Fig. 1

Styela plicata hemocytes (a–x) and frequencies (y). a, a′, i, q Hemoblast, one of the two types of small round cell with big nucleus (see text for explanation); b, b′ j, r lymphocyte-like cell, the other small round cell with big nucleus that is generally smaller than the hemoblast (a, a′, i, q); c, c′, k, s granular amoebocyte, includes granular ameboid cells with characteristic scattered granules and an irregular membrane; d, d′, l, t univacuolar refractile granulocyte, large granular round cells; e, e′, m u univacuolar cell, vacuolated cell type with one conspicuous vacuole; f, f′, n, v compartment cell, includes vacuolated cells with 3–5 vacuoles; g, g′, o, w morula cell, vacuolated cells with numerous vacuoles; h, h′, p, x pigment Cell, includes all pigmented cell types; y relative frequencies of cell morphotypes show granular round cells as most abundant, whereas pigmented cells are least abundant; small round cells (hemoblast and lymphocyte-like cells) represent about a fifth of all cell types (n = 4 individuals, approx. 300 images analyzed). a–h Brightfield, a′–h′ DIC, (i–p) Neutral Red, (q–x) Sudan Black. Hemocyte types (shown above) are based on de Leo [22] and de Barros [36, 45], and morphotypes used to calculate frequencies in (y) and in this study are shown below in gray tags. Scale bars = 5 µm