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Thuridilla bayeri

Painted slug

Sirada Oratanachai (2011)                                                                                                                       

Thuridilla bayeri from Heron Island (20 Sep 2011)


Fact Sheet



Physical Description


Colour Identification


Local Distribution and Habitats

Biogeographical Distribution

Life History & Behaviour




Chemical Evolution

Systematics or Phylogenetics

Morphology and Physiology

External Morphology

Internal Anatomy


Molecular Biology & Genetics

Nucleotide Sequences



References & More Information


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Names & Taxonomy

Synonyms & Common name



Reproduction & Reproductive System

The reproductive system of Thuridilla and other Elysiidea is very complex due to terminology of various structures (Marcue, 1980; Sanders-Esser 1984; Jensen 1992). The reproductive system of T. bayeri is triaulic, which can be refer to hermaphroditic slug with females part having two separate opening connecting via connective ducts to central structure (Jensen 1992). T. bayeri have large spherical vagiana, which open on the right side of pericadium via small duct. Moreover, ampulla is also large and pigmented (figure 1). Thuridilla bayeri is hermaphroditic and reproduce by copulation (Figure 2). The orange, tightly coiled spawn mass are laid flat against the substrate (Marshall 1999; Jensen 1992, EOL 2011). The spawn contain strings of capsule (120-190 µm in diameter), where each capsule contain a single ova (80-85 µm) around a continuous core of yolk (Bourcher 1983).

Figure 1: Schematic drawing of T. bayeri reproductive system. Abbreviations: ampulla (a), bursa copulatrix (bc), follicles (f), genital receptacle (gr), mucus gland (m), penis (p), prostate (pr), vagina (v).
The images is modified from Jensen 1992.
 Figure 2: Copulation of Thuridilla gracilis from nthn Mariana  Islands by Yuji Fujie. Red circle indicating penises of the    organisms. Ref:

Descriptions and functions of reproductive structures:
Bursa copulatrix          
Receive surplus allosperm and autosperm, albumen, and prostatic secretion during fertilization and spawning (spermfilled structure). 

Single hermaphrodite ampulla where autosperm is stored. 
Genital receptacle

Synapmorphy of Thuridilla functino as receptacle for suplus genital products including albumen, prostatic secretion, sperm, and yolk.

 Secretion of alkaline fluid
Penis Penis of T.bayeri is without stylet. Penis composed alomost exlusively of connective tissue and non-longitudinal muscle. Therefore, the penis is probably not for hypodermic impreganation. 

-    The structures that is responsible for extracapsular yolk production has not yet been identified. Thuridilla extracapsular yolk is the same colour with the embryonic yolk (orange), it is possible that the secretion of the material is done by periferal structure or modified follicles (Jensen 1992). However, study should be done to ensure that the hypothesis is right. T. bayeri under go planktotrophic development (Jensen 1992).