Leptichnoides avisexcrementis, Rowson, Ben, Paustian, Megan & Goethem, Jackie Van, 2017

Rowson, Ben, Paustian, Megan & Goethem, Jackie Van, 2017, New species and records of terrestrial slugs from East Africa (Gastropoda, Urocyclidae, Veronicellidae, Agriolimacidae), ZooKeys 723, pp. 11-42 : 12

Leptichnoides avisexcrementis sp. n. Figs 8-10, 23, 33-35, 55-58

Material.

TANZANIA: Holotype NMW.Z.1996.148.00032: 1 ad., Uluguru North FR (6.93°S, 37.7°E), Uluguru Mts., Morogoro District, forest above Tegetero village, approx. 1300 m alt., leg. PT, 22 Jan. 1996 (sample IC). Paratype 1 NMW.Z.1996.148.00033: 1 juv., data as previous but sample IIF. Paratype 2 NMW.Z.1996.148.00034: 1 juv., Kimboza FR (7.01°S, 37.78°E), Uluguru Mts., Morogoro District, lowland forest on dolomitic limestone, approx. 350 m alt., leg. PT, 19 Jan. 1996 (sample IB). Paratype 3 NMW.Z.1996.148.00040: 1 ad., data as previous but 20 Jan. 1996 sample IB. Paratype 4 RBINS.I.G. 33548/MT.3608: 1 ad., data as previous but sample IA.

Description.

External appearance (Figs 9-10). Small slug (to 23 mm long) with unusual colour pattern, imparting a resemblance to a bird dropping: pale cream with two thick grey-brown bands orientated across the dorsum (rather than parallel to it as is so common in slugs), leaving a pale saddle-like band across the mantle. Head and tentacles dark grey-brown, keel and sole pale. Strong dorsal keel along whole length of tail, terminating in a moderately long caudal appendage. Tail and flanks made granulose by raised tubercles. Mantle very large (approx. 50% of body length), with granulose surface, with large shell pore, attached at rear. Juveniles similarly coloured and proportioned.

Shell (Fig. 8). Fingernail-shaped, symmetrical, to 4.1 mm long, consisting of an extremely thin sheet of periostracum, weakly mineralised around the nucleus, adhering to the tissue below and easily torn during extraction.

Jaw and radula (Figs 23, 33-35). Jaw with weak median projection. Radula with central tooth and up to 55 lateral and marginal teeth in a half-row. All teeth strongly tricuspid, mesocones largest, ectocones larger than endocones. Weakly serrated outer edges to the outermost marginals.

Genitalia (Figs 55-56). Visceral cavity does not quite reach tail (posterior 10% of body solid). No stimulator, no calc sac. Atrium very short. Penial complex consisting of: stout free penis: moderately long flagellum; short epiphallus 1 and epiphallus 2, approximately equal in length; moderately long epiphallic caecum. The flagellum and caecum are loosely tangled together like a ball of wool until spread out during dissection. Penial retractor muscle short, arising from diaphragm. Free penis double-walled near the atrium, with a small conical papilla at the first bend of the penis. Vagina absent. Bursa copulatrix duct long, reaching albumen gland. Bursa spherical, thin-walled. A long, straight, muscular organ (characteristic of Leptichnoides ) between atrium and oviduct, with a thick-walled sheath, entering atrium through a coarse papilla. Hermaphroditic duct extremely short, barely perceptible between spermoviduct and large ovotestis, which lies near rear of mantle. Albumen gland small.

Spermatophore (Figs 57-58). Single, partly-digested spermatophore from bursa. Apical bend at junction between ampulla and tail broken during manipulation. Ampulla smooth, thin-walled, 2.5 mm long, little coiled (less than 1 volution). Tail at least 1.6 mm long, of at least 1 volution, apically swollen then tapering. Strongly ornamented with a double keel of large, curved, apparently unforked spines.

Etymology.

