Euchone cortezi Reish, 1968

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 : 27-29

Euchone cortezi Reish, 1968 , re-establishment

( Fig. 14 , Table 2)

Euchone cortezi Reish, 1968: 94 , fig. 19a (erroneously labelled as E. barnardi ), fig. 20a–d.

Material examined. ICML-EMU-14027: TALUD XVI-B, St. 5, BS, 28°48'N 115°24'06"W, 24 May 2014, 772‒ 776 m, 2 specimens, both complete but one broken in two parts (a female with oocytes in thorax) .

Description of material examined. Body pale with whitish glandular ridge on chaetiger 2 and cream colored shields. Trunk 10.7–13.2 mm long (considering both specimens), thorax 0.8 mm wide. Branchial crown 5.1–7 mm long, with six pairs of radioles, thorax with eight chaetigers, abdomen with 21–27 chaetigers. Branchial lobes semicircular; palmate membrane about 1/2 of radiolar length; narrow radiolar flanges along radioles; radiolar eyes absent. Dorsal lips with short radiolar appendage, dorsal pinnular appendages absent; ventral lips and parallel lamellae both present, ventral sacs absent; one pair of ventral radiolar appendages. Anterior peristomial ring lobe entire, triangular, not exposed beyond collar margins; posterior peristomial ring collar with dorsal margins fused to faecal groove, dorsal pockets present, vascular coils not visible. Ventral margin with long mid-ventral incision, forming pair of rounded overlapped lappets ( Fig. 14A–C ). Body with biannulate segments; glandular ridge present on chaetiger 2, equally narrow all around; ventral shields with lateral borders well defined in first 4–5 chaetigers, indistinct in the following segments; interramal eyespots absent. Thoracic pre-chaetal and post-chaetal lobes well developed. Collar chaetae narrowly-hooded, in two oblique rows. Superior thoracic notochaetae narrowly hooded ( Fig. 14G ). Inferior thoracic notochaetae as two transverse groups: anterior row of bayonet chaetae and posterior rows of broadly hooded chaetae ( Fig. 14G ). Thoracic uncini acicular ( Fig. 14H ), with 5–6 rows of teeth above the main fang. Abdominal chaetae elongate, narrowly hooded. Posterior chaetigers with modified, elongate, narrowly hooded chaetae. Uncini from anterior abdomen with squared breast ( Fig. 14I ), with rows of similar-sized teeth above main fang, occupying half its length, handle absent. Uncini from posterior abdomen as rasp-shaped. Pre-pygidial depression composed by 6–7 last abdominal segments, ventral, with pair of triangular flaps at mid-length of anterior margin, lateral margins forming wings ( Fig. 14D–F ). Pygidium triangular, without cirrus ( Fig.14F ), pygidial eyespots not seen. Tube made of fine sand.

Methyl green staining pattern. Homogenous blue coloration ventrally on thorax, except for anterior collar margin, which remains unstained (ventral lappets) ( Fig. 14B–C ). Thorax unstained with methyl green dorsally ( Fig. 14A ). Posterior abdomen with scattered blue dots dorsally and ventrally, triangular flaps at mid-length of anterior margin of pre-pygidial depression remain unstained ( Fig. 14D–E ).

Remarks. Euchone Malmgren, 1866 is a group of 37 currently known species including those reported by Capa et al. (2021), one new species described below and E. cortezi , here re-established. During the last century, the genus was recognizable by the presence of a typical pre-pygidial depression (anal depression), with lateral wings, but according to Bick & Randel (2005), who analyzed the ontogenic variability in specimens of E. analis (type species of the genus), the pre-pygidial depression with lateral wings is visible only in adult stage. Besides, these authors found that the number of abdominal chaetigers forming the pre-pygidial depression and the shape of the depression are highly variable.

In the Californias ( USA and Mexico), seven species of Euchone have been described: E. arenae Hartman, 1966 , from Redondo Beach (California, USA), E. barnardi Reish, 1968 , from Bahía de los Angeles (Gulf of California, Mexico), E. cortezi Reish, 1968 , from Bahía de los Angeles (Gulf of California, Mexico), E. hanckocki Banse, 1970 , from Lasuen Seamount (California, USA), E. limnicola Reish, 1959 , from Long Beach (California, USA), E. magna ( Fauchald, 1972) , from Isla Cerralvo (Gulf of California, Mexico), and E. velifera Banse, 1972 , from off Catalina Island (California, USA) ( Table 2). However, E. barnardi was synonymized with E. incolor Hartman, 1965 (a species from New England), and E. cortezi with E. arenae , in both cases, according to Banse (1970).

