Pleurobranchus reticulatus, Rang, 1832

Grzelak, Katarzyna & Sørensen, Martin V., 2022, Echinoderes galadrielae Grzelak & amp; Sørensen 2022, sp. nov., Zoological studies 55 (15), pp. 1-31 : 24

Comparison between Pleurobranchus reticulatus from Brazil and Gulf of Guinea

The comparison between the results of the present study with the description of Neves et al. (2007) reveals that the specimens of P. reticulatus from Brazil and from the Gulf of Guinea are similar, mainly in relation to the reproductive system (e.g., shape of the penis with a wide leaflet, deferent duct long and highly convoluted and seminal receptacle elongated and convoluted). However, they show some intraespecific variations: in specimens from Gulf of Guinea the gonopore is surrounded by flaps clearly differentiate in two, in specimens from Brazil this arrangement is found ( Fig. 3B ), but also it can be observed a complex arrangement of the flaps, where the differentiation in two flaps is not clear; in the Brazilian specimens, the vagina is slightly convoluted, while in those from Gulf of Guinea, the vagina is very convoluted; spicules were found only in Brazilian specimens. The main difference is regarding the color of the mantle, specimens from Gulf of Guinea can be recognized by the thinner white reticulations on the mantle and the presence of dark tubercles inside the polygonal areas in the adults, while living specimens of the morphotype from Brazil have a yellowish-orange mantle with tubercles of many colors: dark red, red, bright orange, and pale orange with white spaces between the tubercles (reticulations). Despite such differences in mature specimens, juveniles are quite similar. In an early stage, the general color of the mantle is semi-transparent whitish with complex white reticulations; the tubercular spots are purple rose; and, the edge of mantle has a conspicuous yellow/orange line ( Fig. 1B ; Neves et al. 2007: fig. 1C).

Therefore, it is conclude that P. reticulatus from Brazil and Gulf of Guinea are the same morphotype mainly based on reproductive system, but also due the similarity of the general color pattern of the juveniles.

Edmunds (1968) recorded P. areolatus from Ghana, providing a description that matches P. reticulatus , mainly with respect to the oval leaflet attached to the penis edge and the general color pattern, which is a opaque white lines with large black spots in the center of many of the polygons surrounded by this network. This led Cervera et al. (1996) re-identified it as P. reticulatus . The unique difference observed between specimens from Ghana and Brazil is the color of the foot in living specimens, described by Edmunds (1968) as maroon, while in the specimens studied here it is white with orange blotches.

Figures

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. 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.