Chætognath transcriptome reveals ancestral and unique features among bilaterians

Table 4 Distribution and modalities of trans-splicing among metazoans

Phylum: species	Trans-splicing	Percent trans-spliced genes	Number of SL forms	Operons	Percent genes in operons	References
Cnidaria: Hydra vulgaris	+	Very few*	2	?	NA	[85]
Urochordata (tunicate): Ciona intestinalis	+	~2%*	1	+	~2%	[61]
Chætognatha: Spadella cephaloptera; Flaccisagitta enflata	+	~55%	2*	+	ND	This study
Acoela: Convoluta pulchra	+	>5%	1	?	ND	This study
Rotifera: Adineta ricciae; Philodina sp.	+	ND	1	ND	ND	[37]
Platyhelminth: Schistosoma mansoni; seven more species^‡	+	>3%^†	1-2	+	ND	[60,62]
Nematoda: Caenothabditis elegans	+	~50%	2	+	~20%	[58,59]

*This figure was obtained by the analysis of a sample of several cDNA libraries sequenced from the 5' end. ^†This figure was obtained from 3' end sequenced cDNA libraries and may be greatly underestimated. ^‡For a precise list of these species see [62]. NA, not applicable; ND, not determined.

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