEN ZOEAE OF 

 LITHODIDAE AND PAGURINAE 



Zoeae of the family Lithodidae have long been 

 considered similar morphologically to those of the 

 subfamily Pagurinae (family Paguridae) and dif- 

 fer only in reduction or disappearance of the 

 uropods (Gurney 1942; MacDonald et al. 1957). 

 Recent descriptions of zoeae of Cryptolithod.es 

 typicus, Lithodes aequispina, L. antarctica, and 

 Paralomis granulosa (Hart 1965; Haynes 1982; 

 Campodonico 1971; Campodonico and Guzman 

 1981) have extended the range of zoeal characters 

 of the Lithodidae and show that zoeae of the 

 Lithodidae and Pagurinae can be distinguished by 

 size of the eyes and morphology of the carapace 

 and abdominal appendages (Table 1). In general, 

 zoeae of the Lithodidae (except Cryptolithodes 

 typicus ) are characterized by stoutness, small 

 eyes, posterolateral spines in middle or lower half 

 of carapace, uniramous uropods, and no anal 

 spine. Zoeae of the Pagurinae are characterized 

 by slenderness, large eyes, posterolateral spines 

 in the middle or upper half of the carapace, 

 biramous uropods, and an anal spine. The glau- 

 cothoe of the Lithodidae and Pagurinae are read- 

 ily distinguished from each other by their simi- 

 larity to the adults (Haynes 1982). 



TABLE 1. — Characters useful for distinguishing between zoeae 

 of Lithodidae and zoeae of Pagurinae from the northern North 

 Pacific Ocean. Zoeae of Cryptolithodes typicus (Lithodidae i are 

 an exception and are not characterized in this table. 



Lithodidae 



Pagurinae 



1 . General appearance, stout. 

 2 Longitudinal diameter of eye 



less than width of abdomen. 

 3. Posterolateral spines of 



carapace in middle or lower 



half of posterior margin. 

 4 Lateral margins of carapace 



nearly parallel 



5. No anal spine in any stage 



6. More than eight pairs of 

 telsonic spines in some 

 species (excluding minute 

 seta). 



7. Uropods (when present) 

 uniramous and terminal 

 margin blunt with (usually 

 three or four) short setae. 



General appearance, slender 

 Longitudinal diameter of eye 

 greater than width of abdomen. 

 Posterolateral spines of carapace 

 in middle or upper half of posterior 

 margin. 



Lateral margins of carapace 



converge posteriorly. 



Anal spine present until Stage III 



in some species 



Never more than eight pairs of 



telsonic spines (excluding seta). 



Uropods biramous. exopodite 

 styhform terminally with usually 

 more than three or four long setae 

 along medial margin. 



MORPHOLOGY OF LITHODID 

 LARVAE 



Lithodidae of the northern North Pacific Ocean 

 have four zoeal stages and a glaucothoe. Stage I 



zoeae are characterized by sessile eyes, four nata- 

 tory setae on maxillipeds 1 and 2; maxilliped 3 is 

 undeveloped and without natatory setae; pleopods 

 and uropods are absent; and the telson and abdom- 

 inal somite 6 are fused. Beginning in Stage II, the 

 eyes are movable, and maxillipeds have at least 

 six natatory setae. In Stage III, undeveloped 

 pleopods and uropods are present, and the telson 

 and abdominal somite 6 are articulated. In Stage 

 IV, the pleopods are biramous, and the uropods are 

 two segmented and usually have three or four 

 apical setae. Table 2 and the keys are provided for 

 distinguishing described zoeae and glaucothoe of 

 Lithodidae of the northern North Pacific Ocean. 

 Glaucothoe of H. grebnitzkii, P. wosnessenskii, 

 and R. wosnessenskii have not been described. 



TABLE 2. — Characters useful for distinguishing between Stages 

 I-IV of lithodid zoeae of the northern North Pacific Ocean. 

 Paralithodes brevipes may have only three zoeal stages (Kurata 

 1956), thus, may not always conform to the descriptions in 

 this table. 



Described Lithodid Zoeae of 

 the Northern North Pacific Ocean 



la. Carapace without posterolateral spines; 

 uropods absent in all stages; posteri- 

 or margin of telson without medial 

 invagination Cryptolithodes typicus 



lb. Carapace with posterolateral spines; 

 uropods present in later stages (usually 

 Stages III and IV); posterior margin of 

 telson with medial invagination 2 



2a. Posterolateral spines of carapace short 



(< 1/4 carapace length) 3 



2b. Posterolateral spines of carapace long 



( > 1/4 carapace length) 5 



3a. Posterolateral spines and denticles on 

 abdominal somites 3 and 4 about same 

 length; posterior margins of carapace 

 concave Hapalogaster grebnitzkii 



3b. Posterolateral spines obviously longer 

 than denticles on abdominal somites 



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