A new species of the genus Polyschides Pilsbry & Sharp, 1898 (Mollusca, Scaphopoda, Gadilidae) from Brazilian waters
Caetano, Carlos Henrique Soares
Absalão, Ricardo Silva
Zootaxa
2005
871
1
10
6W763
[264,506,1276,1302]
Scaphopoda
Gadilidae
Polyschides
Animalia
Gadilida
2
3
Mollusca
species
xavante
sp. nov.
Description: Shell small, slender, moderately curved, strong and white. The increase in diameter of the shell is very slight and there is no conspicuous swelling; the greatest diameter is located near the anterior aperture. Apical shell aperture nearly circular, cut by four deep notches, forming four triangular lobes: lobe on convex side slightly longer, lobe on concave side truncated, and two lateral lobes. The external surface, appearing smooth under optical microscope, is papillated at higher magnifications. Anterior aperture subcircular, slightly depressed and oblique. Dimensions (range in mm): L 4.89–6.00; Max 0.58–0.84; Dmax 0.37–2.00; Arc 0.21– 0.42; Larc 1.32–2.32; Ha 0.47–0.58; Wa 0.47–0.68; Hp 0.26–0.42; Wp 0.32–0.47. Typematerial: Holotype: IBUFRJ 14.190; Paratypes: MCZ 350337 [5]; MNRJ 10.313 [6]; UERJ 3.045 [6]; MORG 41.075 [6]; MZUSP 43.518 [5], all paratypesfrom typelocality. Typelocality: Sancho Bay ( 03º51'S, 32º26'W), Fernando de Noronha Island, Pernambuco State, northeastern Brazil, 10– 15 m. Known distribution: Western Atlantic; Colombia( Diaz & Puyana 1994) and Fernando de Noronha Island, Brazil. But, possibly, occurring over all north coast of South America. Shallow water species, 0 to 15 m. Etymology: xavanteis the name of an Indian tribe in Brazil. Proposed as a noun in apposition. FIGURES 1–14.(1–4) Polyschides xavante new species, Holotype IBUFRJ 14.190 (5.4mm); (5–8) Polyschides tetraschistus, IBUFRJ 2.552 (8.4mm); (9–13) Polyschides portoricensis, (9) Holotype USNM 314.712 (7.0mm), (10–13) IBUFRJ 13.940 (7.8mm); (14) Polyschides tetrodon, Syntype ANSP 71.070 (5.6mm). Scale bars = 1mm (Figs 3, 7 and 12) and 10 m (Figs 4, 8 and 13). Remarks: Polyschides tetraschistus( Figs. 5–8) is the most similar species to P. xavantein the western Atlantic. Polyschides xavantehas a smaller and more slender shell than P. tetraschistus. Polyschides portoricensis( Figs. 9–13) is easily distinguishable from the former two species by the obvious swelling at the anterior third of the shell. Examination of the external shell surface under high magnification showed that P. xavanteand P. tetraschistusshare a microsculpture formed by papillae, higher and at least in some areas arranged in circular rings over the entire shell in P. xavante( Fig. 4), and smaller and homogeneously distributed in P. tetraschistus( Fig. 8). Polyschides portoricensishas no such microsculpture ( Fig. 13). Comparisons of shell measurements corroborated the distinctions among these species. Table 2lists the mean, standard deviation, minimum and maximum values for each morphometric parameter. All morphometrics parameters differed significantly (Kruskal Wallistest; p<0.001) at least between two of the three species. Polyschides xavanteis significantly different from the other two species in 10 out of 15 parameters ( Table 2). This species is significantly smaller and less arched than P. tetraschistusand P. portoricensis. The maximum diameter, height and width of the anterior aperture, and height and width of the apical aperture were also significantly smaller compared to