Paradoris lora (Er.Marcus, 1965)

Dayrat, Benoît, 2006, A taxonomic revision of Paradoris sea slugs (Mollusca, Gastropoda, Nudibranchia, Doridina), Zoological Journal of the Linnean Society 147 (2), pp. 125-238 : 197-199

PARADORIS LORA ( FIG. 53 )

Discodoris lora Marcus, 1965: 273–274 , figs 14–18.

Type material: Holotype, by original designation: [western Pacific], Caroline Islands, Ifaluk Atoll , reef east of south end of Falarik islet, 4 September 1953, one specimen 12/ 6 mm preserved, leg. D. P. Abbott ( NMNH 575709 ). The holotype was entirely dissected by Ernst Marcus. Only the body wall, the digestive gland, and the gills remain in the jar. The oral area is missing, including the oral tentacles. The reproductive system, the radula, and the jaws are preserved on two slides (F-796 and F-797) in good condition.

Distribution: So far, lora is only known from the type locality.

Habitat: According to the original description, the holotype was found by washing algae from an ‘algal edge exposed at low tide.

Remarks on the original description ( Fig. 53 ): The original description of lora was based on a single 12 mm long specimen. Its dorsal colour, certainly preserved, was ‘yellowish with black dots on notum, concentrated around the larger or the numerous round, unequal warts’. Currently, this specimen is homogeneously whitish, colourless, although minute black dots can be seen with a dissecting microscope. The fact that Marcus (1965) did not mention whether he had described the colour of preserved specimens or the colour of live animals (based on Abbott’s notes) makes me think that he described the colour of preserved specimens. Rhinophores had 12 lamellae and a smooth rhinophoral sheath. The dorsal notum was bearing ‘unequal warts’. It is currently globally smooth, although some tubercles are distinguishable. Marcus described six tripinnate plumes; the edge of the gill pocket was smooth. The upper lip of the bilabiate anterior foot was notched; the oral tentacles were grooved. Marcus did not mention the presence of wide holes on the dorsal notum: some wide holes could be observed with a binocular ( Fig. 53A ). The nervous system, not described by Marcus, could not be examined because it is missing. Marcus described a ‘labial cuticle yellow with up to 80 µm high, 12–15 µm thick rodlets’, but did not mention that there are actually three jaw plates ( Fig. 53E ): two triangular, lateral plates, and one ventral, more or less rectangular plate, grooved in the front. The rodlet tips are irregularly shaped, both pointed and roundish. The radular formula provided by Marcus is correct: 50 × (12-0-12). The radular is symmetrical. Marcus’ (1965: fig. 17) drawing of the radular teeth represented a lateral groove on the outer edge of the hook ( Fig. 53F ). This groove is present. Some outermost lateral teeth have a dorsal spur; the latter, however, is not distinct in all rows, which explains the difference between Marcus’ drawing and my drawing. The last outermost tooth, reduced, may bear a spur on its base. The rest of the digestive system was not described in the original description. Although the reproductive system of lora (slide F-796) has largely been destroyed, Marcus’ original drawing ( Marcus, 1965: fig. 18) could be checked. In particular, Marcus’ representation of the connection between the fertilization duct and the receptaculum seminis is not correct ( Fig. 53B, D ). This connection is similar to what is found in all Paradoris : the fertilization duct connects the bursa copulatrix to the fertilization chamber; on its way, it receives the duct of the receptaculum seminis. According to Marcus’ drawing, the fertilization duct would leave the bursa copulatrix, enter the receptaculum seminis, and then connect the receptaculum seminis to the female gland mass: this arrangement was unexpected. Marcus’ description of a ‘voluminous’ prostate was difficult to check because I could not identify the prostate on the slide. However, if the structure that I identified as the prostate really is the prostate, then the prostate is flattened. The deferent duct and the ‘pleurembolic penis’ (i.e. evaginable distal end of the deferent duct), not preserved on the slide, could not be verified. Marcus did not mention accessory glands or stylet sacs. However, in the distal area of the reproductive system, there is a thick piece of tissue in which some pockets could be interpreted as stylet sacs ( Fig. 53C ). The problem is that it was nearly impossible to look through this tissue by transparency, because of its thickness, and I cannot assert that stylet sacs are present. However, it is possible that Marcus overlooked both accessory glands and stylet sacs; Marcus may have lost the accessory glands when he pulled the reproductive system out from the body cavity.

