External and gastrointestinal parasites of the Franklin's Gull, Leucophaeus pipixcan (Charadriiformes: Laridae), in Talcahuano, central Chile.

Parasitological studies of the Franklin's gull, Leucophaeus pipixcan, are scarce, and knowledge about its endoparasites is quite limited. In order to describe its parasitic community, a total of 60 Franklin's gulls were captured in the coastal area in central Chile, using modified Bal-chatri traps. Ectoparasites were collected from all 60 live individuals through inspection of their plumage, while 30 were examined for endoparasites by standard parasitological necropsy. The prevalence of ectoparasites was 78.3%, including the feather mite Zachvatkinia larica (43.3%) and four species of lice: Actornithophilus piceus lari (15.0%), Austromenopon transversum (6.7%), Quadraceps punctatus (10.0%) and Saemundssonia lari (46.7%). Some 25 of 30 (83.3%) of birds necropsied were parasitized with the following helminths: Aporchis sp. (6.7%), Tetrabothrius cylindraceus (56.7%), Cyclophyllidea gen. sp. (3.3%), Profilicollis altmani (56.7%), Eucoleus contortus (10.0%), Cosmocephalus obvelatus (13.3%), Paracuaria adunca (10.0%), Stegophorus sp. (3.3%) and Tetrameres skrjabini (3.3%). To our knowledge, with the exception of P. altmani, these helminths are reported for first time in the Franklin's gull.


Introduction
The Franklin's gull, Leucophaeus pipixcan (Wagler, 1831), is a migratory bird that travels every year from breeding sites in the United States and Southern Canada (Harrison, 1983) to Central and South America; most individuals stay in the southern hemisphere during the austral summer (Marin & Couve, 2001). Its presence on the Chilean coasts is observed from Arica (18°28'S, 70°17'W) to the extreme south of the country, Aysén (45°24'S, 72°42'W), with accidental records in the Magellan and Antarctic Regions (Couve et al., 2016).
Regarding its endoparasites, there are records of the acanthocephalan Profilicollis altmani (Perry, 1942) Van Cleave, 1947 (= P. bullocki), isolated from this host in South America (Peru and Chile) (Tantaleán et al., 2005;Riquelme et al., 2006;Rodríguez et al., 2017), and the filarioid nematode Eulimdana sp. in Canada (Bartlett, 1992). Despite its wide geographical distribution, reports on its parasitic fauna are scarce, and knowledge about its internal parasites is quite limited. This study aims to provide new records of diversity and prevalence of parasites associated with the Franklin's gull.

Materials and Methods
The study was carried out in Talcahuano, a coastal city in central Chile (36º44'10"S, 73º06'17"W) (Figure 1), during January and February 2008 and March 2009. Sixty Franklin's gulls were captured with modified Bal-chatri traps pre-baited with fish. Captured gulls were visually examined, inspecting their feathers and skin for ectoparasites, which were collected and preserved in 70 GL ethanol. Half of the individuals were released, and the rest were euthanized by cervical dislocation. All procedures were authorized by the Agricultural and Livestock Service (SAG) under the resolutions No 1801 and 811.
The 30 dead birds were stored in plastic bags and immediately taken to the laboratory for parasitological necropsy. The extracted feather lice were cleared and mounted in Canada balsam, as described by Palma (1978) and Price et al. (2003). Mites were cleared in Nesbitt's solution for 72 hours and mounted in Berlese's solution, as described by Krantz & Walter (2009). The identification of lice followed the taxonomic keys by Clay (1949Clay ( , 1959Clay ( , 1962, Price & Clay (1972), Timmermann (1952), and Ward (1955); for mites, the keys by Gaud &Atyeo (1996), andMironov (1989) were applied.
Quadraceps punctatus (Ischnocera: Philopteridae) was collected from the wings with 10.0% (6/60) of prevalence, presenting the lowest mean intensity and mean abundance of lice ( Table 1). The cosmopolitan genus Quadraceps is composed of a wide variety of species and subspecies that parasitize birds of the order Charadriiformes (Price et al.,  . Quadraceps punctatus has been frequently recorded on birds of the family Laridae, mainly in those of the genus Larus, with records from the Palearctic, Nearctic and Neotropical regions, also Australasia (Timmermann, 1952;Price et al., 2003). Quadraceps punctatus is one of the four lice species identified as parasites in L. pipixcan, being previously reported in Canada (Galloway et al., 2014), Belgium (Hellenthal et al., 2004), Galapagos (Palma, 1995), and Chile (González-Acuña et al., 2011). In Chile, this louse has also been isolated from the gulls Larus dominicanus and L. modestus (González-Acuña et al., 2011). Saemundssonia lari (Ischnocera: Philopteridae) was collected from the head and chin regions with 46.7% (28/60) of prevalence, and a total of 106 specimens ( Table 1). Lice of the genus Saemundssonia inhabit preferentially the head of their hosts (Johnson et al., 2012;Yamagishi et al., 2014). Morphologically, it has a triangular anterior margin with a rostral groove, the common characteristic of head lice, that helps them hold on feathers and resist against scratches (Price et al., 2003;Johnson et al., 2012). Saemundssonia lari was the most prevalent parasite in this study, with the highest mean abundance, that presumably related to its capability ecological niche occupied to resist to grooming (Johnson et al., 2012). This cosmopolitan species parasitizes birds of the family Laridae, with reports in those of the genera Gabianus, Larus, Pagophila, Rissa and Xema (Price et al., 2003;Vas et al., 2012), and has been previously recorded from L. pipixcan in Belgium (Hellenthal et al., 2004), Canada (Galloway et al., 2014), Peru (Gomez-Puerta & Cribillero, 2015), and Chile (González-Acuña et al., 2006, 2011.

