Octopus vulgaris Cuvier, 1797. 



Four large individuals and numerous juveniles of this muscular, short- 

 armed species were observed. One was captured and dye marked, while 

 another could be recognized by injuries to several arms. These two 

 individuals were resighted on numerous occasions. This species lives 

 in shallow dens up on the reef face (Fig. 4) and on isolated coral 

 heads where they can command a view, A single specimen, which lived 

 in a den in a small coral-rock complex on the algae flats, was found 

 in or near the same den on many subsequent inspection trips. This 

 suggests a strong territorial behavior. Active during the day, in 

 particular the afternoon hours, they range over the sand flats near 

 their dens gathering food. They bring live shells back to the den or 

 a protected feeding area where they are drilled and the contents eaten. 

 The diet, consisting mainly of bivalves and conchs, was analyzed from 

 the debris or prey midden surrounding each den, A partial list of 

 food organisms is given below. Bivalves: Glycymeris decussata , G. 

 pectinata , Laevicardium laevigatum , Arcopagia fausta, Antigona rigida , 

 Anadara notabilis ; Gastropods : Strombus gigas , S. costatus , and 

 Conus sp. This is the same species that drills Livona pica in shallow 

 inshore waters. Hermit crabs probably also supplement the diet. Only 

 two size classes (DML* 10 cm and 2 cm) were found. Large individuals 

 were immature. Smaller juveniles were extremely abundant in the water 

 column around the night light or on the bottom near the habitat. 



No parasites were observed in the animal examined. 



Squid : 



Three genera and species of squid were encountered and observed during 

 the mission. 



Sepioteuthis sepioidea (Blainville, 1823). 



The largest and by far the most common squid in the area. Extensive 

 observations were made on their social heirarchy and schooling behavior. 

 Attracted by the night light, small aggregations were found around 

 the habitat during hours of darkness. No daylight observations were 

 made. Schools were most commonly composed of from 4 to 6 individuals 

 (Fig. 5) arranged in the water column in a predictable fashion depend- 

 ing on size and possibly sex. The integrity of each school was main- 

 tained through use of characteristic posture and color pattern displays 

 by peripheral individuals. The initial establishment of schools was 

 not observed but aggressive displays appeared to prevent outsiders from 

 joining pre-existing schools. 



Dorsal mantle length 



VI-226 



