Bathycadulus Shell Morphometrics

Scarabino, Victor, Caetano, Carlos Henrique Soares & Carranza, Alvar, 2011, Three new species of the deep-water genus Bathycadulus (Mollusca, Scaphopoda, Gadilidae), Zootaxa 3096, pp. 59-63 : 62-63

Bathycadulus Shell Morphometrics

Table 1 lists the mean, standard deviation, minimum and maximum values for each morphometric parameter for the four species. The Discriminant Function Analysis was able to distinguish between the four species of Bathycadulus (Wilks’ Lambda = 0.00033; F33,92 = 39.37; p <0.01). This analysis correctly classifies 100% of specimens ( Fig 13 B) and the model was constructed with five variables (L, Wa, Wol, Wal and Wl). The Discriminant Functions (DF) based on the raw coefficients of canonical variables are shown below:

The variance explained was of 0.75 for the DF1, 0.17 for the DF2 and 0.08 for the DF3. Figure 13 B plots DF1 vs. DF2, with a robust distinction between the four studied species being obtained. The axis defined by DF1 split the species in three groups: (1) B. segonzaci has strongly positive values (between 6 and 10); (2) B. fabrizioi has strongly negative values (between –5 and –9) and (3) B. queirosi and B. hendersoni have intermediate values, distributed around low positive and negative values (between 0 and 1). Bathycadulus fabrizioi represents an extreme form for the genus, evidenced by the high degree of curvature of the shell, while B. segonzaci shows the opposite pattern. Shell length is the most important variable in the distinction of species along the axis defined by DF1.

MANCOVA of morphometric measures with shell length held constant (L treated as covariate) showed highly significant shape differences between species (Wilks’ Lambda = 0.007, F42, 80.86 = 8.100, p <0.0001).

B. fabrizioi B. hendersoni B. queirosi B. segonzaci

(n = 11) (n = 04) (n = 14) (n = 16)

Figures

FIGURE 13. (A) Schematic representation of a Bathycadulus shell and morphometrical measurements; (B) Discriminant function analysis of shell parameters.