Megalobulimus dryades, Fontenelle & Simone & Cavallari, 2021

Fontenelle, José Heitzmann, Simone, Luiz Ricardo L. & Cavallari, Daniel Caracanhas, 2021, Megalobulimus dryades, a new species from the Atlantic Forest in southeastern Brazil, and redescription of Megalobulimus gummatus (Gastropoda: Strophocheilidae), Papéis Avulsos de Zoologia (Pap. Avulsos Zool., S. Paulo) 61, pp. 1-17 : 2-10

publication ID	https://doi.org/ 10.11606/1807-0205/2021.61.44
publication LSID	lsid:zoobank.org:pub:FE64EA84-C28D-4CE1-AE7A-5C973BBF4D45
persistent identifier	https://treatment.plazi.org/id/C413C457-BEF0-478E-8886-8F0CE9473724
taxon LSID	lsid:zoobank.org:act:C413C457-BEF0-478E-8886-8F0CE9473724
treatment provided by	Carolina
scientific name	Megalobulimus dryades
status	sp. nov.

Treatment

Megalobulimus dryades View in CoL sp. nov.

( Figs. 1-8 View Figure 1 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 View Figure7 View Figure 8 ) http://zoobank.org/ C413C457-BEF0-478E-8886-8F0CE9473724

Strophocheilus gummatus: Morretes, 1949: 143 View in CoL (in part, non Hidalgo).

Megalobulimus (Phaiopharus) gummatus: Morretes, 1952: 113, 1953: 65 View in CoL (in part, non Hidalgo).

Megalobulimus gummatus: Leme, 1973: 318 View in CoL , fig. 38; Sobreira & Molina, 2002; Salgado & Coelho, 2003: 158 (in part); Simone, 2006: 211, fig. 804 (in part); Thomé et al., 2007:22 (in part); Agudo-Padrón, 2010:35, fig. 2, 2011:61, fig. 2; Birckolz et al., 2016: 150 (non Hidalgo).

Type specimens: Holotype: MZSP 120000 View Materials (J.L.M. Leme col., 01/vii/1961).

Paratypes: BRAZIL. São Paulo; Iporanga, MZSP 15594 View Materials , 13 View Materials spm (J.L.M. Leme col., 01/vii/1961) ; Guapiará, Fazenda Intervales, MZSP 28925 View Materials , 2 View Materials sh ( MZSP Exp., 22-26/iii/1992) ; Iguape,NÚcleo Despraiado, MZSP 28773 View Materials , 2 View Materials sh (R.P. Rocha, Bertani & Mestre cols., 03/x/1997), MZSP 28893 View Materials , 2 View Materials spm (N. Moraccioli col.), MZSP 29317 View Materials , 2 View Materials sh (R. Krone col., 1901) . Paraná; Morretes , MZSP 16610 View Materials , 2 View Materials sh (Lange de Morretes col.) .

Type locality: Brazil, São Paulo state, Iporanga Municipality (center coordinates 24°35 ′ S, 48°35 ′ W), ~ 80 m of elevation.

