Select the search type
  • Site
  • Web




Dendrodoris nigra (Stimpson, 1855)

            Black Nudibranch

Elsie-Mary Felix (2014)




Fact Sheet



Physical Description


Life History & Behaviour

Anatomy & Physiology

Evolution & Systematics

Biogeographic Distribution

Conservation & Threats


Anatomy & Physiology

(Research Project)

Dorid nudibranchs possess large rhinophores and branchial plumes surrounding their anus on the dorsal surface. One may think that this could be disadvantageous for a nudibranch when trying to avoid predation as these structures “stick out” and provide extra surface area for capture. As a cryptobranch, Dendrodoris nigra has the ability to retract these structures into pockets but does it utilise any other types of defences to avoid predation?  A research project was carried out to investigate the defence mechanisms associated with Dendrodoris nigra through the examination of its internal anatomy and physiology. Other systems investigated include the sensory, feeding and digestive and reproductive system.

Two Dendrodoris nigra individuals were collected from Moreton Bay in April 2014 and kept in an aquarium system at The University of Queensland.  Once ready for fixation, the specimens were placed in a petri dish with sea water and held on ice until relaxed and no longer moving. The specimens were then transferred using tweezers into a labelled tube with 4% Paraformaldehyde buffer and stored for sectioning. The fixed specimens were sectioned, mounted and stained with Hematoxylin and Eosin by UQ Lab Technicians.  The prepared slides were then examined using a dissecting microscope and an Olympus Differential Interference Contrast (DIC; Normarskl) Microscope.

Sensory System

The rhinophores of D.nigra are perfoliate, also known as lamellate, and appear as a series of flat plates or leaves (Figure 1). In adults, the clavus (the distal portion of the rhinophore above the stalk) tilts backwards and bears approximately 17, sloping lamellae (Brodie et al., 1997). At the base of these lamellae are what thought to be glomeruli which are associated with the detection and processing of olfactory information (Figure 1)(Wertz et al., 2006).

Feeding and Digestive System

As expected, there was no cuticualrization present within the buccal cavity of D.nigra due to its lack of radula present in most Mollusca (Figure 2A)(Wägele et al., 1999).  The buccal cavity is displayed as a large circular cavity with a pore opening. This large area within the cavity is likely to house the suctorial tube in lieu of the radula. Musculature can also be observed surrounding the mouth and may aid in the movement of the mouth while feeding. The digestive enzymes associated with feeding are secreted by the salivary gland located to the right of the buccal cavity (Figure2B)(Wägele et al., 1999). Sponge tissue is externally digested into a “stew” which can then be consumed and the nutrients extracted by the large digestive gland which fills a considerable amount of the body cavity (Figure 2C) (Young, 1966).


As mentioned earlier D.nigra has the ability to retract its highly sensitive chemoreceptive rhinophores and respiratory gill plume. The rhinophore retractile muscles can be seen as extending from each rhinophore into a joint U-shaped concentration of muscle which runs ventrally down the body of the nudibranch (Figure 1)(Wägele et al., 1999). The same pattern can be seen in the retractile muscles of the brachial plum which extend from each plume into a joined U-shaped muscle running up the animal (Figure 3A). It was observed that D.nigra has a soft gelatinous body upon touch and it has been reported that some species of nudibranch contain spicules in their mantle as a mechanical defence (Behrens et al., 2005). No such spicules were observed in the mantle of D.nigra. Other papers have also reported that D.nigra employs chemical defences by secreting acidic mucopolysaccharides from glandular cells in its mantle (Wägele et al., 1999). Glandular cells were observed in the epidermis of the specimens below the main pigment layer (Figure 3D).  The cryptic colouration of D.nigra may also act as a means of defence through camouflage and this can be seen by the dispersed black pigment granules throughout the epithelium, gill and rhinophores (Figure 3B and C)(Wägele et al., 1999).

From the research project carried out it would appear that D.nigra’s primary mode of defence is its acidic mucous secretions and cryptic colouring which it uses to camouflage with its benthic surroundings. Extensive research could help us gain a deeper understanding of the defence mechanisms employed by D.nigra.

Reproductive System

The reproductive organs of nudibranchs are located on their right hand side and include a genital opening from which the copulatory organ emerges (Brodie et al., 1997).  Figure 4 shows an irregular shaped, tube like organ presumed to be the penis of the nudibranch due to its shape and location on the right hand side mid-way between the rhinophores and start of the digestive gland.  Many papers also mention the presence of penial hooks in nudibranchs to avoid separation while mating; however penial hooks could not be identified in the sectioned specimen(Valdés and Gosliner, 1999). One could assume that the oval organ below is related to reproduction and could resemble that of a seminal vesicle.  To the left of both of these structures is a highly muscularised ellipse with muscles running both longitudinally and latitudinally.  While no papers could be located to explain this muscle it may resemble the columnar muscle used in the retraction of gastropods into their shells. As there is no longer a need for this in nudibranchs, the structure may be vestigial.  Other components of the reproductive system were unable to be identified in the sections but include the ampulla, prostate, bursa copulatrix, deferent duct, vaginal duct and vestibular gland (Valdés and Gosliner, 1999).


Behrens, D. W., Petrinos, C. & Schrurs, C. 2005. Nudibranch behavior, New World Publications.


Valdés, À. & Gosliner, T. M. 1999. Phylogeny of the radula-less dorids (Mollusca, Nudibranchia), with the description of a new genus and a new family. Zoologica Scripta, 28, 315-360.

Wägele, H., Brodie, G. D. & Klussmann-Kolb, A. 1999. Histological investigations on Dendrodoris nigra (Stimpson, 1855) (Gastropoda, Nudibranchia, Dendrodorididae). Molluscan Research, 20, 79-94.

Wertz, A., Rössler, W., Obermayer, M. & Bickmeyer, U. 2006. Functional neuroanatomy of the rhinophore of Aplysia punctata. Frontiers in Zoology, 3, 1-11.

Young, D. K. 1966. Systematics, Food and Functional Morphology of the Feeding Apparatus of Some Dorid Nudibranchs, University of Hawaii.