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Short Communication
First occurrence of the rare siphonophore Lilyopsis Chun, 1885 (Hydrozoa, Siphonophora, Prayinae) in South Africa
expand article infoGillian M. Mapstone, Craig N. Foster§, Mark J. Gibbons|
‡ The Natural History Museum, London, United Kingdom
§ Seachange Science Lab, Simonstown, South Africa
| University of the Western Cape, Belleville, South Africa
Open Access

Abstract

A colony of the rare hydrozoan siphonophore Lilyopsis Chun, 1885, was observed for the first time in shallow water in False Bay, South Africa, swimming amongst kelp. A study of a high-quality image of this individual found it to share some characters with the prayine prayid L. fluoracantha Haddock, Dunn & Pugh, 2005, so far known only from Monterey Bay, California, in the eastern Pacific. No Lilyopsis species has previously been reliably identified from either the South Atlantic or the Indian Ocean, so this record represents an expansion of the known worldwide distribution for this genus.

Keywords

Agulhas Current, Benguela ecosystem, Calycophorae, community science, diversity, photo identification, Prayid

Introduction

Siphonophores can be abundant members of coastal and oceanic zooplankton (e.g. Gili et al. 1991), where they play a role as predators (Purcell 1981; Choy et al. 2017; Hetherington et al. 2022) and prey (Bieri 1966; Bjorndal 1997; Nakamura et al. 2015; Eduardo et al. 2020; Hetherington et al. 2022). Although their populations may fluctuate in size (Blackett et al. 2014, 2015, 2016), they are widely regarded as indicators of water mass movement (Russell 1935). However, their value in the latter context relies on up-to-date information regarding distribution, as this allows us to track potential range expansions in response to, for example, changing ocean circulation. Traditionally, the reporting of new species in areas outside known distributional ranges has been the purview of professional scientists, but this is rapidly changing as we harness the interest, enthusiasm and effort of community scientists (e.g. Gibbons et al. 2021). Here, we report on a genus of siphonophore not previously recorded from the South Atlantic from an image taken by one such community scientist.

Materials and methods

A specimen of a siphonophore was photographed by CF taken on 10 May 2018, at a depth of 1.5 m from within a kelp bed along the western shore of False Bay (34°12.484'S, 018°27.662'E, Fig. 1), and a high-resolution copy of the photograph (Fig. 2) used to identify the specimen. The photo was taken using natural light. The length of the colony was estimated at 7 cm based on the distance of the specimen from the camera.

Figure 1. 

Bathymetric chart of False Bay (From Pfaff et al. 2019, https://doi.org/10.1525/elementa.367.f1). Location where the image was taken indicated by black circle; approximate direction of prevailing surface circulation during SE winds shown by yellow arrows.

Figure 2. 

A photograph of a specimen of Lilyopsis taken against a background of the kelp Ecklonia maxima at a depth of 1.5 m in False Bay on 10 May 2018 A original image B enlarged Lilyopsis colony with explanatory labels. The length of the colony was estimated to be 7 cm.

Glossary of terminology used in this paper:

Basigaster – proximal thickened region of gastrozooid where nematocysts are produced.

Bract – protective asexual zooid of cormidium, typically rounded in prayids with lobed distal margin but in Lilyopsis extending into a spur on one side.

Calyconula larva – later larval stage of a calycophoran siphonophore.

Cormidium – serially repeated (iterative) group of zooids on the main stem, or siphosome, each including a gastrozooid, one or more gonophores and typically a bract.

Cormidial bell – a special nectophore in the cormidia of Lilyopsis, some other prayines and some other siphonophores.

Gastrozooid – asexual feeding zooid in a cormidium, with tentacle arising from proximal end.

Nectophore – asexual swimming bell present in most siphonophores, having a muscular nectosac for locomotion opening distally via an aperture termed the ostium.

Siphosome – posterior part of the stem, bearing cormidia in all siphonophores.

Tentilla – specialized side branches on a siphonophore tentacle comprising a complex nematocyst battery.

Results and discussion

The specimen illustrated in Fig. 2, can be identified as the fragile prayine siphonophore genus Lilyopsis Chun, 1855, for its distinctive closely spaced cormidia on the siphosome, each with a cormidial bell, and a pair of extremely transparent nectophores, swimming away from the camera on the right. Lilyopsis nectophores have very large nectosacs relative to those of other prayines. Each nectosac opens via an enlarged ostium oriented at a 45° angle relative to the long axis of the nectophore and one such ostium is just visible in Fig. 2B. The bracts in the siphosomal cormidia of Lilyopsis are spurred, also clearly visible in Fig. 2B (see Fig. 3).

