Are jellyfish increasing in response to ocean acidification?

Ocean acidification may negatively affect calcifying plankton, opening ecological space for noncalcifying species. Recently, a study of climate-forcing of jellyfish reported the first analysis suggesting that there were more jellyfish (generally considered a noncalcifying group)when conditions were more acidic (lower pH) from one area within the North Sea. We examine this suggestion for a number of areas in the North Sea and beyond in the Northeast Atlantic using coelenterate records from the Continuous Plankton Recorder and pH data from the International Council for the Exploration of the Sea for the period 1946–2003. We could find no significant relationships between jellyfish abundance and acidic conditions in any of the regions investigated. We conclude that the role of pH in structuring zooplankton communities in the North Sea and further afield at present is tenuous

Feeding and vertical migration of the chaetognath Sagitta friderici (Ritter Zahony, 1911) in the southern Benguela during spring 1987, with notes on seasonal variability of feeding ecology

The feeding biology and the vertical migration of Sagitta friderici were examined over 24 h at two stations in the southern Benguela during spring (October) 1987. Together with studies conducted during summer (February 1991) and winter (May 1984), they serve to allow valuable generalizations of the biology and ecology of this abundant chaetognath. Populations migrate vertically and feed nocturnally, although the timing and the extent of migration vary between studies. S.friderici exhibits ontogenetic layering and the cross-shelf distribution of maturity stages differs, suggesting that it is able to take advantage of cross-shelf water movement in order to maintain populations in the nearshore waters of the West Coast. S.friderici prey almost exclusively on copepodg (cannibalism is rare), and there is a positive relationship between the lengths of predator and prey that is influenced by the size structure of the prey environment. This casts doubt on the validity of a chaetognath species-specific relationship between predator and prey size. S. friderici selects its prey on the basis of size, and not species. Daily ration is related linearly to prey density, so reflecting the low density of prey and providing support for theoretical predictions regarding ingestion rates under oceanic conditions. The impact of S. friderici predation on the copepod assemblage is generally less than 3% of the standing stock, although it could be much higher under conditions of low copepod biomass and poor secondary production

Hydromedusae off the Orange River Mouth, Southern Africa

A total of 242 zooplankton samples from the upper 100 m of the water column was collected discontinuously from March 1997 to January 1999 off the Orange River mouth on the west coast of southern Africa. Six species of hydromedusae were recovered at generally low abundance, of which Euphysa aurata, Leuckartia octona and Proboscidactyla menoni were dominant. E. aurata and L. octona showed evidence of seasonality in abundance. The low diversity of the fauna was remarkable and it is hypothesized that this might be attributable in part to sedimentation from the Orange River, and in part to locally weak circulation and the wide extent of the continental shelf.Web of Scienc

Carybdea branchi, sp. nov., a new box jellyfish (Cnidaria: Cubozoa) from South Africa.

A common and conspicuous member of the medusan fauna of South Africa has been the subject of repeated taxonomic confusion. After having been mistakenly identified by earlier workers as either Carybdea alata or Tamoya haplonema, this large and colourful carybdeid is described herein as Carybdea branchi, sp. nov. It is distinguished from its congeners on numerous characters: body to about 8cm in life, densely scattered with nematocyst warts over the whole body and abaxial keels of the pedalia; a bulge or lateral thorn on the pedalial canal bend; with 2 dendritic velarial canals per octant, highly diverticulated; with a long manubrium; with greatly bushy epaulette-like phacellae, comprising 20 or more roots tightly clustered; with well developed mesenteries; and with conspicuous brownish pigmented areas over the proximal and distal regions of the pedalia and over the phacellae. A comparative table of the primary diagnostic characters of species in the genus Carybdea is given

Two new nematode species from Saldanha Bay, South Africa: Perepsilonema benguelae sp. nov. and Leptepsilonema saldanha sp. nov. (Nematoda, Epsilonematidae)

Perepsilonema benguelae sp. nov. and Leptepsilonema saldanhae sp. nov. are described and illustrated from coarse sand sediments in Saldanha Bay, along the west coast of South Africa. Perepsilonema benguelae sp. nov. is characterised by a large swollen body in the genital region, the annuli are not clearly orientated into anteriorly and posteriorly directed margins and copulatory thorns are restricted to three pairs in the precloacal region. In Leptepsilonema saldanhae sp. nov. the somatic setae in the pharyngeal region are very long and the first ambulatory setae of the external subventral row are short. Other distinguishing features include the shape of the amphidial fovea and the copulatory apparatus, and the presence of six ventro-lateral copulatory thorns around the cloaca. These descriptions are the first for the family Epsilonematidae from the west coast of South Africa

Cautioning the move from morphology to molecules in the taxonomy of Metazoa: Comments on Lawley et al. (PeerJ 2021;9, e11954) and a plea for considered integration

This paper serves as a commentary on a recently published paper by Lawley et al. (PeerJ 2021;9, e11954). We caution the adoption of practices in the taxonomy of Scyphozoa by Lawley et al. on the basis that they may lead to taxonomic splits and parallel taxonomies in the face of a concerted push towards integrative taxonomy

