Stygiopontius pectinatus Humes, 1987

Ivanenko, Viatcheslav N., Arbizu, Pedro Martínez & Stecher, Jens, 2006, Copepods of the family Dirivultidae (Siphonostomatoida) from deep­sea hydrothermal vent fields on the Mid­Atlantic Ridge at 14 ºN and 5 ºS, Zootaxa 1277, pp. 1-21 : 16-17

Stygiopontius pectinatus Humes, 1987

Material examined. 39 ΨΨ, Mid­Atlantic Ridge, Turtle Pits site, chimney “Tower”, samples 123 ROV­5 and 123 ROV­6, 4°48.6’S, 12°22.4’W, depth 2992 m, washing of alvinocaridid shrimps ( Rimicaris sp.), 11 April 2005 ( Fig. 1 B). 316 ΨΨ, 2 copepodids (stage 1), 3 nauplii (described by Ivanenko, Martínez Arbizu & Stecher, submitted), Mid­ Atlantic Ridge, Red Lion site, chimney "Shrimps Farm", sample 146 ROV­6, 4°47.82’S, 12°22.60’W, depth 3048 m, washing of alvinocaridid shrimps ( Rimicaris sp.) ( Fig. 2 A–B), 16 April 2005.

Differential diagnosis. Inner margin of claw of both antenna and maxilliped pectinate. Segment 3 of exopod of leg 4 with 3 outer spines (formula III,I,4). Segment 2 of endopod of leg 4 with short terminal spine (armature formula of the segment I,1).

Remarks. S. pectinatus is a widespread species with females reported from three hydrothermal vent fields of the MAR and one site of the Mariana Back­Arc Basin (West Pacific); males are unknown. The females were found in the branchial chambers and in washings of alvinocaridid shrimps ( Rimicaris exoculata and Chorocaris chacei ) from TAG at 26°N and Snake Pit at 23°N ( Humes 1987; Humes 1996). They were also found in plankton over Broken Spur at 29°N ( Ivanenko 1998) and in washings of tubes of the polychaete Alvinella pompejana from the Marianna Back­Arc Basin ( Humes 1990a).

Our observation of the alvinocaridid shrimps collected at 5ºS and the oral cone and the swimming legs of S. pectinatus collected on these shrimps supports the suggestion of Humes (1996) that females of this dirivultid live in the shrimps’ branchial chamber and feed on chemoautotrophic bacteria growing on the shrimp’s feeding appendages and the inner surface of branchial chamber ( Van Dover et al. 1988; Segonzac et al.1993; Gebruk et al. 2000b). It is not clear if the copepods clean the branchial chamber off fouling bacteria or utilize bacterial food of the specialized shrimps.

Figures

FIGURE 1. Mid­Atlantic Ridge: A, Logachev hydrothermal field at 14 ° N, IRINA II site, musselbed of Bathymodiolus puteoserpentis, at the southwest from the smoker­complex; B, Turtle Pits hydrothermal site at 5 ° S, active chimney “ Tower ” with alvinocaridid shrimps of different size. (Photos courtesy by MARUM © 2005, University of Bremen.)

FIGURE 2. Mid­Atlantic Ridge, Red Lion hydrothermal site at 5 ° S: A, active chimney " Shrimps Farm ", white spots = swimming shrimps; B, aggregation of alvinocaridid shrimps (Rimicaris sp.) on the chimney " Shrimps Farm ". (Photos courtesy by MARUM © 2005, University of Bremen.)