Figure 3. 

Bracts of the two known Lilyopsis species from below. L. medusa modified from Carré 1969 Fig. 1; L. fluoracantha modified from Haddock et al. (2005 Fig. 5A; bell – of cormidium; gz – gastrozooid).

There are two species currently identified as belonging to the genus Lilyopsis: L. medusa (Metschnikoff & Metschnikoff, 1871) and L. fluoracantha, Haddock, Dunn and Pugh 2005. Lilyopsis medusa was first introduced as Praya diphyes by Graeffe (1860), but because this name was already preoccupied by another prayine prayid, precedence for the species name medusa went to the specimen described by Metschnikoff and Metschnikoff (1871) from Villefranche as Praya medusa. Later, Chun (1885) introduced a new genus Lilyopsis for three prayine species with the generic characters noted above. These included Chun’s own species L. rosea from Naples which he considered different from the L. medusa of Metschnikoff and Metschnikoff (1871) and from the Praya diphyes of both Kölliker (1853) and Vogt (1854). Lilyopsis rosea has been considered a junior synonym of L. medusa for some time, although usage of the specific name did not change until the error was pointed out by Pugh (2009). Praya diphyes of Kolliker and Vogt is now referred to as Desmophyes annectens (Totton 1965).

Lilyopsis medusa was last studied in detail by Carré as L. rosea, based on specimens collected at Villefranche in the Mediterranean, including drawings and photographic images of the siphosome and of male and female cormidia (Carré 1969, figs 1, 2, pl. 1 fig. 5, pl. II fig. 5). More recently, the same species was imaged in the Southern California Bight by Luo et al. (2014, fig. 3ad), with a second image from the same site included in Mapstone (2015, fig. 14E). In all these figures, and earlier ones reproduced by Totton (1965, figs 72A–C) and Bedot (1896, fig. 1), the bracts of the cormidia can be seen to have a spur extending from one side in a posterior direction, but this spur is not particularly elongate. In contrast, the bracteal spurs of L. fluoracantha are conspicuously longer as clearly shown by Haddock et al. (2005, fig. 5A–C) and noted in their species diagnosis.

The siphosome of the present colony from False Bay (Fig. 2) became twisted during swimming, and the most mature cormidia on the stem are on the left in Fig. 2B. In these cormidia each bract has a long posteriorly directed spur and further long spurs are also visible from bracts in cormidia on the right, closer to the nectosome. These bracteal spurs are longer than those shown for Lilyopsis medusa and are most similar to those illustrated and described for L. fluoracantha (Haddock et al. 2005), as shown in Fig. 3. Other similarities include the whitish tentilla on the tentacles of the gastrozooids in both the False Bay specimen and L. fluoracantha, which, although said to be yellowish in life in L. fluoracantha, appear whitish in the published figures (Haddock et al. 2005, fig. 6A, C, E). The gastrozooids of L. fluoracantha also appear similar to those of the present colony, except that they are relatively smaller in the published figure of L. fluoracantha and also have white basigasters (Haddock et al. 2005, fig. 6E).

Some characters of the present colony from South Africa fit well with those of both Lilyopsis medusa and L. fluoracantha (large transparent nectophores and closely spaced siphosomal cormidia, each with a cormidial bell), although nectophore details could not be directly compared since in the False Bay image only one of the two nectophores was visible, and in posterior view (Fig. 2B). Our colony measured c. 7 cm in length, which falls within the range of 5–10 cm for L. medusa (Carré 1969) and 3.6–12 cm for L. fluoracantha (Haddock et al. 2005, fig. 6A and p. 702). At least 18 cormidia can be identified in our colony (Fig. 2B). In L. medusa, 10 to 20 cormidia have been identified by Carré (1969) and up to 25 by Luo et al. (2014), and in L. fluoracantha up to 35 cormidia have been observed (Haddock et al. 2005). The main difference between our colony and those of L. medusa and L. fluoracantha is the bright green basigasters on the gastrozooids (Fig. 2B). In L. fluoracantha the gastrozooids were clear or whitish and cylindrical (Haddock et al. 2005) with a whitish basigaster, as noted above, and it is assumed here that those of L. medusa are similar, since no previous authors have commented on any pigment in this zooid (for example Carré 1969; Chun 1885). Cormidial bells are clearly present in each cormidium of our specimen, but further detail is not discernible (Fig. 2B). In L. medusa a small red disc is present on the two most anterior of the four cormidial radial canals and fine red spots are distributed all around the ostium, but in L. fluoracantha no red pigment was identified in the cormidial bells (Haddock et al. 2005).

