Dondice occidentalis

Dondice occidentalis  (Engel, 1925)

Dondice occidentalis @ Key Largo, Florida (USA) by Manuel Malaquias

Taxonomic note: Dr. Philippe Bouchet (published in Furfaro & Mariottini, 2021) pointed out that the genus Nanuca Er. Marcus, 1957 had priority over the genus Dondice Er. Marcus, 1958. Consequently, the species in this clade should be classified under Nanuca as new combinations. However, García-Méndez et al. (2022) assessed the systematics of Dondice by conducting a molecular phylogenetic analysis on various representatives of Myrrhinidae. Their results showed that both Dondice and Nanuca are monophyletic and valid genera, presenting several morphological diagnostic features that allow them to be differentiated. They also conducted an integrative taxonomic approach focused on Dondice occidentalis (Engel, 1925) and Dondice parguerensis Brandon & Cutress, 1985 in the Western Atlantic, including a broader geographic and morphological range of specimens. They demonstrated that D. occidentalis constitutes a complex of six pseudocryptic species with geographically restricted ranges across the Western Atlantic, and that D. parguerensis is a distinct, valid species. Dondice occidentalis sensu stricto is recognized as the species in the genus with the greatest morphological variation, whereas the five new species, Dondice arianeae, Dondice freddiemercuryi, Dondice juansanchezi, Dondice jupiteriensis, and Dondice caboensis, exhibit consistent morphological patterns, in agreement with their molecular distinctiveness. The study by García-Méndez et al. (2022) increased the number of known Dondice species from four to nine and highlighted the importance of addressing marine biodiversity within an integrative framework.

Synonyms

• Caloria occidentalis  Engel, 1925
• Nanuca occidentalis  (Engel, 1925)

Description
Dondice occidentalis is a slender, elongate nudibranch whose body tapers toward the posterior end. The body is translucent with a single median dorsal line whose color varies by locality: white opaque in Jamaican specimens, thick and white opaque in Bahamian specimens, and light blue in Panamanian specimens. The maximum recorded body length is 50 mm. The head features a single median orange line between the rhinophores, with potential yellowish pigmentation on the edges and two bright blue lateral lines between the oral tentacles and rhinophores (García-Méndez et al., 2022). Cerata are numerous, long, and spindle-shaped, arranged in five to seven clusters along each side, from behind the oral tentacles to the posterior end. They decrease in size and number posteriorly. The cerata are translucent gray, often with large blue or white bands covering the upper two-thirds of each ceras. Subapical dark orange rings are present in Jamaican and Bahamian specimens, while Panamanian specimens exhibit yellowish-white bands (García-Méndez et al., 2022). Rhinophores are smooth at the base, transitioning from translucent to either opaque white or yellowish toward the tips. Their distal part has five to nine rings that. The oral tentacles are long and narrow, translucent with opaque white tips, and sometimes exhibit blue pigmentation at the base or throughout, with yellowish bands at the tips in some individuals (García-Méndez et al., 2022). The foot is translucent, often displaying a light blue line or scattered blue spots, with the posterior end being bright blue. The anterior foot corners are short, tapered, and curved. The reproductive opening is positioned on the right anterior portion of the body, between the first and second ceratal clusters, while the anal opening is dorsolateral, adjacent to the second ceratal cluster (García-Méndez et al., 2022).

Schematic color patterns of the dorsum and cerata of the Dondice species from the Western Atlantic: a-f Dondice occidentalis (Engel, 1925); a-b Specimen from Jamaica; c-d Specimen from Bahamas; e-f Specimen from Panama; g-h Dondice parguerensis Brandon & Cutress, 1985; i-j Dondice freddiemercuryi; k-l Dondice juansanchezi; m-n Dondice arianeae; o-p Dondice caboensis; q-r Dondice jupiteriensis. Extracted from García-Méndez et al (2022).

 

Diferential external traits of the Dondice species from Western Atlantic. Extracted from García-Méndez et al (2022).

 

Biology
Dondice occidentalis is commonly found in seagrass meadows, algae, and hydroids in shallow sandy patches. It primarily preys on hydroids, with previous reports documenting feeding on Eudendrium Ehrenberg, 1834, and bryozoans of the genus Amathia Lamouroux, 1812 (McDonald & Nybakken, 1997). However, further research is needed to confirm its diet, particularly for specimens confirmed as D. occidentalis (sensu stricto) (García-Méndez et al., 2022). This species’ reproductive strategy remains unclear, with conflicting reports on larval development. Clark & Goetzfried (1978) described D. occidentalis as exhibiting a planktotrophic developmental strategy, while Brandon & Cutress (1985) argued for lecithotrophic development. The latter suggested this feature could differentiate D. occidentalis from D. parguerensis. More studies are required to clarify whether developmental mode is a diagnostic trait for this species (García-Méndez et al., 2022).

Etymology

• Occidentalis, from Latin “occidentalis”, western, where the Sun sets.

Distribution
Dondice occidentalis is known from Jamaica (type locality) (Engel, 1925), the Bahamas (Gonzalez et al., 2013; Malaquias, 2014), and Panama (Goodheart et al., 2016). Additional records suggest possible occurrences in Venezuela (Grune Loffler et al., 2014), Campeche Bank in the Gulf of Mexico (Ortigosa et al., 2015), and South Carolina (Eyster, 1980). Molecular analyses suggest that specimens from Florida and Brazil previously identified as D. occidentalis represent distinct species, reinforcing the need for an integrative taxonomic approach (García-Méndez et al., 2022). The Updated Sea Slugs Catalog for the Canary Islands mentions that the report by Ortea et al (2000) of Dondice occidentalis for the Canary Islands is wrong.

More pictures

Bibliography

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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

• Biodiversity Heritage Library
• Flickr pictures
• Interim Register of Marine and Nonmarine Genera
• JaxShells (foto)
• NCBI GenBank
• OBIS - Search by Taxon
• Sea Slug Forum
• The Slug Site
• World Register of Marine Species

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