LARVAL MORPHOLOGY OF PANDALUS TRIDENS AND A SUMMARY 



OF THE PRINCIPAL MORPHOLOGICAL CHARACTERISTICS OF 



NORTH PACIFIC PANDALID SHRIMP LARVAE 



Evan Haynes' 



ABSTRACT 



Larval stages I- VII of Pandalus tndens from plankton of lower Cook Inlet, Alaska, are most similar 

 morphologically to larvae of P. borealis. P goniurus. P. jordani, and P. stenolepis from the North 

 Pacific Ocean. Larvae of P- tndens are distinguished from larvae of P. borealis, P goniurus, and P. 

 jordani by the shape of the rostrum and antennal scale, and spination of the abdominal somites. Larvae 

 of P Iridens differ from larvae of P stennlepis by shape of the carapace, abdominal somites, and telson; 

 length of the antennal flagellum and rostrum; and setation of the antennal scale. Differences in larval 

 morphology support classification of P. tndens as a species rather than a subspecies ofP. montagui. A 

 summary of the pnncipal morphological characteristics of the described larvae of pandalid shrimp 

 found in the North Pacific Ocean is provided. 



In 1976, the Northwest and Alaska Fisheries 

 Center Auke Bay Laboratory of the National 

 Marine Fisheries Service and the Alaska Depart- 

 ment of Fish and Game conducted a survey to 

 determine the seasonal distribution of larvae of 

 king crab and pandalid shrimp in the Kachemak 

 Bay-lower Cook Inlet area (Haynes^). During the 

 survey, Stages I-VII zoeae oiPandalus tridens ( = 

 P . montagui tndens Rathbun 1902) were captured 

 in plankton tows in lower Cook Inlet. Except for 

 Stage I, zoeae of P. tridens have not been described 

 in the literature. In this report I describe and illus- 

 trate each of the seven zoeal stages captured and 

 compare my descriptions with those of pandalid 

 shrimp zoeae given by other authors. 1 also discuss 

 the evidence from larval morphology that sup- 

 ports raising the subspecies, P. montagui tridens, 

 to full species status, P. tridens Rathbun 1902. A 

 summary of the principal morphological charac- 

 teristics of described pandalid shrimp larvae of the 

 North Pacific Ocean is also given. 



METHODS 



During the 1976 survey, plankton was collected 

 by hauling 61 cm bongo samplers vertically from 

 about 1 m above the ocean bottom to the surface at 

 a velocity of slightly <1 m/s. Nets with 0.333 mm 

 mesh and cod end jars with 0.571 mm mesh were 

 used. Zoeae of P. tridens were collected in water 

 120-160 m deep about 16 km west of the Kenai 

 Peninsula in lower Cook Inlet. 



The terminology, methods of measurement, 

 techniques of illustration, and nomenclature of 

 gills and appendages are those used by Haynes 

 (19791. Identification of the zoeae is based on de- 

 scription of Stage I zoeae hatched from known 

 parentage by Ivanov( 1971) and undescribed Stage 

 I specimens hatched from known parentage by 

 Ethelwyn Hoffman of the Auke Bay Laboratory's 

 staff. Only those morphological characteristics 

 useful for readily identifying each stage are given. 

 For clarity, setules on setae are usually omitted 

 from the figures, but spinulose setae are shown. 



'Northwest and Alaska Fisheries Center Auke Bay Laboratory, 

 National Marine Fisheries Service, NOAA, P.O. Box 155, Auke 

 Bay, AK 99821. 



^Haynes, E, 1977. IV Summary status on the distribution 

 of king crab and pandalid shrimp larvae in Kachemak Bav-lower 

 Cook Inlet, Alaska, 1976 In L. L. Trasky, L. B. Flagg. and D C 

 Burbank i editors i, Environmental studies of Kachemak Bay and 

 lower Cook Inlet, vol. 4. 52 p. Alaska Dep Fish Game. Anchor- 

 age. 



Manuscript .uit-pted -March 1979 



FISHERY BULLETIN: VOL 77. NO. 3. 1980 



STAGE I ZOEA 



Total length of Stage I zoea (Figure lA) 3.2 mm 

 (ranges. 1-3. 5 mm; Gspecimensi. Rostrum slender, 

 somewhat sinuate, without teeth, about two- 

 thirds length of carapace, and projects horizon- 

 tally. Carapace with small, somewhat angular 

 dorsal prominence at base of rosti'um and smaller 



625 



