Entobdella squamula ( Heath, 1902 ) Johnston, 1929

Kearn, Graham C., Whittington, Ian D. & Evans-Gowing, Richard, 2007, A revision of Entobdella Blainville in Lamarck, 1818, with special emphasis on the nominal (type) species “ Entobdella hippoglossi (Müller, 1776) Blainville, 1818 ” (Monogenea: Capsalidae: Entobdellinae) from teleost flatfishes, with descriptions of three new species and a new genus, Zootaxa 1659, pp. 1-54 : 16-20

Entobdella squamula ( Heath, 1902) Johnston, 1929

( Figs. 15E, 38)

At least 5 seminal receptacles were visible in most mounted specimens of Epidella (sic) (= Entobdella ) squamula (Source: USNPC; see Table 2) from California flounder, Paralichthys californicus ( Pleuronectiformes : Paralichthyidae ), ( Fig. 38A). The vagina is a tightly coiled and spacious tube running from the region of the vitelline reservoir in an anterolateral direction. No connection between the proximal end of the vagina and the vitelline reservoir was observed, but, in all specimens where the vagina was visible, its path led directly to the vitelline reservoir and not to the seminal receptacles. The distal vaginal opening was not detected and it is not known whether the distal region of the vagina is modified as it is in “ E. hippoglossi types 1 and 2” from H. hippoglossus and “ E. hippoglossi ” from H. stenolepis .

In some mounted specimens of E. squamula from P. californicus (USNPC No. 039579, storage nos. 213- 12, 213-15), circular sub-tegumental fibres were detected near the ventral surface using bright field and phase contrast microscopy ( Fig. 38A). These fibres surrounded the location where the vaginal opening was judged to be, but did not form a compact ring immediately surrounding the vaginal opening as found in “ E. hippoglossi type 2” ( Fig. 40A).

The accessory sclerites of specimens of E. squamula from P. californicus ( Fig. 15E) are similar in shape to those of “ E. hippoglossi types 1 and 2” from H. hippoglossus ( Figs. 15A, B respectively) and “ E. hippoglossi ” from H. stenolepis ( Fig. 15C). They are slightly curved and taper distally, creating the appearance of a spearhead. However, as indicated by Price (1939), the accessory sclerites of E. squamula are shorter relative to the anterior hamuli than in “ E. hippoglossi types 1 and 2” from H. hippoglossus and in “ E. hippoglossi ” from H. stenolepis ( Table 3). The mean ratio of the lengths of anterior hamulus and accessory sclerite in adult E. squamula from P. californicus was 2.32, whereas the mean ratios for “ E. hippoglosssi types 1 and 2” from H. hippoglossus and for “ E. hippoglossi ” from adult H. stenolepis were 1.66, 1.52 and 1.71, respectively ( Table 3). The tendon associated with each accessory sclerite terminates at the anterior end of the anterior hamulus in E. squamula ( Fig. 38A).

Heath (1902) reported papillae on the ventral surface of the haptor. He described them as low rounded knobs and noted that they were especially common on the posterior half of the haptor surface. He observed that the papillae were arranged in rows in the lateral region of the haptor while in the median area they were irregularly disposed. Based on light microscope observations on flattened whole mounts (specimens for SEM were not available), we observed a similar distribution in some of the specimens from P. californicus , but in other specimens papillae were visible in the anterior third of the haptor surface (see for example USNPC No. 039579, Storage No. 213-14) ( Fig. 38A). Bearing in mind the difficulties in observing papillae in the anterior region of the haptor (see above), it is possible that all specimens have papillae in this region. Uncleared, unflattened specimens are required to confirm this. We observed no lobed papillae. Four eyes are conspicuous and glands of Goto are present ( Fig. 38A).

The redescription of Entobdella squamula ( Heath, 1902) Johnston, 1929 by Price (1939) referred to 2 specimens (USNPC 39581), which he regarded as E. squamula , received from E.E. Wehr and collected by R.A. Coombs from an undetermined fish species. According to Price (1939), the host was “presumably from the Gulf of Mexico ”. We found papillae on the ventral surface of the haptor of both specimens and glands of Goto in 1. Eyes were not observed. At least 4 seminal receptacles were present in 1 of the 2 individuals and probably 5 in the other. More material is required to identify the host species and its habitat and to confirm Price’s identification.

Parasites collected by the Lund University Chile Expedition of 1948-49 (LUCE) from Hippoglossina macrops were identified as E. squamula by Brinkmann (1952a) ( Table 2). The mean value of the ratios of the lengths of the anterior hamuli and accessory sclerites for a sample of 6 of these parasites (all adults), calculated from Brinkmann’s (1952a) sclerite measurements (his table 1), was 2.58 ( Table 3), but their accessory sclerites were consistently different in shape from those of the parasites from P. californicus (cf. Fig. 15E and Fig. 15 F, G). In parasites from H. macrops , the distal half of the accessory sclerite is more strongly curved and sclerotised flanges on each side of this curved region create a distinct arrowhead shape. This arrowhead is asymmetrical, not just because of the curvature but also because the flange on the external (lateral) side of the sclerite is broader than the internal flange, unlike the virtually symmetrical spearhead shape of the accessory sclerite of E. squamula from P. californicus ( Fig. 15E). This asymmetrical arrowhead shape is not only consistent in all specimens, irrespective of size, from H. macrops collected by the LUCE but also in specimens collected in 2004 from the same host species at Coquimbo, Chile by Dr M.T. González (see Entobdella sp. 1 , Table 2) ( Fig. 15 F, G).

In the specimens from H. macrops , the tendon associated with each accessory sclerite terminates at the anterior (proximal) end of the anterior hamulus ( Fig. 36A). Ventral haptor papillae are present and confined mainly to the posterior two-thirds of the haptor surface ( Fig. 36A). There is no clear radial arrangement of the papillae lateral to the median sclerites. Four small eyes and glands of Goto are present. Six, possibly 7, seminal receptacles were identified in 1 whole mount ( Fig. 36A) and a similar number of seminal receptacles was observed in histological sections in the region of the germarium (SMNH slide 70987; see Table 2). In 1 whole mount, the tiny vaginal opening was recognised on the ventral surface and this gave access to a narrow entrance tube which joined a more spacious, convoluted main vagina, travelling in a posteromedian direction towards the vitelline reservoir ( Fig. 36A). However, a connection with the vitelline reservoir was not found in whole mounts or in histological sections.