Material examined (non-types): BRAZIL. São Paulo; Sorocaba, MZSP 62129 (1 sh); Mogi das Cruzes, MZSP 28962 (1 sh); Itapecerica da Serra, MZSP 15724 (1 sh); São Sebastião, MZSP 96475 (2 sh); Cubatão, MZSP 64563 (1 sh); Juquetiba, MZSP 92832 (2 sh); Tapiraí, MZSP 16039 (5 sh); São Vicente, MZSP 16615 (1 sh); Itapeva, MZSP 29320 (1 sh), MZSP 96474 (2 sh); Itanhaém, MZSP 42350 (1 sh), MZSP 92833 (1 sh); Guapiará, MZSP 29316 (1 sh); Fazenda Intervales, MZSP 30460 (1 sh); Miracatu, MZSP 49935 (1 spm), MZSP 49936 (1 spm), FPZSP, MZSP 49937,(1 spm), MZSP 49940 (1 spm), MZSP 49941 (1 spm), MZSP 49942 (1 spm), MZSP 49944 (1 spm), MZSP 49945 (1 spm); Pedro de Toledo, MZSP 92837 (1 sh); Itariri, MZSP 48256 (1 spm), MZSP 96477 (2 sh); Peruíbe, MZSP 29309 (1 sh); Biguá, MZSP 92836 (1 sh); Juquiá, MZSP 269 (3 sh), MZSP 90913 (1 sh), MZSP 90914 (1 sh), MZSP 96478 (1 sh), MZSP 96479 (1 sh); Registro, MZSP 48523 (1 sh); Eldorado Paulista, MZSP 29315 (2 sh); Iporanga, MZSP 7996 (1 sh), MZSP 15603 (2 sh), MZSP 15617 (4 sh), MZSP 33031 (8 sh), MZSP 43529 (1 sh), MZSP 43533 (1 sh), MZSP 43689 (1 sh), MZSP 43697 (1 sh), MZSP 92835 (1 sh); Jacupiranga, MZSP 32541 (1 sh); Iguape, MZSP 29311 (1 sh), MZSP 29312 (4 sh), MZSP 71070 (1 sh); Pariquera-aÇÚ, MZSP 29313 (1 sh), MZSP 29318 (1 sh). Paraná; Sengés, MZSP 16603 (10 sh).

Diagnosis: Shell large, with strong rugosities and malleated surface on teleoconch whorls; protoconch darker-colored with a clear lighter subsutural band, with microsculpture consisting of granules and macrosculpture of well-marked axial riblets that branch apically near suture. Peristome homogeneously white, columella oblique and slightly convex. Head-foot very light-colored, dirty white to grayish-bluish; free oviduct appendix present; penis long and uniform with convolutions, lacking developed transverse fold, bearing two short flagella of similar length.

Description

Shell ( Figs. 1-2 View Figure 1 View Figure 2 ): Large (L~ 119 mm), oval, thick, of ~5.4 whorls, imperforate to semiperforate; profile strongly convex, moderately dorso-ventrally compressed (H:W = 0.8) ( Fig. 2D View Figure 2 ); spire short and obtuse; usually not covered by periostracum in adults; color reddish ocher with yellowish-white subsutural band, ranging until last whorl. Protoconch ( Fig. 2D, I View Figure 2 ) with ~3.2 whorls, weakly convex, usually darker than teleoconch, reddish-darkbrown with a clearly marked white-cream subsutural band; first 1¼ whorl smooth, followed by regular, complete prosocline riblets that branch apically near the suture, interspaces 2-3× wider than riblet width, presenting microscopic radial granulation that gradually increases in size toward final nepionic whorls ( Fig. 2I View Figure 2 ). First ¼ teleoconch whorl with regular, thin riblets that are gradually replaced by delicate anastomosing rugosities and malleations that become larger, stronger, and coarser toward the last adult whorls (4½-5). Body whorl inflated, sculpture mostly consisting of strong rugosities and malleations ( Fig. 2 View Figure 2 G-H), but also presenting irregular, widely spaced axial riblets and short radial striae interconnected with the other sculpture elements. Aperture oval ( Fig. 2A, E, G View Figure 2 ), length ~50% of shell length; peristome thickened and slightly reflected, outer lip arched, color white; columella thick, oblique,and slightly convex. Periostracum yellowish-brown, with dark radial bands in the interspaces between axial sculpture elements ( Fig. 2 View Figure 2 G-H), and often darker colored in the malleation cavities;usually preserved on last two teleoconch whorls, with a glossy aspect when present ( Fig. 2H View Figure 2 ).

Head-foot: Tegument in living specimen very light-colored, from dirty white to grayish-bluish ( Fig. 1 View Figure 1 ); each buccal flange bearing seven papillae.

