Hermaea wrangeliae (M. Ichikawa, 1993)

Description

Holotype 10 mm. The body is transparent. The rhinophores are auriculate, with their anterior margin extended to form a ventral lobe that extends beyond the posterior margin. No oral tentacles are present. The indented cerata are arranged in about 12 rows and appear green or brownish because of the liver diverticula branches inside. The rhinophores have three green horizontal stripes and the head is covered with minute white dots. Behind the eyes, in the middle of the neck, a dark spot is present. The border of the ventral side of the foot is marked by a dotted white line. Some paratypes have two light-brown longitudinal stripes on the sole.

Distribution

Type locality: Kuro Island (Okinawa), at 1-2 m depth, on Wrangelia tayloriana. Also rediscovered at two sites on the west coast of Okinawa Island.

Etymology

The species is essentially restricted to the alga Wrangelia tayloriana, and is named after that host alga. Its body shape and colour perfectly match the host.

Remarks

Originally placed in Aplysiopsis; subsequently re-examined on Okinawan material and transferred to Hermaea. Distinguished from the Japanese Aplysiopsis (= Hermaeina) species in the shape and number of cerata, size, and colour pattern.

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References

• Hermaea wrangeliae (genus Hermaea), Lovén S. (1844). Om nordiska hafs-mollusker. Öfversigt af Kongliga Vetenskaps-Akademiens Förhandlingar, Stockholm. 1(3): 48-53.
• Aplysiopsis wrangeliae sp. nov., Ichikawa M. (1993). Saccoglossa (Opisthobranchia) from the Ryukyu Islands. Publications of the Seto Marine Biological Laboratory. 36(3): 119-139. https://doi.org/10.5134/176229
• ヒメハナビラウミウシ, 小野篤司. (2004). 沖縄のウミウシ. ラトルズ.
• Hermaea wrangeliae (Ichikawa, 1993) comb. nov., Trowbridge C.D., Hirano Y.M. & Hirano Y.J. (2009). Rediscovery of the Sacoglossan Opisthobranch Hermaea wrangeliae (Ichikawa, 1993) in Okinawa, Japan. American Malacological Bulletin. 27(1-2): 183-189. https://doi.org/10.4003/006.027.0216