Geitodoris planata

Geitodoris planata (Alder & Hancock, 1846)

Geitodoris planata by Enric Madrenas
Taxonomy
Class: Gastropoda  Cuvier, 1797
Subclass: Heterobranchia  J.E. Gray, 1840
Clade: Euthyneura  Spengel, 1881
Clade: Nudipleura  Wägele & Willan, 2000
Order: Nudibranchia  Cuvier, 1817
Suborder: Euctenidiacea  Tardy, 1970
Infraorder: Doridacea  Thiele, 1931
Superfamily: Doridoidea  Rafinesque, 1815
Family: Discodorididae  Bergh, 1891
Genus: Geitodoris  Bergh, 1891
Species: Geitodoris planata (Alder & Hancock, 1846) [Doris]

Synonyms

  • Discodoris planata (Alder & Hancock)
  • Doris complanata Verrill, 1880
  • Doris planata Alder & Hancock, 1846 (original)
  • Doris testudinaria Risso, 1826
  • Geitodoris complanata (A. E. Verrill, 1880)

Description
The specimens of this species of nudibranch can reach more than 4 cm in length (maximum quoted size is 65 mm, Picton & Morrow, 2010). The body is flattened and this feature is the responsible of the specific name. The general color is reddish-brown, darker or lighter depending on each different animal. The margins of the back can be of a lighter tone than the body. In most cases there are whitish cream or star-shaped areas highly visible on the back. All the back is filled with rounded tubercles of various sizes, the central area with larger ones and the margins with smaller ones. The larger tubers are usually colored pale cream and the other of intermediate size are usually arranged radially starting from the center; this pattern of clear tubercles on the back of the animal creates their typical stellate stains. In some specimens there are bigger cream coloured patches. Some tubercles may be slightly pedunculated. Under binocular lens numerous white lines forming a grid that also tends to converge at the base of the larger tubercles on the back are visible. The rhinophores are brown, with the same colour of the back, especially in the laminar zone where about 20-25 lamellae are tightly located, the terminal mucron is extremely underdeveloped. The alaminar area of the rhinophores is less colored because of the lower density of brown spots and they meet at the dorsal area of the base to form a longitudinal brown band. The rhinophoric sheath is high and its upper edge is lobed, its entire surface has tubercles like the dorsum; when the rhinophore is retracted in the head, the lobes of the rhinophoric sheath are folded so they close the gap. Gills consists on 6-8 tripinnadas gill leaves of the same colour of the body but they have numerous cream coloured white spots that clarify them a little. The gill leaves are quite long and its spine is curved when they are fully extended. The branchial sheath is rather high, its upper edge is slightly lobed and has tubercles as well. When the gill blades retract into the body, the sheath is closed in the form of a transverse and oriented backwards slit. The anal papilla is tubular, colored whitish brown but with brown dots and anal hole has a 4-lobed shape. The anal papilla is pulsatile. The foot is uniform orange-yellow similar to the underside of the mantle, that has small brown spots where fine lines will converge in a radial arrangement. The foot is furrowed and cleft in the anterior side. The mouth has two yellowish short oral palps.

Identifying Note: This species has been confused in the past with other large species of doridacean with tubercles on the back, Doris pseudoargus which is very variable in color and one of its chromatic variations may resemble that of G. planata. However D.pseudoargus has no finger-like oral palps near the mouth, as it does have G. planata. Another species, Discodoris stellifera, also has tubercles on the back and the typical structure of clear starry spots on the back, but the only way to distinguish G. planata from D. stellifera is by a radular analysis, as D.stellifera has the marginal radular teeth finely denticulate while in G. planata these are smooth and spatulate. It is therefore very difficult to identify both species based on external morphology only, and any records of these species based on photographs or visual observations alone, can be and probably are wrong.

 

Biology
The animals of this doridacean species are very sedentary and have slow movements. It is usually found under stones from very shallow water. It feeds on sponges, among which it has been cited Mycale rotalis, an orange sponge that usually lives under rocks. G. planata spawn is a somewhat scalloped and coiled ribbon, 5-6 mm wide, with a total length that can reach 15 cm. Eggs are white or slightly yellowish and are arranged in 2-3 layers in the ribbon, in transparent capsules which can contain one or two eggs. The egg size is about 80 microns and the capsules are about 120 microns.

Etymology

  • Geitodoris. From Greek “geitonos”, neighbor (meaning close or similar) + “Doris”, in Greek mythology, the wife of Nereus, a sea nymph and mother of the Nereids.
  • Planata. From Latin “planus” (flat, even, level) because it has a nearly flat dorsum.

Distribution
Geitodoris planata is distributed throughout all the coasts of Europe, from Norway to the Mediterranean. In the southern shores of Great Britain it is locally abundant. In the Iberian peninsular coasts it has been quoted in all areas but in Galicia and the mediterranean east coast. It is recorded in the Balearic Islands, Açores and Madeira (Cervera et al., 2004). In the Catalan coast it is cited, among other locations, in Cala Sant Antoni (Port Lligat), L’Escala, Cala Bona and Cala Giverola (Tossa de Mar) and Blanes.

Known georeferenced records of the species: Geitodoris planata (z-200).
Sources:
: OBIS : OPK
: GROC 2010-2011 : VIMAR
: Enric Madrenas : Manuel Ballesteros.
: João Pedro Silva : M@re Nostrum
: Bernard Picton : Other sources
: GBIF.ORG : Marine Regions

Abundance

        Western Mediterranean:0 Stars
        Eastern Mediterranean:0.0 Stars
        Atlantic Ocean:0.0 Stars
This chart displays the observation probability for Geitodoris planata
based on our own records.

More pictures

Bibliography

Bibliography based on the works by Steve Long, 2006. Bibliography of Opisthobranchia 1554-2000 and Gary McDonald, 2009. Bibliographia Nudibranchia, with later updates from other resources.

Further reading

Cite this article as:

Ballesteros, Manuel, Enric Madrenas, Miquel Pontes et al. (2012-2017) "Geitodoris planata" in OPK-Opistobranquis, Published: 16/05/2012, Accessed: 23/10/2017 at (http://opistobranquis.info/en/VdqSB)

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