Author: Smirnoff, Donohoo & Gosliner, 2022

Order: Nudibranchia  Family: Goniodorididae

Maximum Size: 18 mm

Sightings: Sunshine Coast

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Trapania tigger Smirnoff, Donohoo & Gosliner, 2022

The genus Trapania has had three major reviews: Rudman, 1987 (7 new species), Gosliner & Fahey, 2008 (16 new species) and the most recent (wherein this species was described) Smirnoff, Donohoo & Gosliner, 2022 (9 new species). This latest review also included molecular sequencing and brings the total of described Trapania species to 54. Trapania is one of eight genera of the Goniodorididae family. The significant external characteristics of Trapania are an elongate body, a pair of curved extrarhinophoral appendages and a pair of curved extrabranchial appendages. The Trapania are true nudibranchs. They are grouped with the phanerobranchs whereby the gill is non-retractile, lacking a protective pocket below the mantle surface into which it could be withdrawn. Instead, they possess the aforementioned extra-branchial processes that serve as a form of protection beside the gill. They also possess similar appendages for the protection of the non-retractile rhinophores – extra-rhinophoral processes, and quite well-developed oral and propodial tentacles believed to act in a combined chemical and tactile sensory function. The body is small, narrow, elongate and is lacking a distinct mantle rim. The foot is narrow. In general, the external morphological arrangement of Trapania is consistent across the genus.

Trapania tigger is elongate, consistently sausage-shaped all the way to the rounded blunt tail that is much less tapered than the majority in the genus. The lamellate rhinophores have large bulbous clubs with a small pointed tip. The extrarhinophoral appendages are thick and stocky, curving around the rhinophores posteriorly to almost meet. The small non-retractile gill is located just posterior to halfway along the body length. It consists of three branches of which the middle is the longest. The extrabranchial appendages are also thick and stocky, closely investing the gill as they curve posteriorly. The laterally directed anterior foot corners are elongate and tapered with the oral tentacles readily visible but not as long. The external appearance of Trapania tigger, colouration and patterning apart, is not dissimilar to the earlier described Trapania reticulata.

The background colour of Trapania tigger is light brown with distinct patches of darker brown arranged as alternating bands, of irregular edging, most noticeable medially and posteriorly. Random white spots are distributed sparsely over the body.

Species of Trapania are most often found upon sponges but it is believed they are feeding, not on the sponge tissue, but instead on the tiny colonial entoprocts that grow in association with the sponge.

Our specimen, shown here, recorded from Flinders Reef, off Cape Moreton, Southern Queensland waters (December 2012) was 18 mm in length, significantly larger (by 50%) than those recorded from the type locality of Mabini, Luzon, Philippines of 12 mm.

The specific epithet of tigger was chosen due to the authors’ notion of the animal’s: “…resemblance to Tigger, a fictional character illustrated by E. H. Shepard from the Winnie-the-Pooh series of stories.”

Trapania tigger is an uncommon species, with distribution being listed in its description as: “Known only from Mabini, Luzon, the Philippines.” Our recording of it in southern Queensland waters indicates a wider distribution.

Previously known on this site as Trapania sp. 01 (Changed May 2022)

David A. Mullins – May 2022

References:
– Rudman, W. (1987). The genus Trapania (Nudibranchia: Goniodorididae) in the Indo-West Pacific. Journal of Molluscan Studies, 53, 189–212.

– Fahey, S. J. (2004). A new species of Trapania (Nudibranchia: Gonodorididae) from Western Australia with comparisons to other Indo-West Pacific Trapania. Zootaxa 514: 1–12.

– Rudman, W. B. (2006 December 21). Kamptozoa (Entoprocta). [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/kamptozoa

– Gosliner, T. M. & Fahey, S. J. (2008). Systematics of Trapania (Mollusca: Nudibranchia: Goniodorididae) with descriptions of 16 new species. Systematics and Biodiversity 6 (1): 53–98.

– Gosliner, T. M., Valdés, Á., and Behrens, D. W. (2018). Nudibranch & Sea Slug Identification: Indo-Pacific – 2nd Ed. New World Publications: Jacksonville, FL.

– Smirnoff, D. S., Donohoo, S. A. & Gosliner, T. M. (2022). Extra-branchial processes manifest extra diversity: systematics of the genus Trapania (Nudibranchia: Goniodorididae) and nine new species descriptions. Zoological Journal of the Linnean Society, 2022, XX, 1–44

– MolluscaBase eds. (2022). MolluscaBase. Trapania Pruvot-Fol, 1931. Accessed through: World Register of Marine Species at: https://www.marinespecies.org/aphia.php?p=taxdetails&id=138043 on 2022-05-22.