FEENEY: EGGS AND LARVAE OF YELLOWCHIN SCULPIN 



Trunk = muscular section of body not including the 

 head, abdominal cavity or caudal fin. 



RESULTS 



Fertilization 



Eight whole egg clutches were externally fer- 

 tilized with freshly stripped sperm, and five con- 

 tained eggs that developed successfully into the 

 embryo stage. Three whole egg clutches were left 

 unfertilized, and none contained eggs that developed 

 successfully into the embryo stage. Three whole egg 

 clutches were split in half; one half was fertilized 

 with sperm and the other was left unfertilized. Eggs 

 in all three of the fertilized halves developed suc- 

 cessfully into the embryo stage; eggs in the unfer- 

 tilized halves did not. Therefore, there was no 

 evidence of internal fertilization. 



Egg Description 



Icelinus quadriseriatus eggs are adhesive and 

 negatively buoyant after being stripped from the 

 female and formed a single clutch of 200-250 eggs 

 (excluding eggs that may have been left in the ab- 

 domen; Goldberg [1980] reported an average clutch 

 size of 284 eggs in 28 gravid fish). The eggs are 

 1.08-1.17 mm in diameter and are initially trans- 

 parent, but the chorion becomes more opaque and 

 textured during development. A pale-green yolk fills 

 most of the egg except for a small perivitelline space 

 (0.024-0.096 mm). 



At spawning there are about 15 yellow oil glob- 

 ules, the largest of which is 0.14 mm in diameter, 

 which coalesce to one oil globule of 0.14-0.19 mm 

 diameter by the eighth day of development. An 

 opaque, flocculant mass is suspended in the yolk 

 next to the oil globules. 



Embryonic Development 



The eggs develop for 12-13 days in 13° -16°C sea- 

 water before hatching. Sixteen hours after artificial 

 fertilization the blastodisc is well formed (Fig. lA). 

 By 38 h the eggs are in the crescent stage of 

 gastrulation (Fig. IB). The germ ring can be seen 

 making its way around the yolk. At 63 hours somites 

 begin to form along the embryo and the eye capsule 

 is present (Fig. IC). At 89 hours the heart (Fig. ID), 

 brain, and otic capsules are visible, and the body is 

 lined with 30 or more myomeres. The heart begins 

 beating after 110 hours, and the vitelline veins can 

 be seen coursing across the surface of the yolk (Fig. 



IE). At 6-7 days the anus forms, the eyes become 

 darkly pigmented (Fig. IF), and the tail begins flex- 

 ing back and forth. A patch of tubercles forms on 

 the interorbital section of the head and persists until 

 immediately after hatching. 



At 7-8 days the embryos develop pectoral buds 

 (Fig. IG) and melanophores begin forming on the 

 anus and surrounding yolk sac. The eyes turn a 

 metallic green and blood begins circulating through 

 the ventral veins and arteries of the body. 



Numerous melanophores cover the yolk sac, anus, 

 and postanal ventral midline (Fig. IH) in late-stage 

 embryos. The head flattens against the chorion and 

 the tubercles spread from the snout to just dorsal 

 to the otic capsule. 



After 10-12 days eggs reared at 13° -16°C begin 

 to hatch. 



Description of Larvae 



The larvae hatch with the oil globules positioned 

 at the anterior of the yolk sac (Fig. 2A). The yolk 

 is absorbed after 6-7 days. The oil globules disap- 

 pear along with the yolk in reared larvae; whereas, 

 the oil globule(s) in field-collected larvae move about 

 the abdominal cavity, are fragmented, possibly in- 

 crease in diameter, or are absent completely (Fig. 

 2B-C). Evidence of the globule's increase in diameter 

 in the field-collected larvae is found in some 

 specimens (6.1-8.0 mm SL) with oil globules from 

 0.26 to 0.36 mm diameter, about twice the diameters 

 of oil globules in the eggs and yolk-sac larvae. 



The percentage of field larvae with oil globules 

 (based on a subsample of 129 larvae) drops from 93% 

 in larvae with yolk sacs (A^ = 15) to 70% in larvae 

 <3.5 mm {N = 79) to 45% in larvae 3.6-6.0 mm (TV 

 = 20) to 27% in larvae 6.1-8.0 mm (N = 15). Lar- 

 vae over 8.0 mm possess minute or no oil globules. 



Reared larvae hatch at 2.7-3.4 mm NL (after pres- 

 ervation); field-collected larvae are found as small 

 as 2.6 mm. The larvae shorten to a varying degree, 

 depending probably on the reaction to quinaldine 

 and Formalin. Reared larvae shrink 5-17% after 

 anesthesia and fixation. 



Myomere counts range from 31-37. Double-stained 

 specimens have vertebral counts of 33-35. 



Morphometries are given in Table 1. From 6.0 to 

 9.4 mm the larvae become more deep-bodied (27- 

 30% SL) and the head length increases to 34% of 

 the standard length. 



A pigmented preanal finfold does not preserve in 

 the field larvae as it does in the laboratory-reared 

 larvae. There is a skin connection between the anus 

 and the rest of the gut, usually with one or more 



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