Dendronotus frondosus (Ascanius, 1774)

Broms, Fredrik, 2024, Diversity of nudibranchs in shallow water habitats in the region of Tromsø, northern Norway, Fauna norvegica 43, pp. 84-109 : 93-95

publication ID	https://doi.org/10.5324/fn.v43i0.5840
persistent identifier	https://treatment.plazi.org/id/03D0903A-C534-B811-EC28-1D390D17F78A
treatment provided by	Felipe
scientific name	Dendronotus frondosus (Ascanius, 1774)
status

Treatment

Dendronotus frondosus (Ascanius, 1774) View in CoL

Dendronotus cf. frondosus

Figure 3C View Figure 3

Material examined: One specimen, THA, 17 August 2021, 15 mm, FB, photographic record ; Two specimens, THA, 28 July 2022, 16, 10 mm, FB, NTNU-VM-85688/NUIT-1189, NTNU-VM-85684/ NUIT-1190 ; One specimen, EKJ, 08 August 2022, 24 mm, FB, NTNU-VM-85642/NUIT-1199 ( Figure 3C View Figure 3 ) .

Localities: EKJ, ESU, HIL, KFH, KFJ, KFS, KVA, RAK, SGU, SKI, THA, TLA, TPO, TPR, TTE, TVK, UTE

Distribution and remarks: The three species Dendronotus frondosus , Dendronotus europaeus and Dendronotus lacteus cannot reliably be identified without radula examination or molecular analysis ( Korshunova et al. 2017c). Specimens displaying all external morphological features typical for D. frondosus are here reported as D. cf. frondosus indicating likely identity. D. frondosus has previously been reported to be commonly occurring along the whole Norwegian coast, including Tromsø, as well as on the Murman coast in northern Russia. However, in light of newly emerged taxonomic knowledge great care must be taken when assessing the information on the reported distribution and earlier records of D. frondosus in the literature may include records of other species. The present study found the species to be a commonly occurring nudibranch in the 2020). For the Tromsø region, Krause (1895) reported D. robustus region at all months of the year. from the area in the late 19 th century ( Krause 1895) but whether this and other records previously reported from the Norwegian mainland ( Evertsen & Bakken 2005) refer to D. velifer or to true D. robustus Dendronotus lacteus (W. Thompson, 1840) remains unknown. This study presents the first reliably documented Dendronotus cf. lacteus records of true D. robustus from the Norwegian mainland. Specimens Figure 3D View Figure 3 were found exclusively on Saccharina latissima with encrusting bryozoans at fouling communities. Animals were observed during Material examined: One specimen, EKJ, 13 November 2021, FB, the same time period over several consecutive years with juveniles NTNU-VM-83913/NUIT-1038; One specimen, TVK, 12 December starting to appear in July. Specimens then gradually grew in size 2021, 58 mm, FB, NTNU-VM-83915/NUIT-1083; One specimen, until they disappeared in late October – early November. The species HIL, 04 September 2022, 55 mm, FB, NTNU-VM-85681/NUIT-1219; is, therefore, considered to have a well-established presence in the One specimen, BRE, 31 July 2023, FB, photographic record (Figure Tromsø region and is anticipated to have a wider distribution along the 3D). coast of the Norwegian mainland than is currently known.

Localities: BRE, EKJ, HIL, KFJ, KVA, RAK, THA, TVK

Distribution and remarks: Previous works do not list

Dendronotus lacteus as part of the Norwegian fauna (Evertsen & Family Dotidae (Gray, 1853)

Bakken 2005). Currently, however, D. lacteus is thought to occur along most of the Norwegian coast ( Bakken et al. 2024a) and the Doto coronata (Gmelin, 1791)

fact that D. lacteus was not previously included in the Norwegian Figure 3F View Figure 3

fauna is possibly because it had previously been recorded as D.

frondosus. More recent studies have further demonstrated challenges Material examined: One specimen, EKJ, 27 January 2021, 10 in identifying sympatric Dendronotus species without additional mm, FB, photographic record; One specimen, TPR, 17 August 2021, radula examination or molecular analysis ( Korshunova et al. 2017c). 12 mm, FB, photographic record; Three specimens, HIL, 26 May Only large animals displaying all external morphological features 2022, 14, 11, 12 mm, FB; NTNU-VM-85690/NUIT-1165 ( Figure 3F View Figure 3 ), and coloration patterns characteristic for D. lacteus are therefore NTNU-VM-85691/NUIT-1166, NTNU-VM-85692/NUIT-1168 .

