Hydroides sp.

Tovar-Hernández, María Ana, León-González, Jesús Angel De & Hendrickx, Michel E., 2025, Polychaeta collected during the research cruises TALUD aboard the R / V “ El Puma ” in the Mexican Pacific: Sabellidae and Serpulidae, Zootaxa 5663 (1), pp. 1-80 : 69

Hydroides sp.

( Fig. 38 )

Material examined. ICML-EMU-14052: TALUD XVI, St. 1, BC, 28º28'18"N 115º45'12"W, 23 May 2014, 2,077 m, 1 specimen .

Description of material examined. Body 4 mm long, 0.8 mm wide. Branchial lobes arranged in semi-circles, with 10 radioles on left lobe, 11 on right lobe. Radioles 3.5 mm long. Filamentous tips bare ( Fig. 38C ). Peduncle cylindrical, smooth, separated from opercular funnel by a constriction ( Fig. 38B ). Peduncle plus operculum 4.1 mm long. Operculum placed on the left side. Pseudoperculum absent. Opercular diameter 0.6 mm. Funnel 0.5 mm long, with 22 radii with rounded tips ( Fig. 38C–D ). Funnel not chitinised. Verticil with 15 amber-coloured spines. Verticil spines fused basally firing a shallow cup. All spines similar in shape and size ( Fig. 38B–E ). Tip of spines blunt, pointing inwards verticil centre ( Fig. 38E ). Spines with a short basal internal spinule each ( Fig. 38D ); with two lateral spinules ( Fig. 38E ). Central disk slightly elevated, with a central tooth ( Fig. 38D ). Thorax with seven chaetigers, including collar ( Fig. 38A ). Collar trilobed. Thoracic membranes do not forming a ventral apron ( Fig. 38A ). Collar chaetae bayonet with two teeth and proximal rasp at the base of distal blade ( Fig. 38F–H ), distal blade with minute teeth, and limbate chaetae present ( Fig. 38F–G ). Abdomen incomplete with eight chaetigers. Chaetae and uncini not examined. Tube unknown.

Remarks. Following the recent key to world species of Hydroides by Kupriyanova et al. (2023) leads to H. elegans ( Haswell, 1883) . Hydroides elegans is one of the most economically and ecologically important species as it is a notorious member of fouling communities and common bio-invader ( Kupriyanova et al. 2023). Hydroides elegans is by far the best-known cryptogenic neocosmopolitan species. It has been reported in shallow waters from most subtropical locations around the world: Mediterranean-Atlantic, Indo-West Pacific including all around Australia, tropical Pacific America, East Atlantic and South Africa ( ten Hove & Kupriyanova 2009). However, there are differences among the specimen from the TALUD project and H. elegans . The tips of spines in Hydroides sp. are broad, blunt and pointing inwards the verticil centre, versus narrow, pointed, not directed inwards the verticil centre in H. elegans . In addition, the thoracic membrane of Hydroides sp. do not form an apron (a short apron is present in H. elegans ).

Depth distribution records of species Hydroides are all restricted to shelf depth, with the exception of H. capensis (350 m, McIntosh 1925, as H. uncinata ( norvegica ) var. multispinosa ) and H. caribensis (250 m, Kupriyanova et al. 2023). The record of 830 m for H. heterocera by Ilan et al. (1994) has been questioned by Ben-Eliahu & ten Hove (2011); that of H. norvegica of 4,808 m by Fauvel (1909) has been proven incorrect by Zibrowius (1977), yet it is still mentioned in checklists, such as Budaeva et al. (2014). Consequently, the specimen here reported off the western coast of the Baja California Peninsula to 2,077 m depth is the first finding of the genus in the continental slope.

Abiotic conditions. The specimen of Hydroides sp. was collected in 2,077 m deep; dissolved oxygen: 2.41 ml O 2 /l. No other environmental data available ( Table 1).

Distribution. West coast of Baja California, Mexico.

Figures

FIGURE 38. Hydroides sp.A) Thorax, ventral view, B) peduncle and operculum, C–E) operculum, different views, F–H) collar chaetae with proximal rasp. Scale bars: A) 0.8 mm, B, D) 0.6 mm, C, E) 0.3 mm, F–H) 20 μm. A–H: ICML-EMU-14052.