FISHERY BULLETIN: VOL. 87, NO. 4. 1989 



Chimaeriformes are listed in Table 1. A ^test 

 weighted for unequal variances (Sokal and Rohlf 

 1969) shows statistically significant differences 

 in the diameters of otoconia from different 

 species (P < 0.05). 



been described in the shark Somniosus pacificus 

 (Lowenstam 1980), albeit with a distinctive 

 polycrystalline appearance at the SEM level that 

 is distinctively different from the aragonite 

 spherule otoconia of chimaeras. 



Table 1. — Mean otoconial diameters ((xm) of all four species of Cfii- 

 maeriform fish, n = sample size, x = mean otoconial diameter, 

 SD = standard deviation. 



Species 



SD 



t 



((.05,49) 



Rhinochimaera sp. 

 Harriotta ralelghana 

 Chimaera sp. 



50 66.72 4.91 



^3.6756 



50 62.19 7.20 2.0094 



^9.1056 



50 50.26 5.83 



^1.4738 

 Hydrolagus novaezelandiae 50 48.19 8.04 



DISCUSSION 



Carlstrom (1963) described the otoconia of 

 Chimaera monstrosa as "almost perfect arago- 

 nite spheres". This study at the SEM level con- 

 firmed the generally spherical nature of chi- 

 maeriform otoconia that was observed at the 

 light microscope level, and revealed considerable 

 detail in variation in size, shape, and crystallin- 

 ity of otoconia from four species of chimaeri- 

 forms. 



There was a statistically significant variation 

 in the diameters of otoconia amongst the species 

 examined. In part, this variation reflected the 

 relative amounts of small and large otoconia in 

 the different species, as well as the maximum 

 size of otoconia. Size variation in otoconia may 

 represent physiological differences between in- 

 dividuals of the same species, interspecific dif- 

 ferences, and perhaps age differences. Testing 

 these alternatives was not possible with the sam- 

 ples at our disposal. 



The predominant type of otoconia among the 

 samples examined was more or less spherical, 

 40-70 |xm in diameter. It was similar in size and 

 in shape to otoconia described in the lungfish 

 (Gauldie et al. 1986a), in the chimaera C. milii 

 (Gauldie et al. 1987), and in a number of teleost 

 species (Dale 1976; Gauldie et al. 1986b). X-ray 

 diffraction studies showed that the spherule 

 otoconia were formed from aragonite. Aragonitic 

 spherule otoconia occurred in the chimaera C. 

 milii (Gauldie et al. 1987) and in the lungfish A'^. 

 forsteri (Gauldie et al. 1986a). However, spher- 

 ule shaped otoconia composed of vaterite have 



The rod-shaped crystals found in the otoconial 

 mass of H. raleighana have not been described 

 in the literature. It is possible that they were 

 bacteria or some other organism. However, 

 their crystalline appearance, which included 

 twinning and surface recrystalHzation (Fig. 4B), 

 as well as their apparent fusion with the spindle 

 and spherule forms of aragonite, strongly sug- 

 gest that they are some form of crystal. 



There was considerable variation in the sur- 

 face texture of the otoconia amongst the species 

 described here and those described elsewhere. 

 The otoconia of H. raleighana had the smoothest 

 surface texture, but were among the larger 

 otoconia. Therefore, one could reasonably con- 

 clude that variation in surface texture may not 

 be due to the rate of crystal gi'owth. In addition, 

 otoliths of Chimaera sp. consisted of otoconia of 

 about the same size, but with gi'eatly differing 

 surface texture. We have assumed that during 

 storage the fluids of the endolymphatic sac were 

 alkaline, but it is possible that in the stress of 

 trawling the endolymph may have become 

 acidic. Thus, variation in surface texture may be 

 a preservation artifact. However, the similarity 

 of the appearance of the surface texture of 

 otoconia to those described from other studies, 

 using different preservation techniques, sug- 

 gests that erosion and recrystalHzation had not 

 occurred. We conclude that the texture of the 

 otoconia surface does not reveal any useful infor- 

 mation about the gi'owth rate of otoconia, but 

 that it may provide clues to probable growth 

 mechanisms. 



For example, the layered appearance of some 



932 



