Omri Bronstein

Opportunistic feeding by the fungiid coral Fungia scruposa on the moon jellyfish Aurelia aurita

The Gulf of Aqaba (Red Sea) is characterized by seasonal plankton blooms which are driven by vertical nutrient upwelling during winter (Genin et al. 1995). In March 2009, following the seasonal upwelling, large numbers of the moon jellyfish (Aurelia aurita) were recorded at the local fringing reefs of Eilat, at depths of 2–20 m (Fig. 1a). During this event, several large (ca. 20–25 cm) solitary corals (Fungia scruposa) were observed to feed on these jellyfish (Fig. 1b, c). A. aurita is known to be eaten by a wide variety of relatively large predators, including fish, sea turtles and even sea birds; however, it has never been reported as a coral’s prey. Despite the fact that hermatypic corals may feed heterotrophically on a broad variety of sources ranging in size from bacteria to mesozooplankton (up to 1,000 lm) (Houlbrèque and Ferrier-Pagès 2009), this is the first report of solitary corals feeding on large gelatinous plankton (ca. 12 cm in diameter) in their natural habitat. Other cnidarians, such as the sea anemone Entacmaea medusivora in Palau, have also been shown to feed on jellyfish (Mastigias papua). However, as opposed to F. scruposa, these sea anemones are constantly surrounded by their prey and they lack photosynthetic endosymbionts (Fautin and Fitt 1991). Our observations revealed that the large-mouthed solitary fungiids can consume relatively large prey organisms, which are not available to other corals, as an additional source of protein. It remains to be shown, however, how fungiid corals manage to capture these large jellyfish while overcoming their motility. This trophic opportunism and reproductive plasticity exhibited by fungiid corals (Loya and Sakai 2008) are suggested as an important asset in determining their evolutionary success.

Photoperiod, temperature, and food availability as drivers of the annual reproductive cycle of the sea urchin Echinometra sp. from the Gulf of Aqaba (Red Sea)

In spite of the efforts invested in the search for the environmental factors that regulate discrete breeding periods in marine invertebrates, they remain poorly understood. Here, we present the first account of the annual reproductive cycle of the pantropical sea urchin Echinometra sp. from the Gulf of Aqaba/Eilat (Red Sea) and explore some of the main environmental variables that drive echinoid reproduction. Monthly measurements of gonado-somatic indexes and histological observations of 20 specimens revealed a single seasonal reproductive cycle, with gametogenesis in males and females being highly synchronized. Gametogenesis commenced in June and peak spawning occurred between September and October. Gonado-somatic indexes were significantly correlated with seawater temperatures but not with photoperiod. The latter cycle lagged behind the gonado-somatic cycle by two months, suggesting that the onset of gametogenesis corresponds to shortening day length, while spawning may be driven by warming seawater temperatures. Gonads remained quiescent throughout the winter and spring (January through May) when temperatures were at their lowest. Chlorophyll-a concentrations increased significantly in the months following spawning (October through January). These high concentrations are indicative of high phytoplankton abundance and may reflect the increase in food availability for the developing larvae. Of the external test dimensions, length presented the highest correlation to body weight, indicating length as the best predictor for body size in Echinometra. Neither sexual dimorphism nor size differences between males and females were detected, and the sex ratios were approximately 1:1 in three distant Echinometra populations. Environmentally regulated reproduction, as occurs in sea urchins, might face severe outcomes due to anthropogenic disturbances to the marine environment. Consequently, there is a need to deepen our understanding of the mechanisms that drive and regulate this process in broadcast-spawning species.

Do genes lie? Mitochondrial capture masks the Red Sea collector urchin's true identity (Echinodermata: Echinoidea: Tripneustes).

Novel COI and bindin sequences of the Red Sea collector echinoid Tripneustes gratilla elatensis are used to show that (1) discordance between mitochondrial and nuclear loci exists in this echinoid genus, (2) Tripneustes gratilla as currently defined possibly comprises a complex of cryptic species, and (3) Red Sea Tripneustes form a genetically distinct clade in the bindin tree, which diverged from other Tripneustes clades at least 2-4million years ago. Morphological reassessment of T. gratilla elatensis shows perfect congruence between identification based on skeletal features and genetic data based on a nuclear marker sequence. Hence the Red Sea Tripneustes subspecies established by Dafni in 1983 is a distinct biological unit. All T. g. elatensis samples analyzed are highly similar to or share mtDNA haplotypes with Philippine T. g. gratilla, as do representatives from other edge-of-range occurrences. This lack of genetic structure in Indo-Pacific Tripneustes is interpreted as a result of wide-spread mitochondrial introgression. New fossil specimens from the Red Sea area confirm the sympatric occurrence of T. g. elatensis and T. g. gratilla in the northern Red Sea during Late Pleistocene, identifying a possible timing for the introgression. In addition, present-day distribution shows a contact zone in the Southern Red Sea (in the Dahlak Archipelago). T. g. elatensis, is yet another example of a Red Sea taxon historically identified as conspecific with its Indo-Pacific relatives, but which turned out to be a morphologically and genetically distinct endemic taxon, suggesting that the level of endemism in the Red Sea may still be underestimated.