here reported as Dendronotus cf. lacteus . Uniformly milky white Localities: EKJ, ESU, HIH, HIL, KVA, ROS, SFJ, THA, TPO, individuals as well as deep-red animals with large white spots dorsally TPR, TVK

on the body dominated. The present records are the first records from Distribution and remarks: Doto coronata has previously been the Tromsø region and represent a new northernmost distribution reported to be common along the entire Norwegian coast, including record for the species. The identity should, however, be confirmed by Troms, all year round from shallow waters down to ca 200 m (Evertsen radula examination or molecular analysis. & Bakken 2005). This study found animals at all months of the year, both in the intertidal and at fouling community localities. The present records confirm the presence in the Tromsø region.

Dendronotus robustus (Verrill, 1870)

Figure 3E View Figure 3

Doto fragilis (Forbes, 1838)

Material examined: One specimen, EKJ, 10 August 2021, 27 Doto cf. fragilis

mm, FB, NTNU-VM-83910/NUIT-1014 ( Figure 3E View Figure 3 ); One specimen, Figure 3G, 3H View Figure 3

EKJ, 16 October 2021, 37 mm, FB, NTNU-VM-83912/NUIT-1037 ;

One specimen, THA, 28 July 2022, 12 mm, FB, NTNU-VM-85660/ Material examined : One specimen, THA, 09 February 2021, NUIT-1188 ; One specimen, EKJ, 08 August 2022, 16 mm, FB, NTNU- 4 mm, FB, NUIT-1042 ( Figure 3G View Figure 3 ) ; Four specimens, SFJ, 04 July VM-85656/NUIT-1203 ; One specimen, EKJ, 17 September 2022, 16 2021, FB, NTNU-VM-84447/NUIT-1057, NTNU-VM-84506/NUITmm, FB, NUIT-1222 ; One specimen, EKJ, 29 July 2023, 25 mm, 1058 ( Figure 3H View Figure 3 ), NUIT-1059, NUIT-1060 ; One specimen, THA, 08 FB, NUIT-1304 ; One specimen, TPO, 09 August 2023, 19 mm, FB, February 2022, 10 mm, FB, NTNU-VM-85711/NUIT-1123 .

NUIT-1314. Localities: SFJ, THA, TPR

Localities: EKJ, THA, TPO Distribution and remarks: Doto fragilis has previously been Distribution and remarks: There has been considerable reported from most of Norway ( Evertsen & Bakken 2005; Lundin et confusion in the literature about this species and several old records al. 2020; Moen & Svensen 2020). Further to the northeast, in Russian have turned out to be misidentifications. For example, records from waters, D. fragilis was observed for the first time in 2006 (Martynov et southern Norway were revised and demonstrated to be D. frondosus al. 2006). In addition, larvae have been detected in the meroplankton already in 1926 ( Odhner 1926). Furthermore, in a recent paper Lundin in the Barents Sea ( Descôteaux et al. 2021). Ongoing taxonomic work et al. (2017) demonstrated that two different distinct species have indicate that D. fragilis belongs to a species complex with three separate previously been mixed up under the name “ Dendronotus robustus ”; clades; a “white morph”, a “red morph” and also Doto hystrix Picton & namely Dendronotus robustus and Dendronotus velifer Sars, 1878 . Brown, 1981 which, despite absence of detectable differences is still Lundin and co-workers found D. velifer to occur in deep waters (50 treated as a separate species ( Martinsson et al. 2021). Considering the – 300 m) whereas “true” D. robustus was found to inhabit shallower ongoing taxonomic challenges in the D. fragilis complex, the specimens waters. According to the authors, “true” D. robustus have never recorded by the present study are here reported as Doto cf. fragilis . Both been positively reported from shallow areas of Norway or Sweden. “white morph” ( Figure 3G View Figure 3 ) and “red morph” ( Figure 3H View Figure 3 ) individuals, as True D. robustus has, however, reliably been reported from areas in outlined by Martinsson et al. (2021) were found. The present records are the high Arctic such as Svalbard and Jan Mayen (Moen & Svensen the first records of the species from the Tromsø region.