Paradoris undefined-b

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 : 209-215

PARADORIS SP. B ( FIGS 57C–E , 72–77 )

Discodoris sp. 1 Ono, 1999: 105 , fig. 168.

Material examined: JAPAN, Ryukyu Islands, Okinawa, Horseshoe Cliffs , 26 May 1996, one specimen 8/ 4 mm preserved, leg. R. F. Bolland, identified as Discodoris by T. M. Gosliner ( CASIZ 115827 ) ; Japan, Ryukyu Islands, Okinawa, Seragaki Tombs , 15 March 1995, one specimen 12 mm long alive, 7/ 3 mm preserved [12 mm long alive], leg. R. F. Bolland, identified as Discodoris by T. M. Gosliner ( CASIZ 105261 ) ; Japan, Ryukyu Islands, Okinawa, Horseshoe Cliffs , 27 February 1993, one specimen 6/ 3 mm preserved, leg. R. F. Bolland, identified as Discodoris by T. M. Gosliner ( CASIZ 089053 ) [9 mm long alive]; Japan, Ryukyu Islands, Okinawa, Horseshoe Cliffs , 21 May 1994, one specimen 10/ 4 mm preserved [12 mm long alive], leg. R. F. Bolland, identified as Discodoris by T. M. Gosliner ( CASIZ 099080 ) .

Distribution: Warm waters of southern Japan, Okinawa ( Ono, 1999; present study).

Habitat: Found crawling on a piece of ‘leafy’ brown algae ( CASIZ 115827), on silty sand/coral rubble ( CASIZ 105261), on a vertical rock wall at a reef forefront ( CASIZ 089053), on a stony coral reef ( CASIZ 099080).

Morphological and anatomical description (including character variation): Colour pictures ( Fig. 57C–E ) of live animals were available for three specimens ( CASIZ 099080 , CASIZ 105261, CASIZ 089053). The ground colour of the dorsal notum is white; it bears many black stripes of different sizes, irregularly arranged. The rhinophores and the tips of the gills are black. The ventral surface is white in preserved specimens: its natural colour is unknown. This distinct, dorsal colour pattern is still distinguishable in all specimens after 10 years in alcohol. In addition to those black stripes, the notum bears minute black dots in the median part of the notum. However, those minute dots are not conspicuous in live animals .

The body is significantly elongated ( Figs 57C–E , 72B ). The longest specimens were 12 mm long alive ( CASIZ 099080, CASIZ 105261). The foot is rounded posteriorly and anteriorly. The width of the foot equals approximately one-third or one-half of the width of the dorsal notum (in preserved specimens). The anterior margin of the foot is bilabiate and the upper lip is notched ( Fig. 72A ). The grooved oral tentacles are digitiform or conical ( Fig. 72A ). The preserved, dorsal notum is globally smooth, although it can bear minute tubercles ( CASIZ 089053) that are not indecora -like. Numerous wide holes are present on the surface of the dorsal notum ( Figs 72E , 73 ). Small holes (diameter <10 µm) and tufts of cilia can also be observed on the dorsal notum, including on gills and rhinophores. In preserved specimens, the margins of the rhinophoral and branchial sheaths are smooth. There are six ( CASIZ 089053), seven ( CASIZ 099080), nine ( CASIZ 115827) tripinnate branchial plumes; the number of plumes could not be determined with certainty in the fourth specimen ( CASIZ 105261). The rhinophores have between eight and 12 lamellae.

The stomach is median, but not narrow ( Fig. 72C ). A caecum is present, on the left, posterior side of the stomach. The intestine is straight and dorsal. The labial cuticle is armed with a pair of lateral jaw plates, and an additional, ventral jaw plate ( Fig. 74 ). Rodlet tips are irregular, pointed or rounded. Rodlets have a curved tip. Some rodlet tips seem to be Tshaped (curved tips with a posterior spur). The length of the radula equals at least three times its width ( Figs 75 , 76 ). The radular sac can be seen by dorsal dissection ( Fig. 72C ). Radular formulae were: c. 30 × (10-0-8) in a 9 mm long specimen, alive ( CASIZ 089053), c. 35 × (13-0-9) in an 8 mm long specimen, preserved ( CASIZ 115827), c. 35 × (14-0-9) in a 12 mm long specimen, alive ( CASIZ 105261), c. 40 × (13-0-10) in a 12 mm long specimen, alive ( CASIZ 099080). The rachidian teeth are absent and the rachidian space is narrow. The rows of lateral teeth are at an angle of approximately 45 degrees with the rachidian axis. All teeth are hamate and have no denticles. The hook of all lateral teeth is grooved on its outer edge. The size of the lateral teeth gradually increases towards the margins, except for the last two or three outermost ones, which are smaller. In most rows, the hook of the outermost teeth has a dorsal spur. In some rows, the base of the outermost tooth bears a spur. All radulae are distinctly asymmetrical: the number of teeth per row is higher on the left side than on the right side. Also, the upper lip of the hook groove is distinctly expanded in a wing-like process on the left side.

The cerebral and pleural ganglia are more or less fused with the pedal ganglia ( Fig. 72D ). The circumoesophageal nerve ring is short. The surface of the ganglia is smooth.

