Abditoporella dimorpha, Sosa-Yañez, Armando, Vieira, Leandro M. & Solís-Marín, Francisco A., 2015

Sosa-Yañez, Armando, Vieira, Leandro M. & Solís-Marín, Francisco A., 2015, A new cheilostome bryozoan genus, Abditoporella (Hippoporidridae), from the eastern Pacific, Zootaxa 3994 (2), pp. 275-282 : 277-279

Abditoporella dimorpha n. sp.

( Figure 1 A–F; Table 1 )

Hippopodinella adpressa: Osburn 1952: 467 , pl. 57, fig. 6; Soule & Duff 1957: 126; Soule 1961: 45; Soule & Soule 1964: 35. Non Lepralia adpressa Busk, 1854: 75 .

Material examined. Holotype: UNAM-ICML-0000045, Faro de Bucerias, Aquila, Michoacan, Mexico, 18º21.159’ N, 103º31.312’ W, 27 m, encrusting dead sea-urchin test (specimen without organic tissues). Paratypes: UNAM-ICML-0000044, Caleta de Campos, Lazaro Cardenas, Michoacan, Mexico, 18º04'15.19'' N, 102º43'44.52'' W, 5 m, encrusting sea-urchin primary spines. Carrizalillo, Lazaro Cardenas, Michoacan, Mexico, 18º03'28.96'' N, 102º42'07.94'' W, 3 m, encrusting sea-urchin primary spines. El Morro Colorado, Lazaro Cárdenas, Michoacan, Mexico, 18º03'05.83'' N, 102º38'34.5'' W, 0–2 m, encrusting sea-urchin primary spines. UNAM-ICML-0000046, Las Gatas, Zihuatanejo, Guerrero, Mexico, 17º37'17.6'' N, 101º33'13.88'' W, 10 m, encrusting sea-urchin primary spines. El Zacatoso Zihuatanejo, Guerrero, Mexico, 17°39'14.15" N, 101°37'20.25" W, 15 m, encrusting sea-urchin primary spines.

Diagnosis. Colony encrusting, unilaminar or multilaminar. White. Autozooids initially longer than wide, narrow distally and broader proximally, becoming irregularly disposed in mature colonies. Frontal shield pseudoporous. Orifice campanuliform, longer than wide, with elongate anter separated from short, broad poster by well-developed condyles. No oral spines. Small avicularium with rounded rostrum present near orifice or placed on frontal shield. Polygonal kenozooids with large pseudopores and no orifice may be present between the autozooids. Embryos endozooidal, brooded in female zooids with dimorphic orifice; brooding zooids with smaller, squatter orifices than non-brooding zooids.

Etymology. From Greek dis, twice, and morphe, form, alluding to the dimorphic orifice.

Description. Zoarium uni- to multilaminar, encrusting gastropod shells, dead tests of sea-urchins or often on sea-urchin spines of Eucidaris thouarsii . Zooids distinct, initially longer than wide (see Table 1 ), with rounded, narrow distal end, broader proximally with straight, angled margins, becoming irregularly disposed, with morevariable outlines in mature colonies, separated by distinct interzooidal furrows. Frontal shield slightly convex, with rugose surface and regularly spaced pseudopores. Orifice campanuliform, longer than wide, with elongate anter separated from short, broad poster by well-developed condyles. No oral spines. Avicularia rare, small, adventitious or interzooidal, often seen near orifice, with complete crossbars; rostrum rounded, smooth, with suboval to subacute mandible. Infrequent polygonal kenozooids between autozooids, with large pseudopores and no orifice. Embryos brooded endozooidally in dimorphic female zooids with smaller orifices than non-brooding zooids; a broad zone of pseudopores, larger than frontal pseudopores, distal to maternal orifice, which has a less-rounded proximal margin. Polypides and ancestrula not seen.

Distribution. Abditoporella dimorpha n. sp. is known from the Gulf of California ( Soule 1961; Salazar- Vallejo & Lopez-Muraira 1983) and Scammon’s Lagoon, Baja California, Mexico ( Soule & Soule 1964) (as Hippopodinella adpressa ), and from the coasts of Michoacan and Guerrero, Mexico (present study) ( Figure 2 ). Specimens were collected from 0 to 27 m depth, but the species can be found to 73 m ( Soule 1961).

Remarks. Abditoporella dimorpha seems to be present on gastropod shells and encrusting spines and dead tests plates of sea urchins ( Soule 1961; present study). The region of the test with the higher number of bryozoan colonies in all sea urchin species was the ambitus and apical zone and the region in the spines with highest bryozoan density was the apical zone of the spine.

Some bryozoologists ( Hastings 1930; Osburn 1952; Soule 1961; Soule & Soule 1964) had described the frontal shield of putative Hippopodinella adpressa (i.e. Abditoporella dimorpha ) as pseudoporous, and characteristic of specimens from the Pacific. Based on type material, it is now established that the frontal shield of O. adpressa has no pseudopores ( Carter & Gordon 2007), thereby distinguishing this species from Mexican specimens. Osburn (1952) described Hippopodinella turrita as having a pseudoporous frontal shield, and this too may be included in our new genus as Abditoporella turrita n. comb. Abditoporella turrita appears to be endemic to the Galápagos ( Banta & Redden 1990). It has smaller orifices (c. 0.12 mm long, 0.08 mm wide) than in A. dimorpha n. sp. (0.11–0.15 mm long, 0.085–0.11 mm wide) and very small pseudopores. These differences were also observed by Osburn (1952). Although Osburn (1952) did not describe or illustrate skeletal sexual dimorphism in A. turrita , he noted that the primary orifice is displaced from the distal region of the zooid as in A. dimorpha n. sp. ( Figures 1 E–F).

Figures

FIGURE 1. Abditoporella dimorpha n. sp. A, group of zooids from a young colony. B, close up of autozooids (Az), several female zooids (Fz) and kenozooid (Kz). C, unbleached colony with autozooidal opercula present. D, autozooids with a group of avicularia (Av); note the buttressed and recessed communication-pore areas at right. E, close up of campanulate primary orifice with tubercular margin of orificial rim. F, portion of growing edge of young colony.

FIGURE 2. Distribution of Abditoporella dimorpha n. sp. and Abditoporella turrita n. comb. on the western Mexican coast.

Tables

TABLE 1. Morphometric data (in mm) for Abditoporella dimorpha n. sp.

	N	MEAN	ST DEV	RANGE Min	Max
Lz	15	0.52	0.04	0.47	0.58
Wz	15	0.31	0.05	0.24	0.39
Lop	15	0.134	0.01	0.11	0.15
Wop	15	0.10	0.01	0.085	0.11
Lav	9	0.06	0.22	0.048	0.067
Wav Lkz Wkz	9 5 5	0.05 0.27 0.24	0.01 0.01 0.07	0.038 0.23 0.13	0.061 0.35 0.39