Pulmonary (pallial) cavity: Plexus of vessels containing divisions and anastomoses of collar vessel tributaries ( Figs. 3A View Figure 3 , 4B View Figure 4 :cv) triangular, of radicular aspect, occupying ~ ⅖ of cavity volume, located between mantle edge and septum. Cardiac area occupying ~ ⅓ of reno-pericardial area ( Fig. 4A View Figure 4 : ht), with equidistant insertions of tributaries of pericardial vessel ( Fig. 4A View Figure 4 : vp). Insertion of palio-diaphragmatic muscle ( Fig. 4A View Figure 4 : pv) in angular pulmonary cavity deep in kidney ( Fig. 4A View Figure 4 : pd). Pulmonary septum ( Figs. 3A View Figure 3 , 4A, B View Figure 4 : se) separating excretory/respiratory areas, covered by plexus of vessels, extending through middle surface of reno-pericardial area ( Fig. 4A View Figure 4 : ef). Pneumostome with strong anal folds anastomoses extending toward its inner edge.

Excretory system: Kidney ( Fig. 4A View Figure 4 : ki) sub-triangular, occupying ~½ of pulmonary septum volume, with protuberance at edge close to nephrostome ( Fig. 4A View Figure 4 : np) near transition between adrenal vessels ( Fig. 4A View Figure 4 : nv) and ad-rectal vessels ( Figs. 4A, B View Figure 4 : rv). Ureter absent. Folds of urinary gutter ( Figs. 4A, B View Figure 4 : ug) beginning near nephrostome level, flanking left side of rectum towards pneumostome ( Fig. 4B View Figure 4 : pn), partially covering rectum at its final half ( Fig. 4B View Figure 4 : rt), ending before anus.

Digestive system: Buccal mass robust ( Fig. 5A View Figure 5 : ot), retractor muscle inserted laterally in radular pouch.

Odontophore rounded ( Fig. 5A View Figure 5 : od), occupying ~¼ of buccal mass volume. Aperture of salivary gland ducts ( Fig. 5A View Figure 5 : sa) located distally and laterally on ceiling of buccal mass ( Fig. 5A View Figure 5 : bm). Jaw arc-shaped, rigid, elasmognate,pigmented ( Figs. 3B View Figure 3 , 5A View Figure 5 : jw), with ~35 irregular, narrow and well-marked axial columns and transverse growth lines. Pair of muscles m7 surrounding radular sac in region preceding exposed radula, anteriorly protected by hardened tissue ( Fig. 5A View Figure 5 : bt); dorsal surface of odontophore cartilages rigid and darker-colored ( Fig. 5 View Figure 5 B-C: oc), with groove obstructed by elliptical scar. Horizontal muscle ( Figs. 5 View Figure 5 B-C: m6) connecting midline of odontophore cartilages; length ~½ of cartilage length. Fusion of main and secondary dorsal tensor muscles of radula ( Fig. 5B View Figure 5 : m5-m4) originating at anterior margin of cartilage, ventral tensor muscle of radula ( Fig. 5C View Figure 5 : m11) along insertion of retractor muscle of buccal mass ( Fig. 5B View Figure 5 : m2), both inserting respectively in subradular membrane ( Fig. 5 View Figure 5 B-C: br). Jaw muscles ( Fig. 5B View Figure 5 : mj) originating at lateral margin of cartilage, surrounding oral tube dorsally.

Radula ( Fig. 3C View Figure 3 ): With ~130 rows of isolated unicuspidate teeth (64-1-64); central tooth 25% smaller than laterals, drop-shaped with posterior apex, basal plate with long apical extensions forming acute angles; lateral teeth elliptical, 2 times as long as wide, with single, short, obtuse cusp;basal plate coniform,with an acute lateral extension.

