Herentia hyndmanni ( Johnston, 1847 )

Berning, Björn, Tilbrook, Kevin J. & Rosso, Antonietta, 2008, Revision of the north-eastern Atlantic and Mediterranean species of the genera Herentia and Therenia (Bryozoa: Cheilostomata), Journal of Natural History (J. Nat. Hist.) 42 (21 - 22), pp. 1509-1547 : 1516-1519

Herentia hyndmanni ( Johnston, 1847)

( Figure 1 )

Lepralia hyndmanni Johnston 1847, p. 306 , Plate 54, Figure 6 .

Lepralia hyndmanni: Busk 1854, p. 74 , Plate 87, Figures 5–8 .

Mastigophora hyndmanni: Hincks 1880 , part: p. 281, Plate 37, Figures 3 , 4 ; non Figures 5 , 6 .

Herentia (Herentia) hyndmanni: David and Pouyet 1978, p. 170 , Plate 1, Figures 5 , 6 . Escharina hyndmanni: Hayward and Ryland 1979 , part: p. 196, Figure 82A, B, non C; Hayward and Ryland 1999, part: p. 232, Figures 95C, D, 98A, B, non C; De Blauwe 2006, p. 137, Figure 20.

Non Escharina hyndmanni: Norman 1909, p. 302 .

Material examined

Lectotype: NHM 1847.9.16. 156, off Sanda Island, Scotland, four colonies on a bored and abraded shell. Paralectotypes: NHM 1847.9.16. 82, 1847.9.16. 132, 1847.9.16. 142, off Sanda Island, Scotland. Additional material: MNHN 6764 (part), off southern Portugal, ‘‘Jean Charcot’’ cruise 1969, Stn 076 (36 ° 34,99N, 11 ° 38,29W), 600 m, two colonies on shell; NHM 1899.5.1. 1154, Antrim, Northern Ireland, figured by Hayward and Ryland (1979, Figure 82A, B; 1999, Figures 95C, D, 98A, B), four colonies encrusting shells and rocks; NHM 1899.5.1. 911, Madeira; NHM 1996.8.29. 1, off Blanes, NE Spain, 200 m, on Lophelia pertusa ; PMC. R.I.H.B-3a, Gulf of Noto, Ionian Sea, ‘‘Piattaforma Siciliana’’ PS/81, and ‘‘Noto ‘96’’ cruises, 33–78 m, living and dead colonies from several stations; PMC. R.I.H.B-3b, Gulf of Catania, Ionian Sea, ‘‘Ciclopi 2000’’ and ‘‘LCT/80’’ cruises, 90–130 m, living and dead colonies on bioclasts from three stations; PMC. R.I.H.B-3c, off Santa Maria di Leuca, Ionian Sea, ‘‘Aplabes 2005’’ cruise, several stations (between 39 ° 28,099– 39 ° 34,849N, 18 ° 239– 18 ° 24,429E), 505–747 m, several living and dead colonies, mostly on colonies or fragments of Madrepora oculata and L. pertusa ; SMF 3028, Cabo de Gata, SE Spain, ‘‘Meteor’’ cruise M51-1, Stn 495 (36 ° 48,0719N, 01 ° 57,1549W), 120 m, dead colony on pectinid bivalve; SMF 3029, Cabo de Gata, SE Spain, ‘‘Meteor’’ cruise M51-1, Stn 496 (36 ° 48,3969N, 01 ° 57,7359W), 70 m, dead colony on cardiid bivalve.

Measurements

ZL 541¡65, 449–710 (2, 20); ZW 466¡74, 349–641 (2, 20); OL 123¡9, 111–139 (1, 20); OW 120¡9, 106–134 (1, 20); ApL 149¡12, 120–159 (2, 12); ApW 153¡7, 142– 168 (2, 12); OvL 281¡26, 228–315 (2, 12); OvW 370¡33, 311–435 (2, 12); AL 118¡8, 103–136 (1, 20); AW 97¡6, 88–112 (1, 20); AnL 261, 233–286 (3, 3); AnW 278, 262–301 (3, 3).

Description

Colony forming small irregular incrustations. Zooecia hexagonal to polygonal, separated by deep grooves between slightly thickened ridges; vertical walls and demarcated areas extended, with a single, comparatively small, round to oval communication pore per neighbouring zooid. Frontal wall flat proximally, rising distally towards slightly elevated orifice, surface even yet very finely grained, imperforate except for a row of 6–12 relatively large marginal pores, reduced to five or six in periancestrular zooecia. Orifice dimorphic, inner distolateral orifice rim with an immersed narrow shelf; anter of primary orifice horseshoe-shaped, about as broad as long and widest distal to mid-distance, proximal margin in autozooecia straight with drop-shaped sinus, condyles conspicuous, as long as proximal margin, extremely broad at lateral margins with the slope-angle increasing towards sinus; aperture in ovicellate zooecia more or less semicircular, larger and slightly broader than long, proximal margin also broader than in autozooecia, condyles distinctly narrower and sloping at a constantly low angle towards sinus. Proximolateral orifice margin framed by a low, narrow, smooth rim of gymnocystal calcification slightly raising laterally and being continuous with the lateral zooecium margin, distolateral border of autozooecium orifice bounded by a slightly raised and curved rim of thick calcification originating from distal basal pore chambers. Four oral spines in the first autozooid, absent in zooids formed during later astogeny.