Discussion: Marcus compared lora with five Discodoris species with a narrow, elongated radula: dubia , egena , erythraeensis , indecora , and liturata . However, Marcus did not mention the existence of P. granulata Bergh, 1884 , which also has a narrow, elongated radula, probably because he overlooked the additional, third, ventral jaw plate present in lora , which, according to Bergh, was one of the diagnostic characters of the genus Paradoris .

According to Marcus, lora differs from indecora in colour (dorsal notum olivaceous with light dots in indecora , yellowish in lora ). This comparison is weakened by the fact that Bergh described a specimen alive but ‘dying’ and Marcus probably described the colour of preserved specimens. Marcus also pointed out that the number of lamellae on the rhinophores was different (12 in lora , and 15–20 in indecora ), but the number of rhinophoral lamellae in indecora varies greatly depending on the size of the animal: small specimens dissected for the present study have rhinophores with only five lamellae.

According to Marcus, lora differs from dubia and egena in the shape of the outermost tooth and in the number of rhinophoral lamellae. Indeed, the hook of the outermost teeth never has a dorsal spur in dubia . The number of rhinophoral lamellae in not a valid difference: in dubia it actually ranges from ten to 20. However, lora clearly differs from dubia in the shape of the prostate (tubular in dubia and flattened in lora ) and in the connections between the fertilization duct, the vaginal duct, and the bursa copulatrix.

According to Marcus, lora differs from liturata in colour. Indeed, the colour of liturata cannot be confused with any other species of Paradoris . Other differences exist, especially asymmetrical radula in liturata . Marcus also mentioned the presence of ‘distally curved labial rodlets’ as another difference between lora and liturata . I could not see on the slide with the jaw plates (slide F-797) whether the rodlet tips of lora are curved, as in other species of Paradoris .

According to Marcus, erythraeensis is ‘morphologically nearest’ to lora , but differs from it in the shape of the outermost tooth and the presence of black spots on the sole. However, spots may have faded through preservation in lora ; also, the presence/absence of spots on the ventral surface cannot be used as a criterion to distinguish these species, given that both species had been named based on a single specimen. Concerning the shape of the outermost tooth, lora is not incompatible at all with erythraeensis . The length of the duct of the receptaculum seminis, which is an important character to address a potential synonymy of lora with erythraeensis , cannot be determined with precision because the connection of the fertilization duct with the female gland mass is unclear in the holotype of lora (slide F-796).

Finally, Marcus mentioned the existence of D. pardalis Baba, 1937 , from the western coasts of Kyushu. As Marcus rightly pointed out, pardalis has a radular formula that is incompatible with lora : pardalis (of which I re-examined the type) does not belong to Paradoris .

The status of lora is highly uncertain because several important characters are unknown (e.g. the colour of live animals, the presence of accessory glands and stylet sacs in the reproductive system). Although a few features help us to know what lora is not, we still do not know what lora is... A synonymy with other species of Paradoris , in particular erythraeensis , also from the Indo-West Pacific, cannot be excluded. It cannot be excluded either that tsurugensis could be a junior synonym of lora .

The holotype of lora does not present the diagnostic feature of sp. 3. Indeed, the lateral jaws of lora are clearly ‘hatchet-shaped’, as usual: therefore, lora is not an existing name for sp. A. The fact that the radula of lora is symmetrical suggests that lora should not refer to liturata and sp. B. This comparison is weakened by the fact that the asymmetry vs. symmetry of radulae seems to vary infra-specifically (see erythraeensis ).

Of course, lora could be a valid species name. However, the data currently available do not allow me to propose a diagnostic feature that could help us reidentify lora . New material is needed from the type locality, the Caroline Islands.

Finally, all the authors who have created new species names in, or transferred existing species to, Paradoris after 1965 (e.g. Marcus, 1976; Baba, 1986; Miller, 1995; Ortea, 1995; Valdés, 2001) have ignored the species name lora , despite the fact that Ernst Marcus had rightly pointed out that the shape of the radula was a close similarity between lora and indecora , a species transferred to Paradoris by Templado (1984).

Figures

Figure 53. Paradoris lora, holotype, NMNH 575709. A, mantle holes, scale = 0.4 mm. B, reproductive system (slide F-796), scale = 1.7 mm. C, distal part of the reproductive system, with three hypothetical stylet sacs (slide F-796), scale = 0.6 mm. D, reproductive system, from dissection, after Marcus (1965: fig. 18), no scale given. E, three jaw plates (slide F-797), scale = 1.5 mm. F, left, outermost teeth, 12th row (slide F-797), scale = 0.1 mm.