Longior Travassos & Kloss, 1958

Morffe, Jans, García, Nayla, Breugelmans, Karin & Adams, Byron J., 2018, Morphological examination and phylogenetic analysis clarify the taxonomic status of Cuban Longior Travassos & Kloss, 1958 (Nematoda: Thelastomatoidea: Hystrignathidae), Zootaxa 4399 (4), pp. 521-542 : 523-524

Longior Travassos & Kloss, 1958

Longior alius García & Coy, 1994

L. alius was described from two females (holotype and paratype), parasites of a single specimen of A. pertyi from La Matazón, El Salvador, Guantánamo province, Cuba. The most distinctive characteristic of the species is the presence of a long and folded isthmus. Such a feature is unique among the Hystrignathidae .

At present, the types of L. alius are lost. Thus, new material needed to be collected for performing molecular and SEM analyses, sufficient to redescribe the species. The specimens used in the current study were collected from A. pertyi (type host) from Limonar, located near the type locality of L. alius . Both La Matazón and Limonar are situated in the same mountain range (Nipe-Sagua-Baracoa, northeastern Cuba) separated by only 5 km. Moreover, Limonar presents the same vegetation units (semideciduous forest and coffee plantations) as La Matazón.

The study of the morphology and morphometrics of the specimens from Limonar demonstrates that they correspond with L. longior . The comparisons of this new material with the original description and line drawings of L. alius show several coincidences in the morphological and meristic features of females. Both populations present the first cephalic annule long and dilated, consistent with L. longior . The character state of the first cephalic annule is a useful diagnostic of the Longior species, since the degree of dilation of the first cephalic annule varies interspecifically. In Cuba, L. longior has a more dilated cephalic annule, highlighting the difference between L. similis (cephalic annule less dilated) and L. elieri (cephalic annule barely dilated).

The long and bent isthmus represents a remarkable difference between L. alius and the rest of Longior species. A natural folding of the isthmus appears to be improbable in species of Hystrignathidae , or even in Thelastomatoidea. All the nominal Longior present an elongate procorpus, with a straight isthmus, similar in diameter to the procorpus. It is more probable that the folded isthmus in the original description of L. alius can be attributed to an artifact produced during the slide mounting of the specimens. Alternatively, the deterioration of the parasites inside the host intestine could also produce a similar artifact, since the nematodes were obtained from an ethanol fixed passalid. In our experience, prolonged residence time of the nematodes inside hosts preserved in ethanol can produce notable alterations of the cuticle and internal structures.

Most of the Longior species have lateral alae that arise at a distance posterior to the basal bulb. The exception is L. semialata Hunt, 1981 , from Saint Lucia, West Indies, which has lateral alae commencing at the level of the vulva ( Hunt 1981). L. alius was described as the species with the shortest lateral alae of the genus, which extend from a distance between the vulva and the anus to the base of the tail ( García & Coy 1994). The first portion of the lateral alae is often difficult to observe since the alae are usually narrower in this region and the point of their origin is obscure. This is even more difficult to identify in specimens that are laterally mounted. Thus, it is probable that the lateral alae of the specimens described as L. alius extend from a distance posterior to the basal bulb to the level of the anus as occurs in the Cuban species.

Several measurements of taxonomic importance are also within the range of the specimens from these two localities ( Table 1): total length, maximum width distance from the nerve ring to the cephalic end and egg diameters. In addition to the latter variable, García & Coy (1994) mention that the longitudinal ridges of the eggs of L. alius are hardly pronounced as opposed to the more conspicuous state of this character in L. longior ( Morffe & García 2011) . Qualifying the degree of development of such ornamentations is quite subjective, since it scales allometrically with the stage of development of the eggs. Also, the proper observation of the egg surface depends on the methods used when mounting specimens, where some internal structures often interfere. The Demanian indexes a, c and V% of L. alius (calculated for this study) are not significantly different from those of L. longior . The more conspicuous differences in the morphometrics are the length of the corpus and isthmus as well as the diameter of the basal bulb, justified by the possible artifact mentioned above. In support of the latter, male specimens that coincide morphologically and morphometrically with the males of L. longior were found in the hosts from Limonar ( Table 2).

Comparison of the sequence of the D2-D3 segment of the 28S LSU rDNA of specimens from Limonar failed to reveal any intra-specific differences between individuals of other populations of L. longior from Western Cuba ( Fig. 9 ). Failing to identify any autapomorphic characters that could provide evidence of lineage independence ( Adams 1998), our molecular and morphological data support the conclusion that L. alius and L. longior are conspecific. Thus, we propose L. alius as a synonym of L. longior . The number of Cuban Longior species is reduced to three: L. elieri , L. similis and the already mentioned L. longior .

Figures

FIGURE 9. Maximum likelihood (ML) tree inferred from D2-D3 28S LSU rDNA for several species of the superfamily Thelastomatoidea (Nematoda: Oxyuridomorpha). Bilobostoma sp. and two species of Hammerschmidtiella (Thelastomatidae) were used as outgroup taxa. Values atthe nodes correspond to bootstrap (>75)/posterior probability (>0.95).