Ooecium initially spherical, later for most part immersed by distal zooecium; exposed frontal surface a broad, curved, flattened and thickened rim, variably inclined to, and rising from, frontal plane.

Avicularium single, situated slightly distal to mid-distance of zooid and proximolateral to orifice near right or left zooid margin, proximal to one (or rarely two) distalmost marginal pore, on a slightly swollen cystid more or less continuous with frontal wall, no zooidal areolar pores between cystid and lateral zooid wall; in earliest astogenetic zooecia the avicularium is situated near proximal zooid margin, progressively moving distally in later zooecia; rostrum suborbicular to oval with a broad, smooth and slightly raised rim sloping towards opesium, distolaterally or laterally oriented; mandible long and slender, setiform, slightly sigmoidal, up to twice the length of an autozooid; crossbar bilateral symmetrical, strong, slightly arcuate with the apex at centre, proximal margin of crossbar (with respect to long axis of rostrum) relatively narrow, straight or slightly concave when viewed from above except from a small semicircular extension protruding from its basal centre, distal part of crossbar set off from the proximal part by a suture, calcification distinctly thickening towards the lateral rostral margins, creating a U-shaped distal margin.

Ancestrula kenozooidal, about as long as wide, with an irregular lobate outline, gymnocystal frontal wall moderately convex, rather flat centrally, smooth, lightly but entirely calcified apart from a small central hole, some six articulated spines forming a circle at about mid-distance between margin and ancestrula centre. Budding pattern as described for genus.

Remarks

We here designate lecto- and paralectotypes from Johnston’s suite of specimens that were listed by Brown (1952, p. 229). The lectotype ( NHM 1847.9.16.156) is shown in Figure 1D .

In contrast to the description of H. hyndmanni by Hayward and Ryland (1979, 1999), oral spines in adult zooids at the colony periphery were neither observed in the available British nor in any other material of this species. Only in the first formed autozooid are four spine bases evident ( Figure 1A ). Because very early ontogenetic zooids were not observed during this study we cannot rule out the possibility that these are, indeed, formed in zooids at this stage of development and are lost during ontogeny when the thick rim encroaches the distal orifice margin. However, it seems rather likely that one of the specimens Hayward and Ryland (1979, 1999) described and figured (Figures 82C and 98C, respectively) belongs to H. thalassae from the northern Spanish shelf (see below). This species has three or four spines and also a more proximally positioned avicularium in adult zooids. Both characters are present in their figures.

Kenozooidal ancestrulae have been observed only in a few small colonies from central Mediterranean deep-waters, in which the ancestrula remained exposed due to fan-shaped colony growth in a single direction. Usually, the ancestrula was found to be either damaged or, in larger colonies, overgrown by periancestrular zooids. Besides the rare occurrence of kenozooidal ancestrulae in bryozoans (see Discussion), another curious feature is the tiny hole in the central gymnocyst ( Figure 1A ), which we initially interpreted as accidental damage. However, all of the five ancestrulae with an undamaged central region had this hole and we are therefore inclined to consider it as representing the remnant of an extremely reduced opesium.

H. hyndmanni has often been reported from the NE Atlantic (Jullien and Calvet 1903; Canu and Bassler 1925; d’Hondt 1970, 1974, 1975, 1979; Hayward and Ryland 1978; Grant and Hayward 1985) and Mediterranean Sea (e.g. Calvet 1907; Gautier 1962; Harmelin 1969, 1978; d’Hondt 1977, 1984; Di Geronimo et al. 1990, 1993). Yet in the absence of detailed descriptions and (SEM) illustrations of the orifice and avicularium, a synonymy is impossible to establish because of morphological similarities with the other species occurring in these regions ( H. majae n. sp., H. andreasi n. sp., H. thalassae , see below). The specimen shown in Zabala and Maluquer (1988, p. 129, Figure 292; Plate 15, Figure E) is very similar to H. hyndmanni but the condyles seem to be distinctly smaller, the avicularium is situated more proximally and its cystid lacks the areolar pores. Important close-ups of orifice, aperture and avicularium necessary for verification are, however, not provided.

H. hyndmanni occurs off the western coasts of the British Isles, as far north as the Shetland Isles (Hayward and Ryland 1979, 1999), and was recently also found at depths of c. 20 m in the southern North Sea off Belgium ( De Blauwe 2006). Furthermore, several specimens from off southern Portugal ( d’Hondt 1973), Madeira, and from the western and central Mediterranean Sea (e.g. Poluzzi and Rosso 1988; Di Geronimo et al. 1998; Rosso 1996 a, 1996b), proved to be morphologically identical to British representatives, confirming the presence of H. hyndmanni in these regions. The easternmost occurrence in the Mediterranean is in the Ionian Sea, from where it was reported by Poluzzi and Rosso (1988), Rosso (1996 a, 1996b) and Mastrototaro et al. (in press). However, it must be noted that some living (Mastrototaro et al., in press) and dead (Rosso et al., in press) specimens from Ionian Sea deep waters (PMC.R.I.H.B-3c) have considerably longer zooecia [ZL 720¡91; 590–918 (4, 15)], whereas all other skeletal characters are of similar size. Furthermore, these colonies usually consist of broad fanshaped lobes spreading in a single direction, which may be an adaptation to deepwater environments (see H. thalassae and Discussion below), while proximal colony regions are often iron oxide-stained. Part of the material listed by d’Hondt (1973, p. 1218) from the Portuguese continental slope belongs to H. hyndmanni . It co-occurs with a species that is closely related to, or possibly conspecific with, H. thalassae (see below).

