FISHERY BULLETIN: VOL. 87. NO. 3, 1989 



L. callyodon resemble the few Atlantic species 

 of Liparis that have been identified (Able et al. 

 1984), except for the unusually heavy melaniza- 

 tion in larvae of this species. Intense melaniza- 

 tion at hatching is more typical of cyclopterine 

 than hparidine larvae (Able et al. 1984). 



Although a relatively large subdermal space 

 surrounding the entire body is typical of lipar- 

 idine larvae, it is only as prominent as that illus- 

 trated in Figure 1 in L. fucensis, which may be 

 the same species as that unidentified illustration 

 previously referred to (by Able et al. 1984). That 

 previously published illustration shows develop- 

 ment of fin rays at a smaller size and with less 

 melanin than in the present paper, but both of 

 these features could result from the shrinkage 

 and bleaching effects of long-term preservation. 

 Another explanation for such differences is that 

 regional differences might occur, as described 

 for larvae of another cottoid species, Oligocottus 

 maculosus (Marliave 1988). On the other hand, 

 the unidentified illustration of a liparidine bub- 

 blemorph was drawn from a CalCOFI sample, 

 which would be just south of the known range for 

 L. fucensis (Hart 1973). 



The larval bubblemorph of L. fucensis was 

 collected in sled trawl tows taken within 1 m of 

 the bottom at a wide variety of depths. In these 

 same tows, larvae of Pacific whiting, Merluccius 

 product us, were caught in the bottom tows at 

 stages in which their swimbladder had devel- 

 oped, whereas earlier stages tended to be uni- 

 formly distributed through the water column 

 (Marliave in press). Since cottoid fishes lack 

 swimbladders at all stages, the evolution of a 

 larval bubblemorph in the cyclopterid L. 

 fucensis, in the cottid Malacocottus zonurus 

 (Washington et al. 1984), and, to a less obvious 

 extent, in the cottids Gilberiidia sigalutes and 

 Psychrolutes paradoxus (Marliave 1975) may be 

 an adaptation imparting neutral bouyancy, 

 which would assist in maintaining a precise 

 depth without costly swimming effort. The fluid 

 of the subdermal space, if maintained at bodily 

 osmolarity well below that of ambient seawater, 

 would reduce overall density and lend to neutral 

 bouyancy. Larvae possess swimbladders in cer- 

 tain other taxa that lack a swimbladder as ben- 

 thic adults, as in the Gobiesociformes (Allen 

 1984); thus, the selective advantage of achieving 

 neutral bouyancy appears to be relatively gen- 

 eral among larval marine fishes. 



Convergence toward the bubblemorph and 

 midwater habitat is found in other genera. Most 

 notably, Peden and Anderson (1978, 1979), 



Anderson (1977), and Peden (1979) discussed 

 either the loose skin, which imparts a sort of 

 bubble morphology, or the midwater habitat 

 (i.e., neutral buoyancy) of the zoarcid genus 

 Lycodapus. Anderson (1977, 1984) further noted 

 that same habitat in Melanostigma, although 

 this genus may possibly deposit demersal eggs in 

 one species, M. atlanticum. Among liparidines, 

 midwater habitat and bubble morphology are 

 most specialized in Nectoliparis and Lipariscus; 

 these genera retain this specialized larval char- 

 acter into adult life (see Peden 1981 regarding 

 midwater habitat). In these four genera, repre- 

 senting two distinctly divergent families with 

 demersal ancestors, eggs producing relatively 

 large and well-developed young are apparently 

 deposited and reared, for most species, in the 

 same midwater habitat as adults. In the case of 

 the better known Lycodapus mandibularis 

 (Anderson 1977; Peden and Anderson 1978; 

 Peden 1979), adults are not known to select bot- 

 tom habitat except accidentally during diel mi- 

 gration (Peden observation from submersible). 

 Young, as small as 19 mm, are found in the same 

 midwater tows as adults (maturity is at 75-90 

 mm in northern samples); owing to the large size 

 of the eggs (Anderson 1977), the young are as- 

 sumed to have hatched at relatively large sizes. 

 Given the development of loose skin, or bubble 

 morphology, in the more specialized and diverse 

 genera of liparidines Careproctus and Para- 

 liparis (Burke 1930; Stein 1978), many of which 

 are from midwater, the bubblemorph, which 

 originally evolved in a LiparisAike ancestor, has 

 apparently been exploited in adult life histories 

 of a large number of species. In some of these 

 liparidine and zoarcid genera, some species may 

 be associated with near-bottom habitats, and the 

 bubblemorph may allow adults to hover just off 

 the bottom similar to fishes with swimbladders 

 (observed in Lycodapus parviceps by Peden 

 from submersible). 



The relatively neutral bouyancy that seems 

 probable for the cottoid bubblemorph might per- 

 mit relatively greater overall gi'owth during the 

 planktonic stage than for larvae of related 

 species that have more typical larval morphol- 

 ogy; e.g., larval Gilberiidia sigalutes grow to 

 about 75% of their average adult size during the 

 planktonic stage (Marliave 1981). This difference 

 in larval growth seems to be the case for the 

 present two Liparis species; the normal-type L. 

 callyodon settles from the plankton at a very 

 small size compared with the bubblemorph of L. 

 fucensis. Bouyancy and potential gi'owth rate 



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