Association JDetween tiie sessile barnacle 

 Xenobalanus globicip'itis (Coronulidae) 

 and the bottlenose dolphin Tursiops 

 truncatus (Delphinidae) from the 

 Bay of Bengal, India, with a summary 

 of previous records from cetaceans 



Arjuna Rajaguru 

 Gopalsamy Shantha 



Systematics Laboratory, National Marine Fisheries Service, NOAA 

 National Museum of Natural History, Washington, DC 20560 



Several instances of association be- 

 tween cetaceans and cirripeds have 

 been reported in the hterature. 

 Among the barnacles, Coronula 

 spp., Conchoderma spp., and Xeno- 

 balanus sp. have been reported 

 from various species of cetaceans of 

 both temperate and tropical waters 

 (Mackintosh and Wheeler 1929, 

 Mackintosh 1942). Devaraj and 

 Bennet (1974) reported a single spe- 

 cimen of Xenobalanus globicipitis 

 found attached to the fluke of a fin- 

 less black porpoise Neophocaena 

 phocaenoides caught off Karwar, 

 west coast of India. This type of 

 phoretic partnership (i.e., transpor- 

 tation by one promotes well-being 

 of the other) between 14 specimens 

 of a sessile barnacle Xenobalanus 

 globicipitis and a host, the bottle- 

 nose dolphin Tursiops truncatus, is 

 recorded here from the Bay of Ben- 

 gal on the east coast of India. This 

 is the first record of the bottlenose 

 dolphin as a host for Xenobalanus 

 globicipitis from the central and 

 northern Indian Ocean. 



Five spinner dolphins Stenella 

 longirostris (Gray 1828) (113.0- 

 177.5cm TL) and six bottlenose dol- 

 phins Tursiops truncatus (Montagu 

 1821) (95.3-367.5cm TL), were col- 

 lected from the Bay of Bengal, off 

 Porto Novo (11°29'N; 79°46'E), 

 southeast coast of India, between 15 

 March 1982 and 1 September 1987. 



These specimens were entangled 

 accidentally in bottom-set gillnets 

 (called Motha Valai, in Tamil ver- 

 nacular) set mainly for sharks. The 

 net is made of thick (no. 7-12) nylon 

 thread (monofilament). The stretched 

 mesh size is 10-12 cm, and there are 

 about 120 meshes from the head to 

 the foot rope; hence the net is about 

 12 m deep. Total length of the net 

 is about 800 m {'^ one-half mile). 

 Fishing operations, which were car- 

 ried out mostly at night, were con- 

 fined to the upper continental shelf, 

 up to 4 km from the coast, to depths 

 of 18-22 m. The dolphins became 

 entangled in the nets both day and 

 night. 



All entangled dolphins were ex- 

 amined for external and internal 

 parasites (several dolphins had in- 

 ternal parasites). No barnacles were 

 found on the spinner dolphins. One 

 small bottlenose dolphin (148 cm 

 male) caught on 28 January 1985 

 had numerous Xenobalanus globici- 

 pitis attached (Fig. lA, B). None of 

 the four larger (>150cm) bottlenose 

 dolphins had any barnacles. All bar- 

 nacles were collected (four from the 

 left fluke, eight from the right fluke, 

 and one from each flipper) and 

 preserved in formalin. The barna- 

 cles were still alive after more than 

 12 hours out of water. Measure- 

 ments to the nearest millimeter 

 (Fig. 2) are given in Table 1. 



In the sessile barnacles, extreme 

 reduction of plates is fotmd in Xeno- 

 balanus. The shell is thin, small, 

 white, irregularly star-shaped, and 

 vestigial, containing only the basal 

 parts of the animal. Connected to 

 this thin, star-shaped shell is a cylin- 

 drical, smooth, flexible, peduncle- 

 like body (Fig. 3). At the distal end 

 of this greatly elongated pseudo- 

 peduncle is a reflexed hood, which 

 bears two stumpy outpushings or 

 'horns,' but terga and scuta are ab- 

 sent. Cirri, mouth, a probosciform 

 penis, and associated organs project 

 from the reflexed hood. The wall 

 plates of this barnacle are em- 

 bedded in the skin of the dolphin, 

 with feeding appendages (cirri) and 

 associated organs suspended by the 

 long fleshy stalk. The body of X. 

 globicipitis was dark -brown in live 

 specimens, with a lighter colored 

 hood; the penis was whitish. 



Although belonging to the sessile 

 group of the Cirripedia, this bar- 

 nacle closely resembles stalked 

 barnacles, especially Conchoderma 

 auritum which is also found on ceta- 

 ceans though never attached direct- 

 ly to the skin of its host. Xenobala- 

 nus globicipitis is always attached 

 directly to the skin of its host 

 (Pilsbry 1916, Barnard 1924). The 

 resemblance is superficial, and is 

 likely adaptive to being dragged 

 through the water by the host. The 

 closest affinities with Xenobalanus 

 are the genera Coronula, Platyle- 

 pas, and Tubicinella (Darwin 1854, 

 Pope 1958). 



The barnacles are found only 

 around the rear margins of flippers 

 and flukes. It is hypothesized that 

 those that settle elsewhere are 

 more easily swept off. A single im- 

 mature barnacle (15 mm TL) was 

 found attached to each flipper of the 

 dolphin (Fig. lA). All 12 mature 

 barnacles (30-39 mm TL) (Table 1) 

 were aggregated at the rear margin 

 of the flukes (Fig. IB). Pilsbry 



Manuscript accepted 19 December 1991. 

 Fishery Bulletin, U.S. 90:197-202 (1992). 



197 



