Figure 7. — Larvae of the Atlantic white marlin, Tetraptu- 

 rus albidus. Upper, 6.5 mm; lower, 11.2 mm in total 

 length. 



Figure 8. — Larva of the Atlantic longbill spearfish, Te- 

 trapturus pfluegeri, 8.3 mm in total length. 



Figure 9. — Larva of the Atlantic sailfish, Istiophorus albi- 

 cans, 11.8 mm in total length. 



specimens from the Coral Sea and 23 from the waters 

 northwest of Australia. The Coral Sea specimens 



measured between 2.5 and 29.5 mm while the latter 

 group of specimens measured 4.0-37.6 mm in total 

 length. All of the specimens lacked the characteristic 

 pigmentation, but from head profile and body form 

 characteristics, they were identified as larvae of sail- 

 fish. 



The areas of capture of sailfish larvae, both those 

 with and without pigmentation, were plotted by unit 

 areas of 1° square (Fig. 10). 



The larvae of sailfish are very sparsely distributed 

 in offshore pelagic waters. Rather, they tend to be 

 found most abundantly near land masses. This is 

 seen to be true for both the pigmented and non- 

 pigmented specimens. The non-pigmented larvae, 

 however, seem to show an even greater affinity for 

 land masses. Generally, both types of larvae were 

 found in waters northwest of Australia (south of lat. 

 10°S), but in the Coral Sea the specimens were ex- 

 clusively those which" lacked pigmentation. 



In regard to the occurrence of the non-pigmented 

 sailfish larvae, Ueyanagi (1963) pointed out the pos- 

 sibility that these may represent a separate subpopu- 

 lation or even be larvae of another species. Since 

 from the taxonomic point of view it is very unlikely 

 that they can be another species, I shall discuss some 

 points here relating to the possibility that these are 

 larvae of a separate subpopulation of sailfish. These 

 points are: 



1) It is unlikely that these are specimens in which 

 the pigments had faded since there are as many as 60 

 such specimens available. While it does appear that 

 the pigments on the lower jaw do fade out after the 

 larvae reach about 60 mm in length, the specimens 

 on hand are all under 40 mm in total length. 



2) If these non-pigmented cases are due to indi- 

 vidual variations, they would be expected to be dis- 

 tributed randomly throughout the distributional area 

 rather than localized as in Figure 10. 



3) It has been seen that pigmentation in the larval 

 stages of closely related species is very similar. For 

 example, the larvae of the Indo-Pacific shortbill 

 spearfish and the Atlantic longbill spearfish both 

 have pigmentation on the branchiostegal membrane. 

 The Indo-Pacific sailfish and the Atlantic sailfish 

 both have a pigmented lower jaw in their larval 

 stages. These pigmentation patterns can therefore 

 be considered to manifest close genetic relation- 

 ships. The non-pigmented types are very probably 

 variations of a genetic nature rather than those re- 

 sulting temporarily from environmental influences. 



Judging from the above-mentioned points, it ap- 

 pears that the non-pigmented larvae of the sailfish 



77 



