I„ TUNAS* 



A. General 



Eo Elxternal form 



The tunas spoken of here are the fishes of the family 

 Thunnidaeo The Thunnidae^, along with the Scombridaep the 

 Cybiidaej and the Katsuwonidae are representative of the 

 mackerel-like fishes or Scombriformes Scholars sometimes 

 lump these four families together into one to which they give 

 the name Scombridaeo 



In general they are large fishes with stout bodies showing 

 a roughly round shape in cross-sectiono The mouth is at the end 

 of the snout and the jaws cannot be extendedo Generally the 

 lower jaw protrudes slightly beyond the unpero Inside both 

 jaws there is a single row of curved sharp conical teeth^, and 

 there are also villiform teeth on the vomers the palatines ^ and 

 the pterygoid bones,, On the palatines there are many calcareous 

 plates covered with villiform teeth^ making the palate feel rough 

 to the touchp This is very different from the fishes of the 

 family Katsuwonidae^ which have smooth palatines o The eye is 

 of a moderate size and is located on a line joining the tip of 

 the snout and the middle of the caudal peduncleo The head^ 

 depending on the species^ is l/3 to l/4 of the body lengthy the 

 proportion changing more or less depending on age,. The length 

 of the head is usually somewhat greater than the body heighto 

 The profile of the belly is slightly rounder than that of the 

 back, and the greatest body depth is roughly at the center of 

 the first dorsals The vent is located at or slightly to the rear 

 of the center of the body without the head. The caudal portion 

 of the body slopes sharply to the caudal peduncles, which is 

 markedly compressed dorsovent rally and has a pair of conspicuous 

 keels on both sideso 



The skin is well developed and thick and its connective 

 tissue is in several layers„ Its fibers are arranged obliquely 

 to the longitudinal axis of the body and each layer is laid down 

 roughly at right angles to the next, Consequentlys when this 

 skin is made into tanned leather, it has the quality of not 

 stretching in the direction in which these fibers are arrangedj, 

 but of stretching obliquelyo 



Translator's note? In his discussion of the anatomy of the tunas the 

 author has supplied English equivalents for most of the anatomical terras 

 employedo The author's terminology has been followed in the translation 

 without any effort to check on the accuracy or suitability of the names 

 given to bones and other anatomical featureso 