Anterior chamber of esophagus ( Fig. 5D View Figure 5 : ae) occupying ~½ of esophagus volume, with thin, translucent wall; inner surface smooth, lacking folds. Salivary glands clustering around anterior esophagus. Middle esophagus ( Fig.5D View Figure 5 : me) with strong longitudinal muscular folds, anastomosed distally. Posterior esophagus chamber-like ( Fig. 5D View Figure 5 : po), with inner serpiginous folds increasing in number at final third, located at opening of duct to anterior lobe of digestive gland ( Fig. 5D View Figure 5 : da) alongside emersion of esophageal typhlosole ( Fig. 5D View Figure 5 : et). Stomach rounded, walls thick, muscular, internally ( Figs. 6 View Figure 6 A-B) covered by muscular folds and a bulging pyloric fold ( Fig. 6 View Figure 6 A-B: pf) parallel to minor gastric curvature; pyloric fold surrounding both esophageal gutter ( Fig. 6A View Figure 6 : sg) originating at end of esophageal typhlosole ( Fig. 6A View Figure 6 : et) and intestinal gutters ( Fig. 6A View Figure 6 : ig) originating at aperture of duct of posterior lobe of digestive gland ( Fig. 6A View Figure 6 : dp), running into intestine ( Fig. 6A View Figure 6 : in).

Inner surface of proximal intestine with large intestinal typhlosole ( Figs. 6 View Figure 6 C-D: it) and parallel folds (p1-p5); distance between folds p1 and p2 slightly wider; fold p4 ( Figs. 6 View Figure 6 C-D: p4) reaching pre-rectal valve ( Fig. 6D View Figure 6 : va), continuing as post-valve central longitudinal fold, low and wide ( Fig. 6D View Figure 6 : p6), surrounded by oblique, post-valvar compact folds ( Figs. 6 View Figure 6 D-E: p7). At final third of rectum ( Fig. 6E View Figure 6 ), fold p6 extinguishing, p7 folds becoming anastomosed into four bulging rectal folds ( Fig. 6E View Figure 6 : rf), progressing in part beyond aperture of anus ( Fig. 6E View Figure 6 : an) into inner edge of pneumostome.

Genital system: hermaphroditic duct ( Figs. 7A, B View Figure7 : hd) inserting apically into talon ( Fig. 7B View Figure7 : ta) at base of accessory glandular sac ( Fig. 7B View Figure7 : al). Carrefour ( Fig. 7B View Figure7 ) locat- ed medially in albumen gland ( Figs. 7A, B View Figure7 : ag). Albumen chamber ( Figs. 7A, B, C View Figure7 : ac) with two inner voluminous folds ( Fig. 7C View Figure7 : fa), forming groove running toward uterus. Spermoviduct ( Figs. 7A, C View Figure7 : eo, D) bearing accessory glandular groove ( Fig.7D View Figure7 :gg); uterus ( Figs.7B,D View Figure7 : ut), spermatic gutter ( Fig. 7D View Figure7 : eg) and narrow prostate ( Figs. 7B, D View Figure7 : pt) occupying ~¼ of perimeter. Free oviduct and vagina ( Figs. 7E, F View Figure7 : ol, vg) uniformly tubular, limited distally by robust free oviduct appendix ( Figs. 7A, E View Figure7 : ve), size well over half of free oviduct size. Inner muscle folds of free oviduct and vagina perpendicular and slightly directed to opening of duct of bursa copulatrix ( Fig. 7F View Figure7 : ob). Bursa copulatrix duct wide and flattened ( Figs. 7A, E View Figure7 : db); bursa copulatrix balloon-like ( Fig. 7A View Figure7 : bc), with thick muscular walls, bearing internal folds transversal to duct insertion.

Penis long and uniformly cylindrical ( Figs. 7A View Figure7 , 8A View Figure 8 : pe), same diameter as free oviduct, drawn and coiled by traction of vas deferens ( Fig. 8A View Figure 8 : dd). Inner penial folds ( Fig. 8C View Figure 8 : ip) longitudinal, with anastomoses, bearing low transverse fold near its tip ( Fig. 8C View Figure 8 : tf), not bulky or pedunculated. Epiphallus broad and short ( Figs. 8 View Figure 8 A-D: ep), ~ ⅕ of penis length, with two uniform and short flagella ( Figs. 8A View Figure 8 , C-D: fl), and two inner folds ( Fig. 8D View Figure 8 : el). Penis muscle sub-apical ( Figs. 8A, D View Figure 8 : mp).

