Amathia distans Busk, 1886

Fehlauer-Ale, Karin H., Vieira, Leandro M. & Winston, Judith E., 2011, Molecular and morphological characterization of Amathia distans Busk and Amathia brasiliensis Busk (Bryozoa: Ctenostomata) from the tropical and subtropical Western Atlantic, Zootaxa 2962, pp. 49-62 : 56-58

Amathia distans Busk, 1886

( Figs 3, 4 , 6, 8, 10 ; Tables 1 and 3)

Amathia distans Busk, 1886: 33 , pl. 7, fig. 1; Marcus 1937: 134 (part) (not pl. 27, fig. 72); 1941: 28, fig. 29; 1949: 27, fig. 42; 1955: 313 (part); Osburn 1940: 339; Winston 1982: 110, fig. 10; d’Hondt 1983: p. 65 (part; form 1, p. 69).

Material examined. Lectotype (chosen here): NHMUK 1887.12.9.925 ( Figures 3 and 4 ), Amathia distans (G. Busk det.), H.M.S. ‘ Challenger ’, Bahia ( Brazil), 10–20 fms (18.29–36.58 m), figured by Busk (1886, pl. vii, fig. 1). Paralectotypes: NHMUK 1887.12.9.926, Amathia distans (G. Busk det.), H.M.S. ‘ Challenger ’, Bahia ( Brazil), 10–20 fms (18.29–36.58 m); NHMUK 1899.7.1.4358–4359, Amathia distans , H.M.S. ‘ Challenger ’, Bahia ( Brazil), G. Busk Collection; NHMUK 1963.2.12.359, Amathia distans , H.M.S. ‘ Challenger ’, Bahia ( Brazil), Dundee Collection. Additional material ( Table 1): MZUSP (498–500), MZUSP (508–510) (donated to NHMUK), São Sebastião, São Paulo State, Brazil.

Redescription. Colonies cuticularized, erect, regularly branched, transparent white to yellowish tan. Frontal surface of stolons and zooids of living colonies with bright yellow pigment spots. Autozooids in biserial clusters, 9 to 19 pairs of long clockwise and/or anticlockwise complete spirals at the distal end around the thickly cuticularized slender stolon; direction of spirals not maintained from maternal to daughter stolons; each maternal stolon buds two daughter stolons, one of which has autozooidal clusters organized in a clockwise spiral and the other in an anticlockwise spiral. Clusters present from distal half of stolon to three quarters of its length. Zooids tubular, connate for almost their entire length, not varying in size with the position of the series. Orifice terminal, circular. Polypides with 8 equal, slightly curved tentacles about 0.23 mm in length, with yellow pigment spots.

Remarks. Amathia distans is distinguished from its congeners by the combined presence of bright yellow pigment spots in stolonal and zooidal surfaces, including lophophores, and by a thickly cuticularized slender stolon (0.09–0.14 mm in diameter). The daughter stolons have autozooids organized in clockwise and anticlockwise directions, with the direction of spirals rarely maintained from maternal to daughter stolons as in A. brasiliensis .

Amathia distans and A. brasiliensis , which were described for the same locality by Busk (1886), were originally distinguished by the colony branching pattern, the stolon diameter and the size and position of the zooid clusters on the stolon. These distinctive characteristics have been confirmed through morphological analyses of syntype specimens deposited at the NHMUK. Here, we have selected and figured ( Figs 1–4 ) the lectotype specimens of both A. brasiliensis (NHMUK 1887.12.9.928) and A. distans (NHMUK 1887.12.9.925).

Specimens attributed to A. distans by different researchers over the years show morphological characteristics that do not completely fit the original description of Busk (1886) and probably pertain to other species. Unfortunately, any potential pigmentation differences cannot be observed in preserved colonies, as the pigment is lost in alcohol; only the characters of zooids, zooid clusters and internodes are available for comparison. Harmer (1915) identified as A. distans specimens characterized by dichotomous colonies with zooids partially joined, usually forming one complete loop in the distal part of the slender internode, about 0.10 mm in diameter. Although the diameter of the stolons measured by Harmer (1915) is similar to that in A. distans Busk , the Siboga specimens have zooids unjoined for two-fifths or more of their length.

