Pleurobranchus reticulatus, Rang, 1842

Grzelak, Katarzyna & Sørensen, Martin V., 2022, Echinoderes galadrielae Grzelak & amp; Sørensen 2022, sp. nov., Zoological studies 55 (15), pp. 1-31 : 26

Distiction between Pleurobranchus reticulatus and P. areolatus of the present study and sensu

Goodheart et al. (2015)

Pleurobranchus reticulatus and P. areolatus were misidentified for a long time because of their simple descriptions, without photographs of living animals. However, living specimens are clearly distinguished by the color of the rhinophores ( Table 1), at least in specimens from Brazil. In mature or juvenile specimens of P. reticulatus , the color of the rhinophores is variable (dark orange, red, dark red or black), but with a single color in each specimen ( Figs. 1 A-B); while in P. areolatus , the color has the same pattern as the dorsum (with white blotches) ( Fig. 1C ). Moreover, P. reticulatus is larger (up to 120 mm long) and has more pinnae (12-16) free from the body wall than P. areolatus (up to 50 mm long, with 9 pinnae). The diameter of the mantle tubercles is quite different in P. areolatus (125 - 375 μm, Fig. 1C ) and P. reticulatus (1-3 mm, Fig. 1 A-B). Additionally, the penis of P. reticulatus has a more developed leaflet attached in the convex portion of the penis ( Figs. 3 C-D) in comparison to P. areolatus ; the gonopore is surrounded by two wide flaps in P. reticulatus , which is absent in P. areolatus ; the prostate is tubular and highly convoluted in P. reticulatus , while in P. areolatus is elongated with the proximal portion rounded, seems detached circle ( Fig. 7D ); and, the jaws of P. areolatus , the smaller species, have more rows and fewer platelets per row (80 transverse rows and 35 platelets per row) than P. reticulatus (59-70 transverse rows and 39-46 platelets per row) ( Table 1). In Brazil, P. reticulatus is a common species, while P. areolatus is rare and until now was only recorded from northeastern Brazil ( Padula et al. 2012).

Figures

Fig. 1. Living species of Pleurobranchus from Brazil. (A-B) Pleurobranchus reticulatus Rang, 1832. (A) adult (MNRJ 11710, 28 mm long alive). (B) juvenile (MNRJ 11710, 5 mm long alive). (C-D) Pleurobranchus areolatus Mörch, 1863 (MNRJ 18760, 27 mm long alive), photographs by V. Padula. (C) dorsal view. (D) ventral view. (E-F) Pleurobranchus iouspi Ev. Marcus, 1984. (E) bright yellow morphotype (MNRJ 33070, 99 mm length of preserved specimen), photograph by C. A. Rangel. (F) reddish morphotype (SAE ML 95, 75 mm length of preserved specimen), photograph by F. Moraes.

Fig. 3. Pleurobranchus reticulatus Rang, 1832. (A) lateral view, detail near gill (MNRJ 13104). (B-D) reproductive system. (B) (MNRJ 18223). (C) detail of connections of reproductive system (MNRJ 10844). (D) penis dissected longitudinally (MNRJ 18223). (E) nervous system (MNRJ 12055). Abbreviations: a, anus; am, ampulla; bc, buccal ganglion; bu, bursa copulatrix; ccpb, connective between buccal and cerebro-pleural ganglia; cp, nerves that leave from the cerebro-pleural ganglion; cpg, cerebro-pleural ganglion; cpp, commissure between the pedal ganglia; dd, deferent duct; e, eye; f, female opening; fg, female gland; gi, gill; gm, gill membrane; nb, nerves that leave from the buccal ganglion; np, nerves that leave from the pedal ganglion; ov, oviduct; p, penial papilla; pb, prebranchial aperture; pf, penial flap; pg, pedal ganglion; pr, prostate; rg, rhinophoral ganglion; rn, rhinophoral nerve; sr, seminal receptacle; tu, tubercles; va, vagina.

Fig. 7. Pleurobranchus areolatus Mörch, 1863 (MNRJ 18760). (A) dorsal view, dotted line indicates the position of the shell internally. (B) ventral view. (C) lateral view, detail near gill. (D) reproductive system. (E) nervous system. Abbreviations: a, anus; am, ampulla; bc, buccal ganglion; bu, bursa copulatrix; ccpb, connective between buccal and cerebro-pleural ganglia; cp, nerves that leave from the cerebro-pleural ganglion; cpg, cerebro-pleural ganglion; cpp, commissure between the pedal ganglia; dd, deferent duct; dg, digestive gland; e, eye; f, female opening; fg, female gland; fo, foot; gi, gill; go, gonopore; nb, nerves that leave from the buccal ganglion; np, nerves that leave from the pedal ganglion; ot, oral tentacle; ov, oviduct; mg, metapodial gland; ne, nephropore; pb, prebranchial aperture; pg, pedal ganglion; pr, prostate; rg, rhinophoral ganglion; rh, rhinophore; rn, rhinophoral nerve; se, shell; sr, seminal receptacle; sta, statocyst; va, vagina.