CalCOFI Reports, Vol. 27, 1986 - California Cooperative Oceanic ...

TRUJILLO-ORTIZ: ACARTIA CALIFORNIENSIS LIFE CYCLECalCOFl Rep., Vol. XXVII. 1986a drop of lactic acid under a dissecting microscope atmagnifications of 50 and 100 X .In the copepodid stages, I counted the abdominalsegments (urosome) and number of swimming legs;the urosome also served for sex determination. Themeasurements in these stages were the same as in thenaupliar stages, except that the furcal setae were not includedin the body length. Prosome (cephalosome andmetasome or thorax) and urosome length, andprosomehrosome ratios were also recorded. The numberof copepodids measured varied from 43 (copepodidV, female) to 83 (copepodid I).I used a 70% alcoholic chlorazol black E (CBE)solution to stain copepodids (10 of each stage) frompreserved samples, in the depressions of a Boererchamber. The sequence was as follows: (1) 2 baths ofdistilled water, 2-3 minutes each to eliminate excessformaldehyde; (2) a 35% alcohol solution bath for 2-3minutes to dehydrate partially; (3) a 70% alcohol solutionbath for 3 minutes to complete dehydration; (4) abath of CBE in 70% alcohol for 1-2 minutes; (5) thesame steps in reverse order (without the fourth); (6)microdissection in a glycerin drop on microscopeslide. This procedure is my modification of that ofOmori and Fleminger (1976).1 made microdissections of the copepodid stages indrops of glycerin under a dissecting microscope atmagnifications of 25 and 50 X . I used sharpened 000entomological needles for all dissections. As theappendages were dissected off, I arranged them innatural sequence in glycerin drops on microscopeslides and covered them with no. 1 round cover slips.For additional information on this method, refer toPantin (1964), Griffiths et al. (1976), and Omori andFleminger (1976).All drawings were made with the aid of a cameralucida mounted in a compound microscope. I observednaupliar stages and their appendages at 400 X . For thecopepodid stages, I observed complete specimens at250 X , and their appendages at 400 X .RESULTSEggThe egg of Acartia cafiforniensis (Figure 4a) isspherical, 0.075 2 0.002 mm in diameter, n = 30 eggs,range 0.069-0.083 mm, SD +- 0.01 mm. The eggs aregranular and clear yellow-brown or yellow-green.Three concentric membranes can be clearly distinguished.The outer membrane is thin, has no fuzz,and usually bears protuberances that make it appearirregular. In fertile eggs, cell differentation is oftenvisible. When hatching, the nauplius emerges, and theremainder of the egg tends to remain spherical. Themiddle membrane is also thin and flexible, andsometimes it partially collapses toward the outermembrane, causing the inner space between them tovary as embryonic development progresses. The innermembrane covers and protects the first naupliar stageduring its development.The newly laid eggs are small and capsular. Theyimmediately sink to the bottom and gradually swelluntil they become completely spherical.Naupliar StagesDuring postembryonic development, six naupliarstages are evident. Average naupliar length is about 2.1times its width. The body is not significantly curvedlaterally. All naupliar stages are oval anteriorly, andnarrow toward the caudal armature. There is ananteroventral pigment spot, generally red, also knownas the naupliar eye. The posterior-inner part is tan, andthe body is generally clear and translucent but slightlyyellow-green. A small internal lipid body is usuallypresent posteroventrally in most of the naupliar stages,and is clearly visible. In lateral view (Figure 5), thelabrum is clearly evident in all naupliar stages; in addition,there are short, thin setules in the labrum’s inferiormargin.The most important distinguishing characters of thenaupliar stages of Acartia cafiforniensis are as follows.Nauplius Z (Table 1; Figures 4b, 5a, 6a, 7a, 8a).Average length of 30 specimens was 0.095 2 0.004mm, range 0.081-0.113 mm, SDfO.01 mm. Caudalarmature has 2 terminal sensory setae and transverserow of setules. First nauplius only slightly resemblesadult, except for oval-shaped labrum bearing setules atbottom margin, and rudimentary antennule, antenna,and mandible.After the first molt, the nauplii enlarge slightly, andthe antennule, antenna, and mandible become morespecialized.Nauplius ZZ (Table 1; Figures 4c, 5b, 6b, 7b, 8b).Average length of 30 specimens was 0.116 0.002mm, range 0.11 1-0.123 mm, SD 2 0.004. Body is eggshaped.The 2 terminal sensory setae of the caudalarmature (Figures 4c, 5b) are longer than in the previousstage; one is ventral, the other dorsal. The labrumis oval, with setules in the lower margin. Posteroventrallythe body has a transverse row of fine setae.Nauplius ZZZ (Table 1; Figures 4d, 5c, 6c, 7c, 8c).Average length of 30 specimens was 0.137 2 0.003mm, range 0.127-0.147 mm, SDf0.007. The bodyremains egg-shaped. The caudal armature now consistsof 2 ventral spines with slightly toothed margins(saw-type), 2 sensorial setae that have the sameappearance as in the previous stage, and a transverserow of fine setae. Posteroventrally the body has 2transverse rows of setae.191