GOOSE BARNACLES 



(CIRRIPEDIA: THORACICA) 



ON FLOTSAM BEACHED AT 



LA JOLLA, CALIFORNIA 



The macroscopic floating biota of the ocean 

 surface — the pleuston — has been comparatively 

 httle studied (see review by Cheng 1975). It com- 

 prises a few species of insects, which skim over the 

 surface; a few species of siphonophores equipped 

 with floats; a few species of barnacles; etc. These 

 organisms can be collected by the use of special 

 nets towed at the level of the ocean surface, but the 

 numbers of such tows made on oceanographic ex- 

 peditions have been comparatively few compared 

 with the much larger numbers of plankton tows 

 made below the sea surface. Under exceptional 

 circumstances, when an onshore wind blows for an 

 extended period, pleustonic organisms are cast 

 ashore in appreciable numbers, presenting un- 

 usual opportunities to study numbers of individu- 

 als of this little known community. Such mass 

 beachings of the siphonophores Physalia and Ve- 

 lella have been reported in several parts of the 

 world (Bingham and Albertson 1974; Cheng 

 1975). This paper presents some data on a mass 

 beaching of pleustonic goose barnacles, mostly at- 

 tached to floating objects and mostly still living, 

 found washed ashore between 5 and 9 July 1974, 



in front of the Scripps Institution of Oceanog- 

 raphy, La Jolla, Calif. 



Methods 



A stretch of beach approximately 1 km long and 

 5 m wide was searched systematically for five 

 successive days, around the time of the low tide in 

 daylight, and every barnacle or piece of flotsam 

 bearing barnacles was collected, taken to the 

 laboratory in plastic bags, and there kept in tanks 

 with running seawater. Some observations were 

 made on the living animals, which remained alive, 

 feeding actively, for several days, and specimens 

 were photographed (Figure lA-F). They were 

 sorted according to substrate, the species were 

 identified, and the lengths of the capitula were 

 measured from base of scutum to apex of tergum 

 (peduncle lengths being variable). 



Observations 



In all, some 329 substrate objects were collected 

 and examined; they bore a total of 2,555 individual 

 barnacles. The data, for all collections, are sum- 

 marized in Tables 1 and 2, and the size distribu- 

 tions of each species on each of the major substrate 

 types are shown in Figure 2A-L. The following 

 generalizations were made on the basis of this 

 material. 



Table l. — Numbers and percentages of substrates bearing barnacles: Lepas 

 (Dosima) fascicularis and Lepas (Lepas) pad fica. 



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