RICHARDSON: PELAGIC EGGS AND LARVAE OF DEEPSEA SOLE 



(table 1 in Pearcy et al. 1977). Such rarity could 

 reflect the reported rarity of adults, or may indi- 

 cate that the principal spawning occurs outside 

 our sampling area, or that the primary occurrence 

 of eggs and larvae may be at depths (>200 m) 

 below those commonly sampled. 



The reproductive strategy of E. bathybius in- 

 volves production of a large egg, probably with an 

 associated reduced fecundity compared with an 

 equivalent sized pleuronectid producing smaller 

 eggs. The egg likely has a moderate pelagic life 

 span lasting at least a few weeks, based on time to 

 hatching for eggs of the related northeast Pacific 

 species Microstomas pacifkus [38 d at 7.5° C; 27 d 

 at 10° C; 18 d at 12.5° C ( Williams =')] which has 

 eggs of 2.04-2.57 mm diameter (Pearcy et al. 

 1977). The larva of £". bathybius is well developed 

 by the time it hatches and probably has an 

 extended pelagic life lasting at least a few months, 

 although size at which transformation is com- 

 pleted and growth rates are unknown. Pearcy et 

 al. (1977) estimated that the related species M. 

 pacificus and G. zachirus may have a pelagic 

 phase lasting about 1 yr. 



DISCUSSION 



The most recent, broad based review of the fam- 

 ily Pleuronectidae that implied relationships was 

 by Norman (1934) who recognized five subfamilies. 

 Within the subfamily Pleuronectinae the genera 

 fall into two main groups: one in which the mouth 

 is moderate to large and the jaws and dentition are 

 well developed on both sides [tribe Hippoglossini 

 of Nelson (1976), with ca. 10 genera, 18 species]; the 

 other in which the mouth is small and asymmetri- 

 cal, with the jaws and dentition more developed on 

 the blind side [tribe Pleuronectini of Nelson (1976) 

 with ca. 16 genera, 42 species]. Norman (1934) 

 stated "The group of Pleuronectine genera includ- 

 ing Microstomas , Embassichthys , Tanakias and 

 Glyptocephalas have generally been marked off 

 from the remainder of the small-mouthed mem- 

 bers [tribe Pleuronectini] of the subfamily as a 

 primary division [within the tribe], distinguished 

 by a generally more elongate body and by an in- 

 creased number of vertebrae, fin-rays and of scales 

 in a longitudinal series. Such an arrangement is 

 clearly an artificial one, and it is doubtful whether 



these [four] genera really form a natural group." 

 He further said that Embassichthys is apparently 

 closely related to Microstomas and Glyp- 

 tocephalas is close to Tanakias whereas Micros- 

 tomas is related to Pseadoplearonectes and 

 Tanakias is apparently related to Dexistes. 



Norman's (1934) discussion of intergeneric rela- 

 tionships was based mainly on external mor- 

 phological features and therefore the phylogeny of 

 the group was not really well defined. Additional 

 evidence is needed to elucidate relationships. One 

 source of additional information is the larval form 

 of fishes which has been used to demonstrate or 

 clarify systematic relationships in other groups of 

 fishes, e.g., scoplarchids (Johnson 1974), gonos- 

 tomatids ( Ahlstrom 1974), myctophids (Moser and 

 Ahlstrom 1974), myctophiforms (Okiyama 1974) 

 marine teleosts in general (Ahlstrom and Moser 

 1976), bothids (Futch 1977), scombroids (Okiyama 

 and Ueyanagi 1978), and serranids (Kendall 1979). 

 Although larval characters that have been used 

 are usually external morphological features such 

 as body shape and form, spination, and melanistic 

 pigmentation, character similarities have been 

 consistently in agreement with intergeneric rela- 

 tionships. 



With this paper, larvae of all species in the four 

 pleuronectine genera mentioned by Norman 

 (1934) are knowoi (Table 3). Larvae are also known 

 for 53 of the 60 pleuronectine species that occur in 

 the North Pacific and North Atlantic (Ahlstrom 

 and Moser 1979). With this knowledge it is possi- 

 ble to point out the similarity and distinctiveness 

 of the larvae in the four-genus complex of Micros- 

 tomas, Embassichthys, Tanakias, and Glyp- 

 tocephalas which appear to form a logical group 

 within the tribe Pleuronectini. Determination of 

 whether this phonetically derived group is a 



Tables. — Selected references containing illustrations of larvae 

 of species in the pleuronectid genera Embassichthys, Glypto- 

 cephalus, Microstomus, and Tanakius. 



^S. Williams, Graduate student. Department of Fisheries and 

 Wildlife, Oregon State University, Corvallis, OR 97331, unpubl. 

 data, June 1976. 



167 



