Stanisicarion aquila

Stanisicarion aquila (Cox, 1868)

Figs. 14J–L, 33, 34B, 36C–E, 38, 39A–D

Vitrina aquila Cox, 1868: 109.

Vercularion aquila: Iredale, 1941: 6–7.

Macularion aquila: Stanisic, 2010 in Stanisic et al., 2010: 312.

Material examined

Types: Holotype: AM C.101185 (Eagle Scrub, Brisbane, Qld).

Non-type material: See table 1.

Description

External morphology: Shell (figs. 14J–L, 34B) medium-sized (14–18.3 mm), amber, 3.9–4.2 whorls, subglobose with a low spire. Body (figs. 36C–E) 40–45 mm long, light orange-brown to grey, tail often darker, depressions of slime network darker (giving tail a diagonally striped appearance), eyestalks dark grey, foot border sometimes orange. Mantle lobes and shell lappets moderately large, pustulose, with numerous, discrete, raised black spots or ridges. Dark line along mantle edge. Tail keeled at tip, keel paler, slime network prominent.

Genital anatomy: Genitalia (figs. 38, 39A–D) with moderately long vagina; bursa copulatrix moderately long, duct distinct, bursa oval. Penis long, slender, internally pustulose; 50–80% of penis contained in penial tunica. Epiphallus longer than penis; epiphallus enters penis through a short, pointed verge, partially fused to the penis wall; epiphallus 2 much longer than epiphallus 1; epiphallic caecum very short; flagellum moderately long, slender, irregularly coiled or twisted. Spermatophore a soft capsule with a simple tail-pipe; terminal end hooked with several small spines.

Remarks

Stanisicarion aquila is currently recorded from Mullumbimby in northeastern NSW to Kenilworth in southeastern Qld (Stanisic et al., 2010), where it is found in rainforest habitats under logs, rocks and fallen palm fronds (fig. 33). This relatively broad range and some variation in external morphology (Stanisic, pers. comm.) led Stanisic et al. (2010) to suggest that S. aquila may represent more than one species. Semislugs from northern NSW have brown bodies with orange markings and discrete raised spots on the shell lappets, while those from Mt Tamborine in southern Qld have cream bodies with orange markings and raised short ridges rather than spots on their shell lappets (fig. 34A–C). Further north still, semislugs from Conondale and the Sunshine Coast are grey rather than cream, with no orange colouring and much less visible spots on the shell lappets (fig. 34A–C). These three morphs form separate clades in the phylogenetic tree, but sampling across the entire range has revealed little anatomical variation and a degree of genetic variation consistent with other widespread species (COI: 1.4%, 16S:2.2%).

A population of this species was also discovered in Cicada Glen in northern Sydney and is assumed to have been introduced, perhaps in plants being brought in to a nearby nursery. It matches the Conondale population in its body colour and genetics.

Both introduced and native populations of S. aquila occur within the range of congener S. freycineti, but S. freycineti is generally found in dry sclerophyll forest and open woodland rather than rainforest and the two species have not been recorded in sympatry. Stanisicarion aquila can be distinguished by its larger, more highly whorled but less globose shell and more highly pustulose shell lappets, usually with visible spots or ridges. It is also sympatric with arboreal semislug Fastosarion papillosus, but can be distinguished by its larger size and evenly pustulose lappets, in contrast to the single row of papillae on the shell lappet of F. papillosus.