Barkeriella museensis Manganelli & Lesicki & Benocci & Barbato & Miserocchi & Pieńkowska & Giusti 2023, SP. NOV.

BARKERIELLA MUSEENSIS SP. NOV. Zoobank registration: urn:lsid:zoobank:org:act: C8C98093-52BB-4E3B-AA82-7268F7FFAD97. Type locality: Tropical greenhouse of the Science Museum (MUSE) of Trento, northern Italy. Type material: Holotype: D. Barbato leg. 4.5.2019 (one ad. dissected, FCG 51208) and 31 paratypes: D. Barbato & G. Bolzonella leg. 4.1.2019 (two subad. sps. dissected, FGC 51205), D. Barbato & G. Bolzonella leg. 10.2.2019 (three subad. sps. dissected + four juv. sps. dissected, FGC 51206; one ad. + one juv. sps. NHC/ MOLL-2022-001 – 002), D. Miserocchi leg. 2.3.2019 (six sps., FGC 51168), D. Barbato leg. 4.5.2019 (five juv. sps. dissected + seven juv. sps. ‘exploded’ + two ad. sps. dissected, FGC 51191). Etymology: The new species was first discovered in the tropical greenhouse of the Science Museum (MUSE) of Trento, Italy. The species is named for the type locality. Diagnosis: See genus diagnosis. Description: Body (Figs 1, 2C): Crawling specimens, small and slender (length no more than 20 mm; width no more than 3 mm). Notum roundish, whitish in colour with a wide, greyish-violet band on each side, separated dorsally by a whitish line coinciding with a trace of keel; notum covered in coarse granulations with a thick mucus layer in irritated specimens; notum extending laterally to completely cover body sides as far as the pedal groove (no sharp delimitation between dorsal and lateroventral sectors of mantle covering); pedal groove separating notum and foot along length of body. In crawling specimens, head protrudes from notum, but in resting or irritated specimens is completely covered by the notum, and bears two white or pinkish upper tentacles and two apically bilobed lower tentacles. Foot long and rather slender with fine transverse ridges (soleolae). NerƲous system (Fig. 2A, B): not studied in detail; central system forms a concentrated ring, consisting dorsally of many ganglia (cerebral, buccal and visceropleural), more or less fused to one another and ventrally of a pair of pedal ganglia. Renal–pulmonary complex (Fig. 2A, B, D): Located anterodorsally with atrophied pulmonary chamber; pericardium disposed obliquely and heart consisting of a single auricle and ventricle. DigestiƲe tract (Fig. 2A, B, D): consisting of buccal bulb with radula, oesophagus, two salivary glands, stomach and intestine. Jaw absent. Buccal bulb long and wide, occupying the internal part of head and neck and consisting anteriorly of the sac of the protrusible proboscis and posteriorly of the radular sac. Oesophagus long and slender, originating about halfway along length of buccal bulb, passing inside the nervous ring, reversing along the spermoviduct and entering the stomach anteriorly. Two large salivary glands discharge via two fine salivary ducts that pass inside the nervous ring into the buccal bulb. The stomach is small, receives a short, thin tube from the digestive gland posteriorly and continues anteriorly with the intestine. Intestine long and slender, reversing and running first along the left, then along the anterior side of the uterine oviduct, and opening in the right pedal groove in the anterior one-fifth to one-quarter of the body, just anterior to the oviductal opening. Long, single-lobed digestive gland (hepatopancreas) in close contact with upper side of gonad and occupying dorsal part of body cavity as far as tip of tail. Radula (Fig. 5A, B): Consisting of a sequence of many V-shaped rows of hook-like unicuspidate teeth, each with about 27 teeth, according to the formula 13L + 1C + 13L. The large central tooth and the first lateral teeth show a worn tip in most cases. The lateromarginal teeth, progressively reduced in dimension, have pointed tips. Genitalia (Figs 2A, B, 3A–C, 4): Of triaulic tritrematic type (three ducts for gametes: one vaginal for receiving allosperm from partner, one oviductal for conveying eggs outside, one penial for carrying autosperm to penis; three genital apertures: vaginal, oviductal and penial). Hermaphrodite gonad long, ventral with respect to the similarly long digestive gland; anterior side of gonad adheres to the posterior side of a large conspicuous glandular structure. This organ possibly consists of a small, whitish albumen gland proximally and a large, subtrasparent, gelatinous uterine oviduct distally. The glandular structure embraces a large, lobed body proximally and the prostate ventrally and continues with the short wide free oviduct that opens into the pedal groove on the right side of the body, about one-fifth to one-quarter of the way along the body, just posterior to the anus. The large lobed body is a roundish non-glandular organ, in which a long, fine hermaphrodite duct ends and three other ducts arise: (1) a fine, long, straight duct ending into two seminal receptacles (i.e. where the allosperm received from a partner is stored, until it can fertilize eggs); (2) a fine, short, twisted duct ending on the posterior side of the glandular structure interpreted as an oviduct (to bring fertilized eggs into the uterine oviduct); and (3) a fine, short duct that enters the prostate and is interpreted as a sperm duct/ seminal duct (to convey autosperm to the prostate and allosperm to the duct of the seminal receptacles?). An oval or