Several Brazilian colonies with both wider and slenderer stolons were identified by Marcus (1937, 1941, 1949, 1955) under the name A. distans . Figures based upon specimens collected in São Paulo State ( Marcus 1937: pl. 27, fig. 72; Marcus 1949: fig. 42) show stolons 0.15–0.35 mm in diameter and were probably based upon both A. distans and A. brasiliensis . Osburn (1940) distinguished Caribbean specimens of A. brasiliensis and A. distans on the basis of stolon diameter of stolon and the degree of zooid joining. Yellow-pigmented zooids were first noted in A. distans collected in Florida by Winston (1982), and have never been reported in specimens of A. distans from the Pacific (D.P. Gordon, pers. comm.). The yellow-spotted Atlantic variety of A. distans (footnote 4, p. 69 in d’Hondt 1983) is considered A. distans sensu stricto. D’Hondt’s figured specimen ( d’Hondt 1983: p. 64, fig. 35C; p. 69, form 2) probably represents a different species, based on the presence of autozooids 0.20–0.25 mm in diameter, wider than those of A. distans Busk ( Table 3). The small specimen from South Australia recorded as A. distans by MacGillivray (1895) has unjoined zooids; this specimen also probably belongs to a different species, which resembles ‘ Amathia distans form 2’ of d’Hondt (1983: p. 69).

Chimonides (1987) discussed other morphological similarities (e.g. shape of clusters of zooids rotating 360° around stolon) and differences (proportion of bare stolon between adjacent zooid clusters and diameter of stolon) between A. brasiliensis and A. distans . Souto et al. (2010) reported a similar appearance amongst A. minoricensis and some widespread species, including A. distans . However, according to those authors, A. minoricensis is readily distinguished from either A. distans or A. brasiliensis by the presence of rhizoids, autozooidal shape, degree of twisting of zooid clusters along stolons and the branching pattern of colonies.

Biological notes. Amathia distans sensu stricto occurs at least from Brazil to Florida on substrata including algae, bryozoans, and anthropogenic surfaces.

NHMUK MZUSP MZUSP MZUSP MZUSP MZUSP 1887.12.9.925 498 499 508 509 510

Autozooid length

Min-Max - 0.310–0.540 0.350–0.470 0.330–0.480 0.390–0.520 0.310–0.520

Mean (SD) - 0.450 (0.070) 0.405 (0.032) 0.414 (0.041) 0.424 (0.039) 0.410 (0.060)

Autozooid width

Distribution. The species was originally described from the Brazilian State of Bahia by Busk (1886: p. 33), and was reported for the shores of the States of Espírito Santo, Rio de Janeiro, São Paulo, Paraná ( Marcus 1937, 1941, 1949, 1955), and Alagoas ( Vieira et al. 2007, 2008). It has since been treated as a widespread fouling species in warm waters, with records for Australia, Indonesia, Florida, Southern California, Gulf of California, and New Zealand (viz. Harmer 1915; Gordon & Mawatari 1992; Soule in Osburn 1953; Menon 1972; Gordon, 2009; K. Tilbrook pers. comm. 2010.). However, some of these records are doubtful and require reinvestigation.

Figures

FIGURES 1 – 4. 1 – 2, Amathia brasiliensis, NHMUK 1887.12. 9.928 (lectotype specimen, chosen here), off Bahia, Brazil; 3 – 4, Amathia distans, NHMUK 1887.12. 9.925 (lectotype specimen, chosen here), off Bahia, Brazil.

FIGURES 5 – 10. 5, Amathia brasiliensis, general view of the whitish-pale living colony; 6, Amathia distans, general view of the bright yellow living colony; 7, A. brasiliensis, close-up of the biserial autozooidal clusters around the wide stolon; 8, A. distans, close-up of autozooidal clusters around the slender stolon; 9, A. brasiliensis, close-up of whitish-pale pigment spots in the frontal surface of stolon and zooids; 10, A. distans, close-up of bright yellow pigment spots in stolon and zooidal surfaces, including lophophores.