Hydroides homoceros Pixell, 1913

Ben-Eliahu, M. Nechama & Ten Hove, Harry A., 2011, Serpulidae (Annelida: Polychaeta) from the Suez Canal- From a Lessepsian Migration Perspective (a Monograph) 2848, Zootaxa 2848 (1), pp. 1-147 : 32-35

Hydroides homoceros Pixell, 1913

Figs 5H, I, 12

Hydroides homoceros Pixell, 1913: 74–75 , pl. 8 fig. 1 [Type localities: Red Sea, Sudan, Suakin; Indian Ocean, Zanzibar, Maldives (9 syntypes, see “Material examined”, below)]; Zibrowius 1979b: 133–134 [ France, Toulon Port, biofouling removed from the aircraft carrier “Foch”; marginal radii of specimens with 2 pairs of lateral processes (H. Zibrowius, pers. comm.)]; Zenetos et al. 2005: 73 [classified as an “established alien invasive species” in the Mediterranean].

Eastern Mediterranean

Hydroides homocera: Ben-Eliahu & ten Hove 1989: 393 ; Ben-Eliahu 1991b: 515–528, fig. 3 [ Israel]; Ben-Eliahu & ten Hove 1992: 35–53 [ Israel]. All three records with single-anchor-shaped marginal radii of funnel (see Fig. 12E ).

Hydroides homoceros: Ben-Eliahu & Fiege 1996: 33–34 , 38 [ Israel]; ten Hove & Ben-Eliahu 2005: 127–145, figs 2a, a’, a” [ Israel, 18–24 m]; Çinar 2006: 228, figs 4 d–f [Levant coast of Turkey, Iskenderun Bay, 1–3 m, X.2005, population with “spur-tipped-anchor-shaped” marginal radii ( Fig. 12B , also depicted by ten Hove 1970a figs 1a–c in specimens from the Persian (Arabian) Gulf), differing from the Israeli population that lacks the spur ( Fig. 12E )].

Suez Canal

Hydroides homocera: Ben-Eliahu 1991b: 526 , fig. 5 [Great Bitter Lake, collected on 13.I.1969, marginal radii of funnel single-anchor-shaped (see Figs 12A, D )].

Gulf of Suez

(1968) Hydroides homocera: Ben-Eliahu 1991b: 526 , fig. 5 [Gulf of Suez, El Bilayim lagoon, first record from Gulf of Suez, collected 10.VI.1968, sample SLR1753 (Por et al. 1972); on Pectinidae . Marginal radii of funnel single anchor-shaped]; Selim 1997b: 93–94, figs 6a–e [Gulf of Suez, Port Taufiq, collected in 1988].

Red Sea, proper-Indo-West-Pacific (excluding citations from Gulf of Suez and Gulf of Aqaba already given above)

Hydroides homoceros Pixell, 1913: 74–75 , pl. 8 fig. 1 [Red Sea spec. with “double-T” (“double-anchor”) marginal radii; Indian Ocean (see “Material examined”, below)]; Monro 1937: 316 [Indian Ocean: Zanzibar, Arabian coast, Maldives, 2 specs. First “resembling Pixell’s descriptions and figure,” thus, with “double-anchor” marginal radii]; Wesenberg-Lund 1949: 356–357, fig. 46a [Persian (Arabian) Gulf; marginal radii of funnel single-anchor-shaped, see Figs 12A, D, E ]; ten Hove 1970a: 55, figs 1a–c [Persian (Arabian) Gulf (see “Material examined”, below); marginal teeth with “more or less blunt” spur surmounting single anchor-shaped form, see Fig. 12B ]; Mohammad 1971: 301 [Persian (Arabian) Gulf, Kuwait; the marginal teeth show a range from Figs. 12B to C as in the Pixell syntypes (present paper)]; Mohammad 1976: 133 [Persian (Arabian) Gulf: Kuwait, the marginal teeth show a range from Figs 12B to C (present paper)]; Mohammad 1981: 131 [Persian (Arabian) Gulf, Kuwait; marginal teeth as above)]; Ben- Eliahu 1991b: 526, fig. 5 [south Red Sea: Dahlak Archipelago, marginal radii double-anchor-shapes, as in Fig. 12C ; ten Hove 1994: 107–114 [Indian Ocean, Seychelles Islands; opercula with marginal radii in-between form of Figs 12B and C , thus, with 2 pairs of lateral processes “double-anchor”, with the tip not rounded but flat, almost indented), present paper]; Wehe & Fiege 2002: 127 [Persian Gulf, Arabian Sea; list of references].

Material examined. Locations adjacent to the Suez Canal, Mediterranean side: Israel: 14 samples, 22 specs. First Mediterranean record of this Lessepsian migrant, INCNH data unpublished, Haifa Bay , 32 m, on Mimachlamys varia , legit E. Gilat (Gilat91) 21.X.1955, det. M.N. Ben-Eliahu ca. 1969, marginal radii singleanchor-shaped as figured by Wesenberg-Lund (1949, fig. 46a), see Fig. 12E , TAU-NS (no number), 1 spec. — Egypt, Sinai: 2 samples. Depth : 9– [22–32]– 55 m.

