FIRST RECORDS OF A GIANT PELAGIC 



TUNICATE, BAIHOCHORDAEVS CHARON 



(UROCHORDATA, LARVACEA), FROM 



THE EASTERN PACIFIC OCEAN, WITH 



NOTES ON ITS BIOLOGY 



Recent studies iHamner et al. 1975; Alldredge 

 1972, 1976a; Silver et al. 1978) have demonstrated 

 the importance of gelatinous macroplankton and 

 their mucous secretions in planktonic com- 

 munities as sources of particulate organic carbon 

 and surface habitat in an otherwise homogeneous 

 environment. Pelagic tunicates of the Class Lar- 

 vaeea appear to be especially important members 

 of this assemblage because they periodically se- 

 crete and release numerous external, mucous, 

 feeding structure.s or "houses." In midwater trawl- 

 ing off southern California we obtained several 

 specimens of a unique, giant larvacean, 

 Bathochordaeus charon Chun 1900. This species 

 may be a major source of suspended organic 

 aggregates, or "marine snow" (Silver et al. 1978), 

 as well as a major consumer of living and detrital 

 particulate organic carbon in mesopelagic regions. 

 Only eight specimens of this unusual tunicate, 

 whose trunk may reach 25 mm long, have been 

 reported. The present material increases the 

 number of known intact specimens to 13 and rep- 

 resents a major extension of the range of the 

 monotypic genus. 



Histon, <if Btilbinhnrchniii charoii Collections 



Collection data for all known specimens are 

 given in Table I. Bathochordaeus charon was first 

 described as a new genus and species by Chun 



(1900:519-521) on the basis of two gigantic speci- 

 mens taken in 1898 in the southeastern Atlantic 

 Ocean by the German Deep Sea Expedition, 

 aboard the Valdivia. Lohmann (1914) described 

 these specimens in greater detail and assigned 

 them to the Oikopleuridae. He later (1931) de- 

 scribed two additional, smaller animals taken in 

 1899 in the Indian Ocean during the same expedi- 

 tion. Garstang (1936, 1937) collected two small 

 specimens off Bermuda, which he described as a 

 new species, B. stygius, because of minor differ- 

 ences from the original descriptions. Fenaux 

 ( 1966) synonymized the two species and Garstang 

 ( 1937) himself believed the differences lay mainly 

 in misinterpretations of morphology by Chun 

 (1900) and Lohmann (1914, 1931). A single speci- 

 men was listed, without description, from the 

 German Atlantic Expedition on the Meteor 

 (1925-27) (Lohmann and Hentschel 1939). 

 Thompson's ( 1948) report of a single small speci- 

 men from eastern Australia was the first record of 

 the genus from the Pacific Ocean. 



These eight specimens were the only reliable 

 records prior to this report. Tokioka (1960) ob- 

 tained five large (to 20 mm long) isolated larva- 

 cean tails from collections of the Shellback ( lat. 13' 

 N, long. 99° W) and EQUAPAC (lat. 8° S, long. 

 164° E) expeditions of the Scripps Institution of 

 Oceanogi-aphy. Tokioka tenatively assigned these 

 to Bathochordaeus charon on the basis of their 

 length; however, all conform in size with 

 Megalocercus sp., another large larvacean which 

 also was taken on these expeditions, and only one 

 of the tails had the characteristic shape ofB. cha- 

 ron. Thus the affinity of Tokioka's ( 1960) material 

 cannot be established with certainty and only one 

 of his specimens is included in Table 1. 



Table l.— Collection and size data for known specimens of the pelagic inmcsXe Bathtxhurdaeus charon. The specimen of Tokioka is 



only tentatively assigned Xo this species (see text). 