A revision of the genus Strongylodesma Lévi (Porifera: Demospongiae: Latrunculiidae) with descriptions of four new species

The sponge genus Strongylodesma is reviewed and redefined, and now accommodates eight closely related species. The type species of Strongylodesma Le´vi is redescribed and an additional two new species are described from the Indo-Pacific: S. novaecaledoniae sp. nov. and S. tongaensis sp. nov. Several specimens previously identified as species of Batzella (Poecilosclerida: Chondropsidae) have been re-assigned to Strongylodesma, as the new species S. purpureus sp. nov. and S. nigra sp. nov. With the description here of new species from the Pacific Ocean and Caribbean Atlantic, the biogeographical distribution of Strongylodesma now appears to be generally tropical with a subtropical South African component, whereas previously it was only known from South Africa. Although species of Strongylodesma have not previously been recorded from the intermediate locations (Western Indian Ocean, South-east Asia, central west Pacific, and New Zealand), re-evaluation here will facilitate more readily the recognition of taxa in these intermediate regions, if they exist, in the future. The species are not widespread, except perhaps along the south-east coast of South Africa, and where they occur they are not abundant. Species occur over a wide depth range, from the intertidal in Tsitsikamma, South Africa, to 140 m in the Caribbean

Trophic ecology of carnivorous zooplankton in the Benguela

Carnivorous zooplankton in the Benguela system have tended to be ignored by all but early taxonomists and a handful of recent researchers. An attempt is made here to address the importance of carnivores in this system but, because the database is poor, it was necessary to apply material from outside the region. The taxa covered include ctenophores, cnidarians (Scyphozoa and Hydrozoa, including Siphonophora), chaetognaths and hyperiid amphipods as well as such minor groups as pelagic gastropods and decapods. Most groups of carnivores within the Benguela are represented by only one or two "common" species. These tend to be epiplanktonic and generally concentrated inshore of the shelf-break, where their distributions are influenced by changes in local hydrography. Their densities frequently exceed those of herbivores. The dominant carnivores share a number of attributes: wide-ranging diets, high assimilation and growth efficiencies and mostly a Type I functional response to food concentration. They fall into two categories. The first is the gelatinous species, which have short lifespans and exhibit rapid growth and often massive reproductive response to high concentrations of food. They are patchily distributed and some appear to have behavioural traits that enable them to stay within localized patches of prey on which they may be dependent because of high metabolic costs. In the second category are crustacean predators and chaetognaths which have slower response times to the food environment but may have longer lifespans, lower daily maintenance needs and an ability to store lipids. They are less dependent on high densities of food organisms and can survive throughout winter, when gelatinous predators are rare. The effect of predation on abundance of copepods is estimated on the basis of both published and unpublished data. Should swarms of predators coincide with a critical gateway of zooplankton or larvae, then there may be total depletion. This applies especially to the nearshore zone of the West Coast and to semi-enclosed bays. The role of carnivorous zooplankton in the diets of commercially important fish species is stressed, but their importance in the regeneration of nutrients may be insignificant

Habitat use by demersal nekton on the continental shelf in the Benguela ecosystem, southern Africa

Videotapes collected by the research submersible Jago in the Benguela ecosystem during spring 1997 were analyzed to determine demersal nekton assemblage composition, fish behavior, and microscale habitat association, and habitat selection. Demersal fish assemblage diversity was generally low, and their composition was a function of substratum type. Individual species showed an often marked association with either rocky or soft substrata (or both), and a strong or weak selection for the associated biota. Soles and dragonets actively selected areas of bioactive soft substrata, to which they are behaviorally and morphologically adapted. False jacopever were associated with crevices in areas of high-relief rocky substrata. Kingklip are piscivorous and were largely confined to holes at the base of rocks and favored areas without a conspicuous epifauna. Juvenile hake and gobies avoided extremely rocky areas and were largely indifferent to the presence of benthic invertebrates—behavior that is consistent with their planktonic diets. These results represent the first direct observations of demersal nekton in the region and are important because they allow better interpretations of the results of trawl studies

Observations on the ecology of Pleurobrachia pileus (Ctenophora) in the southern Benguela ecosystem

The vertical distribution, abundance and size composition of a population of Pleurobrachia pileus was studied during a six-day drogue study conducted off the west coast of South Africa in February 1995. The population was centred in deep water, possibly because of the presence of a potential predator, Beroe sp., at shallower depths. The population of P. pileus failed to display clear patterns of migration, although nocturnal recruitment from deeper water resulted in a deepening of the depth of occupation then. The population was dominated by individuals <4 mm polar diameter, and large animals were confined to the upper water layers. These results are discussed with reference to possible spawning activities. Using published equations relating size to clearance rates, it was estimated that the population could remove up to 27% of integrated mesozooplankton standing stocks, and in excess of 100% (293%) at some depths.Web of Scienc