Pegea Confoederata Research Articles

In-situ observations of swarming pelagic tunicate Pegea confoederata (Forskål, 1775) (Tunicata: Thaliacea) in coral reef habitats of Kuwait

Pelagic tunicates (order Salpida) have the highest filtration rates among filter feeding marine zooplankton. This is the first-ever in situ observation of the salp, Pegea confoederata (Forskål, 1775), in northwestern Arabian Gulf (NWAG), off Kuwait. Swarms of P. confoederata with chain-like blastozooids (∼1 ​m) and solitary oozoids were observed in offshore coral reef habitats. Coastal fishes, Diplodus sargus kotschyi and Abudefdef vaigaiensis, were observed feeding on P. confoederata tests. In Kuwait, higher summer density of phytoplankton (<20 ​μm) supports P. confoederata aggregation. Concerted studies on salps in the Arabian Gulf may offer insights into pelagic carbon cycling pathways and carbon sequestration.

A Novel Association between Larval and Juvenile Erythrocles schlegelii (Teleostei: Emmelichthyidae) and Pelagic Tunicates

We describe the first documented associations between an emmelichthyid and a pelagic tunicate. An in situ observation of larval and juvenile Japanese Rubyfish, Erythrocles schlegelii (Emmelichthyidae) was made during blackwater scuba dives in the epipelagic waters off the coast of the Philippines. The fish were in close association with the pelagic salp Pegea confoederata (Thaliacea; Salpidae), either drifting alongside a colony of salps or residing inside individual salp cavities. Our results describe and illustrate this behavior, highlighting a previously undocumented family of fishes that associates with pelagic gelatinous invertebrates. This finding also demonstrates the importance of community science to further our understanding of the early life history of marine fishes.

Pelagic tunicates (Appendicularia and Thaliacea) of Sri Lanka: two first records with an annotated checklist.

In broadening the understanding of the diversity, distribution and seasonality of gelatinous zooplankton of Sri Lanka, a survey ('Waya-jel-Survey) was carried out in coastal waters of the country from 2016 to 2020, and the collected specimens of pelagic tunicates were taxonomically identified. Further, a comprehensive literature survey was conducted and the previous records on the occurrences of pelagic tunicates within the exclusive economic zone of Sri Lanka were cross-checked and listed in developing the first-ever annotated checklist. Among the samples collected in this study, Pyrostremma spinosum and Thalia sibogae were reported for the first time from Sri Lankan waters while two more thaliaceans, i.e., Doliolum denticulatum and Pegea confoederata, and six appendicularians, i.e., Fritillaria borealis sargassi, F. formica digitata, Oikopleura cophocerca, O. fusiformis, O. longicauda, and O. rufescens were re-recorded. In total, forty species (including two subspecies) in 19 genera, belonging to five families from four orders of the classes Appendicularia (n = 17 species) and Thaliacea (n = 23 species) were reported to be inhabited in Sri Lankan waters. Most of the records were from the Laccadive Sea region while the majority of the species have been reported during the northwest monsoon (December to February) period.

Fine structures of the mantle tissue in the pinkish-brown salp &lt;i&gt;Pegea confoederata&lt;/i&gt; (Tunicata: Thaliacea)

Fine structures of the mantle tissue in the pinkish-brown salp &lt;i&gt;Pegea confoederata&lt;/i&gt; (Tunicata: Thaliacea)

Physical properties of the tunic in the pinkish-brown salp Pegea confoederata (Tunicata: Thaliacea)