Trematodes
Aporchis sp. (Digenea: Echinostomatidae) was collected from the small intestine of two individuals with a prevalence of 6.7% (Table 2, Figure 3a). The genus Aporchis (Stossich, 1905) has a wide geographical distribution being associated with seabirds, and was previously registered in the Palearctic (Bosch et al., 2000;Roca et al., 2001;Santoro et al., 2011;Radwan, 2014), Nearctic (McCauley & Pratt, 1960Hoberg, 1981) and Neotropical regions (González-Acuña et al., 2009). In Chile, this genus was found in the Kelp gull, L. dominicanus, by González-Acuña et al. (2009), with which the Franklin's gull shares habitats during the southern summer, and it is still unknown what other gull species could act as a host in the area. The specific identification could not be achieved because the peristomic disc of specimens lack of their spines which are required for its diagnosis (Yamaguti, 1958). Aporchis sp. in toto is shown in Figure 3a. Its narrower forebody is indicated by the right arrowhead; at the anterior end, the peristomic disc is indicated by an asterisk and the left arrowhead shows the acetabulum. The present study represents the first report of the genus Aporchis in L. pipixcan, expanding its host range.
A few cyclophyllidean tapeworms were isolated from the small intestine of gulls with a prevalence of 3.3% (1/30) ( Table 2). However, its specific identification could not be achieved because the poor preservation of proglottids and loss of rostellar hooks. The scolex is shown in Figure 3b, where the arrowhead indicates its four semi-circular suckers.

