Pandosentis napoensis, Smales, Lesley R., 2007

Smales, Lesley R., 2007, Acanthocephalans of Amphibians and Reptiles (Anura and Squamata) from Ecuador, with the description of Pandosentis napoensis n. sp. (Neoechinorhynchidae) from Hyla fasciata, Zootaxa 1445, pp. 49-56 : 52-53

Pandosentis napoensis n. sp.

( Figs. 1–7 )

Type host: Hyla fasciata Gunther, 1858 (Hylidae) .

Type locality: San Pablo de Kantesiya, Napo, Ecuador (0o15’S; 76o26’W).

Site of infection: Intestine.

Specimens deposited: Holotype, MHNG INVE 37763, paratype, MHNG INVE 37766, Muséum d’Histoire Naturelle, Geneva, Switzerland.

Etymology: The name napoensis refers to the Napo River Basin where the species was collected.

Description: Based on 2 male whole mounted specimens. Body small, tegument smooth, spineless. Proboscis small, sub-globular, with 12–14 longitudinal rows each of 3 hooks. Lacuna system with conspicuous canals connected by prominent circular anastomoses. In mid body, irregular diagonal lacunae connect with circular lacunae ( Fig. 4 ). Giant hypodermal nuclei laterally distributed.

Males: Trunk fusiform 700–1000 long, 160 wide. Proboscis 78–85 long, 68–90 wide. Proboscis hooks all similar in length; hooks I 12–14 long, II 13–14 long, III 12–14 long; each hook within a papilla. Neck 30 long, 120 wide. Proboscis receptacle wall thin, single layered 100 long. Lemnisci 136, 170 long. Testes tandem, contiguous, in middle third of body; anterior testis 115–150 long, 46–70 wide; posterior testis 125–160 long, 60–90 wide. Single cement gland globular to pyriform, 80–100 long, 40–70 wide; cement reservoir, posterior to cement gland; Safftigen’s pouch long, posterior to cement reservoir, adjacent to seminal vesicle.

Remarks: The two males available for study possess the morphological characteristics of the family Neoechinorhynchidae , sub-family Gracilisentinae as defined by Amin (1982). The Gracilisentinae comprises three genera. Pandosentis Van Cleave, 1920 , a monotypic genus, occurs in freshwater fishes from Venezuela ( Van Cleave 1920). Gracilisentis Van Cleave, 1919 comprises three species, one of which, G. variabilis (Diesing, 1856) , occurs in freshwater fishes from Brazil. Wolffhugelia Mané-Garzon & Dei-Cas, 1974 , a monotypic genus, occurs in freshwater fishes in Uruaguay. The three genera resemble each other closely in general body form and morphology. They differ from each other in the form of the lacunar system, the distribution of the hypodermic nuclei, the form of the proboscis receptacle, the presence or absence of papillae in which hooks are embedded, the form of the proboscis, and the proboscis hook formula ( Van Cleave 1920; Thatcher 1991). On this basis, the new species with a lacuna system of conspicuous canals, prominent circular anastomoses and irregular diagonal lacunae at the mid-body; giant hypodermal nuclei laterally distributed; proboscis receptacle with delicate thin, single layered wall, well developed invertor muscles and proboscis hooks embedded in papillae falls within Pandosentis . Unfortunately the detailed morphology of the roots of the proboscis hooks of the specimens of P. napoensis was difficult to distinguish, but they appeared to conform to the description of Van Cleave (1920) in having no distinct line of separation between thorn and root.

Although only two males of Pandosentis napoensis n. sp. were found they were fully mature and could be clearly differentiated from Pandosentis iracundus Van Cleave, 1920 in having 14 longitudinal rows of 3 hooks rather than 22 longitudinal rows of 4 hooks, the lemnisci longer than the proboscis receptacle and the cement gland about the same size as the testes rather than smaller. The characters proboscis hook formula and the relative lengths of the lemnisci and proboscis receptacle are not congruent with the present generic diagnosis of Pandosentis (see Thatcher 1991). The latter character is problematic for the group in that nearly all the specimens studied by Van Cleave (1920) had inverted proboscides, no measurements for the length of the lemnisci were given and the lemnisci appear to be figured as at least as long as the proboscis receptacle ( Van Cleave 1920 Plate 27, Figs 5, 6 ). The establishment of a new genus on the basis of proboscis hook numbers alone, however, does not seem warranted at this time.

Pandosentis iracundus has been reported from two freshwater fish hosts, Aquidens pulcher (Gill) and Crenicichla geayi (Pellegrin) from Lake Valencia, Venezuela ( Van Cleave 1920), as well as from Aquidens sp. and Mesonauta insignis from Pucallpa and Quistococha, Peru ( Tantaleán et al. 2005). Peru does not share a border with Venezuela, however, but with Equador, where P. napoensis occurs, albeit in an amphibian. It is possible that the Peruvian material is also P. napoensis rather than P. iracundus , but unfortunately the identity of the original material could not be confirmed. The marked difference in proboscis hook formulae, however, makes this unlikely.

Although primarily parasites of fishes, the Neoechinorhynchidae also are found in frogs ( Amin 2002) and turtles ( Barger and Nickol 2004). Moreover, Bush et al. (1990) noted the capture of neoechinorhynchid acanthocephalans by amphibians or reptiles, as one example of the importance of the process of host capture in contributing to the species richness of helminth communities. Finding P. napoensis , a neoechinorhynchid, in a frog from Ecuador that has congenors in fishes from Venezuela and Peru may be another example of this process.

Figures

FIGURES 1 – 3. Pandosentis napoensis n. sp. 1. Adult male, ventral view. 2. Proboscis armature, lateral view. 3. Longitudinal row of hooks, lateral view. Scale bars: 1 = 60 µm; 2 = 25 µm; 3 = 10 µm.

FIGURES 4 – 7. Micrographs of Pandosentis napoensis n. sp. 4. Proboscis, specimen 1. 5. Proboscis, specimen 2. 6. Specimen 1 ventral view. &. Lacuna system showing irregular diagonal lacunae connecting with circular canals. Scale bars: 4 = 20 Μm; 5 & 7 = 40 µm; 6 = 200 Μm.