Suez Canal material reported herein: 8 samples with 38 specs. Beets’ Great Bitter Lake samples, no taphonomic residues found, tubes provisionally identified as those of H. homoceros in at least 4 samples— Hebrew University-Smithsonian Expeditions , 1967–1973, 3 samples, 33 specs: Great Bitter Lake , SLC 117, 31 specs; east of Deversoir , Km 97, SLC 50, 1 spec. ; SLC 52, 1 spec., marginal radii of funnel single-anchorshaped, see Figs 12A, D .— Great Bitter Lake “Yellow Fleet” Biofouling Samples, January 13–20, 1975: 4 subsamples, 4 specs. Bremerhaven dry dock, 1 spec.

Locations adjacent to the Suez Canal, Red Sea side: Gulf of Suez, 1 sample.— Gulf of Aqaba : No records .

Red Sea: South Red Sea: 2 samples (? m, 36.6 m).

Sudan, Suakin Harbour, legit C. Crossland 7.II.1905, BM ( NH) 1924.6.13.145, 1 spec., syntype, marginal radii with 2 pairs of recurved lateral processes, i.e., “double-anchor-shaped” ( Pixell, 1913, pl. 8 fig. 1a as in Fig. 12C ) .— Eritrea, Dahlak Archipelago , 15°35’N, 40°44’, 36.6 m, on Malleidae , legit Ch. Lewinsohn, 23.X.1965 , Israel South Red Sea Expedition , 19085 Stn 12, det. M.N. Ben-Eliahu ca. 1985, marginal radii of funnel double-anchor-shaped, as in Fig. 12C .

Indian Ocean, Tanzania, off Zanzibar, scraped from the bottom of the “Juba,” legit C. Crossland, 1901– 1902, 4 syntypes and slide of collar chaetae and uncini, BM ( NH) 1924.6.13.147; although Pixell did not refer to variation in the form of the opercular spines, marginal radii of syntypes range from spur-tipped singleanchor to a more developed spur approaching double-anchor form ( Pixell, 1913, pl. 8 fig. 1a), i.e., a range in form between Figs 12B to C (present paper) .

Arabian Sea : South Arabian Coast , 13.5 m, John Murray stn 53, 2.XI.1933, det. C.C.A. Monro, BM ( NH) 1937.9.2.540–1, 2 specs, marginal radii as in Pixell (1913), and as in Figs 12B to C.— Oman, Gulf of Masirah, Masirah Island, Ras Al Ya; low tide, under stones, Stn 91 / 105, legit R.G. Moolenbeek & H. Dekker, 23.XI.1991, ZMA V.Pol. 3838, marginal radii with spur-tipped single-anchor, see Fig. 12B .

Gulf of Oman, N. Oman, Khor al Quway, north-south running strait, gentle current, from east side of strait, 18.3–36.6 m, Royal Geographical Society (of Great Britain) Musandam Expedition, 1971–72, legit P.E.S. Cornelius; extracted and det. by H. Zibrowius 1972 from dead coral fragments from sandy bottom and limestone area, on coelenterates, BM ( NH) 1972:217, marginal radii double-anchor-shaped, as in Fig. 12C .

Strait of Hormuz, 5 miles S.E. of the Tunb light, 26°12' N, 55°22'E, 38–60 m, Petersen-grab, 7.IV.1938, gravel and shells, Danish Expedition Stn 118, legit B. Løppenthin, det. E. Wesenberg-Lund (1949: 380–381), redet. H.A. ten Hove II.2000, ZMUC, marginal radii of funnel single-anchor-shaped, see Figs 12A, D, E .

Persian (Arabian) Gulf. Sample details unknown, legit Ø. Støckland ca. 2004, det. M.N. Ben-Eliahu XI.2004, marginal radii with single pair of lateral processes topped by a more or less expanded tip (cf., ten Hove 1970a, figs 1a–c), similarly from the Persian (Arabian) Gulf, Fig. 12B .— Bahrain, 4 miles E.N.E. of Bahrain light-ship, Stn 87, m?, legit B. Løppenthin 20.III.1928, ZMA V.Pol. 3002, marginal radii with one pair of recurved lateral pinnules, surmounted by spur (as in ten Hove 1970a, figs 1a–c), more recurved, i.e., more anchor-shaped than those in Fig. 12B .

Suez Canal depth and substrates: Shallow– 10 m, on algae: Digenea ; sponges; on bivalve, Spondylus spinosus ; on tunicate.

Distribution. Lessepsian migrant to the Mediterranean: Israel, Turkey; Suez Canal; Red Sea: Gulf of Suez, Dahlak Archipelago; Indian Ocean: Zanzibar, Seychelles, South Arabian coast, Persian (Arabian) Gulf, Maldives. May occur in living corals ( Millepora , Porites ).

