Isocirrus tropicus (Monro, 1906)

Yanez-Rivera, Beatriz, Tovar-Hernandez, Maria Ana, Galvan-Villa, Cristian Moises & Rios-Jara, Eduardo, 2020, Tubicolous polychaete worms (Annelida) from Bahia de Chamela Islands Sanctuary, Mexico, with the description of a new bamboo worm, Biodiversity Data Journal 8, pp. 57572-57572 : 57572

Isocirrus tropicus (Monro, 1906)

Clymene tropica Monro, 1906 in Monro 1928: 97-98, figs. 17-18.

Isocirrus tropicus .- Salazar-Vallejo 1991: 275 (syntype re-description and relocation).

Euclymene tropica .- Salazar-Vallejo and Díaz-Díaz 2009: 305 (Key).

Materials

Type status: Other material. Occurrence: catalogNumber: LEMA-PO154 ; recordedBy: Beatriz Yáñez-Rivera; individualCount: 4; Taxon: phylum: Annelida; class: Polychaeta; family: Maldanidae; genus: Isocirrus; Location: higherGeographyID: Pacific Ocean; higherGeography: Tropical Eastern Pacific; continent: America; islandGroup: Islas de Chamela; island: Isla Pajarera; country: México; countryCode: MX; stateProvince: Jalisco; municipality: La Huerta; maximumDepthInMeters: 4; verbatimLatitude: 19°33 ’22’’ N; verbatimLongitude: 105°06 ’50’’ W; Identification: identifiedBy: María Ana Tovar-Hernández; Event: samplingProtocol: Scuba dive; eventDate: June 25, 2013; year: 2013; month: 6; day: 25; habitat: On coral; fieldNumber: Site 21; Record Level: language: Spanish; institutionID: Universidad de Guadalajara; collectionID: Colección Biológica del Laboratorio de Ecosistemas Marinos y Acuicultura, Universidad de Guadalajara, México; institutionCode: UDG; collectionCode: LEMA

Description

Incomplete worms 6-36 mm long, 0.5-1.4 mm wide and +12 segments. Cephalic plaque oval with lateral margins notched (Fig. 4 A), basal margin with eight shallow crenulations (Fig. 4 B, E); digitiform palpod in lateral view (Fig. 4 C); nuchal organs straight, parallel, almost full length of plaque. No ocelli, no segmental collars. First segments with acicular spines. Following chaetigers with manubriavicular uncini with three teeth above the main fang with subrostral bristles (hairs or barbules) (Fig. 4 F). Ventral mid-line ridge prominent, from segment 7 to end of body (Fig. 4 H). One pre-anal achaetous segment with tori. Anal funnel present (Fig. 4 D) with 26 distinct alternating triangular cirri: 3-4 long alternated with one short, the longest are 2-3 times the length of short ones (Fig. 4 G). Anus terminal (Fig. 4 G).

Taxon discussion

Originally described from Taboga (Pacific coast of Panama) to 7-9 m depth in sand at low tide ( Monro 1928). It was re-described and transferred to Isocirrus by Salazar-Vallejo (1991), based on the presence of acicular spines on chaetigers 1-3 and the presence of anal cirri of similar length. According to Salazar-Vallejo (pers. comm. 2020), the inclusion of Euclymene tropica in their key was a mistake ( Salazar-Vallejo and Díaz-Díaz 2009); it must be included within Isocirrus , but having subequal anal cirri.

Figures

Figure 4. Isocirrus tropicus (Monro, 1928). A) Body, anterior part, lateral view, B) cephalic plaque and first two chaetigers, lateral view, C) everted proboscis, D) anal funnel, lateral view, E) dorsal margin of cephalic plaque, F) manubriavicular uncini from 5 th chaetiger, G) anal plaque, posterior view, H) mid-ventral whitish ridge starting in chaetiger 7. Scale bars: A) 3 mm, B) 2 mm, C) 1 mm, D) 1.3 mm, E) 1.8 mm, F) 400 x magnification, G) 0.5 mm, H) 1.5 mm. Arrows in A pointed to lateral notches of cephalic plaque. In B, arrows pointed to crenulated margin of cephalic plaque.