the other species. The maximum diameter in P. xavanteand P. tetraschistusis located closer to the aperture than in P. portoricensis. TABLE 1. List of the material examined during this study. Reg. number Locality Depth (m) N Polyschides portoricensis USNM 314.712 (holotype) Mayaguez Harbor, Puerto Rico 45 1 IBUFRJ 13.940 Amasseds #4134, off Amapá (02º 21' N, 48º 29' W) 72 30 CMPHRM 1.706 Geomar II #129 (02º 53' 00'' N, 48º 17' 00'' W) 111 3 CMPHRM 1.707 Geomar II #2413 (04º 18' 48'' N, 50º 17' 06'' W) 89 6 UERJ 3.043 off Salinópolis, Pará 27 1 MORG 34.743 Maceió, Alagoas 52 MORG 32.072 Ilha de Itaparica, Bahia intertidal 20 IBUFRJ 14.189 Revizee Central I #VV16 (21º 10' S, 40º 27' W) 28 1 Polyschides tetraschistus CRPC 1.482 Abaco, Bahamas( 26º 00' 00" N, 77º 24' 28" W) 6 CRPC 9.042 Abaco, Bahamas( 26º 44' 30" N, 77º 12' 30" W) 23 6 MZUSP 25.769 off Pará ( 00º 02' N, 45º 48' W) 75 1 CMPHRM 1.702 Geomar III #149 ( 01º 55' 30'' N, 47º 41' 00'' W) 57 10 ...... continued on the next pageThe multivariate Discriminant Function Analysis was able to distinguish between the three species (Wilks' Lambda = 0.02; F14,194 = 71.16; p<0.0000). This analysis classifies 100% of the cases correctly ( Fig. 15). The model was constructed with seven parameters (L, Max, L: Max, Wa, Ha: Wa, WI, Larc: L). The variables Ha and Dmax, which were highly correlated with other variables (Ha vs. Max, r= 0.91; Ha vs. Wa, r= 0.93; Dmax vs. LI, r= 0.94), were excluded. The Discriminant Functions (DF) based on the raw coefficients of canonical variables are shown below: TABLE 1continued Reg. number Locality Depth (m) N MZUSP 18.742 off Amapá (04º 29' N, 50º 12' W) 103 2 CMPHRM 1.707 Geomar II #2413 (04º 18' 48'' N, 50º 17' 06'' W) 89 3 MORG 21.762 Foz do Amazonas 80 9 MORG 20.480 off Goiabal, Amapá 100 2 MORG 34.744 off Ilha do Rosário, Maranhão 28 22 MORG 21.728 off Pará 55 6 DOUFPE 4.492 Bacia Potiguar, Sergipe 2 MORG 24.621 Fernando de Noronha, Pernambuco 40 1 MORG 23.800 Abrolhos, Bahia 2 MORG 27.672 Salvador, Bahia intertidal 4 MORG 40.456 Revizee Central #VV31 (18º52’S / 39º35’W) 23 8 MORG 25.578 Ilha de Trindade, Espírito Santo 2 UERJ 3.042 Geomar XVI #5 (21º 53' S, 40º 22' W) 55 10 UERJ 3.044 Geomar XVI #1 (21º 35' 90" S, 40º 20' 50" W) 43 2 UERJ 3.041 Geomar XVI #9 (22º 06' 80" S, 40º 31' 20" W) 59 2 UERJ 3.040 Geomar XVI #140 (22º 42' S, 41º 13' W) 64 4 IBUFRJ 7.066 Cabo Frio VII #6165 (22º02' S, 42º46' W) 56 1 IBUFRJ 2.394 Cabo Frio VII #6165 (22º02' S, 42º46' W) 56 3 IBUFRJ 2.393 Cabo Frio VII #6147 (22º53' S, 41º50' W) 50 4 IBUFRJ 2.395 Cabo Frio VII #6199 (23º17' S, 44º15' W) 48 8 IBUFRJ 1.447 Geocosta Rio I #52 (23º40' S, 43º57' W) 101 1 IBUFRJ 2.552 Arraial do Cabo, Rio de Janeiro intertidal 1 MORG 28.614 off Bacia de Campos, Rio de Janeiro 60 2 MORG 23.060 off Rio Grande, Rio Grande do Sul 26 9 MORG 22.892 off Rio Grande, Rio Grande do Sul 30 45 MORG 22.946 off Rio Grande, Rio Grande do Sul 50 78 MORG 27.029 Parcel do Carpinteiro, Rio Grande do Sul 2 MORG 20.066 off La Paloma, Uruguay 40 6 Polyschides tetrodon ANSP 71.070 (syntypes) off Cape Florida 155 5 CRPC 1.653 Abaco, Bahamas (26º 00' 00" N, 77º 24' 28" W) 3 DF1 = 5.25487 L+ 0.76610 Max 4.35310 L: Max 5.88253 Wa 1.98005 Ha: Wa+ 3.23778 WI+ 0.57313 Larc: LDF2 = 2.84063 L+ 6.55201 Max+ 2.28387 L: Max 2.56450 Wa+ 0.30526 Ha: Wa 0.25672 WI 0.19054 Larc: L P. xavante(n=29) P. portoricensis(n= 27) P. tetraschistus(n= 50) KW Dunn’s test TABLE 2.Shell morphometric parameters with minima (min), maxima (max), mean values and standard deviation (SD) for Polyschides xavante n. sp.