Hincksina chimaera, Reverter-Gil & Souto, 2023

Reverter-Gil, Oscar & Souto, Javier, 2023, New and non-indigenous species of Bryozoa from Iberian waters, European Journal of Taxonomy 885, pp. 33-64 : 48-52

Hincksina chimaera sp. nov.

urn:lsid:zoobank.org:act:DB4EA99A-8640-4AA7-9E45-B2168D570764

Figs 8 , 12B ; Table 6

? Hincksina flustroides – Álvarez 1992: 276.

Hincksina flustroides – Templado et al. 2006: 207 (part).

Differential diagnosis

Hincksina with 8–10 mural spines, frequently flattened and occasionally bifid, and a pair of oral spines usually flattened, somewhat triangular, with the beginning of a bifurcation, parallel or aligned oblique to zooidal midline and converging distally. Avicularia interzooidal, with the rostrum semielliptical or rounded-triangular, usually pointing distolaterally. Ovicell endozooidal in distal avicularium or autozooid, often producing a central peak.

Etymology

From Latin ‛ chimaera ’, and this from Greek ‛ xίμαΙΡα ’ (‛ chímaira ’), according to Greek mythology a monstrous creature composed of different animal parts. The term alludes to the morphology of the species, mixing up characters of three other Iberian Hincksina .

Material examined

Holotype MEDITERRANEAN SPAIN • colony on a polychaete tube; Alboran Island ; 35.92750° N, 03.05000° W; stn 305A; depth 33–49 m; 23 Jul. 1996; Fauna Ibérica IV exped.; MNCN 25.03/2450 ( Fig. 8D–F ).

Paratypes MEDITERRANEAN SPAIN • several ovicelled colonies on a concretion; Alboran Island ; 35.95283° N, 03.04167° W; stn 324A; depth 51–58 m; 28 Jul. 1996; Fauna Ibérica IV exped.; MNCN 25.03/2412 ( Fig. 8A–C ) • 2 colonies on a concretion, both marked in red; same collection data as for preceding; MNCN 25.03/2174 • several ovicelled colonies on a concretion; same collection data as for holotype; MNCN 25.03/2488 • 1 small colony on a concretion, marked in red; same collection data as for holotype; MNCN 25.03/2549 • several colonies on a concretion; same collection data as for holotype; MNCN 25.03/2602 .

Other material examined

Hincksina sp.

MEDITERRANEAN SPAIN • several small, eroded fragments; N of Alboran Island; 35.95283° N, 03.03333° W; depth 45–52 m; 1991; Fauna Ibérica I exped.; MNCN 25.03/223 .

Hincksina longispinosa Harmelin & d’Hondt, 1992

MEDITERRANEAN SPAIN • 1 ovicelled colony, with more species, on a concretion; SW of Alboran Island; 35.87333° N, 03.14017° W; stn 317A; depth 87–213 m; 27 Jul. 1996; Fauna Ibérica IV exped.; MNCN 25.03/2402 ( Fig. 9 ).

Description

Colony encrusting, multiserial, unilaminar. Autozooids elongate oval, arranged in irregular series, separated by shallow grooves. Vertical walls with two or more uniporous pore plates per neighbouring zooid. Gymnocyst reduced to the proximal region, cryptocyst a narrow band with a coarse nodular surface, opesia extensive. A pair of oral spines cylindrical or more usually flattened, directed upwards, somewhat triangular, with the beginning of a bifurcation with uncalcified pores in the tips, parallel or aligned oblique to zooidal midline and converging distally. Frontal membrane overarched by 8–10 (occasionally fewer) mural spines, initially cylindrical but frequently flattened, well developed and reaching the zooidal mid-line; occasionally bifid. Spines apparently unjointed at their base. Avicularia interzooidal, distal to many zooids, usually pointing distolaterally but often distally or even laterally; oval in outline and distinctly longer than wide, widest proximal to condyles; rostrum semielliptical or rounded-triangular, at an acute angle to colony surface, mandible hinged on a pair of short triangular condyles delimiting an approximately semicircular proximal area with an immersed calcified shelf; interior of mandible with a large central oval lucida; gymnocyst usually reduced to cystid corners. Ovicell endozooidal in distal avicularium or autozooid; ooecium continuous with the gymnocyst of the avicularian or autozooidal cystid, forming a short but broad hemispherical cap; proximal margin raised centrally, often producing a central peak. Ancestrula not preserved.