Remarks. Tube with 3 prominent longitudinal ridges of equal height; transversal ridges not prominent, giving the tube relatively smooth sides (ten Hove 1970a: 55, figs 1–8; Figs 5H–I). Very slight pink cast in some tubes. Of ca. 20 inhabited tubes, the longitudinal ridges were prominent in nearly all the tubes (although not equally prominent throughout the length of the tube, e.g., one of four fragments of the single tube in Fig. 5H appears covered with a granular layer). Some of the three-ridged tubes on Beets’ shells were provisionally identified as Hydroides homoceros (see App. Table 2B), however, due to the lack of taphonomic residues, presence in the Canal in 1950 is considered as likely but not conclusive. The first complete specimens (inhabited tubes), were collected in the Great Bitter Lake (east of Deversoir-Km 97 [SLC50] in 1969, see App. Table 2C).

The operculum of Hydroides homoceros , and specifically the tips of the marginal radii of the funnels, shows an interesting variability in form ( Figs 12A–E ) and all of the forms are present in the Persian Gulf. The “double-anchor” ( Pixell 1913) and “single-anchor” ( Wesenberg-Lund 1949) forms can be considered as the most extreme of these forms. The proximal paired lateral spinules may range in form from anchor-shaped to a more pointed “T-shaped” as in Figs 12D–B. A distal pair of lateral spinules may be developed similar to the proximal pair (= “double-anchor”, Fig. 12C ), or the distal lateral spinules may be reduced to a more or less rounded spur, “spur-tipped-T-shaped” ( Fig. 12B ); alternatively, distal lateral spinules may be lacking entirely ( Fig. 12D ).

The “double-anchor-shape” ( Fig. 12C ) is similar to that figured in Pixell (1913, pl. 8 fig. 1a) and in Mohammad (1981 fig. 2c), but, in re-examining their material, we also found specimens with marginal radii ranging in form between Figs 12B and C . This “double-anchor” form has been reported from the Indian Ocean, Zanzibar, Maldives ( Pixell 1913), the Arabian coast, Oman ( Monro 1937), from the Persian Gulf, Kuwait ( Mohammad 1981, see references above), from the Seychelles (present paper), and the southern Red Sea - Dahlak Archipelago ( Ben-Eliahu 1991b, Fig. 12C ). Specimens from Oman showed some additional variation (present paper). It follows that in these populations there is more variability in the form of the marginal radii than given in their formal descriptions.

The “spur-tipped-anchor-shaped” form is shown in Fig. 12B ; ten Hove (1970a, figs 1a–c) illustrated some of the variability in the tip of the spur; the population was from the Persian Gulf. The single-anchor form ( Figs 12D, E ) reported from the Persian (Arabian) Gulf by Wesenberg-Lund (1949), has been found in the Gulf of Suez (present paper and Selim 1997b: 87, 93–94, figs 6a–e). It also characterizes both the Suez Canal population ( Figs 12A, D ), and the Lessepsian migrant populations on the Levant coast of Egypt and Israel (ca. 80 individuals) ( Figs 12D, E ). That only one of several forms present in the Persian (Arabian) Gulf has been found in the Gulf of Suez, colonized the Suez Canal and the Mediterranean coast of Israel, is an illustration of “a founder effect” (Mayr 1966, Ben-Eliahu 1991b). Interestingly, the H. homoceros specimens removed from the aircraft carrier “Foch” in Toulon Port ( Zibrowius 1979b) belonged to the “double-anchor” Pixell type (H. Zibrowius, pers. comm.), thus, settlement on the “Foch” presumably occurred in the Indian Ocean or the Red Sea proper ( Ben-Eliahu 1991b). A single specimen recently collected from the Levant coast of Turkey (Iskenderun) by Çinar (2006, fig. 4d–e), belongs to the “spur-tipped-T-shaped” form (in Figs 12B, C , closer to B than to C). The distribution of the form (Persian (Arabian) Gulf, ten Hove 1970a, and Turkey, Çinar 2006) provides a convincing illustration of a disjunctive population founded through ship-transport.

Hydroides homoceros has a juvenile 2-tier opercular ontogenetic stage belonging to the H. “ priscus ” type, one of several species in which this stage has been found (ten Hove & Ben-Eliahu 2005, fig. 2a).

Figures

FIGURE 12. Variability in opercula of Hydroides homoceros from different regions. A—Operculum characterized by “single-anchor-shaped” (or T-shaped) marginal radii (see also “D”) from Great Bitter Lake population (sample SLC 117, see App. Table 2C), B—Specimen with “spur-tipped-T-shaped” marginal radii from the Persian (Arabian) Gulf, leg. anon., sample sent to NBE for identification via the late T. Holthe, C—Specimen with “double-anchor” marginal radii from the Dahlak Archipelago (Israel South Red Sea Expedition sample ISRSE 65-TAU-MO-Malleidae 1814), D— Enlarged tip of marginal radius from Fig. A—5th radius from left—from Bitter Lake, Suez Canal—resembles that of specimens from Mediterranean population, E—Lessepsian migrant specimen from the coast of Israel (legit E. Gilat, Gilat sample 1821B, 10.XI.1969, Ashqelon, 22 m). Scale: 100 µm.