The taxonomy and phylogeny of Echinometra (Camarodonta: Echinometridae) from the red sea and western Indian Ocean.

The number of valid species in the genus Echinometra (Echinodermata, Echinoidea) and their associated identification keys have been debated in the scientific literature for more than 180 years. As the phylogeny and dispersal patterns of these species have been widely used as a prominent model for marine speciation, new insights into their taxonomy have the potential to deepen our understanding of marine speciation processes. In this study we examine Echinometra taxonomy, combining morphology and molecular tools. We present the taxonomy and phylogeny of Red Sea and Western Indian Ocean Echinometra. The currently available morphological keys were found to be limited in their ability to delineate all species within this genus. Nonetheless, morphological similarities between the Red Sea and Western Indian Ocean populations were high, and delimited them from the other species. These latter populations together formed a monophyletic clade, genetically distant from any of the other Echinometra species by more than 3%. Combining both traditional taxonomy and molecular evidence, we found that these populations were neither Echinometra mathaei nor E. oblonga, as previously considered. The morphological discrepancies of these populations, and their genetic divergence from the other Echinometra species, suggest that they should be considered as a new Echinometra species.

Daytime spawning of Porites rus on the coral reefs of Chumbe Island in Zanzibar, Western Indian Ocean (WIO)

The majority of scleractinian corals spawn during nighttime (Harrison and Wallace 1990). Daytime spawning is rare, and mostly occurs in early morning or late afternoon with only several species reported to spawn during midday (e.g., Pavona sp. and Fungia danai; Plathong et al. 2006; Mangubhai et al. 2007). The most common combination of sexuality and mode of reproduction currently known for scleractinian corals is hermaphroditic spawning (63%), while gonochoric brooding is the least common combination (7%) (Baird et al. 2009). However, in the genus Porites, the relative abundance of gonochoric brooders is almost five times higher than in the majority of other scleractinia, involving up to 33% of currently known species (Baird et al. 2009). During a survey of the Chumbe Island Coral Park (06o16.7¢S, 039o10.4¢E), several colonies of P. rus, measuring 1.5–5 m in diameter, were observed spawning in midday on the islands western reef flats (Fig. 1). Thirteen (13) colonies were observed spawning during low tide, at depths of 1–3 m, between 11 and 12 a.m on November 26, 2010, 5 days after the full moon. Big clouds of sperm were released to the water column in bursts that lasted over 20 min. In the western Pacific, P. rus has been identified as a gonochoric spawner (Penland et al. 2004); however, no reports on P. rus sexuality or mode of reproduction in the WIO currently exist in the literature. Here, we present the first documentation of P. rus spawning at this part of the WIO and the first midday spawning observation for this species. Furthermore, since egg release was not observed in any of the spawning colonies (as might be expected), our findings suggest P. rus in the WIO to be a gonochoric brooder in contrast to its western Pacific conspecific.

First record of the non-indigenous ascidian Microcosmus exasperatus, Heller 1878, in Cyprus

The solitary ascidian Microcosmus exasperatus (Class: Ascidiacea, Family: Pyuridae) is found in both tropical and sub-tropical waters. In the Mediterranean it has been recorded on the coasts of Israel, Lebanon, Turkey, and Tunisia. Here we report its first record from Cyprus, where it was found forming aggregations on ropes in a marina. It was also recorded there on the hull of a 7-meter pleasure craft. We provide both molecular and morphological diagnostics to facilitate the accurate identification of M. exasperatus, as its external appearance resembles that of M. squamiger, which is a widely-distributed species in the western Mediterranean. The occurrence of M. exasperatus on ship hulls and its ability to form large aggregations on artificial substrata may accelerate introduction of the non-native epifaunal organisms that cover its tunic, consequently altering local biodiversity. Thus, we strongly recommend monitoring the progression of this invasive species in the eastern Mediterranean.

Reproduction of the long-spined sea urchin Diadema setosum in the Gulf of Aqaba - implications for the use of gonad-indexes.