Remarks

Hincksina chimaera sp. nov. exhibits a curious mix of characters from three other Iberian species of the genus: H. flustroides , H. synchysia and H. calpensis Reverter-Gil, Souto & Fernández-Pulpeiro, 2012 .

At first sight, H. chimaera sp. nov. closely resembles H. flustroides , also showing a high number of large marginal spines (8–10), flattened and sometimes bifid (especially the first pair) overarching the frontal membrane ( Fig. 8 ). Moreover, the ovicell of Hincksina chimaera sp. nov. presents a developed central peak ( Fig. 8E ), which is characteristic of H. flustroides according to Berning et al. (2021).

In contrast, H chimaera sp. nov. shares with H. synchysia the size, shape, orientation and abundance of avicularia ( Figs 6 and 8 ). In addition, the ovicell can be immersed in an autozooid or in an avicularium ( Fig. 8C–D ), a character that Berning et al. (2021) considered exclusive of H. synchysia . The number of marginal spines is, however, lower in H. synchysia (6–9) than in H. chimaera (8–10).

Finally, the oral spines of H. chimaera sp. nov. closely resemble those present in the ovicelled zooids of H. calpensis (see Reverter-Gil et al. 2012: fig. 2b, d), being erect, flattened and somewhat triangular, with the beginning of a bifurcation and uncalcified pores in the tips, which are parallel or aligned oblique to the zooidal midline and converging distally ( Fig. 8B–D ).

The development of the spines is variable, as in other species of the genus ( Berning et al. 2021), but contrary to what was stated by those authors, their development does not seem to be related to the degree of exposure of the colony to the substrate, but with the ontogeny of the colony, because the marginal and oral spines are often finer and more cylindrical near the periancestrular region whereas they are more developed and flattened in the areas furthest away from the colony. This is visible in sample MNCN 25.03/2488, which contains five colonies in different positions in a concretion. A similar variation also occurs in H. calpensis , although in this species the spines are much more markedly developed, forming a frontal shield.

Hincksina chimaera sp. nov. was previously reported from the Alboran Sea by Templado et al. (2006), as H. flustroides (in part) without further information. We have revised the original material, conserved at the MNCN (see material examined and Figs 8 , 12B ). Almost all the material actually corresponds to H. chimaera , but a single sample (MNCN 25.03/2402, Fig. 9 ) corresponds to an ovicelled colony of Hincksina longispinosa Harmelin & d’Hondt, 1992 . This species was known only from its original description in the Gulf of Cadiz at 135–521 m depth, but it was very recently reported in the Alboran Sea at slightly shallower depths (112–120 m) by Ramalho et al. (2022). The present colony also comes from a similar depth (87–213 m) ( Fig. 12B ).

The record of H. flustroides made by Álvarez (1992) from the Alboran Island is doubtful, as the original paper does not include a description or figures, whilst the original sample (MNCN 25.03/223) contains only some small, eroded fragments impossible to identify at species level.

New sampling will be necessary in the Alboran Sea to verify if H. chimaera sp. nov. replaces here the Mediterranean H. synchysia or if both species do coexist, as is the case for H. longispinosa .

Figures

Fig. 8. Hincksina chimaera sp. nov., Alboran Island.A–C. Paratype (MNCN 25.03/2412).D–F. Holotype (MNCN 25.03/2450). A. Growing edge of colony showing interzooidal avicularia and autozooids. Note the thin spines, some bifurcated. B. Detail showing avicularia, oral spines and bifurcated spines (bottom left). C. Ovicells immersed in avicularia and in distal autozooid. D. Ovicelled zooids and avicularia. Note two ovicells associated with the same avicularium and flattened marginal spines. E. Ovicelled zooids and avicularia. Note the developed central peak in the ovicell. F. Flattened marginal and oral spines.

Fig. 12. Iberian distribution of the species treated in the present paper (see legends in the figures). A. Arbopercula angulata (Levinsen, 1909) and Caberea cantabra sp. nov. B. Species of Hincksina Norman, 1903.

Fig. 9. Hincksina longispinosa Harmelin & d’Hondt, 1992 (MNCN 25.03/2402), Alboran Island. A. Group of ovicelled zooids with avicularia. B. Interzooidal avicularia.

Fig. 6. Hincksina synchysia Berning et al., 2021 (MNCN 25.03/2639), Hormigas Islands (Murcia, Mediterranean Spain). A. Autozooids and avicularia. B. Ovicells immersed in autozooids and in avicularia.