Lilyopsis fluoracantha was described from just five specimens collected, or captured on video, between 1998 and 2004 near Monterey Bay, California, at depths between 327 and 476 m (Haddock et al. 2005), although 13 more have been identified in the same region (pers. comm. Kyra Schlining). There are more records for L. medusa which is considered a warmer water species worldwide, but rare. Most specimens have been collected at Villefranche-sur-Mer in the Ligurian Sea of the Mediterranean where upwelling has been known since antiquity (Madin 1991). From this location, or nearby off Nice, L. medusa has been described by Graeffe (1860), Metschnikoff and Metschnikoff (1871), Fewkes (1883), Moser (1917), Carré (1969) and Carré and Carré (1969). However, it has also been reliably reported twice in the Tyrrhenian Sea off Naples (Chun 1885; Schneider 1898), in the North Atlantic once from the Canaries by Chun (1888), in the Caribbean (Minemizu et al. 2015) and elsewhere by Haddock et al. (2005). In the Pacific, L. medusa has been recorded from the Southern Californian Bight (Luo et al. 2014, at 84 m), from the central tropical Pacific in the Bay of Ambon (Moluccas Indonesia, Bedot 1896), in Sagami Bay (Lindsay and Miyake 2009) and in Suguru Bay (Minemizu et al. 2015) in the western Pacific, and also off Australia (Haddock et al. 2005). This species has been additionally collected as a calyconula larva by SCUBA divers in Monterey Bay, California (Pugh 2009). Other records for the genus exist but the specific identity is unknown (e.g. Hoving et al. 2020).

So far Lilyopsis fluoracantha has only been observed or collected in deep water from Monterey Bay where the water temperature varied between ~6.5 and 8.5 °C (pers. comm. from Kyra Schlining at MBARI, July 2020). In contrast, reliable records for L. medusa show that it typically inhabits shallower and warmer water worldwide, between, for example, 14 and 24 °C in Villefranche Bay (Villefranche Sea Temperature 2021), 13 and 28 °C in the Bay of Naples (Bay of Naples Sea Temperature 2021) and 27 and 29 °C in the Bay of Ambon, in the Moluccas (Bay of Ambon Sea Temperature 2021), although one record is from 84 m in the Southern California Bight, where the water temperature was only 8 to 11 °C (Luo et al. 2014). Our Lilyopsis specimen was imaged in False Bay during the austral autumn where the water temperature was c. 15 °C. False Bay is one of the largest true embayments in South Africa (Fig. 1), and although circulation is approximately clockwise, it is influenced by prevailing winds. Because the bay sits at the NW edge of the Agulhas Bank, it is also subject to the vagaries of the Agulhas Current (Gründlingh and Largier 1991, de Vos et al. 2021). SE winds predominate in summer, which lead to upwelling at Cape Hangklip in the SE corner of the bay, offshore water transport and the development of a strong northward temperature gradient (Pfaff et al. 2019). During winter, NW winds serve to mix waters in the bay, and they promote onshore water movement (Pfaff et al. 2019). While we can speculate as to its origin, it is clear that Lilyopsis is not resident in False Bay because it has only been observed once during the many years that one of us (CF) has been snorkeling daily at the site in False Bay. Neither has it been observed by another frequent community scientist, Peter Southward (see Gibbons et al. 2021).

Conclusions

In general, our specimen shares more characters with L. fluoracantha than it does with L. medusa, but the bright green basigasters of the gastrozooids do seem to be unique, although may not be a robust character for species separation. Perhaps, therefore, it represents a third Lilyopsis species, or maybe a variant of L. fluoracantha, since in both species the bracts have elongate spurs. It will be necessary to collect a specimen in the future for genetic analysis if this is ever possible, which could confirm its identity as L. fluoracantha. Meanwhile, we assign our specimen to the genus Lilyopsis Chun, 1885, in the subfamily Prayinae Chun, 1897, of the calycophoran family Prayidae Kolliker, 1853.

Acknowledgements

We thank Kyra Schlining of Monterey Bay Aquarium Research Institute for information about observations and samples of Lilyopsis fluoracantha from the Monterey Bay area. GMM thanks The Natural History Museum, London for access to literature and other facilities as an NHM Scientific Associate. We are grateful to Bert Hoeksema and Dhugal Lindsay for their comments on the manuscript, which have helped to clarify the text.

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