HAYNES: PANDALUS GONWRVS LARVAE 



1 . mm 



0. 5 mm 



Figure 6. — Stage VI (megalopa) of Pandalus goniurus: A, ros- 

 trum; B, telson. 



1 . mm 



0. 5 mm 



Figure 7. — Stage VII (first juvenile) oi Pandalus goniurus: A, 

 rostrum; B, telson. 



COMPARISON OF LARVAL STAGES 



WITH DESCRIPTIONS BY 



OTHER AUTHORS 



Ivanov (1965) described and illustrated the first 

 stage zoeae of P. goniurus that he reared in the 

 laboratory from known parentage. His descrip- 

 tions agree in all aspects with mine except for the 

 third maxillipeds: Ivanov's zoeae had 9 natatory 

 setae on the exopodite compared with 12 natatory 

 setae in my zoeae. 



The only other description of P. goniurus larvae 

 known to me is that of Makarov (1967) who con- 

 structed a series of zoeal stages from plankton of 

 the western Kamchatka coast based on Ivanov's 

 description of Stage I. Makarov's descriptions of 

 each stage are brief and include primarily de- 

 velopment of the rostrum, antennal flagellum, 

 dactylopodite of the second pereopod, pleopods, 

 and telson. Makarov's zoeae are essentially iden- 

 tical to mine through Stage V but Makarov's 

 Stages VI and VII possess mostly zoeal charac- 

 teristics, rather than postzoeal as mine do. For 

 instance, in Stage VI the rostrum of Makarov's 

 specimens is not bifid and does not bear ventral 



teeth, and the telson still bears six pairs of spines 

 terminally. In my Stage VI specimens, the ros- 

 trum is bifid, bears five or six distinct ventral 

 teeth, and the telson bears only four pairs of spines 

 terminally. In Stage VII, the rostrum of Makarov's 

 specimens is bifid but bears only three or four 

 poorly developed teeth ventrally and the telson 

 still bears six pairs of spines terminally. In my 

 Stage VII specimens both the rostrum and telson 

 are essentially fully developed as in the adult. 

 Apparently P. goniurus from the western Kam- 

 chatka coast has at least two more zoeal stages 

 than P. goniurus from Kachemak Bay. 



The morphological differences between larval 

 Stages VI and VII of P. goniurus from the western 

 Kamchatka coast and from Kachemak Bay, 

 Alaska, may reflect variation in number of molts 

 in response to environmental conditions. Variabil- 

 ity in number of molts required to reach a specific 

 point in development in the Crustacea is well 

 known. In a review of the literature, Costlow 

 (1965) showed that variability in number of molts 

 occurs in the Cirripedia, Euphausiacea, Natantia, 

 Reptantia, Anomura, and Brachyura regardless of 

 whether the larvae are reared in the laboratory or 



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