Kirkegaardia panamaensis Blake & Dean 2019, new species

Kirkegaardia panamaensis new species

Figures 12–13

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Material examined. Caribbean Sea, Carib 1, R/V Alpha Helix , Panama, in small lagoon between leeward side of Isla Popa and Cayo Ferro, Sta. ND-30-500, 09°12.8ʹN, 82°02.7ʹW, 08 July 1977, dredged along mangrove bank, depth 1–2 m, holotype (USNM 1557526).

Description. Holotype complete, an elongate species with an inflated anterior region (Figs. 12B; 13A), narrow middle and posterior segments, and an expanded posterior end (Figs. 12C, 13B). Holotype 7.9 mm long for 90 setigers; 0.4 mm wide across inflated anterior region, middle body segments 0.3 mm wide, narrowing to 0.2 mm in posterior segments; expanded posterior end 0.3 mm wide. Pre-setiger region about 1.25 times as long as wide (Figs. 12 A–B; 13A). Anterior or thoracic region with 14 setigers, parapodia slightly elevated (Fig. 12A), dorsum similarly elevated; venter bulbous, greatly enlarged (Figs. 12B; 13B). Anterior setigers six times as wide as long; middle and posterior segments 1.5 times as wide as long, rounded in cross section; expanded posterior end 14 setigers long and 6–8 times as wide as long, convex dorsally with a wide mid-ventral groove or channel (Figs. 12C; 13C). Color in alcohol light tan.

Prostomium conical with rounded tip, eyespots absent, nuchal organs not observed (Figs. 12 A–B, 13A). Peristomium nearly square, with three subequal annulations (Fig. 12 A–B). Dorsal tentacles at posterior border of third peristomial annulation (Fig. 12 A–B). First pair of branchiae posterior-lateral to dorsal tentacles on anterior border of setiger 1; second pair of branchiae also on setiger 1, dorsal to notosetae (Fig. 12 A–B); branchiae on subsequent segments also dorsal to notosetae; branchiae long, filamentous (Fig. 13A), not observed on middle or posterior segments.

Parapodia low mounds; anterior notopodia with 4–6 blade-like capillaries, with fine denticles visible on shorter capillaries at about setiger 9; abdominal setigers with 5–6 notosetae with more robust denticles at setiger 27, reduced to three notosetae posteriorly until widened posterior region usually with two notosetae. Thoracic neuropodia with 4–6 flattened capillaries with fine denticles visible from about setiger 5, abdominal setigers usually with five neurosetae, robust denticles also becoming visible at about setiger 27, neurosetae reduced gradually to three denticulated capillaries in posterior setigers including widened posterior end (Fig. 12D), reduced to a single neuroseta adjacent to 5–6 segmented asetigerous pre-pygidial region; notosetae slightly longer than neurosetae.

Expanded posterior end with deep ventral groove or channel (Figs. 12C; 13B); pygidium simple rounded lobe ventral to anal opening.

Methyl Green stain. No pattern, de-stains rapidly; stain retained longest in expanded thoracic segments, but not concentrated on venter as in related species.

Remarks. Superficially, Kirkegaardia panamaensis n. sp., with an inflated anterior region, elongate narrow middle segments and an inflated posterior end superficially resembles Aphelochaeta monilaris Hartman, 1960. However, the presence of denticulated capillaries clearly defines the species as belonging to Kirkegaardia. Among known species of Kirkegaardia that have expanded anterior and posterior ends, K. panamaensis n. sp. is most similar to K. baptisteae Blake, 1991 from the U.S. Atlantic continental shelf and K. dutchae Blake, 2016 from the Puget Sound, U.S. Pacific coast, in that all have expanded anterior and posterior ends, a ventral groove or channel on the posterior end, and lack dorsal thoracic channels or grooves.

Of the two, K. dutchae shows the greatest similarity to K. panamaensis n. sp. in that both species have the first and second pair of branchiae on setiger 1. The two species differ in that denticulated capillaries are lacking in notopodia of K. dutchae and are present in K. panamaensis n. sp. Further, the anterior and posterior ends of K. panamaensis n. sp. are conspicuously more expanded than in K. dutchae. In addition, MG stain is prominently retained on ventral thoracic glands in K. dutchae and such glands and MG staining reaction are not present in K. panamaensis n. sp.

Etymology. This species is named for the collection site in Panama.

Distribution. Panama, subtidal at 1–2 m along a mangrove bank in a small lagoon between the leeward side of Isla Popa and Cayo Ferro.