BADCOCK and BAIRD; SYSTEMATICS OF STERNOPTYX 



Table l.— Photophore development ofStemoptyx pseudodtaphana and S. diaphana , expressed in stages. 

 Asterisk denotes earliest stage for photophore group completion; parentheses indicate photophore nomen- 

 clature in Baird 1971. 



Stage 



SL range 



(mm) 



Number of photophore s per photophore group (each size; 



OP^ ORB BR PV IP OV OP2 AN VAV 



(SO) (PO) (BR) (AB) (I) 



OV OP2 AN VAV SC OPi SAN No of 

 (SP) (PTO) (AN) (PAN) (SC) (PRO) (SAN) specimens 



'Smallest observed size. 



^All specimens equal or larger have all photophores. 



In this account, where reference to a particular 

 photophore within a group is made, numbering is 

 in an anteroposterior direction (e.g., AB(PV) 10 is 

 the posteriormost photophore pair). 



Measurements and Counts 



The peculiar morphology of marine hatch- 

 etfishes has necessitated a number of modifica- 

 tions to measurements commonly used to describe 

 teleost fishes. While most of those used here have 

 been described by Baird (1971), it is difficult to 

 precisely determine reference points in the genus 

 Sternoptyx. All measurements used here are 

 defined as the shortest distance between two 

 stated points. Standard length (SL) in juveniles 

 and adults was measured to the nearest 1 mm, but 

 in postlarvae, to the nearest 0.1 mm. Other mea- 

 surements of all specimens were taken to 0.1 mm. 

 Measurements were as follows (letters refer to 

 points on Figure 1): 



Standard length (SLl: from the tip of the snout 

 (A) to the furthermost extension of the caudal 

 peduncle (E): 



Body depth: from the dorsal blade origin (B) to 

 the midpoint of the ventral body margin (D): 



SAN photophore depth: from the dorsalmost 

 point (G) of the photophore SAN to the dorsal body 

 margin (F) at the base of the posteriormost dorsal 

 ray; 



Midline height: from the anteroventral edge (I) 

 of the photophore group AN to the trunk midline of 

 horizontal septum (H) on a line passing through 

 the photophore SAN; 



SAN photophore height: from the anteroventral 

 edge (I) of the photophore group AN to the dorsal- 

 most point (G) of the photophore group SAN; 



Trunk depth (TD): from the posterior end of the 

 dorsal fin base (F) to the anteroventral edge (I) of 

 the photophore group AN; 



Trunk length: from the point of the trunk mid- 

 line defined by the midline height measurement 

 (H) to the posteriormost extent of the caudal 

 peduncle (E); 



Photophore lengths (AN and SC): the distance 

 between the farthest extensions of the darkly 

 pigmented photophore margins; 



Dorsal fin base: from the origin of the first (K) to 

 that of the last (F) dorsal ray; 



Dorsal blade height: from the dorsal body mar- 

 gin (C) to the blade tip (J), along blade axis; 



Orbital diameter: the length of the longest orbi- 

 tal axis (fleshy orbit); 



Suborbital length: from the midventral point of 

 the orbit (M) to the tip (L) of the preopercular 

 spine. 



It was not possible for one person to measure or 

 take counts on all the specimens examined. The 

 results obtained, however, were in good agree- 

 ment, although it is inevitable that some variation 



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