Schizotheca buski, Reverter-Gil & Fernández-Pulpeiro, 2007

Reverter-Gil, Oscar & Fernández-Pulpeiro, Eugenio, 2007, Species of genus Schizotheca Hincks (Bryozoa, Cheilostomata) described in the Atlantic-Mediterranean region, with notes on some species of Parasmittina Osburn, Journal of Natural History 41 (29 - 32), pp. 1929-1953 : 1940-1943

Schizotheca buski sp. nov.

( Figures 4F, G , 5A–C )

Schizotheca fissa (Busk) : Cook 1968, p 204.

Material examined

Holotype: NHM-1899.7.1.5199: Cape Verde Islands. HMS Herald. Busk Coll . Paratype: NHM-1899.7.1.5063: John Adams Bank. HMS Herald. Busk Coll.

Other material. NHM-1899.7.1.4467: Cape Verde. HMS Herald. Busk Coll. NHM- 1899.7.1.4468: John Adams Bank. Busk. Coll. NHM-1899.7.1.5226: Cape Verde. HMS Herald. Busk Coll. NHM-1963.4.18.22: Cape Verde. HMS Herald. Busk Coll. NHM- 1963.4.18.23: Cape Verde. HMS Herald. Busk Coll. MNHN-2694: Talisman 1883 , D. 104. Cape Verde.

Etymology

We dedicate this species to the British bryozoologist G. Busk, who first studied the specimens described here as a new species.

Description

Colony encrusting, unilaminar. Autozooids oval, arranged in linear series and separated by fine sutures, indistinct in calcified zooids; frontal surface flat, covered in thick granulation and imperforate, except for two to five conspicuous circular marginal pores.

Primary orifice almost circular; anter with denticulations concealed in frontal view by a rim of calcification; poster with a scarcely perceptible wide sinus and two long inconspicuous condyles. Peristome circular, thick, more evident proximally and covered by the granulation of the frontal wall of the zooid; the appearance is of two thick proximal tongues separated by a median U-shaped notch. Four to five oral spines, reduced to two in ovicellate or calcified zooids.

Autozooids occasionally with a small lateral avicularium, oval or lanceolate, located at the level of the peristome or slightly below, orientated laterally; foramen very extensive, occupying two-thirds to three-quarters of the rostrum; cross bar fine and without denticle.

Vicarious avicularia similar in size to the autozooids; orientation variable, but generally facing towards the edge of the colony; mandible triangular, distally hooked; foramen approximately half of the rostrum; cross bar lacks denticle. Rostrum of vicarious avicularium is three times the size of the adventitious avicularium.

Vicarious avicularia usually situated in rows consisting exclusively of avicularia and by irregular kenozooids of similar size or smaller than autozooids, with frontal wall of similar appearance to the autozooids; kenozooids may occasionally bear an adventitious avicularium similar to those existing in autozooids. In one specimen (1899.7.1.5199; Figure 5B ) the kenozooid was formed by recalcification of a vicarious avicularium, with the rostrum substituted by a porous plate.

Ovicell hyperstomial, prominent, imperforate, covered by the calcification of the distal zooids, which imparts to it an uneven appearance. Fissure wide, vaguely triangular, situated vertically.

Ancestrula not observed.

Measurements

NHM-1899.7.1.5199 (holotype). AZL: 0.41¡0.06 (25); AZW: 0.28¡0.04 (25); OL: 0.09¡0.006 (10); OW: 0.10¡0.01 (10); OVL: 0.14¡0.01 (20); OVW: 0.20¡0.01 (20); VAL: 0.33¡0.04 (11); VAW: 0.16¡0.02 (11); AAL: 0.11¡0.02 (19); AAW: 0.06¡0.01 (19); VAL/AAL53.08.

Remarks

Schizotheca buski sp. nov. is characterized by: encrusting colonies consisting of zooids with a circular orifice with a scarcely perceptible wide sinus and two small, long, inconspicuous condyles; the peristome has the appearance of two thick tongues separated by a median Ushaped notch; adventitious oral avicularium with oval rostrum (the only one of the species dealt with here that is not triangular) and on occasions lanceolate, and by vicarious avicularia with a triangular mandible distally hooked, situated in rows and mixed with kenozooids, separating sections of the colony. The vicarious avicularium is three times the size of the adventitious avicularium.