As global warming and climate-change proceeds ever more rapidly, organisms depending on seasonal cues to synchronize reproduction face an unclear future. Reproduction in Diadema setosum in the Gulf of Aqaba (Red Sea) is seasonal, with mature individuals occurring from July to October. Gonad indexes (GI), in contrast, indicate that spawning occurs from August through December and suggests two main spawning events. Histological analysis, however, indicate that the second peak of GI values cannot be related to spawning, but rather correspond to recovering individuals. In Diadema, examination of GI values alone may thus lead to erroneous conclusions. GI was moderately-strong positively correlated with sea-surface temperatures, but not with chlorophyll-a concentrations or photoperiod. Spawning coincides with the onset of the annual chlorophyll-a increase, however, which might be advantageous for nutrition of the developing larvae. First significant GI increase coincides with the shortening of day-length, which may act as a cue for D. setosum gametogenesis. Gametogenesis is highly synchronised between sexes, although the mature phase of females exceeds that of males. The non-complete overlap may represent sampling bias or represent an adaptive strategy for enhancing fertilisation success. Skewed sex ratios (♀:♂ 1:0.59, n = 360) in the Gulf of Aqaba may be related to pollution.

Needle in a haystack—genetic evidence confirms the expansion of the alien echinoid Diadema setosum (Echinoidea: Diadematidae) to the Mediterranean coast of Israel

Diadema setosum (Leske, 1778), a widespread tropical echinoid and key herbivore in shallow water environments is currently expanding in the Mediterranean Sea. It was introduced by unknown means and first observed in southern Turkey in 2006. From there it spread eastwards to Lebanon (2009) and westwards to the Aegean Sea (2014). Since late 2016 sporadic sightings of black, long-spined sea urchins were reported by recreational divers from rock reefs off the Israeli coast. Numerous attempts to verify these records failed; neither did the BioBlitz Israel task force encounter any D. setosum in their campaigns. Finally, a single adult specimen was observed on June 17, 2017 in a deep rock crevice at 3.5 m depth at Gordon Beach, Tel Aviv. Although the specimen could not be recovered, spine fragments sampled were enough to genetically verify the visual underwater identification based on morphology. Sequences of COI, ATP8-Lysine, and the mitochondrial Control Region of the Israel specimen are identical to those of the specimen collected in 2006 in Turkey, unambiguously assigning the specimen to D. setosum clade b. This lends support to the hypothesis of a single introduction event and fits well with the habitat suitability and distribution model for D. setosum published recently. The more rapid and larger range extension along a south-eastern, counter-current trajectory may reflect a strong habitat preference for D. setosum in this area of the Levantine Basin as predicted by the model.

On the genus Spirobranchus (Annelida, Serpulidae) from the northern Red Sea, and a description of a new species

Abstract. Species of the genus Spirobranchus, commonly known as Christmas tree worms, are abundant throughout tropical Indo-Pacific and Atlantic Oceans. Information on the species inhabiting the Red Sea in general and the Gulf of Eilat (Gulf of Aqaba) in particular, has so far been very limited. Here we present a multigene phylogenetic analysis, examining both mitochondrial (Cyt-b) and nuclear (ITS2 and 18S) markers, to support the presence of four distinct Spirobranchus species in the Gulf of Eilat: S. corniculatus (including three taxa previously regarded as full species: S. gaymardi, S. cruciger, and S. corniculatus), S. cf. tetraceros, S. gardineri and a new species Spirobranchus aloni, likely endemic to the Red Sea (including two morphotypes with slightly different opercular morphology). The results presented here emphasise that the combination of molecular and in-depth morphological evaluation holds great prospects for a better understanding of species divergence and relationships.

The first mitochondrial genome of the model echinoid Lytechinus variegatus and insights into Odontophoran phylogenetics

Assembly of publically available next-generation sequence data facilitated the generation of three camarodont echinoid mitogenomes: two for the Green Urchin (Lytechinus variegatus) and one for the Red Urchin (Mesocentrotus franciscanus). The data generated are exploited in a phylogenomic analysis of the superfamily Odontophora, originally proposed for echinoids with tooth supports on the epiphyses of the jaw. The analysis highly supports this taxon and its current subdivision into three families: the Echinometridae, Toxopneustidae, and Strongylocentrotidae. The analysis furthermore implies that historical taxonomic issues between two members of the genus Strongylocentrotus (S. pallidus and S. droebachiensis) may have a genetic basis. The novel mitogenomes for the model species L. variegatus complements the draft genome available for this taxon, one of only three genome-enabled echinoid species. The assembly method applied herein, follows a divide-and-conquer approach that provides for reduced computational requirements and facilitates resolving assembly problems when processing ultra-high coverage next-generation sequence data.