Convolutriloba macropyga sp. nov., an uncommonly fecund acoel (Acoelomorpha) discovered in tropical aquaria

Abstract

A new species of Convolutriloba Hendelberg & Akesson, 1988, collected from an aquarium in Marietta, Georgia, USA, and cultured at the University of Georgia comprises exceptionally large individuals, up to 10 mm in length. Like other members of the genus, Convolutriloba macropyga sp. nov. reproduces asexually and possesses symbiotic zoochlorellae, but it also routinely reproduces sexually, laying relatively large eggs that hatch into aposymbiotic juveniles with a statocyst and frontal organ ( which are absent in the adults). C. macropyga has a narrow tolerance for extremes of temperature and salinity: it cannot survive outside of a temperature range of 18–28 degrees C and suffers 50% lethality at salinity as low as 24 ppt and as high as 44 ppt. It cannot survive total darkness for longer than 23–26 days, even with prey provided, suggesting an obligate symbiosis with its algal endosymbiont. A method for inducing sexual reproduction in other convolutrilobids is presented, as are suggestions for successful shipping of these acoels.

A Flatworm from the GenusWaminoa(Acoela: Convolutidae) Associated with Bleached Corals in Western Australia

“…All of these features are typical of currently described Waminoa (Tyler et al, 2006). By contrast Convolutriloba flatworms are brown, red, or green; shaped like a shield with a number of caudal notches; and possess sagittocysts, which were not present here (Shannon and Achatz, 2007).…”

“…In addition to those described in nature, at least three species of epizoic flatworms have been described on corals in aquaria (Shannon and Achatz, 2007). All of these flatworms have been associated with either genus Convolutriloba Hendelberg & Akesson, 1988 or Waminoa Winsor, 1990 and all are classified within the family Convolutidae (Tyler et al, 2006).…”

Radical modification of the A–P axis and the evolution of asexual reproduction in Convolutriloba acoels

“…4, C and D) in which buds are produced with an A-P polarity opposite that of the parent. Both Hendelberg and Å kesson (1988) and Shannon and Achatz (2007) describe budding as being initiated from a pair of posterior budding sites, one on either side of the medial lobe of the tail. However, Hendelberg and Å kesson (1988) indicate that in C. retrogemma only one bud at a time develops per site, while Shannon and Achatz (2007) indicate that in C. macropyga multiple buds may be present at each budding site (such that more than two buds may be developing at once on an individual).…”

“…Both Hendelberg and Å kesson (1988) and Shannon and Achatz (2007) describe budding as being initiated from a pair of posterior budding sites, one on either side of the medial lobe of the tail. However, Hendelberg and Å kesson (1988) indicate that in C. retrogemma only one bud at a time develops per site, while Shannon and Achatz (2007) indicate that in C. macropyga multiple buds may be present at each budding site (such that more than two buds may be developing at once on an individual). We have cultured both species under identical conditions and find that the typical mode of budding for both is from a pair of posterior budding sites each producing one bud at a time, as initially described for C. retrogemma.…”

Xenacoelomorpha's significance for understanding bilaterian evolution

“…transcriptomes (Cannon et al, 2016 [4 ]; Rouse et al, 2016 [17 ]) Nemertodermatida Illumina transcriptomes (Cannon et al, 2016 [4 ]) Meara stichopi Embryonic material (Børve and Hejnol, 2014 [11 ]) Nemertoderma westbladi Embryonic material (47) Acoela Illumina transcriptomes (Srivastava et al, 2014 [18 ]; Cannon et al, 2016 [4 ]) Isodiametra pulchra (breeding, Rieger et al, 1988) Convolutriloba (breeding, Shannon and Achatz, 2007) Hofstenia miamia (breeding, Srivastava et al, 2014 [18 ]) Symsagittifera roscoffensis Whole mount in situ hybridization (Hejnol and Martindale, 2008 [9]) Functional interference (RNAi) (48) Microinjection (49) Husbandry/breeding(50,51) …”