Caulleriella convexacapa Blake & Dean 2019, new species

Caulleriella convexacapa new species

Figure 4

urn: lsid: zoobank.org: act: B07703A2-5183-40AB-B807-329E864BF45D

Material examined. Caribbean Sea, Honduras, Isla de Utila, Carib 1, R/V Alpha Helix, Sta. MS-47-500, 16°4.5ʹN, 87°59.2ʹW, 14 July 1977, intertidal, meiobenthic sled, depth 10–20 cm, sand and grass bed 15 m off southwestern shore of island holotype (USNM 1557500) and 1 paratype (USNM 1557502).— Panama, Carib 1, R/V Alpha Helix, Sta. ND-31-500, 09°12.8ʹN, 82°02.8ʹW, 08 July 1977, subtidal, dredged, depth 4 m, in sand and grass around Deer Island, off Peninsula Valiente, between Crawl Cay and Canal de Tigre, outside Laguna Chiriqui, paratype (USNM 1557501); Sta. 23-333-149, 09°34.6ʹN, 78°43.2ʹW, 30 June 1977, bottom plankton sample, 15 m from mangrove shore, Caobos Cay, in Hollandes Cays group between Mayflower Channel and Caribbean Sea, 0–4 m, paratype (USNM 1557503).— Panama 69 Project, off Colón, Sta. 69-26, 09°24.4′N, 79°52′W, 24 May 1969, 0–3 m, 1 specimen (USNM 1557504).

Description. Holotype complete, 2.0 mm long for 51 setigers, thorax 0.2 mm wide; paratypes 1.9–3.9 mm long for 39–68 setigers, thoracic width 0.2–0.3 mm. Anterior or thoracic segments narrow, crowded, numbering 16 setigers in holotype, 12–19 setigers in paratypes; notopodia and neuropodia widely separated. Notopodia of thoracic segments extending slightly above dorsum. Color in alcohol pale tan.

Pre-setiger region about as long as wide (Fig. 4 A–B). Prostomium conical, rounded on anterior margin, eyespots absent, with a pair of faint pigmented nuchal organs on posterior lateral margin also visible dorsally on peristomium. Peristomium as long as wide, biannulate with first annulation longest; with large dome-shaped dorsal crest extending posteriorly to mid-dorsal surface of setiger 2 (Fig. 4 A–B). Dorsal tentacles arise at posterior border of peristomium on either side of dorsal crest. First pair of branchiae lateral to dorsal tentacles on setiger 1, dorsal to notosetae (Fig. 4 A–B), following branchiae in same location; individual branchia long and thin.

Anterior notosetae simple capillaries with 2–3 setae per fascicle. First notopodial bidentate hooks from setiger 12 in holotype, 9–13 in paratypes; hooks accompanied by capillaries. Three to five hooks in mid-body accompanied by a single capillary (occasionally 2), grading to 4–7 hooks without accompanying capillaries in posterior region. Five to eight bidentate hooks present in all neuropodia from setiger 1; neuropodial hooks occasionally accompanied by a single capillary (2 in one setiger). Bidentate hooks with a small apical tooth above the main fang (Fig. 4D); hood absent.

Pygidium a simple rounded lobe (Fig. 4C).

Methyl Green stain. No pattern. Body stains uniformly green except prostomium and far posterior segments; pygidium not staining.

Remarks. Caulleriella convexacapa n. sp. is similar to C. mediterranea Lezzi, 2017 from the Italian coast of the Mediterranean in that both species have neuropodial hooks from setiger 1 and a similar range for the start of notopodial hooks. Both species also have a biannulate peristomium and dorsal tentacles that arise on the posterior peristomium lateral to the first branchiae on setiger 1. C. convexicapa n. sp., however, has a large dorsal peristomial crest that extends posteriorly onto setigers 1–2; no dorsal crest is reported for C. mediterranea. In addition, the bidentate hooks of C. mediterranea have a crest or hood on the convex side of the shaft; there is no crest or hood present on the bidentate hooks of C. convexicapa. n. sp.

Caulleriella convexacapa n. sp. is also similar to C. suroestense Blake, 2018 from the Juan Fernandez Islands off the Chilean coast in having a biannulate peristomium with a dorsal crest and the first branchiae arising dorsal to the notosetae on setiger 1 but capillaries are present in posterior notopodia in C. suroestense and absent in C. convexacapa n. sp. In addition, the notopodial hooks begin on setigers 27–28 in C. suroestense and on setiger 12 (9–13) in C. convexacapa n. sp. Furthermore, the apical tooth of the bidentate hooks of C. suroestense is closely applied to the shaft instead of the more typical erect apical tooth as in C. convexacapa n. sp.

Etymology. The epithet is from the Latin convexus for protuberant and caput for head, in reference to the rounded elevated dorsal crest on the peristomium that continues over the dorsal surface between the first two setigers.

Distribution. Honduras, from shallow (10–20 cm) sand and seagrass beds off Isla de Utila.