Exechonella floridiana, 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 : 32-33

Exechonella floridiana n. sp.

( Fig. 12 , Table 11)

Material examined. Holotype: USNM 545918 , encrusting a shell-hash concretion. Atlantic Ocean , Walton Rocks , South Hutchison Island, St. Lucie County, Florida, coll. 99–11, 1999, by Dr. J.E. Winston.

Etymology. Named after the Florida Peninsula, where the species has been found.

Description. Colony encrusting, unilaminar, multiserial. Autozooids pentagonal, hexagonal or oval in shape, separated by narrow grooves. Narrow marginal gymnocystal rim is seen in some zooids. Primary orifice subcircular, almost as long as wide, poster (one-third) smaller than the anter (two-thirds), both of rounded/oval outline. Anter wall underlain by an inner lamina which ends form triangular condyles, with their blunt points slightly extending beyond the edge of step-like curve and directed to the orifice midline. A low thick-walled peristome is slightly longer than wide when seen from above. Its proximal part wide and flat, with a smooth central area and wrinkled lateral sides. Frontal shield smooth, perforated by 29–40 rather closely spaced foramina, each with wide and smooth gymnocystal rim raised slightly above the frontal shield, towards a small central opening. Fusions between the rims of 2–4 foraminal rims are frequent. Marginal pores are mostly oval and elongated. Avicularia are present on the outer raised rim of two larger lateralmost foramina that frequently have two openings. Each avicularium has a thin round mandible and the central nipple-like structure underneath. Kenozooids with 2–3 pores closed by cuticular plate. Vertical zooidal walls narrow or wide, represented by multiporous mural septula with 1– 2 rows of communication pores. Ancestrula is unknown.

South Hutchison Island, Florida, Atlantic Ocean

m±sd r n AzL 774±68 712–879 10 AzW 580±53 515–682 11 OrL 223±7.6 205–227 11 OrW 217±10 197–227 11 FoN 40±3.6 29–40 11 FoD 56±7 40–70 40 OD 19±4.2 10–30 40 Remarks. Exechonella floridiana n. sp. is characterized by its primary orifice subcircular, with the poster (one-third) slightly smaller than the anter (two-thirds), both of rounded outline. Peristome is low and thick-walled with its proximal part wide and flat. Avicularia frequently have two openings. Also the general proportion between the length of the orifice and that of the frontal shield shows a relation of 1: 1–1.5 in E. floridiana n. sp. and 1: 2 in the rest of the species from the E. antillea -complex.

Dr. Winston kindly sent us the colony from her collection made in Florida that was originally identified and labeled as E. antillea . The comparison of this specimen with the holotype of E. antillea showed that it is a new species. Its orifice poster is of almost the same width as the anter, while poster is clearly narrower in E. antillea . The proximal edge of the peristome in the latter species is rather narrow with a small knob-like projection, and it is wide and flat in E. floridiana n. sp. It also shows a peculiar ‘avicularian’ foramina that often possess two openings that are not covered with a mandible. In contrast, avicularia-bearing foramina in E. antillea possess only one opening that is often covered by the rounded mandible.

Exechonella floridiana n. sp. is also strongly reminiscent E. pumicosa by its peristome shape. Comparison with the holotype showed that the former species has less foramina (29–40) per zooid with larger openings of 19 µm in average whereas there are 40–62 foramina of just 9 µm in the latter species. Also, the foraminal rims seem to fuse more often, making longer ‘chains’ of foramina in E. pumicosa .

Distribution. Exechonella floridiana n. sp. was found in the Atlantic Ocean, off the Walton Rocks, South Hutchison Island, St. Lucie County, eastern coast of Florida.

Figures

FIGURE 12. Exechonella floridiana n. sp. Atlantic Ocean, Florida (A ‒ D: holotype USNM 545918, non-cleaned colony). A, general view of holotype from above. B, close-up of autozooid with two avicularia (arrowheads) associated with lateralmost foramina. Details of primary orifice are visible (operculum removed). C, close-up of autozooid with two avicularia (arrowheads) associated with lateralmost foramina. Each lateral foramen has two openings. D, lateralmost foramen with avicularium and two openings. Scale bars: A = 500 µm; B = 200 µm; C = 100 µm; D = 50 µm.