Derogenes sp.

Bouguerche, Chahinez, Huston, Daniel C., Karlsbakk, Egil, Ahmed, Mohammed & Holovachov, Oleksandr, 2024, Untangling the Derogenes varicus species complex in Scandinavian waters and the Arctic: description of Derogenes abba n. sp. (Trematoda, Derogenidae) from Hippoglossoides platessoides and new host records for D. varicus (Müller, 1784) sensu stricto, Parasite (Paris, France) 31 (26), pp. 1-25 : 6-11

Derogenes sp. (unpublished Derogenes limula of Looss, see discussion) ( Figs. 2–4 )

Host: Parablennius tentacularis (Blenniiformes: Blenniidae ), tentacled blenny.

Locality: Trieste, Italy, Central Mediterranean [ 25].

Site in host: Intestine.

Material examined: One specimen from Parablennius tentacularis off Trieste, Italy (SMNH-208361), from the collection of A. Looss in the Invertebrates collection of the Swedish Museum of Natural History (SMNH), Stockholm, Sweden (identified and labeled by A. Looss as Derogenes sp. ). One specimen from P. tentacularis off Trieste, Italy (SMNH-222309), stained from the wet collection of A. Looss (894) at freshwater species.

Abbreviations: NEA, Northeast Atlantic. NWA, Northwest Atlantic.

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C. Bouguerche et al.: Parasite 2024, 31, 26

Abbreviations: CM, Central Mediterranean. WM, Western Mediterranean.

C. Bouguerche et al.: Parasite 2024, 31, 26

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Abbreviations: NWP, Northwest Pacific; N., number of specimens.

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C. Bouguerche et al.: Parasite 2024, 31, 26

Description: Measurements in Table 6 . Body stocky, rounded anteriorly, pointed posteriorly ( Figs. 4A, 4C, 4D ), visibly larger at level of ventral sucker ( Figs. 4C–4D ). Tegument crenulate, with fine spines ( Fig. 4B ).

Oral sucker elongate, oval. Pharynx muscular, subglobular ( Figs. 4A, 4C, 4D ). Oesophagus short, caecal bifurcation at level of pharynx. Drüsenmagen absent ( Fig. 4D ). Caeca broad, extending to posterior region of hindbody, as far as uterus ( Fig. 4B ). Ventral sucker round to transversely oval, voluminous ( Figs. 4A, 4C, 4D ), larger than oral sucker.

Testes paired, oval, small, in hindbody, immediately posterior to ventral sucker ( Fig. 4A ). Ovary oval, voluminous, located between tested to slightly posteriorly to testes ( Figs. 4A, 4C, 4D ).

Vitellarium paired, in hindbody, posterior to testes; vitelline masses rosette-shaped, deeply lobed, connected one to another by a visible isthmus; composed both of 6–7 lobes ( Figs. 4A, 4C, 4D ). Uterine coils extending from posterior third of forebody to posterior end ( Figs. 4A–4D ), existing also in intervitelline masses space. Eggs numerous, large ( Fig. 4A–4D ). Excretory vesicle and position of bifurcation of stem not examined; excretory arms extending into forebody and unite dorsally to genital terminalia and dorsally to oral sucker.

Remarks: Derogenes sp. that we described above was found in A. Looss’ s collection, labelled as “ Derogenes limula ”. As there are no published records of a species under that name, A. Looss probably intended to describe this Derogenes specimen from P. tentacularis as a new species, with the name “ D. limula ”. The eggs of this Derogenes sp. that we described above are over 40 µm and the species is thus consistent with “the large eggs group”. We compared the single specimen of Derogenes sp. (or “ D. limula ” as initially labeled by A. Looss) ex P. tentacularis to the Mediterranean congeneric Derogenes species. The present specimen Derogenes sp. ex P. tentacularis differs from D. minor , D. robustus , D. affine , and D. latus by its larger eggs. It resembles D. ruber in egg size (61 × 39 in Derogenes sp. vs. 62 × 39 in D. ruber ) and in having lobed, tear-shaped vitelline masses. However, Derogenes sp. ex P. tentacularis can be readily distinguished from D. ruber by being smaller in all body measurements including the body (855 × 253 vs. 7869 × 1847). Derogenes sp. ex P. tentacularis can be easily distinguished from D. varicus s. s. and D. abba n. sp. by having lobed vitelline masses.

the SMNH; identified and labeled by A. Looss as “ Derogenes limula ”.

Archival documents: in addition to a single slide mounted by A. Looss (SMNH-208361) ( Fig. 2 ), the archives include two unpublished line drawings ( Figs. 3A and 3B ), combined and reproduced in Figures 4A–4E .

Figures

Figure 2. “Derogenes limula” ex Parablennius tentacularis (SMNH-208361).

Figure 3. “Derogenes limula” ex Parablennius tentacularis. Unpublished line drawing by A. Looss.

Figure 4. “Derogenes limula” ex Parablennius tentacularis based on A. Looss’s unpublished line drawings. A, Whole body, ventral view. B, Whole body, lateral view. C, Whole body, ventral view. D, Whole body, ventral view.