First report of an egg-predator nemertean worm in crabs from the south-eastern Pacific coast: Carcinonemertes camanchaco sp. nov

Abstract

Nemertean worms belonging to the genus Carcinonemertes have been tied to the collapse of crab fisheries in the northeastern Pacific Ocean. A new species is described from egg masses of two commercial crabs, Cancer porteri and Romaleon setosum, inhabiting the central-north Chilean coast. This is the first species of Carcinonemertes described from the southeastern Pacific Ocean. Total body length of Carcinonemertes camanchaco sp. nov. ranged from 2.38 to 4.93 and from 4.29 to 8.92 mm, in males and females, respectively. Among others, traits that distinguish this new species from other previously described congeneric species include: presence of two gonad rows on each side of the intestine, a simple (not decorated) mucus sheath, and a relatively wide stylet basis. Maximum likelihood and Bayesian inference phylogenetic analyses distinguished this new species from all other species of Carcinonemertes with available cox1 sequences in GenBank. Prevalence and mean (± SD) intensity of C. camanchaco sp. nov. was 24% and 2.6 (± 2.07) worms per egg mass in C. porteri and 38.1% and 3.8 (± 2.4) worms per egg mass in R. setosum. The formal description of this new species represents the first step towards the understanding of this worm's impact on the health of crab fisheries in the southeastern Pacific Ocean.

Three new species in Tetrastemma Ehrenberg, 1828 (Nemertea, Monostilifera) from sublittoral to upper bathyal zones of the northwestern Pacific

“…A histology-free description with DNA barcoding has been progressively introduced to nemertean systematics in the past decade (e.g., Kajihara 2015 ; Gonzalez-Cueto et al 2017 ; Simpson et al 2017 ; Kajihara et al 2018 , 2022 ; Chernyshev et al 2020 ; Hookabe et al 2021a , b ; Leiva et al 2021 ; Abato et al 2022 ). This approach has been applied to two cases, one of which is a description of species with internal characters interspecifically differentiated and observable without histology (e.g., number of proboscis branches in Gorgonorhynchus Dakin & Fordham, 1931 [ Kajihara 2015 ; Hookabe et al 2021a )].…”

A Sponge-dwelling Ribbon Worm, <i>Tetrastemma carneum</i> sp. nov. (Nemertea: Monostilifera) Collected off Ofunato, Japan

“…Eumonostiliferous nemerteans are primarily free-living and often found in cryptic habitats, such as under rocks, in crevices, among organic debris, and in muddy sediments (Strand and Sundberg 2015). As many as 50 monostiliferan species are known to live as commensals or parasites, including Asteronemertes Chernyshev, 1991 from ambulacral grooves of solasterid and pterasterid starfishes (Kyao 1954;Chernyshev 1991), Carcinonemertidae from egg masses of decapod crustaceans (e.g., Leiva et al 2021), Cryptonemertes Gibson, 1986 found beneath pedal discs of sea anemones (Gibson 1986), Gononemertes Bergendal, 1900and Vieitezia Junoy, Andrade, and Giribet, 2011 from ascidians (e.g., Junoy et al 2011), and Malacobdella Blainville, 1827 inhabiting mantle cavities of bivalves (e.g., Alfaya et al 2015). The evolutionary transition from ancestral free-living lifestyles to commensal/parasitic ones is considered to have occurred multiple times within Monostilifera independently (Chernyshev and Polyakova 2019).…”