Arhythmorhynchus comptus ( Acanthocephala : Polymorphidae ) from shorebirds in Patagonia , Argentina , with some comments on a species of Profilicollis

Adult and immature Arhythmorhynchus comptus (Acanthocephala: Polymorphidae) were found parasitizing the Baird’s Sandpiper, Calidris bairdii, and the White-rumped Sandpiper, Calidris fuscicollis (Aves: Scolopacidae), from several locations in Patagonia, Argentina. This is the first record of A. comptus in the southern part of South America and from C. fuscicollis and C. bairdii, expanding both its geographical and host distribution. Additionally, immature specimens belonging to the genus Profilicollis were found in both bird species.

and their larvae, but also includes worms and spiders (Piersma et al. 1996).
The White-rumped Sandpiper, Calidris fuscicollis (Vieillot, 1819), nests from June to August in the central Canadian Arctic, then migrates through central North America, stopping at lakes in Canada.Upon arrival in South America, they migrate through the center of the continent and along its Atlantic coast.They can be seen in Patagonia from March to April on intertidal mudflats, salt marshes, ponds and lagoons.They consume invertebrates such as adult and larval insects, spiders, mollusks, crustaceans, and polychaetes, as well as seeds (Piersma et al. 1996).
The parasitic fauna of migratory birds has been the subject of numerous studies in different parts of the world (e.g., Canaris and Kinsella 2000, 2001, 2007;Canaris et al. 2003;Didyk et al. 2007).However, in South America very little is known about parasites of shorebirds and of seabirds in general.Understanding of parasite life cycles can generate substantial information to understand habitat use and the time spent by the host in a given environment (Bush 1990;Rohde 1993).Studies of the parasitic fauna of these two phylogenetically related species of migratory birds could be an important contribution to ecological and biogeographical studies.
Site of infection: intestine P and MI = 27% and 1.75 in C. bairdii; 8.3% and 2 in C. fuscicollis.
Adult specimens -General: Body very long and narrow.Anterior trunk covered by spines in a small area, limited to that region.In the first part, the trunk is widened, then it thins and finally wides again towards the end of the body.Cylindrical posterior portion of the trunk sometimes invaginated in the anterior portion.Samples of hosts were examined from locations in both marine and freshwater environments (Figure 1).
Hosts were dissected in the field and viscera were fixed in 10% formalin.In the laboratory, acanthocephalans were recovered from the intestine and preserved in 70% ethanol.Some specimens were not relaxed before fixation and therefore not all had proboscises fully everted.For morphological study, specimens were studied in temporary mounts of lactophenol or eugenol using an Olympus BX51 ® microscope (OM).Some male specimens were dissected to a better observation of the cement glands.Several specimens were dried using the critical point method, examined by scanning electron microscopy (SEM) (Jeol 6360LV ® , Tokio, Japan), and photographed.Drawings were made with the aid of a camera lucida.Measurements are given in micrometers unless otherwise indicated as the range followed by parentheses.Eggs were measured through the body wall.For taxonomic identification, acanthocephalans were analyzed following specific bibliography (Van Cleave 1916;Van Cleave and Rausch 1950;Yamaguti 1963;McDonald 1988).The prevalence (P) and mean intensity (MI) were calculated following Bush et al. (1997).
Voucher specimens were deposited in the Colección Helmintológica del Museo de La Plata, Buenos Aires, Argentina, and in the Parasitological Collection of the Host: Calidris bairdii.
Measurements of males and females, of A. comptus are shown in Table 1.
Locality: Bahía Bustamante (45°07ʹ34ʺ S, 066°32ʹ14ʺ W), Chubut province, Argentina.Voucher specimens MLP He 7116, 7117 and CNP 137.Morphometric and morphologic characteristics of adult acanthocephalans studied here enable them to be identified as A. comptus.However, slight differences in measurements of some features from those recorded by previous authors were observed (e.g., total length of female, neck length, body spine length, number of hook per row) (see Table 1).In present specimens it could be observed a great number of hooks per row than those observed by Van Cleave and Rausch (1950).The present specimens show some similarities to Arhythmorhynchus capellae (Yamaguti, 1935) and Arhythmorhynchus eroliae (Yamaguti, 1939).However, the two latter species have larger number of rows and hooks per row than A. camptus, which has the lowest number of hooks per row in the genus.Although there are other reports of A. comptus, authors did not provide morphometric data (e.g., Canaris and Kinsella 2007) that could be compared with the present specimens.
There are discrepancies in the number of cement glands in this species and in others of the genus (Golvan 1960;Yamaguti 1963).However, the observation of such structures is quiet difficult due to the thickness of the body wall.We observed only two cement glands after the dissection of some males.According to Van Cleave and Rausch (1950), A. comptus is the only species of the genus with two cement glands.
Members of the genus have been recorded previously in North and Central America in birds of the family Scolopacidae.In Alaska A. eroliae was reported from the Ruddy Turnstone Arenaria interpres (Linnaeus, 1758) (Canaris and Kinsella 2007), and A. longicollis (Villot, 90-100 × 20-25 it was not possible to identify the specimens to species level.However, based on the number and distribution of hooks on the proboscis and previous reports in the area (i.e., South Atlantic coast), it is probable that they are P. chasmagnathi.However, further experimental or molecular studies are needed to confirm this hypothesis and to corroborate the identity of the species.
Baird's and White-rumped sandpipers breed in the high Arctic and migrate extremely long distances to winter in the southern cone of South America (Chandler 2009).The birds arrive in northern South America around early October and to their wintering areas (e.g., Patagonia Argentina) about a month later.According to Atrashkevich (1979), the life cycle of A. comptus includes freshwater isopods as intermediate hosts.Development from the infective cystacanth to the adult acanthocephalan takes around 30-49 days (Atrashkevich 1979).Because both adults and juveniles were found in birds from Patagonia collected in January, then infections were acquired in South America during the fall migration.Future studies are needed to show whether the life cycle can also be completed on the wintering grounds.
The present report increases the knowledge of acanthocephalans of migratory birds and represents the first record of A. comptus in South America and from C. fuscicollis and C. bairdii, expanding both the geographical and host distribution.
| Acanthocephalans from shorebirds in Argentina Centro Nacional Patagónico, Puerto Madryn, Argentina.A total of 29 adult acanthocephalans were found attached to the intestine wall of C. bairdii (n = 21) and C. fuscicollis (n = 8).Ten immature specimens were also recovered, nine from C. bairdii and only one in C. fuscicollis.Morphometric and morphological characteristics of adults allowed identification as A. comptus.Immature specimens were identified either as A. comptus or Profilicollis sp.
Here we provide new morphological details on Arhythmorhynchus comptus Van Cleave & Rausch, 1950 based on specimens recovered from Baird's Sandpiper, C. bairdii, and the White-rumped Sandpiper, C. fuscicollis, from Patagonia, Argentina, expanding its geographical and host distribution.Additionally, we report immature specimens belonging to the genus Profilicollis Mayer, 1931 found in both bird species.

Table 1 .
Comparative measurements of Arhythmorhynchus spp.from different hosts and localities.References: L (length), W (width)