Cuthonidae (Odhner, 1934)

Broms, Fredrik, 2024, Diversity of nudibranchs in shallow water habitats in the region of Tromsø, northern Norway, Fauna norvegica 43, pp. 84-109 : 100

Family Cuthonidae (Odhner, 1934)

Cuthona nana (Alder and Hancock, 1842) Figure 5E

Material examined: Two specimens, TPO, 16 February 2022, 6, 10 mm, FB, NTNU-VM-85731/NUIT-1131, NUIT-1137 ; Three specimens, THA, 10 November 2022, 9, 15, 13 mm, FB, NUIT-1241, NTNU-VM-85646/NUIT-1242 ( Figure 5E ), NUIT-1245 ; One specimen, THA, 14 January 2023, 13 mm, FB, NTNU-VM-85647/ NUIT-1268 .

Localities: HIL, KVA, THA, TPO, TPR

Distribution and remarks: Cuthona nana has previously been reported from the entire Norwegian coast ( Evertsen & Bakken 2005). There are also three known records from the Barents Sea ( Martynov et al. 2006). The species is typically found on hermit crab shells where it feeds on Hydractinia echinata Fleming, 1828 ( Lundin et al. 2020). Despite being reported to be found mainly at ca 10-35 m depth and almost exclusively on places with colonies of Hydractinia echinata the present study found C. nana to be commonly occurring in shallow waters. Animals were typically found crawling on artificial surfaces with little identifiable prey. In such habitats, specimens were, nonetheless, observed both copulating and spawning. The species was observed during all seasons except summer and reproduction seemed to occur almost all year round. The present study verifies the presence of C. nana in the Tromsø region.

Figures

Figure 5. A. Coryphella verrucosa, verrucosa form, NTNU-VM-85676/NUIT-1261, B. Carronella sp., NTNU VM-84466/NUIT-1121, C. Edmundsella pedata, NUIT-1035, D. Cuthonella concinna, NUIT-1011, E. Cuthona nana, NTNU VM-85646/NUIT-1242, F. Amphorina andra, yellow form, NTNU-VM-85702/NUIT-1236, G. Amphorina andra, white form, NTNU-VM-84468/NUIT-1032, H. Amphorina andra, white-orange form, NTNU- VM-84496/NUIT-1006-1, I. Amphorina pallida, strongly pigmented form, photo record, 12 December 2020, J. Amphorina pallida, pale form, photo record, 01 February 2022, K. Eubranchus exiguus, NUIT-1334, L. Eubranchus rupium, photo record, 17 August 2021. Scale bar: 10 mm. All photos: Fredrik Broms.