580 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



Table 150. Data on the Eggs and Larvae of Zoarcidae Known to Date. 



' Maximum ovanan diameters. 



generally cursory (except that of Kendall et al., 1 983). In general, 

 zoarcid eggs are large (about 4-9 mm, except in some diminutive 

 species), spherical and usually with a single oil globule that may 

 have coalesced from a few smaller globules. Spawned eggs are 

 orange-yellow or purple with a somewhat darker orange or yel- 

 low oil globule (Anderson, 1981; Kendall et al., 1983) and have 

 a narrow perivitelhne space. Benthic egg masses are held to- 

 gether by a sticky, gelatinous mass that is not especially thick- 

 ened. Incubation times are known for only three species. Eggs 

 "hatch" in the ovary of Zoarces viviparus afler two months and 

 embryos develop for another two months therein (Fig. 307). 

 Embryos develop a dense vitelline vascular network that aids 

 in yolk resorption, respiration and assimilation of nutrients from 

 the mother's ovarian fluid (Soin, 1968). Olsen and Merriman 

 ( 1 946) found that eggs of southern populations of Macrozoarces 

 americanus had an average incubation time of 2.5 months, 

 whereas eggs of northern populations took about 3.5 months to 

 hatch. Gosztonyi (1977) observed the eggs of Iluocoeles effusus 

 (as /. elongatus) from the Patagonian intertidal to require two 

 months to hatch during the austral autumn. 



Larvae 



As with observations on eggs, zoarcid "larvae" are not well 

 known, if this stage is developed at all. Although a few early 

 stages have been collected during ichthyoplankton surveys (Rass, 

 1949; Mattson and Wing, 1978; Altukhov, 1979), they are no- 

 tably absent in collections of other surveys where adults are 

 abundant, such as the Bering Sea (Musienko, 1963; Waldron 

 andVinter, 1 978) and offOregon (Richardson and Pearcy, 1977). 

 This is probably due to their short planktonic time. Early life 

 history stages of only five zoarcid species have been illustrated 

 (Kendall et al., 1983) and all these are reproduced here (Figs. 

 307, 308). 



Females of Lycodapus mandihularis, Gymnelus viridis and 



"Maynea''' californica^ are known to spawn larger eggs at in- 

 creasingly larger adult sizes, thus zoarcid hatching sizes vary. 

 In large eelpouts, like Macrozoarces and Zoarces. young hatch 

 at about 30-40 mm, but diminutive species, like Melagoslignia 

 and Derepodichthys are probably only about 1 mm at hatching. 

 At hatching, the yolk sac is rapidly taken into the gut. White 

 (1939) reported "the complete external disappearance of the 

 yolk" to occur in about 20 seconds in Macrozoarces americanus 

 that were stimulated to hatch in a pan of cold sea water. I have 

 observed a similarly rapid internalization of the yolk in larvae 

 of the liparidid Carcproclus sp. (Anderson and Cailliet, 1974). 

 Perhaps rapid yolk uptake is typical of fishes with a protracted 

 developmental period. 



Newly hatched zoarcids strongly resemble adults. The major 

 difl^erences are the larger eyes and more rounded snout in the 

 young (Fig. 308). At the free-swimming, yolk-ingestion stage, 

 all fin rays have formed. The stage and direction of fin formation 

 in embryos is unknown in Zoarcidae. Most of the cephalic lat- 

 eralis pores were formed in larvae of Bolhrocara hollandi (as 

 Allolepis hollandi) noted by Okiyama (1982a). Post-hatching 

 Macrozoarces that I examined for this study had not developed 

 all their lateralis pores, a case similar to that of Gymnelus spp. 

 (Anderson, 1982). These planktonic young Macrozoarces had 

 absorbed their yolk and measured 33.8-36.0 mm SL. The young 

 fish were generally well ossified, except central regions of the 

 neurocranium and suspensorium. Jaw and pharyngeal teeth were 

 developed and a few had eaten copepods. In the smallest spec- 

 imen, the pectoral actinosts, scapula and coracoid were a fused 

 mass of cartilage, but these were separated and ossified in just 

 slightly larger specimens. Vertebrae were square in shape (rect- 



' This species properly belongs in an unnamed, monotypic genus 



(Anderson. 1984). 



