Crepis verticillata Harmer, 1926

Reverter-Gil, Oscar, Souto, Javier & Fernández-Pulpeiro, Eugenio, 2011, Revision of the genus Crepis Jullien (Bryozoa: Cheilostomata) with description of a new genus and family and notes on Chlidoniidae, Zootaxa 2993, pp. 1-22 : 10-13

Crepis verticillata Harmer, 1926

( Figs 23–33 ; Table 7)

Crepis verticillata Harmer, 1926: 319 , pl. 15, figs 13–18. Not Crepis verticillata: Gordon 2009: 49 .

Material examined. Lectotype: NHMUK 1928.9.13.83, Crepis verticillata, Siboga , western Torres Straits, 1888, coll. A. Haddon, on Eudendrium infundibuliforme Kirkpatrick. Paralectotype: NHMUK 1928.9.13.84, Crepis verticillata, Siboga Stn 141, western Torres Straits, 1888, coll. A. Haddon, on Eudendrium infundibuliforme Kirkpatrick. Paralectotype: NHMUK 1928.9.13.85, Crepis verticillata, Siboga , western Torres Straits, coll. A. Haddon, 24/2/1898.

Description. Colony small, creeping, composed of whorls of autozooids along a uniserial stoloniform axis. Central autozooids of whorl comprising a distal dilatation and long, filiform cauda cemented to hydroid substratum. Dilatation cucullate (hood-like), with smooth exterior-walled (gymnocystal) calcification; frontal surface generally inclined about 45° to the substratum, occasionally more or less so, or even vertical. Gymnocyst only developed proximally. Cryptocyst flat, covering less than two thirds of frontal area, with faint reticulate pattern on its surface, visible only in dry material. Operculum smaller than opesia, occupying more than a half its length. Cauda originating from central zooid of whorl, an oblique, incomplete septum partially cutting off a small chamber at basal side of terminal wall of parent zooid; central zooid of whorl producing two lateral zooids joined to proximolateral end of parent dilatation; communication via a blister-like rosette-plate; lateral zooids lacking cauda, deflected about 45° to central axis. Each secondary zooid may produce another lateral zooid, also lacking cauda and inclined at 45°. In this way, a whorl of five zooids joined by their proximal parts is formed, partially encircling hydroid substratum. Lateral walls and cryptocyst well calcified; basal wall, attached to the substratum, incompletely calcified, leaving an elongate fenestra in median zooid and a more oval fenestra in the other zooids of the whorl. Spines, heterozooids and ovicells absent. New branches formed by lateral budding from main axis. Ancestrula unknown.

Remarks. The description and original figures of C. verticillata by Harmer (1926) are very complete and accurate. However, we have added here some data that were not originally included, such as measurements taken from the original material and photographs by SEM.

Crepis verticillata presents some characteristics that depart from other species of the genus. Firstly, the frontal surface of the dilated portion of the zooid is inclined to the substratum at a variable angle, generally about 45° but sometimes as much as 90°. In the other species of the genus the frontal wall is more or less parallel to the substratum.

Secondly, the budding and production of new branches in the different species of Crepis always takes place from the autozooidal dilatation, whereas C. verticillata follows a different pattern. In this species lateral zooids are also produced, but these appear in a terminal position, lack a cauda and are grouped in whorls. However, the ability to creating new branches may not have been totally lost; a calcareous rootlet formed by one of the lateral zooids in a whorl was reported by Harmer (1926: 319, pl. 15, fig. 14, and Fig. 33 in the present paper), that, in his opinion, may perhaps form the commencement of a new axis. On the other hand, Harmer (1926) stated that he had not observed any branching of the main axis of the colony; however, in the samples NHMUK 1928.9.13.83 ( Fig. 30 ) and NHMUK 1928.9.13.84 ( Figs 31, 32 ) we found up to four lateral branches, overlooked by the author; these are produced by lateral budding of a new axis from a cauda.

As mentioned above, in some of the colonies of C. sidneyi from Singapore ( Figs 14, 15 ) and Darwin ( Figs 16, 17 ), there is a tendency towards axial growth, with zooids having long caudae, while the lateral zooids exhibit a very short cauda that is distally curved. In one case, the lateral zooid joins the maternal zooid laterally as in C. verticillata ( Fig. 16 ), which inclined Gordon (2009) to ascribe specimens from Darwin to this species. This type of growth could be an adaptation to filiform substrata (erect bryozoans and hydroids); it does not occur in colonies of C. sidneyi collected from other substrata. From this perspective, the morphology of C. verticillata seems to become one more evolutionary step in this direction, exhibiting a complete adaptation to this type of substratum. The zooids form whorls around the hydroid, with the lateral zooids losing not only the cauda but also the ability to produce new distal zooids. The ability to produce new axis is then restricted to the central zooid of a whorl, which alone produces a long axial cauda, constituting an evolutionary novelty in the genus. In all cases, the branching seems to occur concurrently with branching of the hydroid, allowing the colony to take advantage of the limited area of available substratum.

To conclude, although the morphology of C. verticillata may seem at first very different from the other species of Crepis , we infer that its characters do not preclude inclusion in this genus.

Crepis verticillata is known only from western Torres Straits.

SD, Standard deviation; N, number of measurements.

Figures

FIGURES 23 – 29. Crepis verticillata Harmer, 1926. 23, view of colony on hydroid substratum (NHMUK 1928.9. 13.83, lectotype); 24, same, a whorl of three zooids; 25, a whorl of five zooids detached from the substratum; note the development of the gymnocyst (NHMUK 1928.9. 13.85, paralectotype); 26, same, a whorl of three zooids detached from the substratum; 27, same, autozooid with the frontal surface inclined at a right angle; 28, same, autozooid with the frontal surface inclined at 45 º; 29, same, basal view of a whorl, with basal fenestrae.

FIGURES 30 – 33. Crepis verticillata Harmer, 1926. 30, a lateral branching (NHMUK 1928.9. 13.83, lectotype); 31, 32, caudal branching (NHMUK 1928.9. 13.84, paralectotype); 33, same, a calcareous rootlet on a lateral zooid.

FIGURES 12 – 17. Crepis sidneyi n. sp. 12, a colony on a flat substratum (NHMUK 1882.2. 23.16, holotype); 13, same, detail of branching; 14, autozooids showing long caudae (NHMUK 1929.9. 13.82, paratype); 15, same, central autozooids with long caudae and lateral autozooids with short caudae; 16, several autozooids, one of them lateral and without cauda (Darwin, photo by D. P. Gordon); 17, same, central autozooids with long caudae and lateral autozooids with short caudae (photo by D. P. Gordon).