Distribution and habitat: Megalobulimus dryades sp. nov. was initially recorded in the Vale do Ribeira region, in São Paulo state. It is found mainly in the middle and lower Rio Ribeira do Iguape Basin in southern São Paulo and northeastern Paraná states ( Fig. 9 View Figure 9 ). Apparently,

this species has a high environmental tolerance, and its range may have been expanded by humans who used its shells in handicrafts. Agudo-Padrón (2010, 2011) recorded its presence in Santa Catarina state, identified as M. gummatus (non Hidalgo).

Ecology: Sobreira & Molina (2002) studied the reproduction of M. dryades sp. nov. (referred to as M. gummatus in their study) based on three specimens from Vale do Ribeira. Egg-laying occurred in two periods, a longer one between April and May and a shorter one between September and November. Specimens laid 2 to 5 eggs per clutch, with average hatching of 52.4% after a development period of 60 days (n = 21). The mean egg size was 28.6 × 21.3 mm (n = 26).

Etymology: The comprehensive classification of the Brazilian phytogeographic regions proposed by Carl

Friedrich Philipp von Martius (1840 -1869) divided the country into phytogeographic provinces named after nymphs from Greek mythology. The name Dryades was used to designate the region roughly corresponding to the current Brazilian Atlantic Forest. This biome has been reduced to about 15% of its original territorial coverage. The Vale do Ribeira region is the largest continuous reserve of this threatened biome, thus our inspiration for the specific epithet, which is used herein as a noun in apposition.

Measurements: Holotype, L: 119 mm; W: 70 mm; H: 57 mm; S: 5.5; P: 3.5; Paratypes (n = 23; ± standard deviation) L: 118 ± 8 mm; W: 72 ± 4 mm; H: 54 ± 3 mm; S: 5.4 ± 0.2; P: 3.2 ± 0.2.

Remarks: The first shells of M. dryades sp. nov. were collected by naturalist Adolph Hempel and archaeologist Ricardo Krone (Paratype on Fig. 2 View Figure 2 E-F) in the Vale do Ribeira region in the late 19 th – early 20 th centuries, and were deposited in the Museu Paulista (currently MZSP). When Morretes (1949, 1953) published his catalog of mollusks from Brazil,he considered those samples as representatives of southern populations of M. gummatus inhabiting the states of São Paulo and Paraná.This concept was maintained in subsequent compilations ( Salgado & Coelho, 2003; Simone, 2006). Meanwhile, the concomitant erroneous use of another name, Megalobulimus chionostoma ( Mörch, 1852) , to refer to true M. gummatus specimens caused further taxonomic confusion.

Apart from the white peristome and a glossy periostracum, the shells of M. dryades sp. nov. and M. gummatus present some coincidental features such as large size, a dorsoventrally compressed outline, similar protoconch macrosculpture, and pigmented shell matrix with a white subsutural band ( Figs. 2D View Figure 2 , 10 View Figure 10 ). However, M. dryades sp. nov. differs in having a darker protoconch with a clearly marked lighter subsutural band, with a sculpture lacking any distinct spiral elements, consisting of more pronounced axial riblets that branch apically near the suture, and microscopic granules. It also has a lower spire, a body whorl with a strongly corrugated surface with malleations, a less reflected but thicker peristome with a more rounded outer lip, and a thicker, oblique, and slightly convex columella.

The soft parts of M. dryades sp. nov. are lighter-colored externally compared to M. gummatus . Internally, differences in the digestive system reside in the more robust mandible with narrow, well-marked columns, and the configuration of the radular teeth. The genital systems are also distinct, as M. dryades sp. nov. has a long and uniform penis and an epiphallus bearing two flagella. The presence of a talon and a free oviduct appendix further distinguishes it from M. gummatus , which in turn seems more closely related to species of the so-called “ M.ovatus species complex” sensu Leme (1989, 1993) due to the lack of these two last characters. Finally, both species present isolated distributions and distinct habitats (see M. gummatus , below).