Peronia watts, Dayrat & & Goulding & Tricia C., 2025

Peronia watts , new species

( Figs. 4–9)

Type locality. Fig. 4. Nightcliff foreshore, eastern side of Darwin Harbour, Darwin, Northern Territory, Australia, 12°22.570′S, 130°50.867′E, 12 June 2019, on large moist claystone boulders in a small rocky cove at low tide GoogleMaps .

Type material. Holotype, 45/ 30 mm [6387 H], designated here ( NTM P.59582).

Additional material examined. Australia, same collection data as for the holotype, 1 specimen 38/ 26 mm [6388] ( NTM P.59583) GoogleMaps ; Australia, same collection data as for the holotype, 1 specimen 38/ 24 mm [6389] ( NTM P.59584) GoogleMaps ; Australia, same collection data as for the holotype, 1 specimen 45/ 25mm [6390] ( NTM P.59585) GoogleMaps ; Australia, same collection data as for the holotype, 1 specimen 33/ 22 mm [6386] ( NTM P.59586) GoogleMaps ; Australia, same collection data as for the holotype, 1 specimen 40/ 25 mm [6391] ( NTM P.59587) GoogleMaps .

Distribution. Endemic to Darwin, Northern Territory, Australia.

Etymology. Peronia watts , new species, is named after Adam’s faithful dog that passed away during field work. The specific name ‘ watts ’ is a noun in apposition ( ICZN, 1999: Article 31.1).

Habitat. Fig. 4. The only specimens known were found crawling on large and moist claystone (porcellanite) boulders in a small rocky cove at low tide. It can be locally abundant in Darwin Harbour, but seems to be restricted to that specific habitat.

Colour and morphology of live animals. Fig. 5. The dorsal colour of crawling animals is greyish-brown. After relaxation, the dorsal colour is light brown mottled with darker areas. Ventrally, the foot sole is light yellowish and the hyponotum is whitish. The dorsal notum is covered by dozens of papillae of various sizes. Some papillae bear up to four black dorsal eyes at their tip. The number of papillae with dorsal eyes is variable (10–13). The largest live animals were 45 mm long. Once preserved, all specimens are 30 mm long and 20 mm wide. Dorsal gills are few and restricted to the posterior end of the dorsal notum. They cannot be seen on live animals and can only be seen after relaxation. Live animals are very squishy, moist, and secrete an abundant sticky mucus when handled.

Digestive system. Figs. 6, 7. Radular formulae are 82 × 145 – 1 – 145 ([6387 H] NTM P.59582), 75 × 150 – 1 – 150 ([6388] NTM P.59583), and 75 × 150 – 1 – 150 ([6389]

NTM P.59584). The median cusp of the rachidian teeth is up to 45 μm long. The hook of the lateral teeth is up to 70 μm long. The intestinal loops are of type I, with a transitional loop oriented between 3 to 6 o’clock.

Reproductive system. Figs. 6, 8, 9. In the anterior (male) parts, the muscular sac of the accessory penial gland is between 5 and 7 mm long. The hollow spine of the accessory penial gland is narrow, elongated, and straight or only very slightly curved, and its shape (including at its tip) varies between individuals. Its length ranges from 0.9 to 1 mm. Its diameter at the conical base ranges from 100 to 130 μm. Its diameter at the tip ranges from 40 to 50 μm. The retractor muscle is thin. It can be very short, and much shorter than the penial sheath ([6387 H], [6389]), as long as the penial sheath ([6388]), or up to three times as long as the penial sheath ([6386], [6390], and [6391]). Whether the retractor muscle is short or long, it does not insert anywhere inside the visceral cavity. Inside the penial sheath, the penis is a narrow, elongated, soft, and hollow tube. Its distal end measures from 1.2 mm ([6386]) to 1.7 mm ([6389]) and bears conical hooks which are up to 70 μm long.

Diagnostic features. Peronia watts , new species, is characterised by unique external and internal traits (see Table 3). It is the only Peronia species known to produce an abundant sticky mucus when handled. Internally, it is by far the Peronia species with the highest number of teeth per half row (up to 150), which is remarkable considering the relatively small size of individuals (up to 45 mm long) when compared to P. peronii (up to 115 teeth per half row for individuals up to 140 mm long). It also is the only species known in which the retractor muscle of the penis, whether long or short, does not seem to insert anywhere in the visceral cavity. The hooks of the penis are also long (up to 70 μm) considering the size of the individuals.