Luciano F. La Sala

Intestinal Acanthocephaladiosis in Olrog's Gulls (Larus atlanticus): Profilicollis chasmagnathi as Possible Cause of Death

In 2003 and 2005, mortality events were observed among hatch-year Olrogs gulls (Larus atlanticus) in a breeding colony in the Bahía Blanca estuary, Argentina. Freshly dead chicks were collected for parasitologic and parasite-associated pathologic studies. Profilicollis chasmagnathi was found at various intensities in all of the birds examined (n=28). On gross and histopathologic examinations, severe lesions ranging from intestinal obstruction to complete perforation were present in small and large intestines of the birds. Larval forms of P. chasmagnathi were being found in prey items of L. atlanticus in the study area, which suggests that diet may play a central role in the epidemiology of disease and mortality events in this species.

Some Digeneans from Olrog's Gull Larus atlanticus Olrog, 1958 (Aves: Laridae) from the Bahía Blanca Estuary, Argentina

Abstract Five species of digeneans (4 Microphallidae, 1 Echinostomatidae) were recovered from a total of 85 Olrogs gulls, Larus atlanticus (dead chicks). Birds were collected from a breeding colony in the Bahía Blanca estuary, Argentina, during breeding seasons 2003 (n = 6), 2005 (n = 66), and 2006 (n = 13). Digeneans were identified as Maritrema bonaerensis, Maritrema orensensis, Odhneria odhneri, Levinseniella cruzi, and Himasthla escamosa. Except for M. bonaerensis, all other helminth species represent new host records, and all the digeneans reported constitute new locality records. Likely intermediate hosts for digeneans, such as Neohelice granulata (Crustacea: Decapoda), Cyrtograpsus angulatus (Crustacea: Decapoda), and Heleobia australis (Mollusca: Gastropoda), were also studied. The metacercariae of M. bonaerensis were found in the crabs N. granulata and C. angulatus, and cercariae closely resembling those of M. bonaerensis, L. cruzi and H. escamosa were found in the mollusc H. australis.

Enteric Infections by Trematodes and Nematodes in Olrog's Gull, Larus atlanticus

SUMMARY. Trematodes and nematodes can be pathogenic helminths of birds. Every year during the breeding season, there is variable mortality among chicks from the largest Olrogs gull (Larus atlanticus) colony in Argentina. During two consecutive breeding seasons of Olrogs gull, we studied epidemiological and pathological aspects of infections by digeneans (Microphallidae) and nematodes (Acuariidae) in Olrogs gull chicks. Prevalence of nematode infection was 80.3% in 2005 and 89.2% in 2006, and mean intensity was 23.7 in 2005 and 50.8 in 2006. The risk for infection rose 34.3% and the intensity of infection 6.7% for every increase of 1 mm in head–beak length. The nematodes occupied the proventricular glands and caused disruption of their structure and mild inflammatory proventriculitis. Prevalence of digenean infection was 97.0% in 2005 and 97.3% in 2006. In 10-day-old live chicks, prevalence was 98.0% in 2006 and 95.3% in 2007. Infection was associated with severe catarrhal enteritis, lymphocyte/eosinophil-rich inflammatory responses, extensive fibroblast proliferation around the parasites, and disruption of the architecture of the adjacent crypts.

First Report of Olrog's Gull Depredation by Sympatric Kelp Gulls

Abstract We observed adult Kelp Gulls (Larus dominicanus) capture and eat Olrogs Gull (L. atlanticus) chicks in the Bahía Blanca estuary, Argentina. This estuary holds the largest breeding colony of Olrogs Gulls. There are no previously published reports of Kelp Gulls capturing and eating Olrogs Gull chicks. Our data support suggestions made by other authors about the possible existence of conflicts in colonies where both species breed in close proximity.

Breeding Biology of Olrog's Gull in Bahía Blanca Estuary, Argentina

Abstract Aspects of the breeding biology of the world largest Olrogs Gull (Larus atlanticus) colony, in the estuary of Bahía Blanca, Argentina, were assessed for 101, 66, and 47 nests in 2005, 2006, and 2007, respectively. Mean (± SD) clutch size in 2005 was 1.86 ± 0.73 eggs per nest and modal clutch size was two eggs (range  =  1–3). The incubation period was 1.67 days longer for A-eggs than for B-eggs (27.44 ± 1.22 days vs. 25.77 ± 1.36 days, respectively; P < 0.001). Incubation length for C-eggs was 25.75 ± 0.96 days. The largest eggs were 31.5% (length), 21.3% (breadth), and 66.5% (volume) larger than the smallest eggs. Mean egg volume in 2006 and 2007 decreased with hatching order, but the magnitude of this change was more pronounced in 2007 than in 2006. Variation in all egg measurements was larger among than within clutches. Hatching success within three-egg clutches was 76.9% in 2005, 81.7% in 2006, and 91.3% in 2007 (P  =  0.20). Total egg loss in 2005 reached 16.7% and complete clutch loss was 43.8% during the incubation period. Parameters quantified in this study provide a comparative benchmark for future research on factors affecting breeding parameters in Olrogs Gull from this and other colonies, and lay the foundation for developing effective conservation strategies for the species.

Efecto de la temperatura sobre la viabilidad de larvas de Trichinella spiralis

The aim of this work was to study the effect of temperature on the viability of free and encysted larvae of Trichinella spiralis from southwest Buenos Aires province, Argentina. Larvae were treated at variable temperatures (-30 °C, -20 °C, 4 °C, 20 °C, gradual heating between 0-100 °C). The time necessary to kill 100 % of larvae was calculated. During the first days of freezing, larval mortality significantly increased as a function of time. Regardless of temperature, encysted larvae survived longer than the free ones. At -30 °C, -20 °C, and 20 °C there were no significant differences between the survival curves for each larval stage. At 4 °C, mortality was less severe for encysted larvae. All free and encysted larvae died at 61 days and 95 days (-30 °C), 160 days and 180 days (-20 °C), 280 days and 330 days (4 °C) and 460 days and 590 days (20 °C), respectively. Cooking at 90 °C and 100 °C during 15 minutes killed 100 % of free and encysted larvae, respectively. Our results suggest that temperatures and exposure times traditionally used to treat meat products with a potential to transmit T. spiralis are not entirely efficient.

Some Nematodes from Olrog's Gull, Larus atlanticus Olrog, 1958 (Aves: Laridae), and Prey Crabs from the Bahía Blanca Estuary, Argentina

Abstract Three species of nematodes (Acuariidae) were recovered from a total of 108 adult and chick Olrogs Gulls, Larus atlanticus. Birds were collected from a breeding colony in the Bahía Blanca estuary of Argentina, during the breeding seasons of 2005 (n  =  66 chicks, 3 adults), 2006 (n  =  37 chicks, 1 adult), and 2007 (n  =  1 chick). Nematodes were identified as Pectinospirura argentata, Skrjabinoclava andersoni, and Sciadiocara sp., and all represent new host and locality records. Prevalence of infection among chicks during the 2005 and 2006 breeding seasons was 80.3% and 89.2%, respectively, and 67% for adults in 2005. Also, third-stage acuarid nematodes were found in possible intermediate hosts, Neohelice granulata (Crustacea: Decapoda) and Cyrtograpsus angulatus (Crustacea: Decapoda).