Placobdella columbiensis

External morphology

The dimensions of the holotype, in mm, are as follows: total length 17, length to the male gonopore 4.8, maximum width 6.4, width at the level of the male gonopore 4.8, capsule length [missing], capsule width 1.4, cotyle diameter 3.4. The body is flattened, with a maximum width in the abdominal region equal to 35% of the total length. The capsule is not prominent and is formed by somites I through IV; the mouth opens at the level of I a1/a2—that is, at the anterior lip. The cotyle is of moderate size; its diameter is slightly greater than half the maximum body width. Somites I and II are poorly separated; somite III is 2-annulate—although the furrow (a1 a2)/a3 is faint—and bears one pair of eyes on the anterior annulus; somite IV appears 2-annulate, and on its ventral aspect, its fused annuli form the posterior lip of the capsule. From metamere V to XXIII, the somites are complete on both dorsal and ventral aspects and are of uniform development. On the dorsal aspect, they conform to the formula (a1 a2) > a3 (where a1+a2 is one-third larger than a3), and on the ventral aspect, to the formula (a1 + a2) > a3 (where a1+a2 is one-third larger than a3). In other words, each segment is composed of a single, larger anterior annulus which, on its ventral face, exhibits a secondary furrow separating a1 from a2. Sensillae are not visible in superficial view. The dorsum is tuberculate. On each ring (a1 + a2)—commencing from somite VI—one observes a large median tubercle, two smaller inner lateral tubercles, and two even smaller outer lateral tubercles; several accompanying minute tubercles are arranged in two transverse rows, situated medial to the five principal tubercles and aligned with their posterior margins. On each ring a3, there exists a transverse row of tubercles—approximately twice the size of the minute tubercles on the preceding ring—among which two paramedian tubercles are particularly prominent. This arrangement results in a distribution of main tubercles across 7 longitudinal rows: 1 median row (at a1–a2), 2 paramedian rows (at a3), 2 inner lateral rows, and 2 outer lateral rows (at a1–a2). Ventrally, the annuli are smooth. The rim of the acetabulum is covered with small warts. The male gonopore is located at XI/XII, while the female gonopore opens at XII (at a1–a2). Upon clearing the paratype, the presence of 7 lateral pairs of crop diverticula is confirmed; these exhibit secondary lobulations, with the first pair located in segment XIII and the seventh pair—which follows a descending course—located in segment XIX. The coloration is yellowish-brown; the tubercles are light yellow. A median stripe of this same hue extends from the anterior somites (I through III)—staining the tubercles entirely—as far back as segment X. The background coloration is a pale chestnut-brown, stippled with minute blackish dots that are, in fact, merely contracted chromatophores. It is presumed that, in life, this coloration would have been darker.

Habitat & range

Habitat

Freshwater

Region

South America

Recorded from

Colombia