The material ascribed here to Schizotheca buski sp. nov. was originally studied by Busk, and labelled by this author with a MS name. This same material was later studied and expressly cited by Cook (1968), the author who re-labelled it as S. fissa . There are also two colonies from Cape Verde in the Jullien collection deposited in the MNHN, Paris (MNHN-2694: Talisman 1883 , D. 104), which do not appear to have been cited in any publications; they also correspond to S. buski sp. nov.

Schizotheca buski sp. nov. shows some similarities to S. fissa , but the species are distinguished by the growth of the colonies (small, subcircular, with zooids arranged in clear alternating rows in S. fissa ; more extensive, consisting of zooids that are not organized in clear rows, in S. buski ); the marginal perforations of zooids, as S. buski has a larger number of very conspicuous perforations; the primary orifice, suborbicular, with slightly rectangular condyles in S. fissa , and almost circular, larger, with two small, long condyles in S. buski ; the development of peristome; the number of oral spines, six to four in S. fissa , and four to two in S. buski ; the shape and position of vicarious avicularia, randomly distributed in S. fissa , and situated preferentially in rows in S. buski . Furthermore, in S. buski the adventitious avicularia have an oval or lanceolate rostrum, and the ovicells have a wider proximal fissure.

Schizotheca buski sp. nov. also shows some similarities to S. carmenae sp. nov. However, the two species are distinguished, amongst other characteristics, by the shape of the orifice (semielliptical and longer than wide in S. carmenae , almost circular in S. buski ); by the condyles, round in S. carmenae and long in S. buski ; by the shape of the peristome notch, much narrower and conspicuous in S. buski , and by the shape and size of the adventitious avicularia.

There is a certain degree of variation in the shape of the adventitious avicularium in S. buski . In some colonies, from Cape Verde, it is constantly oval (NHM-1899.7.1.4467, NHM-1899.7.1.5199, NHM-1899.7.1.5226, NHM-1963.4.18.23), whereas in those originating from John Adams Bank (off Brazil) the adventitious avicularia are lanceolate (NHM-1899.7.1.4468, NHM-1899.7.1.5063) ( Figure 5A ).

However , this difference must not be due to geographical variability and is perhaps of no taxonomic relevance, as one of the Cape Verde colonies (NHM-1963.4.18.22) has both types of avicularia .

Figures

Figure 4. (A–E) Schizotheca carmenae sp. nov.: (A) growing edge of the colony, showing adventitious avicularia (MNHN-7519); (B) growing edge of the colony, showing adventitious and vicarious avicularia (MNHN-7426, holotype); (C) primary orifice (MNHN-7426, holotype); (D) an ovicellate zooid with adventitious avicularia (MNHN-7426, holotype); (E) group of zooids at the growing edge, showing adventitious and vicarious avicularia (Sagres, Portugal, photograph: J.-G. Harmelin). (F, G) Schizotheca buski sp. nov.: (F) general view of the colony, showing two rows made of vicarious avicularia and kenozooids (NHM-1899.7.1.5199, holotype); (G) growing edge of the colony, showing vicarious avicularia (below) and oval adventitious avicularia (left above) (NHM- 1963.4.18.23).

Figure 5. (A–C) Schizotheca buski sp. nov.: (A) group of ovicellate zooids with lanceolate adventitious avicularia (NHM-1899.7.1.5063, paratype); (B) a vicarious avicularium and a kenozooid with a porous plate (left) (NHM- 1899.7.1.5199, holotype); (C) primary orifice (NHM-1899.7.1.5199, holotype). (D–F) Schizotheca tuberigera: (D) group of autozooids, some ovicellate, with adventitious avicularia and a vicarious avicularium (MNHN-14121); (E) group of kenozooids with adventitious avicularia (MNHN-13831); (F) primary orifice (MNHN-14061).