First Record of the Nudibranch Tenellia adspersa (Nordmann, 1845) in Portugal, Associated with the Invasive Hydrozoan Cordylophora caspia (Pallas, 1771)

João Encarnação,Maria Alexandra Teodósio,Thomas Seyer,Francisco Leitão

doi:10.3390/d12060214

Abstract

The estuarine nudibranch Tenellia adspersa (Nordmann, 1845) was recorded for the first time in Portugal, while sampling for fouling fauna of artificial structures along the salinity gradient of the Guadiana estuary (SW Iberian Peninsula). Two specimens were found in association with the invasive hydrozoan Cordylophora caspia (Pallas, 1771) and kept in the laboratory for taxonomy purposes. After two days, batches of eggs were seen in C. caspia branches, while the nudibranchs were also actively feeding on the hydrozoan polyps. The fast generation times of T. adspersa, along with its food preference for C. caspia, might suggest a positive role of the nudibranch on controlling this invasive hydrozoan in the Guadiana estuary. Introduction routes and facilitation interactions are discussed.

Highlights

Nudibranchs, the most diverse group of sea slugs (Gastropoda: Heterobranchia), are a widely distributed and diverse group of molluscs, found at their highest diversity in marine shallow coastal areas, with fewer associated with estuarine and brackish habitats [1,2]
The study species, T. adspersa, considered a cosmopolitan species nowadays, the historical records point out to an European origin, with the first description of the species being made in the Black
The available literature using some of these synonyms, confirms its cosmopolitan distribution across the North-East Atlantic Ocean and Mediterranean Sea [8,9]

Summary

Introduction

Nudibranchs, the most diverse group of sea slugs (Gastropoda: Heterobranchia), are a widely distributed and diverse group of molluscs, found at their highest diversity in marine shallow coastal areas, with fewer associated with estuarine and brackish habitats [1,2]. The cosmopolitan aeolid Tenellia adspersa (Nordmann, 1845), along with the recently described Bohuslania matsmichaeli (Korshunova, Lundin, Malmberg, Picton and Martynov, 2018), are widely recognized as the only nudibranchs associated with brackish-water habitats [2,3,4]. The available literature using some of these synonyms, confirms its cosmopolitan distribution across the North-East Atlantic Ocean and Mediterranean Sea [8,9]. Only a few recent records across Europe have been published, namely in the Baltic Sea [4] or the Mediterranean Sea [10]

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