Amastigia aviculifera, Vieira, Leandro M., Gordon, Dennis P., Souza, Facelucia B. C. & Haddad, Maria Angélica, 2010

Vieira, Leandro M., Gordon, Dennis P., Souza, Facelucia B. C. & Haddad, Maria Angélica, 2010, New and little-known cheilostomatous Bryozoa from the south and southeastern Brazilian continental shelf and slope, Zootaxa 2722, pp. 1-53 : 7-8

Amastigia aviculifera n. sp.

( Figures 3–7 , Table 3)

Material examined. Holotype. MZUSP 0 276, Brazil, project REVIZEE South SCORE, RV ‘Prof. Wladimir Besnard’, station 6664.

Diagnosis. Colony erect with multiserial branches; autozooids with 4–6 to six distal spines, no scutum; large frontal avicularium on proximal gymnocyst; basal surface with one vibraculum at distal end of each zooid and single axial vibraculum; ovicellular ectooecium entirely uncalcified frontally, with distal paired avicularia .

Etymology. The epithet aviculifera alludes to the paired avicularia at the distal end of ovicell.

Description. Colony erect, represented by small fragment about 25 mm long, with multiserial branches of 2-6 (often three) alternating zooidal series, about 1.2 mm in width and narrowing basally. Zooids narrowed basally; with concave oval opesia occupying the distal half of zooid length, bordered by granular cryptocyst, narrow and deeper, but well developed proximally. Distal spines present: internal autozooids with four distal spines, two in each side; marginal autozooids with two inner and three or four outer spines; ovicelled zooids with two spines in each side of orifice. Frontal scuta absent. One gigantic frontal avicularium present on proximal gymnocyst of most autozooids, with stout cystid; rostrum triangular, slightly serrated, with large triangular mandible, directed proximolaterally; crossbar absent. Axil with a single vibraculum. Basal surface with one vibraculum at basal end of each autozooid; cystid oblong, about 0.37 x 0.18 mm, with setal groove directed medioproximally; setae long as two autozooids. Rhizoids present on the basal surface of the colony. Ovicell longer than broad, smooth, with ectooecium entirely uncalcified frontally; paired moderate-sized avicularia occurring at the distal end of the ovicell, the triangular rostrum pointed obliquely outward.

n min–max mean SD Autozooid length 20 0.488–0.611 0.542 0.039 Autozooid width 20 0.124–0.228 0.284 0.024 Opesia length 20 0.278–0.352 0.322 0.022 Cryptocyst length 20 0.043–0.047 0.055 0.005 Avicularia length 20 0.161–0.278 0.211 0.038 Ovicell length 5 0.173–0.222 0.196 0.019 Ovicell width 5 0.073–0.216 0.185 0.016 Remarks. Amastigia aviculifera n. sp. is the first record of the genus in Brazilian waters. Among South Atlantic species of Amastigia , only three have zooids without scuta: A. antarctica ( Kluge, 1914) (type species of Anderssonia Kluge, 1914 ), A. kirkpatricki (Levinsen MS, in Harmer, 1923) and A. pateriformis ( Busk, 1884) . Amastigia aviculifera resembles A. kirkpatricki in autozooid size and in the shape of the gigantic avicularia and basal vibracula, but differs in the number of distal spines and the presence of two moderatesized avicularia at the distal end of the ovicell. Gordon (1984) described a new subspecies, Amastigia antarctica subtropicalis from New Zealand, that appeared closely related to A. antarctica . Later, Hayward (1995) redescribed the two Antarctic species, characterising A. antarctica as lacking distal oral spines and the abfrontal heterozoids comprising slender avicularia ; A. kirkpatricki was typified by having triserial branches, oral spines, and basal vibracula with long setae. Amastigia pateriformis lacks scuta or distal spines; it was collected at abyssal depths off Valparaiso, Chile, by H.M.S. ‘Challenger’.

Among South Atlantic species with scuta, Amastigia aviculifera resembles A. benemunita ( Busk, 1884) in having colonies with tri- to quadriserial branches. However, the presence of large frontal scuta is quite distinct in A. benemunita ; the specimens without scuta differ from those of A. aviculifera in the number of distal spines ― one inner and three outer distal spines in A. benemunita and two inner and three or four outer in A. avicularia ― and the shape of the frontal avicularia , which are larger in Brazilian species.

Two Pacific species were characterized by zooids without scuta, viz. Amastigia rudis ( Busk, 1852a) and Amastigia biseriata Osburn, 1950 . Amastigia rudis has small, paired, distolaterally directed avicularia , placed at the distal end of the ovicells and smaller than those in A. avicularia ; in addition, the very large avicularia on the proximal gymnocyst have hooked rostra, whereas the rostra of the large avicularia in the Brazilian colonies are serrate and unhooked. Amastigia biseriata Osburn, 1950 is distinguished by narrower, biserial branches (triserial only at bifurcations), a single distal spine on each side of the orifice, and most zooids with small lateral avicularia and the ovicells wider than long. The avicularia at the distal end of the ovicells in A. avicularia are more laterally directed than in the three species described by Gordon (1986) from New Zealand ― viz. Amastigia fiordica Gordon, 1986 , A. magna Gordon, 1986 , and A. puysegurensis Gordon, 1986 .

Distribution. Brazil: off São Paulo state, 500 m (present study).

Figures

FIGURES 2 – 7. 2, Chaperia brasiliensis n. sp., MZUSP 0 274 (holotype specimen), off São Paulo, Brazil. 3 – 7, Amastigia aviculifera n. sp., MZUSP 0 276 (part of holotype specimen), off São Paulo, Brazil. 3, Frontal view of multiserial branch; 4, close-up of paired avicularia at the distal end of the ovicell and one ovicelled zooid; 5, close-up of triserial branch with large frontal avicularia; 6, close-up of biserial branch, note the presence of six distal spines and large proximal avicularium; 7, close-up of two basal vibracula.