From Latin avis, bird, and excrementis, faeces, in reference to the species’ resemblance to a bird dropping.

Distribution and habitat.

We initially suspected this species to be endemic to forest in the Uluguru Mts., where several such taxa occur (e.g. Verdcourt 2006, Tattersfield and Rowson 2011). However, apparently conspecific material has since been collected further south in Tanzania, in forest at approx. 80 m alt., Hippo Hole, 20 km west of Kirenjerange, Lindi Region (9.57°S, 39.28°E) (J. M. C. Hutchinson, pers. comm., 2017). The following additional material from the NMW collections is referred to Leptichnoides verdcourti (Forcart, 1967), suggesting that both species range from southern coastal Tanzania to the lower altitude forests of the Eastern Arc Mts.: TANZANIA: NMW.Z.1995.016.00013: 1 ad., Pindiro FR (9.53°S, 39.27°E), Kilwa District, coastal forest at 350 m alt., leg. PT, 26 Feb. 1995 (sample II). NMW.Z.1995.016.00014: 3 juvs., Ngarama FR (9.33°S, 39.33°E), Kilwa District, coastal forest at 400 m alt., leg. PT, 25 Feb. 1995 (sample II). NMW.Z.1997.007.00009: 1 juv., Sali FR (8.95°S, 36.40°E), Mahenge Mts., Ulanga District, montane forest at 960 m alt., leg. AK, NO, CFN, MBS & PT, 5 Feb. 1997 (sample II). NMW.Z.1997.007.00010: 1 ad.?, Mzelezi FR (8.79°S, 36.72°E), Mahenge Mts., Ulanga District, forest on dolomitic limestone at 645 m alt., leg. AK, NO, CFN, MBS & PT, 6 Feb. 1997 (sample IC). NMW.Z.2003.001.00033: 1 juv., Mkungwe FR (6.90°S, 37.91°E), Uluguru Mts., Morogoro District, submontane forest, approx. 900 m alt., leg. BR & CFN, 7 Feb. 2003 (sample I misc).

Remarks.

Leptichnoides has not previously been recorded from East Africa ( Verdcourt 2006) and was until now known from a single species, L. verdcourti (Forcart, 1967) recorded from Mozambique, Zimbabwe, and (as an introduction) from Seychelles ( Forcart 1967, Van Goethem 1977, Gerlach 2006). Van Goethem (1977) noted that an unnamed species from Comoros ("Species D") might also belong to Leptichnoides . The long, straight muscular organ between the atrium and the oviduct is characteristic of the genus. In the studied collections, material from several eastern Tanzanian lowland localities appears referable to L. verdcourti so the genus is clearly well established in Tanzania. Here we describe L. avisexcrementis on account of its small size and markedly distinct colouration which allows it to be readily separated from Tanzanian and other material of L. verdcourti , in which the body is more conventionally patterned with dark brown irregular longitudinal bands and spots (as figured in Forcart 1967 and Gerlach 2006).

The new species is also the only Leptichnoides from which a spermatophore has yet been reported. Although partially digested, it differs remarkably from that of all other East African slugs in the form and large spines. Although the spines are unforked, there is a resemblance to the spermatophores of the less fully-limacised, West African slugs of the " Estria-Rhopalogonium group" of Van Goethem (1977) and of urocyclid semi-slugs ( Van Mol 1970). The spermatophore and animal show some resemblance to that of the Comoros slug genus Comorina Simroth, 1910, but the sole species C. johannae Simroth, 1910 was said to have a substantial dart sac not present in any other flagellum-bearing members of the Urocyclinae ; whether the "dart sac" is homologous with the muscular organ in Leptichnoides is uncertain. Van Goethem (1977) had no material of Comorina , and ranked it as incertae sedis, wondering whether it belonged in Urocyclidae or even whether the genitalia were correctly described by Simroth (1910). New material of Comorina is needed to resolve this.