Exechonella californiensis, Cáceres-Chamizo & Sanner & Tilbrook & Ostrovsky, 2017

Cáceres-Chamizo, Julia P., Sanner, Joann, Tilbrook, Kevin J. & Ostrovsky, Andrew N., 2017, Revision of the Recent species of Exechonella Canu & Bassler in Duvergier, 1924 and Actisecos Canu & Bassler, 1927 (Bryozoa, Cheilostomata): systematics, biogeography and evolutionary trends in skeletal morphology, Zootaxa 4305 (1), pp. 1-79 : 28-29

Exechonella californiensis n. sp.

( Fig. 10 , Table 9)

Exechonella antillea: Osburn 1950 , p. 95–96, pl. 10, figs 9–10.

Material examined. USNM 10741 . Pacific Ocean, Gulf of California, 24° 22’ 15” N, 110° 19’ 15” W. Albatross Station D. 2825, depth 7 fathoms, 30 April 1888.

Etymology. Named after the Gulf of California, where the species has been found.

Description. Colony encrusting, unilaminar, multiserial. Autozooids pentagonal or hexagonal in shape, often with a narrow gymnocystal rim, separated by grooves. Prominent slits are also seen between some zooids. Primary orifice wide pear-shaped, almost as long as wide, poster (one-third) tending to be quadrate (angular), anter (twothirds) with a rounded outline. The anter has an inner lamina which ends at well-defined, usually ‘boot’-shaped (triangular) condyles with rounded tip directed to the orifice midline, and normally not extending beyond the edge a step-like curved area below. Collar-like peristome low, thin-walled, pustulose externally with short blunt processes in some zooids. It is normally oval, but often parallel-sided laterally, low, flat and rather narrow proximally. Proximal edge of the orifice straight or slightly concave. Frontal shield smooth or slightly pustulose, perforated by 28–35 well-separated rounded or oval foramina, each with a wide smooth (often wrinkled) gymnocystal rim, raised slightly above the frontal shield and sloping towards the small central opening; fusions between the rims of two foramina occasionally seen in some zooids. Small marginal pores are predominantly oval. Avicularia not observed. Kenozooids of various shapes and sizes and with 3–8 pores are often met near lateral and/ or proximal autozooidal margins. Ancestrula not observed.

California, Pacific Ocean

m±sd r n AzL 894±78.7 729–1000 9 WzL 639±33.5 571–683 10 OrL 224±24.2 190–260 9 OrW 222±12.3 200–240 9 FoN 31±2.02 28–35 12 FoD 63.12±7.24 42–73 25 OD 26.52±4.45 20–35 25 Remarks. Originally this species was described by Osburn (1950) from the Gulf of California, Pacific Ocean , as E. antillea (see above). The differences between the holotypes of these two species are the following: (1) primary orifice in the Californian material is almost as wide as long (224×222 µm), but it is longer than wide (210×198 µm) in the Atlantic material; (2) in the Gulf of California specimen the proximal orificial edge is straight or slightly concave, but in the Curaçao material it has a small knob-like central projection; (3) the peristomial rim bears blunt projections in some zooids in the Californian material, whereas it is smooth in E. antillea ; (4) zooids in the Californian specimen have 28–35 frontal shield foramina and fusions of the foraminal rims are infrequent, however in the holotype of E. antillea some 34–52 frontal shield foramina were seen, and fusions of the foraminal rims are common; (5) ‘gaps’ or slits between the frontal shields of the neighbouring zooids are common in E. californiensis n. sp. specimen whereas they are absent in the Caribbean one (these slits are reminiscent of the ‘pits’—in fact, not fully-formed parts of the frontal shield—observed in the species of E. ampullacea -complex); (6) no avicularia have been seen in the material from California thought they are present in the E. antillea holotype specimen. Instead, kenozooids are very abundant in the E. californiensis n. sp. holotype specimen. Considering all these differences an existence of two separate species seems obvious.

Distribution. The present species is currently known from the Gulf of California only.

Figures

FIGURE 10. Exechonella californiensis n. sp. Pacific Ocean, California (A ‒ D: holotype USNM 10741, non-cleaned colony). A, general view of holotype from above. B ‒ C, close-up of autozooids showing shape of primary orifice and kenozooids (k). D, zooidal orifice with removed operculum. Scale bars: A = 500 µm; B ‒ D = 200 µm.