The reproductive system is located on the right side of the body, between the buccal mass and the digestive gland ( Fig. 72C ). Only three reproductive systems could be dissected ( Fig. 77 ): no reproductive system was found in one immature specimen ( CASIZ 089053 ) . Also, the female gland mass was very small in the three other reproductive systems, which indicates that these individuals were not fully sexually mature. The white ampulla is convoluted, with a single loop. The division between male and female ducts (hidden within the female gland mass) could not be seen by dissection. The flattened prostate is divided into a proximal, whitish part and a yellowish, distal part ( CASIZ 105261 ) ; this division is faded, certainly because of preservation ( CASIZ 099080 , CASIZ 115827). The white deferent duct is convoluted. No distinct penis or papilla was found at the distal end of the deferent duct. The vaginal duct seems to be straight and the fertilization duct seems to be loosely convoluted ; these features, however, were very difficult to observe and are largely hypothetical. Also, the length and the position of these ducts may differ in fully mature specimens (with a large female gland mass). The duct of the receptaculum seminis was very inconspicuous and its length could not be determined with certainty: it seems to be short. The disappearance of the fertilization duct into the female gland mass (where it connects to the fertilization chamber) was not distinguishable. The size of the bursa copulatrix, spherical-ovate, equals approximately three or four times the size of the receptaculum seminis, slightly elongated. Both pouches are smooth and not attached to each other. In the distal part of the reproductive system, several accessory, ramified glands and stylet sacs were observed: one or several ramified gland(s) and two stylet sacs ( CASIZ 105261 ) ; two stylet sacs and one gland ( CASIZ 115827 ) ; no glands or stylet sacs could be found in one specimen ( CASIZ 099080 ) .

Diagnostic feature: The colour of the dorsal notum is a potentially good diagnostic feature ( Figs 57C–E , 72B, F ). However, its individual variation still needs to be evaluated (see sp. C).

Discussion: There is little doubt that these four individuals belong to a single entity: their dorsal colour and their internal anatomy are not distinguishable. All minor differences are easily explained with individual variation. Whether or not this entity is new is more problematic. On the one hand, the dorsal pattern, distinct from all other Paradoris (with the possible exception of tsurugensis ), suggests that this entity is new. On the other hand, the present description is biased because these four specimens were not fully mature, as suggested by the small size of the female gland mass (and the absence of a reproductive system in one specimen). One cannot exclude that adult, sexually mature specimens of sp. B could have different characters. For example, the colour and the radular formula may differ from what we know based on those four immature individuals. Therefore, I think that it is crucial that we know the anatomy of adult, sexually mature specimens before we address in greater depth the taxonomic status of sp. B, and give it a name.

Figures

Figure 57. Live animals. A, sp. A, CASIZ 099299 (#1 or #2) or CASIZ 165833, total length (preserved) = 20 (#1), 17 (#2), or 16 (165833) mm. B, same as (A). C, sp. B, CASIZ 089053, total length (preserved) = 6 mm. D, sp. B, CASIZ 105261, total length (alive) = 12 mm. E, sp. B, CASIZ 099080, total length (alive) = 12 mm. F, sp. C, CASIZ 110387, total length (preserved) = 5 mm. Colour pictures by T.M. Gosliner (A, B), R. Bolland (C–E), and C. Carlson (F).

Figure 72. Paradoris sp. B. A, anterior, ventral view, CASIZ 115827, scale = 2 mm. B, dorsal view, CASIZ 115827, scale = 3.6 mm. C, general anatomy, CASIZ 115827, scale = 1.7 mm. D, central nervous system, dorsal view, CASIZ 115827, scale = 0.5 mm. E, mantle holes, CASIZ 105261, scale = 0.5 mm. F, dorsal view, CASIZ 105261, scale = 2.2 mm.

Figure 73. Paradoris sp. B, dorsal notum. A, CASIZ 105261, scale = 20 µm. B, CASIZ 105261, scale = 10 µm. C, CASIZ 115827, scale = 100 µm. D, CASIZ 115827, scale = 20 µm.

Figure 74. Paradoris sp. B, jaw rodlets. A, ventral, median jaw, CASIZ 105261, scale = 20 µm. B, CASIZ 105261, scale = 10 µm. C, CASIZ 115827, scale = 10 µm. D, CASIZ 099080, scale = 10 µm. E, two lateral plates (each artificially divided) and the median plate, CASIZ 099080, scale = 100 µm.

Figure 75. Paradoris sp. B, radular teeth. A, left rows, CASIZ 115827, scale = 20 µm. B, right rows, CASIZ 115827, scale = 20 µm. C, radula, CASIZ 115827, scale = 200 µm. D, radula, CASIZ 099080, scale = 100 µm. E, rows, CASIZ 099080, scale = 20 µm. F, left, outermost teeth, CASIZ 099080, scale = 20 µm.

Figure 76. Paradoris sp. B, radular teeth. A, left rows, CASIZ 105261, scale = 10 µm. B, right rows, CASIZ 105261, scale = 10 µm. C, left, outermost teeth, CASIZ 089053, scale = 10 µm. D, right, outermost teeth, CASIZ 089053, scale = 10 µm.

Figure 77. Paradoris sp. B, reproductive system. A, general view, with a stylet sac in the distal part (second sac and accessory gland not visible), CASIZ 115827, scale = 0.8 mm. B, general view, CASIZ 105261, scale = 0.7 mm. C, distal part, with one accessory gland and one stylet sac (second sac not visible on this side), CASIZ 115827, scale = 0.5 mm. D, general view, CASIZ 099080, scale = 1.1 mm. E, distal part, with one accessory, ramified gland (or several glands) and two stylet sacs, CASIZ 105261, scale = 0.5 mm.