(xa), P. portoricensis(po) and P. tetraschistus(te). L, length; Max, maximum diameter; Dmax, distance of point of maximum diameter from anterior aperture; Arc, maximum curvature; Larc, distance of point of maximum curvature from the apex; Ha, anterior aperture height; Wa, anterior aperture width; Hp, apical aperture height; Wp, apical aperture width; LI and WI are the Shimek´s indices. All parameters were significantly different between species (KruskalWallis test; p<0.001), the horizontal lines represents absence of statistical differences. mean (SD) min max mean (SD) min max mean (SD) min max L 5.47 (0.30) 4.89–6.00 7.39 (0.52) 6.16–8.63 6.84 (1.60) 4.29–9.25 25.32 Max L: Max Dmax Arc 0.71 (0.06) 7.79 (0.59) 0.93 (0.39) 0.31 (0.06) 0.58–0.84 6.92–9.18 0.37–2.00 0.21–0.42 1.28 (0.09) 5.78 (0.41) 2.13 (0.32) 0.40 (0.07) 1.05–1.53 4.93–6.56 1.53–2.74 0.26–0.58 1.04 (0.25) 6.57 (0.68) 1.08 (0.29) 0.36 (0.09) 0.48–1.44 5.22–8.96 0.46–1.88 0.19–0.58 59.36 68.57 60.24 17.27 Larc 1.78 (0.29) 1.32–2.32 2.67 (0.39) 2.16–3.74 2.71 (0.57) 1.65–3.71 49.96 Larc: L 0.32 (0.04) 0.24–0.42 0.36 (0.06) 0.24–0.42 0.40 (0.05) 0.31–0.51 35.07 Ha 0.51 (0.04) 0.47–0.58 0.82 (0.05) 0.68–0.92 0.79 (0.17) 0.56–1.13 57.55 Wa 0.55 (0.04) 0.47–0.68 0.78 (0.05) 0.65–0.89 0.87 (0.19) 0.60–1.21 62.11 Ha: Wa Hp 0.93 (0.08) 0.35 (0.04) 0.82–1.11 0.26–0.42 1.04 (0.06) 0.49 (0.05) 0.88–1.14 0.42–0.63 0.90 (0.04) 0.48 (0.09) 0.79–1.05 0.33–0.67 42.57 50.43 Wp 0.36 (0.03) 0.32–0.47 0.54 (0.04) 0.42–0.63 0.58 (0.09) 0.38–0.71 56.55 Hp: Wp 0.95 (0.07) 0.83–1.06 0.90 (0.06) 0.82–1.09 0.90 (0.12) 0.13–1.00 11.09 LI 0.37 (0.11) 0.20–0.61 0.57 (0.05) 0.48–0.66 0.38 (0.06) 0.25–0.52 52.88 WI 0.78 (0.07) 0.70–0.93 0.72 (0.05) 0.66–0.81 0.82 (0.06) 0.68–1.14 37.83 Revision of the Brazilian material revealed the occurrence of three species of Polyschidesalong the coast: P. tetraschistus, P. portoricensisand P. xavante. Henderson (1920: 116)based his description of P. portoricensison a single specimen collected in Mayaguez Harbor, Puerto Rico, and stated "Some uncertainty attaches to the apical features, which I hope may be removed by receipt of better material." Our material has deeper notches than reported by Henderson. Although Henderson´s description did not mention the presence of a pleat on the inner surface of the apex ventral lobe ( Fig. 12), such differences may be related to the state of conservation of the typematerial. Diaz and Puyana (1994: fig. 1049) also illustrated such a pleat in P. portoricensis.This species was previously recorded in the Caribbean Sea ( Puerto Rico: Henderson 1920; Warmke & Abbott 1962) and north Brazil(off Amapá: Rios 1994). The new material examined here extends its geographical distribution southward, to the state of Rio de Janeiro (21º S). Polyschides tetrodonwas not included in the morphometrical analysis, because there are no valid reports of this species from Brazil. Examination of the typeillustration ( Fig. 14) shows that it may be close to P. portoricensis, since both species share a swelling in the shell. Polyschides tetrodonhas a more fusiform shell and shorter shell length (ca. 5 mm). The shell showed by Diaz and Puyana (1994: 258, pl. 71, fig. 1050) as P. tetrodonis, in fact, P. x a v a n t e.