Documentation of the Mantleslugs Philomycus carolinianus and Megapallifera mutabilis (Gastropoda: Philomycidae) in Wisconsin Megan Paustian1,*, Janis Annesley2, Joan Jass2, and Barbara Klausmeier2 Abstract - Evidence for the presence of the native philomycid slugs Philomycus carolinianus (Carolina Mantleslug) and Megapallifera mutabilis (Changeable Mantleslug) in Wisconsin is given through data on body length, external morphology, traits of the jaw, color pattern, genital morphology, and comparison to the known distribution data for members of the genera. These are the first published records from Wisconsin for these two species. Because of their potential for becoming agricultural pests, nonindigenous slugs have received substantial coverage in the contemporary literature (Cowie and Robinson 2003, McDonnell et al. 2009). However, the native philomycid slugs of the eastern United States have remained less well known. Hubricht (1985) noted that collectors historically overlooked these slugs and that collected specimens had often been allowed to degrade, limiting their potential for study. In contrast to other slug families in the order Stylommatophora, philomycids have a mantle that covers not only an anterior portion of the dorsal surface but extends over nearly the entire back of the animal. For this family in North America, Turgeon et al. (1998) listed three species in the genus Megapallifera, ten in the genus Pallifera, and eight in the genus Philomycus. Members of the genus Pallifera are relatively small in size (body length <30 mm; Burch 1962), while Megapallifera and Philomycus species are relatively large (body length >50 mm; Burch 1962, Hubricht 1956). On the basis of mantle extent and body length, the Wisconsin specimens under discussion here are philomycids and belong either to the genus Megapallifera or to Philomycus. The identity of many philomycid individuals is uncertain due to convergent morphologies among many species, insufficient characters used in species identification, and the likely existence of cryptic (heretofore unrecognized, genetically unique) species. The wide-ranging species Philomycus flexuolaris (Rafinesque) exhibits major variability in mantle coloration, including some individuals that are easily confused with P. carolinianus by non-experts (Grimm 1996; M. Paustian, pers. observ.). However, Hubricht (1951) recognized P. flexuolaris as a distinct species with pigment spots that are larger and have blurred rather than sharp outlines. While the ranges of the two species overlap in the East, Hubricht (1952) considered Kentucky and Ohio too far west for P. flexuolaris. Pilsbry (1948) indicated that the genitalia of P. carolinianus and P. flexuolaris were much alike except for the somewhat smaller dart sac of the latter (a feature not readily apparent to these authors). Additional morphological features useful for distinguishing the two species have yet to be found. 1Section of Mollusks, Carnegie Museum of Natural History, Pittsburgh, PA 15213. 2Life Sciences, Milwaukee Public Museum, Milwaukee, WI 53233. *Corresponding author - mpaustia@gmail.com. Notes of the Northeastern Naturalist, Issue 20/3, 2013 N1 2013 Northeastern Naturalist Notes Vol. 20, No. 3 N2 M. Paustian, J. Annesley, J. Jass, and B. Klausmeier Kenneth I. Lange assisted in our collection of six lots (collection events) of slug specimens, which were deposited in the Milwaukee Public Museum (MPM) (Fig. 1, Table 1). The philomycid slugs were found on fallen logs during targeted surveys for slugs and incidentally during invertebrate field surveys in southern Wisconsin. Slugs collected were drowned and then transferred to 70% alcohol for preservation. Animals were dissected with a Leica MZ12 and a Meiji Techno RZ stereomicroscope, and internal anatomy was drawn with the aid of a camera lucida attachment. A photograph of a mounted jaw of Megapallifera mutabilis (Hubricht) (Changeable Mantleslug) (lot 3) was taken using a Zeiss EVO 40 scanning electron microscope (SEM) (Fig. 2A). Traits of the jaw, reproductive anatomy, and mantle coloration support the placement of lots 2, 3, and 6 in the species M. mutabilis. The SEM image of the jaw (Fig. 2A) shows the distinct stout ribs by which Binney defined the genus Pallifera (currently genera Pallifera and Megapallifera; Binney 1875:fig. 42). These animals do not possess a dart sac (Fig. 3A), a defining character of Philomycus (Pilbsry 1948). Specimens do not belong to sister species M. wetherbyi (Binney) (Blotchy Mantleslug) or M. ragsdalei (Webb) (Ozark Mantleslug), which occur some distance south (M. wetherbyi: east Tennessee and southeast Kentucky; Figure 1. Localities of slugs collected in Wisconsin. Species abbreviations are Mm for M. mutabilis and Pc for P. carolinianus. Northeastern Naturalist Notes N3 2013 Vol. 20, No. 3 M. Paustian, J. Annesley, J. Jass, and B. Klausmeier Table 1. Collection data of MPM Wisconsin specimens. Coordinates are derived from locality data through GoogleEarth, and lengths are taken from the preserved animals. Species abbreviations are Mm for M. mutabilis and Pc for P. carolinianus. MPM Length lot Date County Locality Coordinates Collector Count (mm) Species 