Chernova and Stem: A new species of Psednos from the western North Atlantic Ocean 



249 



Figure 3 



Radiograph of Psednos rossi n.sp., holotype. USNM 372726. Juvenile, 37.2 mm SL. Sta. EL-00-033, off Cape Hatteras. 



behind the head (vs. anus below the posterior third of the 

 head). The very oblique, almost vertical mouth occurs 

 often in species of the P. micrurus group, five of which 

 have the mouth at 75-85° to the horizontal (P. anoderkes, 

 P. cathetostomus, P. microps, P. mirabilis, P. sargassicus). 

 However, they all differ as described above. 



Discussion 



The physical features of Psednos rossi are unique in the 

 genus. The straight vertebral column and body are outside 

 the previous diagnosis of the genus, because all previously 

 known species are humpbacked owing to the curved spinal 

 column. Nevertheless, P. rossi clearly belongs in Psednos 

 rather than Paraliparis because it has the other generic 

 characters of Psednos (Chernova, 2001); particularly, 

 its sensory canal system and pores are of Psednos type, 

 having an interrupted infraorbital canal behind the eye. 

 We suggest that its remarkable body shape is an extreme 

 transformation of the usual Psednos body shape and is 

 associated with the change of the mouth from oblique and 

 of normal size to vertical and very large. In this process 

 the anterior movement of the bony elements of the jaws 

 greatly enlarges the branchial cavity. 



The morphology of Psednos rossi invites speculation 

 about its ecology. The very large superior mouth with verti- 

 cal jaws, eyes located close to the dorsal contour of the head 

 and oriented to look forward and up, and straight body sug- 

 gest adaptation to feeding on detritus and animals (such as 

 copepods) above it in the water column. These adaptations, 

 similar to those of hatchetfishes (family Sternoptychidae), 

 are highly advantageous for a mesopelagic mode of life. 

 Sudden opening of the very large vertical lower jaw could 

 produce a strong orobranchial suction, simultaneously 

 bringing food into the mouth and thus saving energy for 

 this fish, which is probably a poor swimmer. 



Work over the last several years has made it clear that 

 Psednos species exist at mesopelagic depths in the North 

 Atlantic, Indian, North Pacific, and South Pacific Oceans. 

 We confidently expect discovery of additional species from 

 meso- and bathypelagic waters. 



Acknowledgments 



We wish to thank S. W. Ross, K. J. Sulak, and J. V. 

 Gartner Jr. for collecting the specimens, bringing them 

 to our attention, and loaning them to us for description. 

 Collections were supported by the U.S. Geological Survey, 

 State of North Carolina, North Carolina Coastal Reserve 

 Program, and the Duke/UNCW Oceanographic Consor- 

 tium. The figures are drawn by the senior author, who 

 was supported by the Russian Science Foundation Grants 

 02-04-48669 and 00-15-07794. 



Literature cited 



Andriashev, A. P. 



1986. Review of the snailfish genus Paraliparis (Scorpaeni- 

 formes: Liparididae) of the Southern Ocean, 204 p. The- 

 ses Zoologicae 7, Koeltz Scientific Books, Koenigstein 



1992. Morphological evidence for the validity of the anti- 

 tropical genus Psednos Barnard ( Scorpaeniformes, Lipari- 

 didae) with a description of a new species from the eastern 

 North Atlantic. UO, Tokyo 41:1-18. 



1993. The validity of the genus Psednos Barnard (Scor- 

 paeniformes, Liparidae) and its antitropical distribution 

 area. Vopr. Ikhtiol. 33(11:5-15 [in Russian] J. Ichthyol. 

 33 (5):81-98. [English translation.] 



Andriashev, A. P., and D. L. Stein. 



1998. Review of the snailfish genus Careproctus (Lipari- 

 dae, Scorpaeniformes) in Antarctic and adjacent waters. 

 Contr. Sci. Nat. Hist Mus. Los Angeles Cty. 470:1-63. 



