HAYNES: DESCRIPTION OF PANDALUS HYPSINOTUS ZOEAE 



COMPARISON OF ZOEAL 



STAGES WITH DESCRIPTIONS BY 



OTHER AUTHORS 



Berkeley Q930j described and figured the first 

 stage zoeae of P. hypsinotus that she reared in 

 the laboratory. She also obtained the probable 

 second and third stages from the plankton, but 

 these were not described. Stage I zoeae reared by 

 Berkeley differed in several respects from mine, 

 but mostly in segmentation and setation of ap- 

 pendages. For instance, Berkeley showed the tel- 

 son separated from the sixth abdominal segment 

 by a joint whereas I do not. She described the tip 

 of the antennal scale as unsegmented, but my 

 zoeae have the tip divided into six segments. The 

 endopodites of the first and second maxillipeds of 

 her zoeae are unsegmented, and the exopodites of 

 the maxillipeds and first and second pereopods 

 are unjointed at their bases. In my zoeae, the 

 endopodites of the first and second maxillipeds 

 are segmented, and the exopodites of the maxilli- 

 peds and first and second pereopods are jointed at 

 their bases. Segmentation of appendages, espe- 

 cially in the early zoeal stages, is most clearly 

 seen in exuviae. Because Berekeley was unable 

 to obtain exuviae from her laboratory-reared 

 specimens, she probably missed seeing the 

 segmentation of most appendages. 



Kurata's Q964) description of Stage I zoeae of 

 P. hypsinotus was also based on specimens reared 

 in the laboratory; the remaining stages (II-V) he 

 described were obtained from the plankton. The 

 most important differences between Kurata's 

 description and mine are: Stage I — Kurata's 

 zoeae bear a chela on the second pereopod and the 

 antennal scale is four segmented. In my zoeae the 

 chela does not appear until Stage III and the an- 

 tennal scale is six segmented. Stage 11 — The tip 

 of the antennal scale is two segmented in Kur- 

 ata's zoeae but four segmented in mine. Stage 

 III — On Kurata's zoeae, the marginal spines of 

 the telson vary from one to three pairs, and the 

 inner flagellum of the antenna is twice as long as 

 the antennal scale and has 9 or 10 joints. My 

 Stage III zoeae always have two pairs of marginal 

 spines and the inner flagellum of antenna is 3 

 times the length of the antennal scale and has 19 

 joints. Stage IV — The telson of Kurata's zoeae 

 decreases in width posteriorly; the inner flagel- 

 lum of antennule is two segmented; the tip of the 

 first pereopod bears a small chela; and the cara- 

 pace bears a supraorbital spine. The telson of my 



Stage IV zoeae increases in width posteriorly; the 

 inner flagellum of antennule is four segmented; 

 the tip of the first pereopod bears a simple dac- 

 tylopodite in all stages i^including adults;; and 

 the supraorbital spine occurs only in Stages II 

 and ni. Stage V — The telson of Kurata's zoeae 

 bears 6-6 spines terminally; the carpopodites of 

 the second pereopods and the pleopods are with- 

 out joints; and the ceu^apace still bears a supra- 

 orbital spine. In my specimens, the telson bears 

 3-t-3 spines terminally; the carpopodites of the 

 left and right second pereopods bear 14-16 and 7 

 joints respectively; the pleopods are jointed; and 

 the carapace does not bear a supraorbital spine. 



The cause for the morphological differences 

 between Kurata's description of the morphology 

 of the zoeae and mine is unknown but apparently 

 is not a result of my zoeae being reared in the 

 laboratory. My zoeae showed no variation in 

 number of zoeal stages and only negligible 

 morphological variation between individuals of 

 the same stage. Also, there were no morphologi- 

 cal differences between my zoeae reared in the 

 laboratory and the zoeae of P. hypsinotus avail- 

 able from local plankton collections (^Stages I-III). 

 The morphological differences between Kurata's 

 zoeae and mine may be due to geographical vari- 

 ation. Berkeley Q930) has showTi that pandalid 

 zoeae from the northeast Pacific are further ad- 

 vanced on hatching than those from the Atlantic, 

 although she did not have enough information to 

 compare identical species from both areas. Unfor- 

 tunately, Kurata's descriptions from Stage II 

 onw£u-d were based on specimens from the plank- 

 ton. Verification of geographical variation in 

 zoeal morphology will be possible only when 

 identification is based upon zoeae of known 

 parentage and the magnitude of variation is 

 established for each stage. 



Segmentation of the antennal scale was used 

 by Lebour Q940j as one criterion for classifying 

 the early stages of pandalid zoeae into two 

 groups. The first group includes pandalid species 

 described by various authors as possessing a seg- 

 mented scale (Dichelopandalus bonnieri (Caul- 

 leryj, Pandalus montagui Leach, and P. propin- 

 quus G. O. Sars). The second group includes 

 pandalid species described by Berkeley (1930) as 

 possessing an unsegmented scale (P. stenolepis 

 Rathbun, P. hypsinotus, P. danae, and P. platy- 

 ceros). Price and Chew fl972) showed Lebour's 

 grouping to be invalid for P. platyceros. Kurata 

 (1964) described zoeae of P. hypsinotus as hav- 



341 



