Alloeocomatella Messing, 1995,

Summers, Mindi M., Messing, Charles G. & Rouse, Greg W., 2017, The genera and species of Comatulidae (Comatulida: Crinoidea): taxonomic revisions and a molecular and morphological guide, Zootaxa 4268 (2), pp. 151-190: 159-160

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Alloeocomatella Messing, 1995


Alloeocomatella Messing, 1995 

Table 1, Fig. 1View FIGURE 1 A –D, Fig. 2View FIGURE 2

Type species. Alloeocomatella polycladia Messing, 1995a  .

Other included taxa (1). Comissia pectinifer  AH Clark, 1911a.

Description. Mouth excentric in fully developed individuals; up to 30 arms; centrodorsal always welldeveloped, rounded pentagonal, and with cirri ( Figs. 1View FIGURE 1 B); all brachitaxes of 2 ossicles united by synarthry; first syzygy at 3+4 on arms arising from IBr (and IIBr when 20 or fewer arms present); arms arising from IIBr and IIIBr (specimens with>20 arms) with first syzygies at 1+2 and/or 3+4 (rarely 1+2 alone); distal intersyzygial interval usually 3; distalmost pinnule comb on P4–P8; comb of>20 (up to 39) tall, narrow, triangular, teeth confluent with outer edge of pinnule; comb not tapering significantly distally ( Fig. 1View FIGURE 1 C).

Distribution. Tropical Indo-western Pacific from northern Australia west to Chuuk Atoll and New Caledonia, east to the Maldive Islands, and north to Okinawa and Guam ( Kirkendale and Messing 2003; Messing 1995a, 1998b; Meyer 1986; Pilcher & Messing 2001). Depth range: 3 to at least 25 m (one record of 100 m [AH Clark 1931]). Known definitely from 6–18 m ( Alloeocomatella polycladia  ) and 3–23 m ( A. pectinifera  ) ( Messing 1995a).

Molecular results. Specimens identified as Alloeocomatella polycladia  and A. pectinifera  return as three distinct clades in parsimony and likelihood analysis ( Fig. 2View FIGURE 2), with a minimum of 5.7% uncorrected COI distance among them. Noticeable morphological variation was observed for Alloeocomatella polycladia  (e.g., size; numbers of arms, cirri, cirrals, and rows of cirri, distal intersyzygial intervals, presence/absence of distal spinose margins on arms), yet intra specific difference for COI was less than 0.6% among specimens collected at Lizard Island and Papua New Guinea (n=4). In contrast, little morphological variation has been recorded for Alloeocomatella pectinifera  , yet there was up to 7% COI divergence among specimens from only Madang, Papua New Guinea  . This high variation could suggest two species of Alloeocomatella pectinifera  . Two distinct A. pectinifera  clades; A. pectinifera  type A (2.3–4.3% uncorrected intra specific divergence (n=6)) and A. pectinifera  type B (one specimen only) were recovered in the phylogenetic analyses. The type locality for A. pectinifera  is Christmas Island, an Australian territory in the Indian Ocean near Indonesia. Until samples are examined from there, the question of whether A. pectinifera  represents one versus more species must be left unresolved. 

Remarks. Alloeocomatella  includes two species that co-occur and are widely-distributed in the Indo-western Pacific. Both are easily distinguished from other comatulids in the field by their rich red, red-orange or red-purple color ( Fig. 1View FIGURE 1 A, D), generally softer consistency, greater flexibility, and smoother texture (due to fewer and weaker pinnule spines). They also array pinnules in a single pinnate plane, like barbs on a feather ( Fig. 1View FIGURE 1 D), unlike the tetrad arrangement characteristic of most confamilials. Both species are cryptic during the day. At night, A. pectinifera  keeps its centrodorsal concealed but extends 4–8 of its ten arms usually upward and in parallel ( Fig. 1View FIGURE 1 A). Arm length reaches 50 cm, the longest of any extant crinoid. A. polycladia  has up to 30 arms; specimens with ~20 or fewer arms remain concealed at night with several arms extended; larger specimens perch completely in the open ( Messing 1995a). Following collection, A. polycladia  curls its arm tips ( Fig. 1View FIGURE 1 D), while A. pectinifera  arms remain extended and straight. We have not yet found any morphological distinctions between Alloeocomatella pectinifera  types A and B.


University of Coimbra Botany Department