The geographic distribution of echiurans in the Atlantic Ocean (Phylum Echiura)

Abstract

This report provides a checklist of the echiurans from the Atlantic Ocean and maps their distribution. Investigations on the taxonomy of this group since the publication of the monograph by Stephen and Edmonds (1972) on the phyla Sipuncula and Echiura have yielded two new genera, 12 new species and 13 new records. Currently the echiuran fauna of the Atlantic comprises three families, 25 genera and 63 species. The family Bonelliidae contains 35 species in 18 genera; the Echiuridae is represented by six genera and 27 species, and the Urechidae by a single species Urechis chilensis (Müller). This study shows that the Atlantic has a relatively high species diversity, comprising about 38% of the known world fauna. Bonelliids alone comprise about 56% of the echiuran fauna of the Atlantic. An analysis of distribution is given in relation to general biogeographic regions and faunistic provinces. Dichotomous keys for the identification of genera and species of echiurans from the Atlantic is provided. The North Temperate component is the richest and most diverse, making up about 68% of the Atlantic echiuran fauna; 25 species have been recorded from within the tropics; and the South Temperate component is poorly represented, with only about 19% of the total fauna. The cosmopolitan component is also poorly represented, with only four species, so far, known. Thirteen species of echiurans are provisionally considered to be endemic to the Atlantic. Members of the Echiuridae are usually shallow-water inhabitants of intertidal and subtidal zones while bonelliids exhibit a higher species richness on deeper bottoms of all oceans, mostly at depths of 1000–6000 m in the Atlantic.

Molecular Phylogeny of Echiuran Worms (Phylum: Annelida) Reveals Evolutionary Pattern of Feeding Mode and Sexual Dimorphism

“…2). Among echiurans, the members of the sexually monomorphic group (Echiuridae, Thalassematidae and Urechidae) usually live in littoral and sublittoral waters, whereas those of the sexually dimorphic group (Bonelliidae) are commoner in bathyal and abyssal depth [4], [5]. It is well known that marked sexual dimorphism with dwarf males has evolved in various deep-sea animals (e.g., Osedax , anglerfishes, and pedunculate barnacles) [13]–[15].…”

“…Approximately 165 species of echiurans have been described in the shallow to deep waters of all oceans [4], [5]. Most live in burrows in soft sediments, although some live in crevices in dead corals or rocks [1]–[3].…”

Marine fauna of Mljet National Park (Adriatic Sea, Croatia). 7. Echiura

“…From a systematic point of view the green spoonworm Bonellia viridis belongs to the phylum Echiura, class Echiuroidea, order Bonellida, family Bonellidae, and the genus Bonellia (Murina, 1984;Biseswar, 2009). Previously, echiurids and sipunculids were systematized in a polyphiletic subclass Gephyrea (Quatrefages, 1865;Baird, 1868;Sluiter, 1912;Fischer, 1922), a subclass that is no longer used.…”

“…In the entire Mediterranean Sea, six species of echiurans (Echiura Newby, 1940) were recorded (Murina, 1984;van der Land, 2001;Anonymous, 2008;Biseswar, 2009). However, in the Adriatic Sea only two species were identified: Bonellia viridis Rolando, 1821, andMaxmuelleria gigas (M. Müller, 1852) both belonging to the family Bonellidae Baird, 1868. In the summers of 1995-2002, the student Thais Society for Underwater Research was engaged in studies of benthic communities and biodiversity of marine fauna in the Mljet National Park.…”

A new species of deep-sea Bonelliidae, Vitjazema micropapillosa(Phylum: Echiura), from the North Atlantic Ocean

“…Males are usually diminutive and endosymbiotic on the female. Biseswar (2009) provided a checklist of the echiurans from the Atlantic Ocean and mapped their distribution. According to this author, the echiuran fauna of the Atlantic currently comprises three families, 25 genera and 63 species.…”