DESCRIPTION OF EARLY STAGE ZOEAE OF 



SPIRONTOCARIS MURDOCHI 



(DECAPODA, HIPPOLYTIDAE) REARED IN 



THE LABORATORY 



Larvae of Spirontocaris murdochi Rathbun have 

 not been described in the literature. During stud- 

 ies on rearing larvae in the laboratory for descrip- 

 tive purposes, I succeeded in rearing zoeae of S. 

 murdochi through Stage III. The first three zoeal 

 stages of S. murdochi are described, illustrated, 

 and compared with descriptions of morphological- 

 ly similar hippolytid zoeae. 



Methods and Rearing Results 



I obtained an ovigerous female Spirontocaris 

 murdochi carrying late-stage embryos while sam- 

 pling pandalid shrimp in Auke Bay, Alaska, for 

 toxicity studies. The female was caught 2 April 

 1979 at a depth of 18 m at lat. 58° 21.6' N, long. 

 134° 39.3' W. Stage I zoeae released from the 

 female were reared in 250 ml jars containing 

 about 200 ml of filtered seawater. The jars were 

 checked daily for exuviae, and a few zoeae were 

 preserved every other day. The zoeae were offered 

 live plankton strained through a 0.333 mm mesh, 

 but there was no evidence that the zoeae ate the 

 plankton. (For a more complete description of the 

 methods, see Haynes 1982.) Most of the zoeae 

 molted to Stage II, but only two zoeae molted to 

 Stage III. 



Techniques of measurement and illustration 

 are those of Haynes (1976, 1979). At least five 

 zoeae of Stages I and II were used to verify seg- 

 mentation and setation. 



Description 



The terms used in the descriptions and nomen- 

 clature of appendages are from Haynes (1976, 

 1979). Only those morphological characteristics 

 useful for readily identifying each stage are giv- 

 en. Setation formulae are the number of setae per 

 segment from the distal to the proximal segment. 

 The telsonic setae are numbered as pairs begin- 

 ning with the inner (medial) pair. For clarity, 

 setules on setae are usually omitted, but spinu- 

 lose setae are shown. 



The following characteristics apply to zoeal 

 Stages I, II, and III. The rostrum is slender, spini- 

 form, without teeth, about one-fourth the length 

 of the carapace, and projects horizontally. The 

 ventral and posterior margins of the carapace are 



smooth except for pterygostomian spines. Man- 

 dibles are without palps; there is no proximal 

 setose seta on the maxillule; and the maxillipeds 

 are without epipodites. Abdominal somites 4 and 

 5 have posterolateral spines (the fifth pair is 

 slightly longer than the fourth pair in Stage I, 

 but both pairs are nearly the same length in 

 Stages II and III). An anal spine is present. 



Stage I Zoea 



Mean total length of Stage I zoea (Fig. 1A), 3.4 

 mm (range 3.2-3.6 mm; six specimens). Eyes 

 sessile. Carapace with two minute rounded prom- 

 inences: One at posterior edge, other at base of 

 rostrum. 



ANTENNULE (Fig. IB). — Protopodite of first 

 antenna, or antennule, simple, unsegmented, 

 tubular, with heavily plumose seta terminally. 

 Conical projection tipped with four aesthetascs: 

 Three long, one of intermediate length. 



ANTENNA (Fig. 1C). — Second antenna, or an- 

 tenna, with inner flagellum (endopodite) and 

 outer antennal scale (exopodite). Flagellum un- 

 segmented, slightly shorter than scale, styliform, 

 tipped by plumose seta and shorter spine. Anten- 

 nal scale distally divided into five joints (distal 

 joint incomplete) and fringed with 10 heavily plu- 

 mose setae along terminal and inner margins. 

 Tip of antennal scale curved toward outer margin. 

 Protopodite with spine only at base of flagellum. 



MANDIBLES (Fig. ID).— Incisor process of left 

 mandible has four teeth in contrast to triserrate 

 incisor process of right mandible. Both left and 

 right mandibles with movable premolar denticle 

 (lacinia mobilis). Left mandible with subterminal 

 tooth. 



MAXILLULE (Fig. IE). — First maxilla, or max- 

 illule, with coxopodite, basipodite, and endo- 

 podite. Coxopodite (proximal lobe) with seven 

 spines: Five spinulose, two simple. Basipodite 

 (median lobe) with 10 short, smooth spines ter- 

 minally. Two-segmented endopodite originates 

 from lateral margin of basipodite: Proximal seg- 

 ment with two spinulose spines, distal segment 

 with three spinulose spines. 



MAXILLA (Fig. IF). — Second maxilla, or max- 

 illa, has platelike exopodite (scaphognathite) 

 with five plumose setae along outer margin and 



FISHERY BULLETIN: VOL. 82, NO 3, 1984. 



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