Murphydoris polkadotsa Paz-Sedano & Cobb & Gosliner & Pola 2024, sp. nov.

Murphydoris polkadotsa sp. nov.

(Figs. 1H, 5E‒H, 6A‒B)

Zoobank: urn:lsid:zoobank.org:act: E69A3117-6231-45C0-8202-630B61D6F168

Murphydoris sp. 2 — Cobb (2014).

Type material. Holotype. QM MO 86038, La Balsa Park, Mooloolah River, Queensland, Australia, 1–5 m depth, it was 1 mm preserved, live 5 mm, 03 October 2020, col. by G. Cobb, 96% EtOH, dissected (SEM: radula, labial cuticle).

External morphology (Fig. 1H). Preserved specimen 1 mm in length, live up to 5 mm. Body elongated, with reduced notal border, lacking papillae. Posterior part of notal border with elongated extension that resemble papilla on each side of body, likely modified gill branches. Papilla narrow at base, wider at tip. Rhinophores nonretractile, slightly short, elongated and slender, smooth. Rhinophoral sheaths absent. Oral tentacles reduced to a muscular structure surrounding the mouth. Reproductive opening located on right lateral side, in anterior third of body. Mantle covered by spicules.

Color pattern (Fig. 1H). Body translucent, iridescent white and rounded dark brown patches. Rhinophores and gill branches white with light yellow tips, may have dark brown patches. Muscular structure around mouth and posterior tip of foot, light yellow.

Foregut anatomy (Figs. 5E‒G, 6A). Buccal bulb very small, thick and muscular (Fig. 6A). Oval and dorsal buccal pump expanding posteriorly. Rounded radular sac expanding ventrally. Esophagus relatively wide, begins from buccal bulb behind buccal pump. Salivary glands big and rounded, arises at junction of esophagus with buccal bulb. Nervous system covers this junction, covering salivary glands. Esophagus continues posteriorly and inserts into digestive-hermaphroditic gland. A very thin and weak labial cuticle surrounds lips and expands within buccal pump. Cuticle elements not appreciated. Approximate radular formula 15‒16 × 1.1.0.1.1. Due to the small size of the radula, any tooth could have been lost during its examination. Inner lateral tooth with single large cusp, and wide, triangular base (Fig. 5E–F). Cusp large and pointed, masticatory margin with 14–17 small, thin and pointed denticles (Fig. 5E–F). Denticles with homogeneous shape and size along masticatory margin, outermost ones slightly smaller. Outer part of base ends in a pointed external edge. Outer lateral tooth much smaller (Fig. 5G). Base of outer lateral tooth rectangular, top with two thin and pointed cusps (Fig. 5G).

Reproductive system (Figs. 5H, 6B). Reproductive system located in anterior third of body.Thin hermaphroditic duct begins at ovotestis, located inside digestive-hermaphroditic gland. Hermaphroditic duct expands into pyriform ampulla. Postampullary duct emerges from narrowest end of ampulla and divides into two different, thin ducts. Short, oviduct enters inside female gland mass. Second duct connects with prostate. Duct widens into very elongated, sausage-shaped prostate, that narrows and continues as thinner vas deferens. Vas deferens slightly longer than prostate. Vas deferens expands to ejaculatory duct at most distal part. Penis with penial spines (Fig. 5H). Penial spines smaller and hoked at base of penis, becoming larger and thinner to the most distal part. Vagina very short, similar in width to penial bulb. Vagina short, connects with bursa copulatrix. Near base of bursa copulatrix arises a thin and large duct that connects with an elongated, pyriform receptaculum seminis. Receptaculum seminis slightly bigger than bursa copulatrix. From approximately the half of the vagina arises a very thin uterine duct that enters female gland mass.

Etymology. Murphydoris polkadotsa refers to the song “ Itsy Bitsy Teenie Weenie Yellow Polkadot Bikini”, famous in the 1960s. The dots on the animal are split into two parts a top and a bottom, resembling the revelatory bikini of the song.

Distribution. Australia (Cobb 2014; present study).

Natural history. The species has been found on silty, sandy substrates and rocks up to 6 m deep.

Remarks. Species of Murphydoris are distributed in the Indo-Pacific Ocean (Paz-Sedano et al. 2022). Among the described species, M. polkadotsa sp. nov. shares a white background coloration with M. cobbi Paz-Sedano, Smirnoff, Candás, Gosliner & Pola, 2022, M. maracabranchia Paz-Sedano, Smirnoff, Candás, Gosliner & Pola, 2022, and M. puncticulata Paz-Sedano, Smirnoff, Candás, Gosliner & Pola, 2022 (Paz-Sedano et al. 2022). However, the species have external and internal differences. Murphydoris cobbi, M. maracabranchia and M. puncticulata have a colored band behind the rhinophores, while the brown patches of M. polkadotsa sp. nov. are distributed throughout the body (Paz-Sedano et al. 2022). Moreover, the rhinophores of M. cobbi and M. puncticulata are white, while in M. maracabranchia they are red or orange. In M. polkadotsa sp. nov. they are white with brown patches and yellow tips (Paz-Sedano et al. 2022). The shape of the gill branches is also different, being wide and elongated, wing-shaped in M. cobbi, with several branches from the same stalk in M. puncticulata, and elongated, papillated shape in M. polkadotsa sp. nov. (Paz-Sedano et al. 2022). Regarding the internal anatomy, the inner lateral tooth of M. cobbi has small notches in the masticatory margin while M. polkadotsa sp. nov. has several thin denticles. The size of the bursa copulatrix and receptaculum seminist of M. cobbi is much larger than in the other species of Murphydoris. Also, the uterine duct arises from the vagina in M. polkadotsa sp. nov. while it starts in the duct connecting the bursa copulatrix and the receptaculum seminis in M. maracabranchia, and from the base of the bursa copulatrix in M. puncticulata (Paz-Sedano et al. 2022).