Banse (1970: 399) had the opportunity to examined one paratype of E. cortezi hosted at the USNM (38405) and stated: “I consider E. cortezi to be a synonym of E. arenae , a species that Reish (1968) had not included in the Discussion of his record. The variability in the number of abdominal segments and the disagreement of the height of the palmate membrane ( Hartman, 1966, Reish, 1968) must be noted”. Euchone arenae was described as with 13–15 abdominal chaetigers, six of these composing the pre-pygidial depression, and a palmate membrane less than a fourth of the radiolar length ( Hartman 1966), whereas E. cortezi was described as with 12–13 abdominal chaetigers, 5–6 of these forming the pygidial depression, and the palmate membrane extending for one half of the radiolar length ( Reish 1968).

Except for the length of the palmate membrane, the numbers of abdominal chaetigers and segments in the pre-pygidial depression are discrete features which do not strongly support the synonymy. In order to analyze the shape of the pre-pygidial depression, the original description of E. cortezi was reviewed and an edition mistake was detected. Reish (1968: 94) inserted a figure called “ Fig. 20a ” referring to the pre-pygidial depression for E. cortezi , but the “figure 20a” shows a thoracic chaeta and the figure legend stated “ Figure 20 .— Euchone cortezi [sic], sp. nov.: a posterior end showing anal depression, b, double winged capillary seta”…., obviously it is an edition mistake.

Besides, Reish (1968: Fig. 19a ) shows a pre-pygidial depression extending for five chaetigers but the figure legend stated that “ Figure 19 .— Euchone barnardi [sic], sp. nov.: a, a double winged capillary seta from…”. Euchone barnardi was described in Reish (1968: 93), with a pre-pygidial depression occupying three chaetigers; the pre-pygidial depression showed in his figure 19A has five chaetigers, as described for E. cortezi (not three, as for E. barnardi ), consequently this fact also confirms the edition mistake.

Thus, reviewing the pre-pygidial depression in Reish (1968: Fig. 19a ), the presence of two triangular flaps in the mid-anterior margin is remarkable ( Table 2). These flaps were also found in the specimens from the TALUD XVI-B cruise reviewed herein ( Fig. 14D–E ). For comparison, the original drawing of E. arenae by Hartman (1966: pl. 6, fig. 6) shows a pre-pygidial depression with smooth anterior margin, without any flap ( Table 2). The triangular flaps at the anterior margin of the pre-pygidial depression constitute a distinctive feature to separate members of both species (present in E. cortezi , absent in E. arenae ), in addition to the extension of the palmate membrane (a half of the radiolar length in members of E. cortezi , less than a fourth of the radiolar length in representatives of E. arenae ). As material examined here is also from the Gulf of California and matches the original description and drawings by Reish (1968), we use the available name E. cortezi for the ecoregion, proposing also its re-establishment.

Abiotic conditions. The specimens of E. cortezi were collected from 772‒1,030 m deep, under the following environmental conditions. Temperature: 5.00°C; salinity: 34.42; dissolved oxygen: 0.22 ml O 2 /l; %MO: 8.95; sediments dominated by silt (72.7%) ( Table 1).

Distribution. Central Gulf of California ( Reish 1968), off the West coast of Baja California, Mexico (present study).

Figures

FIGURE 14. Euchone cortezi Reish, 1968. A) Thorax, dorso-lateral view, B) same, ventro-lateral view, C) same, ventral view, D) pre-pygidial depression lateral view, E) same, ventro-lateral view, F) same, dorso-lateral view. G) thoracic chaetiger with narrowly and broadly hooded chaetae, H) thoracic uncini, I) uncini from anterior abdomen. Scale bars. A–B) 1.5 mm, C–F) 0.8 mm, G) 100 μm, H) 50 μm, I) 25 μm. A–F: ICML-EMU-14027.

FIGURE 19. Jasmineira agustinae sp. nov. A) Entire worm, ventral view, B) base of crown, dorsal side, C) radiolar tip, D–E) crown and anterior thorax, left and right side, respectively, F) abdomen and pygidial cirrus. Abbreviation: vc–vascular coils. Scale bars: A) 5 mm, B, D–F) 1 mm, C) 0.25 mm. A, C, F: holotype ICML-EMU-14032, B: paratype ICML-EMU-14034E, D–E: paratype ICML-EMU-14033A.

FIGURE 20. Jasmineira agustinae sp. nov. A) Dorso-lateral view of collar, B) ventral view of collar, C) mid-ventral collar margin and parallel lamellae, D) dorsal collar margin, E) ventral collar margin, F) right vascular coil, G) left vascular coil, same individual. Abbreviations: bp—breaking plane, gr2–glandular ridge on chaetiger 2, pl–parallel lamellae, vc–vascular coils, vsc–ventral shield of collar. Scale bars: A–B, D–E) 1 mm, C) 0.5 mm, F–G) 0.3 mm.A–C: paratype ICML-EMU-14033C, D–G: paratype ICML-EMU-14034E.