H. hyndmanni is an offshore species that has been reported from depths between 20 and 750 m encrusting hard substrata in offshore environments to the edge of the continental shelf and the upper slope. However, in the Ionian Sea several small colonies have been recovered from c. 500 m encrusting hardgrounds and even slightly consolidated silty substrata ( AR, pers. observation). Brooding colonies were observed in the Ionian Sea in October ( AR, pers. observation) and, off the Isle of Man, in November ( Eggleston 1969 fide Hayward and Ryland 1979, 1999) .

Figures

Figure 1. Herentia hyndmanni (Johnston, 1847). (A, B) PMC.R.I.H.B-3c, Ionian Sea; (C, E, F) NHM 1899.5.1.1154, off Northern Ireland; (D) lectotype, NHM 1847.9.16.156, off western Scotland. (A) Kenozooidal ancestrula and first autozooecium; while the ancestrular gymnocyst is bored and damaged, we consider the central hole (arrow) as representing the remnant of an extremely reduced opesium; note the spine bases on the distal orifice margin of the autozooecium, the central pair of spines is already covered by the calcified rim encroaching the distal orifice margin; (B) ancestrula and early astogenetic colony; note the presence of a central hole in the ancestrula and the relatively proximally positioned avicularia in the autozooecia; (C) autozooecia and an ovicellate zooecium at the colony growth margin; note that in this and the other photos showing ooecia the vertical component, i.e. the distally raised ooecium hood, is understated; (D) general aspect of unbleached colony; (E) close-up of orifice and avicularium; (F) ovicellate zooecium; note slightly narrower condyles compared to those of autozooecia. Scale bars: 100 mm (A); 200 mm (B–D); 50 mm (E, F).

Figure 3. Herentia andreasi n. sp., off Madeira. (A, C) Paratype, NHM 2007.10.9.2; (B, D) holotype, NHM 2007.10.9.1. (A) Autozooecia at the colony growth margin; note the incompletely formed frontal wall in zooecium at left and the uncalcified central area in the basal wall of the incompletely formed zooecium at top of image; (B) auto- and ovicellate zooecia during later ontogeny; (C) close-up of orifice and avicularium; (D) close-up of ovicellate zooecium; note the different shapes of sinus and condyles compared to orifice of autozooecium. Scale bars: 200mm (A, B); 50 mm (C, D).

Figure 4. Herentia thalassae David and Pouyet, 1978. MNHN 7619, off NW Spain; note that the vertical component in these perpendicular views is greatly understated, the distal parts of the zooecia and ooecia are distinctly raised. (A) General aspect of colony; (B) close-up of ovicellate zooecium; (C) close-up of autozooecium. Scale bars: 400 mm (A); 100 mm (B, C).

Figure 5. Therenia cryptooecium n. sp. Holotype, NHM 1972.1.2.16A, Ghana, off Tema. (A) General aspect of colony; note the presence of three ovicellate zooecia (arrows); (B) autozooecia at the colony margin; note differences in condyle length between orifices; (C) close-up of autozooecium orifice and avicularium; (D) close-up of ovicellate zooecium, which is characterized by a slightly larger aperture and shorter condyles. Scale bars: 200 mm (A); 100 mm (B, D); 50 mm (C).

Figure 6. Therenia rosei n. sp. Holotype, NHM 1975.1.12.17A, Aegean Sea. (A) Autozooecia; (B) ovicellate zooecia; (C) close-up of autozooecium orifice and avicularium; (D) close-up of ovicellate zooecium; note difference in condyle morphology compared to orifice of autozooecium. Scale bars: 200 mm (A, B); 50 mm (C, D).

Figure 7. Therenia peristomata n. sp. Holotype, NHM 2007.10.9.3, off Madeira. (A) General aspect of zooecia at the colony growth margin; (B) early astogenetic zooecia showing a rather flared peristome; note that the ancestrula has been covered by the lowermost zooecia; (C) close-up of autozooecium orifice and avicularium; (D) ovicellate zooecium; note slight differences in condyle morphology to orifice of autozooecium. Scale bars 200 mm (A, B); 50 mm (C, D).

Figure 8. Geographic distribution of Herentia and Therenia species in the North Atlantic and Mediterranean Sea. Note the co-occurrence of three species (H. hyndmanni, H. andreasi n. sp. and T. peristomata n. sp.) at Madeira, and the wide range of H. hyndmanni.