Figure 1.

Basal sperm motility parameters in five bivalve species, DUI and SMI, without chemoattractants. (a) Average path velocity (µm s⁻¹). (b) Straight-line velocity (µm s⁻¹). (c) Curvilinear velocity (µm s⁻¹). (d) First principal component of the PCA combining sperm velocity parameters. (e) Second principal component of the PCA. Data are presented as means ± s.e.m. Differences (p ≤ 0.05) in a post hoc Tukey's test are indicated by different letters. DUI species: My. edulis (My. ed, n = 11), R. philippinarum (R. ph, n = 9). SMI species: Me. mercenaria (Me. me, n = 9), N. obscurata (N. ob, n = 5), P. magellanicus (P. mg, n = 11). A detailed summary is reported in the electronic supplementary material, tables S2 and S3. (Online version in colour.)