Hyperostosic Bones from 

 the Mew Zealand Snapper 

 Chrysophrys auratus (Sparidae) 



Robert W. Gauldie 



Fisheries Research Centre, P O Box 297, Wellington, New Zealand 

 Present address: Hawaii Institute of Geophysics 

 University of Hawaii at Manoa, Honolulu, Hawaii 96822 



Zophie Czochanska 



Organic Chemistry Division 



Department of Scientific and Industrial Research 



Private Bag. Gracefield, Wellington, New Zealand 



General hvperostoses ai'e well known 

 in fossil fish bone literature (Tiffany 

 et al. 1980). Hyperostosic bones 

 have been described as occurring as 

 nodules on the ventral pterygio- 

 phores as well as other bones of Re- 

 cent fishes (Olsen 1971, Fierstine 

 1968, Konnerth 1966). Consistent 

 occurrence of hyperostosic bones in 

 many species has been taken to in- 

 dicate that they are not pathological 

 (Fierstine 1968). 



Various roles have been suggested 

 for hyperostosic bones ranging from 

 aids in fin erection (Fierstine 1968) 

 to hydrostatic correction (Breder 

 1952). The hydrostatic suggestion 

 arose from the observation that 

 hyperostosic bones are "filled with 

 fat" (Breder 1952), and oils in fish 

 bones have been proposed as an aid 

 to neutral buoyancy (Lee et al. 

 1975). Hyperostoses in sparids of 

 the genus CJirysophrys have also 

 been used as characters to separate 

 Pagrus major from Chrysophrys 

 auratus (Yasuda and Mizuguchi 

 1969). 



Hyperostosic bones occur in the 

 snapper Chrysophrys auratus and 

 are usually highly vascularized. We 

 were interested in (1) the possible 

 relationship between size of hyper- 

 ostosic bones and fish size aiKl (2) 

 the significance of the fatty-acid 

 composition of hyperostoses to the 

 biology of the fish. 



Materials and methods 



Snapper were measured as fork 

 length, filleted along one side to 

 reveal the hyperostosic bones, and 

 photographed on a measuring board. 

 The h,\T3erostosic bones and a sam- 

 ple of the vertebrae from each fish 

 were dissected out and frozen at 

 - 15°C until the fat content was 

 analyzed. The relative sizes of hy- 

 perostosic bones were measured 

 from the photographs. Two hyper- 

 ostosic bones usually occur in the 

 snapper, commonly on the seventh 

 (preural) haemal spine and less com- 

 monly on the sixth haemal spine 

 from the tail in specimens of the size 

 range (31-48 cm) used in this study. 

 Both were measured. The eighth 

 and ninth vertebrae from the tail 

 were removed and analyzed as non- 

 hyperostosic comparisons. 



One bone was cut through the hy- 

 perostosis, mounted in epoxy resin, 

 and ground down to about 50-^4m 

 thickness and photographed with a 

 WILD M400 stereomicroscope. 

 Whole fish were x-rayed using a 

 Faxitron Model 804 Radiographic 

 Inspection Unit. Ten of the speci- 

 mens examined were aged fi'om the 

 otoliths using an annual check-ring 

 method (Paul 1976). 



Reference to trade names does not imply en 

 dorsement by the National Marine Fisheries 

 Service, NOAA. 



Flesh and connective tissues were 

 scraped off the bones. Prior to chop- 

 ping, bones bearing the hyperosto- 

 ses were cut diagnoally. Bones were 

 weighed, chopped into small pieces, 

 and extracted three times with chlo- 

 roform-methanol (2:1 v/v) in an ul- 

 trasonicator bath (Sanophon Ultra- 

 sonic Ind.) containing iced-water for 

 10 minutes and finally extracted 

 once with chloroform. The extracts 

 were combined, filtered, and evapo- 

 rated at 40° C in a rotary evapora- 

 tor and weighed. Extracted lipids 

 were stored under nitrogen at - 15°C 

 pending analysis. 



Fat-free bone residues were dried 

 to constant weight. The lipid ex- 

 tract is expressed as a percentage 

 on a dry matter basis (Table 1). 

 Lipids were separated into classes 

 by column chromatography and 

 preparative thin-layer chromatog- 

 raphy. All solvents used were redis- 

 tilled prior to use. Portions of total 

 lipids dissolved in chloroform were 

 initially separated into fractions on 

 30 g and 12 g columns (depending 

 upon sample sizes) packed with sili- 

 ca acid (Koch-Light Lab. 5024h, 

 100-200 mesh) previously activated 

 at 110°C. The elution procedure in- 

 volved chloroform for neutral lipids 

 and methanol for polar lipids. By 

 combination of silicic-acid column 

 chromatography and preparative 

 thin-layer chromatography, neutral 

 lipids were resolved into their con- 

 stituent categories (Tables 1, 2). 



Preparation of methyl esters and 

 gas-liquid chromatography (GLC) 

 was carried out in the following 

 way. Aliquots of total lipid extracts, 

 which contained fatty acids com- 

 bined as glycerides and phospholi- 

 pids, and transesterified with BF;i- 

 methanol (Van Wijngaarden 1967). 

 Fatty-acid methy esters were ana- 

 lyzed by GLC using a Pye Unicam 

 GCV and a Philips PU 4500 capil- 

 lary chromatograph fitted with 

 flame ionization detectors. Both 



Manuscript accepted 9 August 1989. 

 Fishery Bulletin, U.S. 88:201-206. 



201 



