Oithona fonsecae Ferrari & Bowman 1980

Oithona fonsecae

MATERIAL.—5 from PN-11-60, 31 and 37 from PN-23-60, 1 from PN-43-200, and 8 from PN-70-200.

FEMALE.—Length range 0.49–0.60 mm; Pr/ Ur-1.4. Head rounded in dorsal and lateral views (Figure 6a, b). Pg4 with tiny hairs along posterolateral border. Url (Figure 6d) dorsal surface with 2 long central hairs followed by a long transverse row of smaller hairs, roughly U-shaped; posterior and lateral to this row, 2 rows separated by a gap at midwidth. CR length 3 times width. B2Md (Figure 6f) with 2 thick, slightly curved spines bearing small spinules; Re 5-segmented with 5 setae; Ri with 5 setae, lateralmost plumose; 1 small setae arising near base of Ri. RiMx1 (Figure 6g) with 3 setae, 1 arising near base; B2Mx1 with 3 spines, 2 with long marginal spinules. Se ReP1–4: 1–1–3, 1–1–3, 1–1–3, 1–1–2; Re1P1 with 1 Si. Ri2P4 proximal seta slender, without flange; distal seta much thicker, slightly curved with well-developed flange on distal ; Ri3P4 proximal seta longer and thinner than distal setae of Ri2, curvature less pronounced, flange on distal ¼. P5 with small seta near base. Knob near genital opening with spine curved dorsally, ventral to this a second smaller spine (Figure 6c).

MALE.—Length range 0.49–0.51 mm; Pr/Ur-1.5. Head slightly more truncate than female in dorsal view, laterally rounded; rostrum absent. Flap of Cph tongue-shaped, reaching slightly beyond Pg1. Pore signature (Figure 6k) similar to that of O. hebes; anterodorsal cluster of 2 oblique columns; followed posteriorly by long horizontal row; ventral to horizontal row, 11 columns, the last on Cph flap. Ventrally each column continues anteriorly as a horizontal series of organs; the first 2 columns appear continuous through a horizontal series. In addition to 11th (last) column, Cph flap has several peripheral organs and 2 smaller oblique rows extending from dorsal edge of flap. CR length 2 times width. B2Md (Figure 6n) with 2 spines; much thinner than on female, 1 naked, other ornamented with thicker, longer spinules than in female. Remaining aspects of Md and Mx1 similar to female, although slightly reduced. Armature of P1–4 as in female except Si Ri2 and 3P4 not modified. P5 with reduced seta at base. Genital flap with 1 long plumose seta and reduced seta ventral to it.

MATERIAL.—Female holotype (USNM 172186), 27 and 31 paratypes (USNM 172187, 172188) from PN-23-60, 09°34.6′N, 78° 59.5′W, in small lagoon of Caobos Cay in Hollandes Cay Group, between Mayflower Channel and Caribbean Sea, Panama, 30 Jun 1977.