OBSERVATIONS ON THE BEHAVIOR OF THE SCAVENGING LYSIANASSOID ORCHOMENE-ZSCHAUI (CRUSTACEA - AMPHIPODA) FROM SOUTH GEORGIA (SOUTH-ATLANTIC)

Orchomene zschaui (Pfeffer, 1888) dominated the catch of scavengers at tracted to heads of dead elephant seals suspended above the sea bed at Husvik, South Georgia. No ovigerous female, and few juvenile, amphipo ds were captured. Activity was nocturnal. No lunar rhythm in catch rat e was detected: encounters with bait (by visiting shoals of amphipods? ) seemed to be by chance. Habitat choice experiments revealed a kineti c preference for dark vs light places, antipathy towards sand and a co nsistent choice of alternatives which offered high surface contact. Am phipods survived 4 ppt salinity for 30 min. Temperatures between -2 an d +10-degrees-C were tolerated, but rapid removal from +2-degrees-C to +12-degrees-C resulted in heat shock effects. In the field, amphipods nestled into the pelt of the seal head, often near a facial orifice, and began penetration of the epidermis, creating larger and larger hol es with time. The stomach of O. zschaui occupies 41% of body length. A nalysis of stomach contents showed that consumption of dark epidermal tissue (as strips) only preceded white blubber, i.e. never followed it . The degree of stomach fullness of amphipods captured at night increa sed progressively through the hours of darkness. The rate at which sto mach fullness declined with time depended on the material consumed: 9 to 10 d for seal epidermis, 2 d for blubber. Replete amphipods lose so me 20% of total dry weight if starved for 23 d.