Acanthocephala
Profilicollis altmani (Polymorphida: Polymorphidae) was the only acanthocephalan found in this study, collected from the small intestine of 56.7% (17/30) of gulls (Table 2; Figure 3c). Figure 3c shows an individual of P. altmani with its spherical proboscis (right) and in detail (upper left side) the rows of small hooks present on the surface of this structure (indicated by asterisks). (Stimpson, 1857) and Hemigrapsus crenulatus (Milne-Edwards, 1837) (Balboa et al., 2009;González-Acuña et al., 2009), both widely distributed along the coast of Chile (Retamal, 1981). Profilicollis altmani has been reported in Charadriiformes from the Neotropical region (Tantaleán et al., 2005;Riquelme et al., 2006;Gonzáles-Viera et al., 2009;González-Acuña et al., 2017;Rodríguez et al., 2017;Gomez-Puerta & Naupay, 2019), being previously isolated from Franklin's gulls in northern and central Chile and Peru (Tantaleán et al., 2005;Riquelme et al., 2006;Rodríguez et al., 2017), areas where it has also been recorded on its intermediate hosts and sympatric birds (Riquelme et al., 2006;Iannacone et al., 2007;Balboa et al., 2009). The present study provides a new report of this parasite-host association in central coasts of Chile, where L. pipixcan has been shown to be a better host that increases the abundance of P. altmani when it arrives to this area (Riquelme et al., 2006). Parasites of the Franklin's gull in Chile
Cosmocephalus obvelatus (syn: C. firlotlei) (Creplin, 1825) (Spirurida; Acuariidae) was collected from the esophagus and proventriculus of 13.3% (4/30) of the individuals (Table 2, Figure 3d), the usual location, since larvae initially invade the proventriculus and later settle in the esophagus (Wong & Anderson, 1982a). Figure 3d shows the anterior end of an individual of C. obvelatus, the arrowhead indicates the cephalic cordons. On the upper left side is shown the posterior end of a male worm. The asterisks are indicating the pre-anal and post-anal papillae, on the ventral surface, and the arrowhead indicates the left spicule, which is triangular at its distal border.
Paracuaria adunca (Creplin, 1846) (Spirurida; Acuariidae) was isolated in the 10% (3/30) of birds (Table 2; Figure 3e). These nematodes were collected from the proventriculus and under the koilin layer of gizzard, which is in agreement with Anderson & Wong (1982) and Wong & Anderson (1982b). Figure 3e shows an individual of this species. In the center of the figure, is shown the anterior part of the worm with its two pseudolabia and striated cuticle. The position of the deirid is posterior to the nerve ring (white asterisk) and its tridentate shape is shown in detail on the left picture. The posterior end of male worm (upper right side) has 2 dissimilar spicules; right spicule is short and stout, rounded at its basis (arrow), and left spicule is long, slender (arrowhead) and presents a triangular and serrated distal tip, shown in detail on the bottom right side.
Through experimental studies, Anderson & Wong (1982) showed that amphipod crustaceans and fishes act as a source of transmission for P. adunca, with the latter group as the main source of infection in seagulls. Due to the above, this nematode mainly parasitizes piscivorous birds as has been reported in Europe, Asia, North America, South America and Cuba (Baruš et al., 1978;Wong & Anderson, 1982b;Diaz et al., 2004Diaz et al., , 2011Sanmartín et al., 2005;Álvarez et al., 2006;Santoro et al., 2011;Hannon et al., 2016). In Chile, it has been documented for the first time in the raptor M. chimango that is attributable to its piscivorous food habits (Oyarzún-Ruiz et al., 2016), and in the Kelp gull, L. dominicanus, (González-Acuña et al., 2009), a host species for which exists other records in Latin America (Diaz et al., 2004(Diaz et al., , 2011. To our knowledge, this is the first report of the Franklin's gull as a host of this nematode. Stegophorus sp. (Spirurida: Acuariidae) and other unidentified acuariid larva were isolated under the koilin layer of the gizzard from two different gulls, both with a prevalence of 3.3% (1/30) (Table 2; Figure 3f). The specific diagnosis for Stegophorus could not be achieved because the isolated specimen corresponded to an immature female worm (Anderson et al., 2009). Figure 3f shows the only specimen of Stegophorus sp. isolated. On the left is shown the anterior end with two pseudolabia covered at its posterior border by teeth (asterisks). The position of the deirid is over the union between the buccal capsule and muscular esophagus (arrowhead), it has a rounded tridentate shape shown bordered by asterisks on the right side. Detail of pseudolabia, which appears as a collarette with several teeth, are indicated on the bottom right side by arrowheads. This genus has been reported previously in several piscivorous birds such orders Procellariformes, Sphenisciformes and Charadriiformes (Baruš et al., 1978;Mutafchiev et al., 2014). Those species reported parasitizing charadriiform birds (e.g. the genera Larus and Stercorarius) are the following: Stegophorus arctowskii Zdzitowiecki & Dróżdż, 1980, Stegophorus macronectes (Johnston & Mawson, 1942, Stegophorus stellaepolaris (Parona, 1901) and Stegophorus stercorarii Leonov, Sergeeva & Tsimbalyuk, 1966(Sagerup et al., 2009Mutafchiev et al., 2014). These parasites, like other acuariid nematodes, are probably transmitted mostly by consumption of fishes which could act as paratenic hosts (Anderson & Wong, 1982;Wong & Anderson, 1982a;Anderson, 2000). To our knowledge, the present record of the genus Stegophorus is the first for the Franklin's gull.
Tetrameres skrjabini (Panova, 1962) (Spirurida: Tetrameriidae) was isolated from a single gull with a prevalence of 3.3% (1/30) ( Table 2). One male specimen was found in the esophagus lumen, and seven females were found into the proventriculus glands, location typically adopted by this genus in the case of females, but not males, who are usually found on the lumen or mucosa of the proventriculus (Kinsella & Forrester, 2008). This genus has an indirect life cycle, with crustaceans acting as intermediate hosts in aquatic environments (Anderson, 2000;Kinsella & Forrester, 2008), while birds of the orders Anseriformes, Ardeiformes, Gruiformes and Charadriiformes act as definitive hosts (Mollhagen, 1976;Kinsella & Forrester, 2008). In spite of the above, T. skrjabini has been reported more frequently in birds of the subfamilies Sterninae and Larinae (Mollhagen, 1976), with reports in Europe (Sanmartín et al., 2005;Álvarez et al., 2006;Kavetska et al., 2012;Parejo et al., 2015), Asia, North America (Mollhagen, 1976) and South America (González-Acuña et al., 2009). In the Neotropical region, it has only been isolated from L. dominicanus in south-central Chile (González-Acuña et al., 2009). The latter locality is close to that of the present study, where it lives in sympatry with L. pipixcan (González-Acuña et al., 2011). This is the first report of this nematode as a parasite of L. pipixcan worldwide.

Conclusion
The present study contributes to the current knowledge on the diversity of parasites associated with Franklin's gulls, reporting for this host five ectoparasites (feather mites and chewing lice) and nine gastrointestinal parasites. New host-parasite associations are reported, including the following helminths: Cyclophyllidea gen. sp., Aporchis sp., Eucoleus contortus, Cosmocephalus obvelatus, Paracuaria adunca, Stegophorus sp., and Tetrameres skrjabini as endoparasites of L. pipixcan.