Octopus briareus Robson, 1929. 



Of fourteen animals sighted, three (all females) were captured, marked 

 and released. All were resighted on several occasions during the 

 course of the mission (Fig. 1), One (T4) was observed twelve days 

 after capture. Nocturnally active, this species ranges throughout 

 the reef area seeking crustaceans and small fish which abound there. 

 The fact that this species is regularly capable of capturing fish 

 demonstrates an agility and predator -prey relationship that has not 

 often been reported for Octopods. They hunt by throwing themselves 

 over small coral heads (Fig. 2) or crevices, spreading the web (Fig. 3) 

 to trap unwary prey and then reaching under with the arms to capture 

 the victims or to drive them to the beak or mouth. Individuals appear 

 to be territorial since resightings were made in much the same areas as 

 captures. Semipermanent dens are located along the edge of the reef 

 where the coral abuts with the sand. The openings are often marked by 

 a finger of red sponge. Two size classes were present in the area 

 studies (DML* 10 cm and 7 cm). No juveniles were observed. 



No mesozoans were recovered from the renal sacs. The kidneys of the 

 three animals examined were unusual in being dark red. This may indi- 

 cate a large proportion of fish in the diet. The wall of the caecum 

 and intestine in all three was lined with white cysts of the protozoan 

 coccidian parasite, A ggregat a, This would indicate a predominately 

 decapod crustacean diet at some previous time, since the alternate hosts 

 for this protozoan parasite are usually decapod crustaceans. 



Octopus macropus Risso, 1826, 



Twelve animals were sighted, six (3 males and 3 females) were examined 

 in the habitat, and five were subsequently tagged and released. No re- 

 sightings were made. This large octopus species is active at night on 

 the sand flats to the west of the habitat. During the day they live deep 

 under the reef in semipermanent dens which are blown out of the sand. 

 Not territorial, they appear to range widely over the flats. Predomi- 

 nately hermit crab feeders, they use their exceedingly long arms to feel 

 out shells and explore around and under isolated coral heads. Three size 

 classes were observed (DML* 18 cm, 8 cm and 2 cm), the largest were 

 mature . 



No mesozoans were recovered. No Aggregata nor cestode cysts were present 

 in the gut wall. Several small white cysts (probably cestode) were 

 attached to the wall of the aorta. 



* Dorsal mantle length 



VI-225 



