Paracamallanus cyathopharynx (Baylis, 1923) Syns.

Nofal, Ashlee P., Dos Santos, Quinton M., Jirsa, Franz & Avenant-Oldewage, Annemari`e, 2022, Camallanid nematodes from Clarias gariepinus (Burchell, 1822) in the Crocodile River, Gauteng, South Africa: Exploring diversity and divergence in an acid-mine drainage impacted environment, International Journal for Parasitology: Parasites and Wildlife 19, pp. 196-210 : 206-207

4.2. Paracamallanus cyathopharynx

The morphometry of P. cyathopharynx conforms to the description by Baylis (1923), the redescription by Moravec and van As (2015b), as well as other studies ( Moravec, 1974b, 2019; Svitin et al., 2019; Rindoria et al., 2020). However, in the description of P. cyathopharynx from C. anguillaris by Baylis (1923), the tridents are depicted as very small and barely extending past the anterior buccal capsule. Moravec and van As (2015b) recorded larger tridents, similar to the current and other studies, and suggest that the smaller tridents reported by Baylis (1923) were not sufficiently sclerotised. Additionally, Baylis (1923) reported ten to twelve longitudinal ridges in the female anterior buccal capsule,

206

while Moravec (2019) reported nine to ten in females, and the current study as well as other records of this species reported nine in both males and females. This calls for a re-evaluation of the specimens studied by Baylis (1923) and females studied by Moravec (2019).

A pair of small anterior tridents was observed by Rindoria et al. (2020) who also isolated the buccal capsules of P. cyathopharynx . These small tridents were situated on either side of the oral opening, anterior to the large pair of tridents. Although the current study used the same method of soft tissue digestion to isolate the buccal capsules, these small tridents were not observed. This may either be due to the premature removal of the buccal capsule from the digestion buffer, or digestion was left too long, and the small tridents fell off or were digested.

Rindoria et al. (2020) described two lateral spines posterior to the buccal capsule in males, and a single and small deirid in females near the level of the nerve ring. Lateral spines are not recorded in previous reports of P. cyathopharynx and based on the SEM images provided by Rindoria et al. (2020), both of these structures (lateral spines and deirids) appear to be identical. These structures were also situated in the same region on males and females, therefore likely deirids instead. The present study identified deirids in both males and females conforming to Moravec and van As (2015b) and Moravec (2019). Baylis (1923) and Svitin et al. (2019) do not mention deirids, whereas Moravec (1974b) refers to these as “cervical papillae”.

Moravec (1974b) mentions two very small processes on the tail tip of males. Moravec and van As (2015b) and Moravec (2019) described an additional single, “sharply-pointed cuticular process” on the tail tip in larger male specimens. Boomker (1982) and Svitin et al. (2018) also studied P. cyathopharynx but did not mention these structures. Thereafter, Rindoria et al. (2020) reported four processes of which two are large and two very small. They acknowledge variation in their results in comparison to previous reports and suggested the possibility of intraspecific morphological variation amongst adult specimens which may be linked to sexual maturity or age. In the current study, two digit-like processes were observed. Furthermore, Moravec (1974b) mentioned that the small processes were only visible in the dorsoventral view and indistinct in young specimens. We concur with the observation regarding the orientation of the specimen.

Digit-like processes in females varied between three and four in adults and larvae, respectively. Moravec (1974b), Moravec and van As (2015b) and Svitin et al. (2019) reported three in adults, with Moravec and van As (2015b) reporting four to six digits in subgravid/ovigerous females. Following this, the specimens studied by Rindoria et al. (2020) with four (Kenyan specimens) and five (Tanzanian specimens) digits are more likely subgravid females. There is some confusion on this topic as Moravec (2019) recorded P. cyathopharynx third and fourth-stage larvae bearing three processes.

Furthermore, variation occurred in the size of the female specimens which were extremely variable throughout studies, the largest recorded by Svitin et al. (2019). Other measurements were also variable, some ranges broader than others, but these mostly overlapped. This variation is possibly due to different life cycle stages analyzed together accidently. In terms of males, the morphometry is more consistent, other than the left spicule and number of postcloacal papillae. In the current study, the left spicule was larger, possibly due to visualization, as it is inconspicuous when not isolated. In the present study, six postcloacal papillae were recorded, corresponding to Moravec and van As (2015b), Moravec (2019) and Svitin et al. (2019). However, Rindoria et al. (2020) recorded four postcloacal papillae.

The morphometry of the posterior part of the posterior buccal capsule was included for the first time, which could prove to be a useful morphometric variable to consider in future studies. Svitin et al. (2019) included morphometry for the oesophageal cup for P. cyathopharynx for the first time. However, they did not mention that the posterior buccal capsule is split into two distinct parts as was mentioned by Moravec (1974b, 2019) and Rindoria et al. (2020). This may reflect on confusion caused by inconclusive terminology used for these structures.

Both spiculae of P. cyathopharynx were isolated and observed using SEM for the first time. Moravec and van As (2015b) refer to the distal part of the right spicule as a separate part, which Rindoria et al. (2020) describes as harpoon-shaped. From the present material, the distal part is a continuation of the right spicule bearing a hook-like structure at the base. This structure was visible in both LM and SEM. It can be seen in the images by Rindoria et al. (2020), however, no mention or illustration of this structure has been provided previously.

Suspected morphotypes were found amongst the buccal capsules of adults. Morphological distinction in the buccal capsules has not been discussed previously for the species, unless comparing larval and adult stages. In Rindoria et al. (2020), both morphotypes observed in the present study are illustrated. Morphotype B is linked to a female in the figure legend, while the sex of the other is not mentioned. In the current study, adult males and females exhibited both morphotypes which were also present in both genetic lineages. In terms of the statistical analyses, there is a high degree of natural morphological variation between the specimens as seen by the random scattering of specimens in all PCA plots. Thus, the suspected morphotypes based on buccal capsule morphology are not supported by these statistical analyses or any other morphology. The most probable explanation of buccal capsule variation is intraspecific morphological variability amongst adults related to age or sexual maturity. Moravec (1974b, 2019) studied P. cyathopharynx larval stages, and did not mention or illustrate a posterior buccal capsule divided into two parts in the third or fourth-stage larvae. This could indicate that the posterior part of the posterior buccal capsule is a characteristic of adults. Following this, all specimens morphometrically analyzed in the current study are considered adult. However, it is possible that age plays a role in the buccal capsule shape. Alternatively, this could be an example of morphological plasticity, perhaps in response to the different regions of the distal intestine inhabited by the specimens.