Idanthyrsus mexicanus Kirtley, 1994

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

Idanthyrsus mexicanus Kirtley, 1994

Idanthyrsus mexicanus in Kirtley 1994: 105-106, fig. 6.12.

Materials

Type status: Other material. Occurrence: catalogNumber: LEMA-PO158 ; recordedBy: Beatriz Yáñez-Rivera; individualCount: 6; Taxon: phylum: Annelida; class: Polychaeta; order: Sabellida; family: Sabellariidae; genus: Idanthyrsus; 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: 7; verbatimLatitude: 19°33 ’22’’ N; verbatimLongitude: 105°06 ’50’’ W; Identification: identifiedBy: María Ana Tovar-Hernández; Event: samplingProtocol: Scuba dive; eventDate: June 26, 2013; year: 2013; month: 6; day: 26; habitat: On rock-coral; fieldNumber: Site 21; Record Level: language: Spanish; institutionID: Universidad de Guadalajara; collectionID: Colección Biológica del Laboratorio de Ecosistemas Marinos y Acuicultura; institutionCode: UDG; collectionCode: LEMA

Description

Gregarious worms commonly known as "honey comb worms". Tubes constructed with sea shells fragments, echinoderm spines debris, sand and small gravel (as well as I. cretus ). Complete specimens 8-11.1 mm long, 1-2 mm wide, with 27-30 abdominal chaetigers and a caudal peduncle 2-3 mm long. Body divided into four specialised regions: operculum, parathorax (with three segments), abdomen and caudal region (Fig. 7 A). Operculum composed by a crown and a peduncle, forming two not fused lobes. Median organ short, not longer than opercular lobes. Outer palea with straight blades; base of blades with transversal thecal fringes (Fig. 7 E), lateral denticles straight (Fig. 7 F), longer and narrower towards tips (Fig. 7 G). Inner paleae straight with markedly, transversal thecae and pointed tips (Fig. 7 H-J). A pair of nuchal hooks curved (Fig. 7 B) without hoods or limbations on concave sides of hooks (Fig. 7 C). Abdominal uncini with six pairs of teeth in side view (Fig. 7 D).

Distribution

This constitutes the fist record since its establishment by Kirtley (1994).

Taxon discussion

This species was described from Bahía Tenacatita, west of the islets off Barra de Navidad, between 45.7 and 64 m depth. A second species from Western Mexico is Idanthyrsus armatopsis Fauchald, 1972 Fauchald (1972) described from bathyal depths (1200 -1400 m) in the Gulf of California. Idanthyrsus mexicanus and I. armatopsis shares the presence of nuchal hooks without hoods, but the inner paleae in I. mexicanus have pointed tips versus blunt tips in I. armatopsis. Number of teeth of abdominal uncini was not described by Kirtley (1994) to I. mexicanus , but specimens here reported from Chamela Bay have six teeth in side view versus 7-8 teeth in I. armatopsis . The median organ in I. mexicanus (not described in original description by Kirtley 1994) is short, extending only 1/4 above lateral opercular lobes, whereas in I. armatopsis , this organ extends 1/2 above lateral opercular lobes.

Figures

Figure 7. Idanthyrsus mexicanus Kirtley, 1994. A) Entire body, dorso-lateral view, B) operculum, dorsal view, C) nuchal hook, D) abdominal uncini, lateral view, E) base of outer opercular palea, F) mid-region of a outer opercular paleae, G) near distal end of outer opercular palea, H-J) inner opercular paleae. Scale bars: A) 3 mm, B) 1.5 mm, C, J) 400 x magnification, D-I) 1000 x magnification.