Notes: FOOD AND PARASITES FROM TWO HOURGLASS DOLPHINS, LAGENORHYNCHUS CRUCIGER (QUOY AND GAIMARD, 1824), FROM PATAGONIAN WATERS

FERNANDEZ, MERCEDES; BERON-VERA, BARBARA; GARCIA, NESTOR A.; RAGA, J. ANTONIO; CRESPO, ENRIQUE A.

MARINE MAMMAL SCIENCE

WILEY-BLACKWELL PUBLISHING, INC

Año: 2003 vol. 19 p. 832 - 836

0824-0469

In May 2001 and January 2002, two hourglass dolphins stranded at Playa Unión (43°20´S, 65°00´W), Rawson, and Playa Paraná (42°49´S, 64º53´W), Puerto Madryn, Chubut. Necropsy was carried out following standard procedures (Norris 1961). Only stomach, intestine, and blubber were exarnined in the first animal, since the rest of the organs were decayed. The second animal was in good condition and underwent complete examination. Age was determined after counting dentina layers on longitudinal sections of teeth (Crespo et al. 1994). Sexual maturity was determined following Kasuya and Marsh (1984). Morphometric data, pictures, and the two skeletons (collection numbers Lagcru001 and Lagcru 002) are available from the collection of the Laboratorio de Mamíferos Marinos (LAMAMA), (Centro Nacional Patagónico, Puerto Madryn, Argentina).The Playa Unión dolphin (LC 1) was a sexually mature male, with eight growth layer groups (GLGs), and 1.64 m in length. A total of 31 plerocercoids of the cestode Phyllobothrium delphini (Phyllobothriidae) were collected from the sub­ cutaneous blubber around the abdominal surface. The animal had wounds around the abdominal area, where the cysticerci were located, possibly inflicted by sharks. Worms belonging to two genera of digeneans (Campulidae) were found in the intestine: Hadwenius sp. 1 ( 199 specimens) and Oschmarinella sp. (11 specimens). A total of 1,189 Anisakis simplex sensu lato (Nematoda: Anisakidae) were collected from the stomach. These included third and fourth larval stages (125 and 138, respectively) and adults (at least 577 males and 349 females).The Playa Paraná dolphin (LC 2) was a sexually mature male, with nine GLGs, and 1.78 m in length. Fifteen plerocercoid of the species P. delphini were found in the subcutaneous blubber of the abdominal surface. Two species of Hadwenius were collected, Hadwenius sp. 1 (one specimen) from the stomach, which belonged to the same species as that found in the Playa Unión dolphin, and Hadwenius sp. 2 (21 specimens) from the distal end of the hepatopancreatic duct. A total of 134 A. simplex sensu lato were collected from the stomach representing third and fourth larvae stages (121 and 4, respectively). No adults were collected. Five ulcers were detected in the main stomach, one of them with one larva A. simplex attached.The lesser shining bobtail squid, Semirossia tenera , was the most abundant prey in the LCl dolphin, followed by small Patagonian squid, Loligo gahi, and juvenile Argentine hake, M erluccius hubbsi (Table 1). S. tenera is a demersal-benthic species (Roper et al. 1984), the Patagonian squid is demersal-pelagic (FAO 1983, Nigmatullin 1989, Hatfi.eld et al. 1990), whereas adults of the Argentinean hake are demersal (Angelescu and Prenski 1987). However, individuals of the latter species taken by this dolphin where from a younger pelagic life stage. The presence of these prey species might indicate that this doiphin fed in surface waters. Severa! crustaceans (probably from benthic habitat) and other benthic species such as the cephalopod Eledone massyae, and the demersal-pelagic squid Illex argentinus were also part of the diet. We also recorded the annelids Glycera sp. and Eunice magellanica, which might have come from digestive contents of sorne of the hourglass dolphin preys.The most abundant prey species in the LC2 dolphin was the pelagic fish species Protomyctophum sp. (Myctophidae). Although specific determination was not possible, due to the lack of reference material, it is thought to be P. normani. Two species of this genus, P. normani and P. tenisoni, are known from the southwestern South AtlanticOcean (Menni et al. 1984). Based on the otoliths, eight individuals were identified as Protomyctophum sp. Fifty-seven individuals were identified as Protomyctophum sp. based on 113 cristalines. One Argentinian hake of pelagie: life stllge was found in the stomach contents, as well as the cephalopods Illex argentinus and L. gahi.