roundish, variably pedunculate lobe, possibly a bursa copulatrix, is disposed on the other side of the large lobed body (i.e. the side opposite that on which the three ducts arise). The large lobed body possibly includes a fertilization chamber. The prostate is a long tubular structure, adhering ventrally to the glandular structure and elongated anteriorly; proximally, near the point where the sperm duct enters, it receives another duct, interpreted as the vagina; distally it is connected to a sort of variably large vesicle, near the base of which the vas deferens arises. The vagina is a long tubular duct that starts from the proximal portion of the prostate, extends along the anterior side of the large lobed body towards the right side of the body and ends with the vaginal opening in the pedal groove about one-third of the way along the body from the head. The distal male genitalia include the vas deferens, the penis and Simroth’s gland. The vas deferens consists of two portions: the initial (proximal) longer portion running inside the body wall, coinciding with the anterior part of the foot; the final (distal) shorter portion that re-enters the body cavity and finishes at the proximal end of the penis where the penial retractor also joins. The penis is a short tubular organ that ends in the male genital atrium side by side with Simroth’s gland. Its proximal portion contains a pointed penial papilla. The genital atrium opens on the anterior right side of the head. Simroth’s gland is a long tubular structure, pinkish in colour in adult specimens and consisting of two parts: the shorter initial portion (facing the distal penis) is twisted and enveloped in a transparent sheath, oval in shape; the longer final portion, which is free of the sheath, forms a bunch by twisting irregularly on itself, then extends backwards along the glandular structure to end level with the digestive gland and the gonad. Shell: Absent. A variable number of vitreous, disclike, ovoidal or roundish granules of variable size are scattered on the dorsal surface of the body cavity, up to the glandular structure and digestive gland. Gene sequences: Partial sequences of the following genes characteristic of Barkeriella museensis were deposited in GenBank: COI – OM827003 – OM827005; 16S rDNA – OM827013 – OM827015; 18 S rDNA – OM 827024 – OM 827026; (5.8 S rDNA) + ITS2 + (28S rDNA) – OM827032 – OM827034; H3 – OM827043 – OM827046. Remarks: It is not easy to trace the geographical origin of this slug: the family to which it belongs – the rathouisiids – has a natural range that encompasses the eastern Palaearctic, the Indomalayan and the northern Australasian regions. Its presence in the Afromontane greenhouse of MUSE in Trento (northern Italy) is surely linked to introduced exotic plants. While species of African vertebrates (fish, amphibians and birds) were introduced for display purposes, many soil invertebrates were unintentionally transported with root balls, despite the museum’s strict control measures to prevent new invasions. Slugs can easily travel in this way as eggs or hatched individuals, and can spread into their surroundings (Bergey et al., 2014). The greenhouse of MUSE (600 m 2; 130 species of plants; temperature 30 °C, humidity 70–80%) was completed in 2013 to recreate different montane forest environments of eastern Africa (namely those of the Udzungwa Mountains in eastern Tanzania), but not all the plant species used so far come from that area. Some trees, shrubs, herbs and vines native to South-East Asia or tropical America were chosen as substitutes for closely related or apparently similar eastern African plants, difficult or impossible to obtain through regular channels. Even the plants native to eastern Africa were not imported directly from there, but in most cases were purchased from plant nurseries in Italy or Europe or obtained by exchange with other institutions. In such facilities, plants from different continents are often raised in the same areas, allowing different pools of soil invertebrates to spread from one to the other. Thus, the rich soil fauna which inhabits the MUSE tropical greenhouse is composed of a mixture of species (flatworms, earthworms, woodlice, mites, centipedes, insects and molluscs) from several biogeographic regions. All slug specimens were found in a restricted part of the greenhouse between January and May 2019. A subsequent survey in February 2022 was unsuccessful. The sector of the greenhouse where B. museensis was collected was radically restructured in the period 2020–22. Some plants were replaced and certain soil features were affected as a result. In that period, a population of the burrowing Suriname cockroach Pycnoscelus surinamensis (Linnaeus, 1758) spread throughout the greenhouse, reaching high densities everywhere and probably causing further changes to soil properties. The reorganization may have led to disappearance of the slug.Published as part of Manganelli, Giuseppe, Lesicki, Andrzej, Benocci, Andrea, Barbato, Debora, Miserocchi, Danio, Pieńkowska, Joanna R. & Giusti, Folco, 2023, A small slug from a tropical greenhouse reveals a new rathouisiid lineage with triaulic tritrematic genitalia (Gastropoda: Systellommatophora), pp. 76-103 in Zoological Journal of the Linnean Society 197 (1) on pages 96-98, DOI: 10.1093/zoolinnean/zlac054, http://zenodo.org/record/747413