Explore the vast range of titles available.

Rhodaliids, a specific family of siphonophores inhabiting the benthic zone, have remained enigmatic due to their rarity and elusive nature. These unique organisms, primarily found in open ocean habitats, exhibit distinctive features and are characterized by complex structures. During the Red Sea Decade Expedition, two rhodaliid specimens were collected at the sea bed at water depths of 438 and 495 meters. Regardless of challenges in specimen preservation, detailed morphological analysis revealed unique characteristics. Genetic analysis, employing the 16S rRNA marker, revealed one specimen closely related to Thermopalia taraxaca , while the taxonomic traits of this specimen suggested the identification of Archangelopsis jagoa . While most of the morphological features of the second specimen were also very similar to A. jagoa , some differences in coloration suggest the discovery of either an unusual colour variant or a potential new species within this genus. Notably, this study reports the first sequencing of A. jagoa . This species demonstrated a capacity to thrive in low-oxygen environments, challenging conventional assumptions about their habitat requirements. Despite difficulties in specimen handling and genetic analysis limitations due to a lack of comprehensive data, this research sheds light on the elusive world of benthic rhodaliids.

Five species of siphonophores are newly recorded in the Colombian Caribbean Sea: the physonects Athorybia rosacea (Forsskål, 1775), Nanomia bijuga (Delle Chiaje, 1844), and Agalma okenii Eschscholtz, 1825 and the calycophores Amphicaryon ernesti Totton, 1954 and Hippopodius hippopus (Forsskål, 1776), from samples collected with deep-water trawls in six hydrocarbon exploration areas (GUA OFF 3, COL 1, COL 2, COL 3, COL 4; COL 10) where research projects were undertaken in 2013 and 2018 by the Marine and Coastal Research Institute \"Jose Benito Vives de Andreis\" in agreement with the National Hydrocarbon Agency.

In this review the history of discovery of siphonophores, from the first formal description by Carl Linnaeus in 1785 to the present, is summarized, and species richness together with a summary of world-wide distribution of this pelagic group within the clade Hydrozoa discussed. Siphonophores exhibit three basic body plans which are briefly explained and figured, whilst other atypical body plans are also noted. Currently, 175 valid siphonophore species are recognized in the latest WoRMS world list, including 16 families and 65 genera. Much new information since the last review in 1987 is revealed from the first molecular analysis of the group, enabling identification of some new morphological characters diagnostic for physonect siphonophores. Ten types of nematocysts (stinging cells) are identified in siphonophores, more than in any other cnidarian; these are incorporated into batteries in the side branches of the tentacles in most species (here termed tentilla), and tentilla are reviewed in the last section of this paper. Their discharge mechanisms are explained and also how the tentilla of several physonect siphonophores are modified into lures. Of particular interest is the recent discovery of a previously unknown red fluorescent lure in the tentilla of the deep sea physonect Erenna, the first described example of emission of red light by an invertebrate to attract prey.

A new species of Physophora, belonging to the physonect family of siphonophores Physophoridae is described. It can easily be distinguished from the only other recognised species in that family, P. hydrostatica, by the presence of two types of bracts. The arrangement of the palpons and bracts throws new light on the cormidial organisation of the physophorids, and comparisons are made between both species. The validity of an enigmatic physophorid species, Discolabe quadrigata, is discussed.

Three new species of siphonophores (Rhodaliidae), a little known, uniquely benthic, family of Physonectae (Hydrozoa, Cnidaria), are described from specimens observed and collected at depths between 120 and 360 m off Indonesia and South Africa by the submersible JAGO. Special reference is made to in situ observations and video close-ups that revealed detailed information on locomotory, fishing and feeding behaviour.

Two species referable to the physonect siphonophore family Apolemiidae are re-described: Apolemia uvaria (Lesueur, 1815), the type species, and Tottonia contorta Margulis, 1976. Descriptions, based mainly on three colonies from the Mediterranean (A. uvaria) and three taken off California (T. contorta) contain new information on some zooids and update previous information on others. Figures show the arrangement of nectophores on the nectosomal stem, budding zones, possible degenerative zones and all zooid types (except gonophores in A. uvaria). The morphology of these two species is discussed in relation to a third species Ramosia vitiazi Stepanjants, 1967. These descriptions provide a benchmark for up to 10 putative new species of apolemiids believed to exist but not yet described. [PUBLICATION ABSTRACT]