Hincksina neptuni (Jullien in Jullien & Calvet, 1903 )

Berning, Björn, Spencer Jones, Mary E. & Vieira, Leandro M., 2021, Revision of the European species of the genus Hincksina Norman, 1903 (Bryozoa, Cheilostomatida, Flustridae), Zootaxa 5081 (3), pp. 333-352 : 342-344

Hincksina neptuni (Jullien in Jullien & Calvet, 1903) n. comb.

( Fig. 4 )

Membraniporella neptuni Jullien in Jullien & Calvet, 1903: 38, pl. 5, fig. 2; Calvet 1907: 397.

Material examined. Lectotype (here designated): MOM INV-22462, Hirondelle, 14/8/1888, Stn 226, 38°31.32’N 28°34.52’W, Faial-Pico Channel (Azores), 130 m, colony fragment on bioclast, on slide. Non-type material examined using SEM: MNHN-IB-2008-1999, Talisman , 13/8/1883, Stn 125, 38°29.1’N 28°37.3’W, Faial-Pico Channel (Azores), 80–115 m, one large colony on bivalve shell, Calvet coll., http://coldb.mnhn.fr/catalognumber/mnhn/ ib/2008 - 1999; MNHN-IB-2017-783, Biaçores, 22/10/1971, Stn P. 23, scuba dive near Santa Cruz ( Flores, Azores; no exact position provided), 18 m, one colony on rock from vertical cliff, leg. H. Zibrowius ; OLL 2021/2, same specimen information as MNHN-IB-2017-783, one colony on rock.

Description. Colony encrusting, unilaminar, multiserial.Autozooids elongate oval, relatively large (ZL 540±40, 485–622, 20; ZW 285±27, 237–344, 20), arranged in irregular series ( Fig. 4A, D ), dried skeleton translucent, zooids separated by shallow grooves. Vertical walls with two or more uniporous pore plates per neighbouring zooid. Development of gymnocyst extremely reduced, cryptocyst practically absent, opesia therefore almost as large as zooecium (OpL 505±33, 445–561, 20; OpW 230±26, 189–272, 20) ( Fig. 4B, D, F ). Opercular region laterally framed by a pair of flattened, palmicorn oral spines, ramifying into 3–5 short branches, aligned slightly oblique to zooidal midline ( Fig. 4B, C, E ); frontal membrane in mature zooids overarched by 10–14 (most often 12) laterally compressed mural spines that increase in size distally, more or less antler-shaped, growing upright from their base and abruptly broadening vertically (i.e. the thickness remaining the same when viewed from above) and bending inwards at an angle of c. 90° towards the zooid interior, usually producing a short vertical offshoot at the bend and occasionally one or more offshoots along the main spine which is thinning and bending upwards distally; lateral spines extending to about the zooidal mid line, barely touching the opposite spines, proximal spines shorter and usually with fewer vertical offshoots, distalmost spine pair largest and with most vertical offshoots, slightly slanting distally, i.e. leaning towards oral spines making the broad vertical flanks visible from above ( Fig. 4A–D, F ); both oral and mural spines in late astogenetic zooids unjointed.

Ovicell endozooidal, positioned in distal avicularium, ooecium continuous with the gymnocyst of the avicularian cystid forming a short but broad hemispherical cap (OvL 93±15, 67–115, 20; OvW 187±20, 153–215, 20), proximal margin raised to produce a central peak ( Fig. 4E ).

Avicularia interzooidal, very frequent ( Fig. 4A ), positioned on a square cystid, gymnocyst occasionally relatively well developed proximally, confined to the corner opposite of the rostrum distally, avicularium pointing distally (more rarely distolaterally), c. 2.5x longer than wide (AL 267±27, 216–305, 20; AW 102±11, 83–123, 20), widest just proximal to condyles, occasionally extending over frontal membrane of distal zooid ( Fig. 4B, F ); rostrum usually very elongate triangular with a rounded tip, often slightly curved distally and gently to steeply raised, mandible hinged on a pair of short straight condyles that delimit a semielliptical proximal area (ML 184±16, 157–213, 20; MW 85±9, 73–105, 20), entire opesia elongate oval, framed by an immersed calcified shelf of roughly constant width laterally and proximally, distal shelf occupying more than half of rostrum, interior mandible marked by a large subcircular lucida ( Fig. 4F ).

Ancestrula and early astogenetic stages unknown.

Remarks. Originally placed in the genus Membraniporella Smitt, 1873 (family Cribrilinidae Hincks, 1879 ), its endozooidal ovicells with a cap-shaped ooecium, the presence of interzooidal avicularia with condyles as hinges for the mandible, oral and mural spines, and the absence of basal pore chambers justify assigning Membraniporella neptuni to the flustrid genus Hincksina . Hincksina neptuni is closely related with Hincksina alice (see below) owing to the pointed avicularia, a character separating these from all other known Recent Hincksina species , and arguing for a close relationship with the genus Gregarinidra Barroso, 1949 . On the other hand, the mural spines of H. neptuni are branching and therefore also similar to those in H. alice , but their shape (laterally compressed and more or less falciform) is rather similar to those of Hincksina sceletos from Madeira. Another character shared with H. sceletos are the unjointed oral and mural spines in late astogenetic zooids in H. neptuni . As the pointed avicularium seems to be the only difference between these and other Hincksina species , we have decided to assign H. neptuni and H. alice to the genus Hincksina rather than to Gregarinidra (see also Discussion).

While no potential types from Jullien’s collection are present at the MNHN ( Tricart & d’Hondt 2009; B. Berning, pers. observ.), a single specimen from the type locality is kept in the Calvet collection at the MOM, which is here chosen as lectotype. It was filed under “ Membraniporella azorensis Jullien ”, which was apparently the name initially intended by Jullien to be given to this species, as indicated by the original labelling on the front of the slide. On the reverse side it was presumably also Louis Calvet who later noted “ M. azorensis MS. decrit comme M. neptuni ”. During preparation of the manuscript to their 1903 work, Calvet must have therefore ‘overruled’ Jullien’s initial decision and named the species Membraniporella neptuni . This is noteworthy because the first part of the work, and accordingly the authorship of newly introduced taxa, was credited to Jullien while Calvet was supposedly only contributing notes and additions to this part of the manuscript when continuing the work after Jullien’s death ( Jullien & Calvet 1903, p. 11). This example is one of several, however, in which Calvet edited Jullien’s manuscript in a substantial way (B. Berning, pers. observ.).

Hincksina neptuni is known only from the Azores, where it encrusts shells and rocks. It has been reported from the Faial-Pico Channel in the central group of islands (80–130 m), where it occurs sympatrically with H. alice , and from the island of Flores in the western group (18 m) .

Figures

FIGURE 4. Hincksina neptuni (Jullien in Jullien & Calvet, 1903) n. comb. A. Overview of lectotype with auto- and ovicellate zooecia (MOM INV-22462). B. Slightly oblique view on two autozooids (MNHN IB-2008-1999). C. Oblique view on the two fan shaped, oral spines (top), the distalmost pair of mural spines proximal to these (centre), and two pairs of more proximally positioned mural spines (bottom) (MNHN IB-2008-1999). D. Incompletely developed zooids at colony growth margin, note the relatively thin vertical zooecial margins from which the mural and oral spines will develop by epithelial folding during later ontogeny. E. Ooecium (lectotype, MOM INV-22462). F.Avicularia with mandibles still in place (lectotype, MOM INV-22462). Scale bars: A, D, 200 µm; B, F, 100 µm; C, E, 50 µm.