1 28 May 1993 Sheboygan Kettle Moraine State Forest, 43.6633°N, 88.1366°W J.P. Jass 1 42 Pc Butler Lake parking lot, T14N R20E, Sec 20.8W 2 15 June 2007 Sauk Devil’s Lake State Park 43.4167°N, 89.8276°W K.I. Lange 1 38 Mm T11N R06E, Sec 19 3 2 June 2008 Sauk Devil’s Lake State Park 43.3874°N, 89.7486°W K.I. Lange 1 36 Mm T11N R06E, Sec 35 4 21 Aug 2009 Sauk Devil’s Lake 43.348889°N, 89.841028°W B.R. Klausmeier 2 30, 31 Pc 5 28 Aug 2009 Sauk T11N R06E, Sec 19 SE 43.4167°N, 89.8276°W K.I. Lange 4 17, 18, 23, 40 Pc and Sec NE 6 10 Sept 2011 Sauk Near Leland, by entrance 43.3584°N, 89.9838°W K.I. Lange 1 22 Mm to Honey Creek Valley, T10N R04E, Sec 11 NE SW 2013 Northeastern Naturalist Notes Vol. 20, No. 3 N4 M. Paustian, J. Annesley, J. Jass, and B. Klausmeier M. ragsdalei: Missouri, Arkansas, and west Oklahoma [Hubricht 1985]) and which have strong chevron patterns on the mantle, unlike the observed specimens (Fig. 4A). Rather, the Wisconsin animals have the two atrial pads typical of M. mutabilis (Fairbanks 1990:fig. 9). The known range of M. mutabilis extends over the southeast US (Burch 1962) to south Ontario, Canada (Grimm 1996) and as far west as Texas, Missouri, and Iowa (Hubricht 1985). The nearest locality to Wisconsin in which the species had previously been found is Muscatine County, on the east border of Iowa (Hubricht 1985). These are the first published records of M. mutabilis from Wisconsin. We identified the remaining lots 1, 4, and 5 as Philomycus carolinianus (Bosc) (Carolina Mantleslug) based on geographical distribution, mantle patterns, and jaw and reproductive anatomy. These slugs have a smooth jaw (Fig. 2B) and a dart sac (Fig. 3B), which are characteristic of Philomycus. Binney (1875) assigned the philomycid jaw with its ribless anterior margin to the genus Tebennophorus (currently genus Philomycus). Pilsbry (1948) distinguished Philomycus from other genera of Philomycidae by the presence of a dart sac, containing a calcareous dart, located on the vagina. As by far the most northwesterly ranging Philomycus species mapped by Hubricht (1985), P. carolinianus has distribution records that extended west beyond the Mississippi River into Iowa, with Wisconsin just beyond the northwest corner of its range and counties of record in both Illinois and Iowa along the Wisconsin state line. The other seven members of the genus have known distributions limited to areas far from Wisconsin (none in adjacent states). The key feature of P. carolinianus is a mid-dorsal double longitudinal row of black spots, much darker than the gray-brownish mottling patterning the rest of the dorsum, (Burch 1962), which is characteristic of the MPM lots 1, 4, and 5 (Fig. 3B). To date, only very brief reports have supported the presence of philomycids in Wisconsin. Chadwick (1905) and Hubricht (1985) gave records for Pallifera dorsalis from six counties, and Jass (2004) listed P. carolinianus from one county. This report now provides distinctive anatomical evidence that Wisconsin, at least in its southern half, is within the range of both P. carolinianus and M. mutabilis. Figure 2. Jaw structure of (A) M. mutabilis and (B) P. carolinianus. A scanning electron micrograph exhibits longitudinal ridges in the jaw of M. mutabilis (lot 3), while the jaw of P. carolinianus (lot 5) is smooth. (Jaws are each about 1.5 mm wide.) Northeastern Naturalist Notes N5 2013 Vol. 20, No. 3 M. Paustian, J. Annesley, J. Jass, and B. Klausmeier Figure 3. Proximal genitalia of (A) M. mutabilis (lot 3) and (B) P. carolinianus (lot 4). Shown are the atrium (AT), dart sac (DS), free oviduct (FO), penis (PE), penial retractor muscle (PRM), spermatheca (SP), spermatheca duct (SPD), spermoviduct (SPO), vagina (VA), and vas deferens (VD). M. mutabilis lacks a dart sac, while P. carolinianus possesses a dart sac on the vagina. (Bar = 5 mm.) 2013 Northeastern Naturalist Notes Vol. 20, No. 3 N6 M. Paustian, J. Annesley, J. Jass, and B. Klausmeier Figure 4. Mantle patterns of (A, B) M. mutabilis (lot 6) and (C, D) P. carolinianus (lot 1). The mantle of M. mutabilis exhibits a double row of blotchy gray-brown spots along the dorsum, a continuous gray-brown line with a sharp upper edge and graded lower edge on each of the sides, and no chevrons on the dorsum. The mantle of P. carolinianus shows the species’ typical color pattern of brown mottling, two longitudinal rows of distinct black spots on the dorsum, and a discontinuous line of brown mottling along each of the lower sides. (Bar = 5 mm.) Northeastern Naturalist Notes N7 2013 Vol. 20, No. 3 M. Paustian, J. Annesley, J. Jass, and B. Klausmeier Acknowledgments. This work is dedicated to the memories of Rose M. Henderson 1945–2012 and our coauthor Joan Jass 1944–2012. A devoted researcher, Joan enthusiastically introduced people to the world of underappreciated invertebrate animals during her 42 years as Curator of Invertebrate Zoology at the Milwaukee Public Museum. We are grateful to the following sources of specimens and financial support. Devil’s Lake State Park specimens were collected and donated to the museum collection by retired Park Naturalist Ken Lange. 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