BackgroundInvisibility in the water column is a crucial strategy for gelatinous zooplanktons in avoiding detection by visual predators, especially for animals distributed in the euphotic zone during the daytime; i.e., surface dwellers that do not undergo diel vertical migration. Salps, a member of the subphylum Tunicata (Urochordata), usually have a transparent body that is entirely covered with a cellulosic matrix, called the tunic. Some non-migrator species are known to exhibit a nano-scale nipple array on the tunic surface. However, the physical properties of the salp tunic has been poorly investigated, except for Thetys vagina, in which the tunic was expected to show low reflectance based on the refractive index of the tunic. Pegea confoederata is a non-vertical migrant salp showing pinkish-brown body. We measured the hardness, water content, absorption spectra, and refractive index of its tunic to evaluate its fragility and visibility.ResultsThere are nipple-like protuberances about 80 nm high on the surface of the tunic in P. confoederata. The tunic is very soft; the maximum force to pierce the tunic with a steel rod (1 mm diameter) was < 1 N. The water content of the tunic was > 95%. The absorption spectra of the tunic had no prominent peaks in the wavelength range of 280–800 nm, indicating the tunic is nearly transparent. The difference in refractive indices between tunic and seawater was estimated as 0.002–0.015 at 589 nm. Rigorous coupled wave analyses (RCWA) of light reflection based on 3-dimensional models supported an anti-reflective effect of the nipple array on the tunic surface, which was estimated to vary slightly depending on the forms and the arrangement patterns of nipple-like protuberances in an array.ConclusionsThe tunic of P. confoederata is very soft and contains more water than those of sessile tunicates (ascidians). Based on the refractive index of the tunic, light reflection is expected to be very low, making this salp’s tunic barely visible in water column. Our results suggest that the nipple array may produce an anti-reflective effect.

Report for eight species of Salpinae (Thaliacea: Salpida: Salpidae) from Korean waters

In this study, aggregate and solitary zooids of salps were collected from Southern and East Sea of Korea. By morphological characteristic examinations, eight species in the subfamily Salpinae were identified as new records in Korean waters: Pegea bicaudata (Quoy and Gaimard 1826); Pegea confoederata (Forskal 1775); Ritteriella amboinensis (Apstein 1904); Ritteriella retracta (Ritter 1906); Salpa aspera Chamisso, 1819; Salpa maxima Forskal, 1775; Traustedtia multitentaculata (Quoy and Gaimard 1834); and Weelia cylindrica (Cuvier 1804). These species were redescribed and reported with illustrations of the photographs. There are 16 species from the subfamily Salpinae which were reported from Korea.

Swarm of Salps in the Northern Arabian Sea During Winter Season of February 2011

Swarm of Salps in the Northern Arabian Sea During Winter Season of February 2011 Samples were gathered to identify the diversity and distribution of salps in the Northern Arabian Sea during February 2011, the survey was made by FORV Sagar Sampada (Cruise No. 284). During the survey period, 15 species of the shops were identified among them the dominant species was Pegea confoederata with higher abundance followed by Metcalfina hexagone and Iasis zonaria. The abundance of salps was increased from south to north most stations and it was varied between 10.05 and 609.93ind.m-3.

A contribution to the knowledge of the thaliacean faunas of the eastern mediterranean and the red sea

ABSTRACT In the sector of the Mediterranean east of the 22nd meridian, five species of Salpidae (Thalia democratica, Salpa fusiformis, Ihlea punctata, Pegea confoederata and Cyclosalpa pinnata polae) and five species of Doliolidae (Doliolum denticulatum, Doliolum nationalis, Doliolina sp., Doliolina intermedium (?)' and Dolioletta sp.) were caught during a series of cruises. At the same time, four species of Salpidae (Thalia democratica, Salpa cylindrica, Brooksia rostrata and Ritteriella amboinensis) and two species of Doliolidae (Doliolina mulleri krohni and Doliolum denticulatum) were recorded in the Gulf of Elat (Gulf of 'Aqaba), Two further species, Salpa maxima and Dolioletta gegenbauri tritonis, previously recorded from this area, were not found again in these last catches. Pyrosomidae are missing in both areas. The two faunas are very different, having in common only a few widely distributed species.

Comparative jet wake structure and swimming performance of salps

Salps are barrel-shaped marine invertebrates that swim by jet propulsion. Morphological variations among species and life-cycle stages are accompanied by differences in swimming mode. The goal of this investigation was to compare propulsive jet wakes and swimming performance variables among morphologically distinct salp species (Pegea confoederata, Weelia (Salpa) cylindrica, Cyclosalpa sp.) and relate swimming patterns to ecological function. Using a combination of in situ dye visualization and particle image velocimetry (PIV) measurements, we describe properties of the jet wake and swimming performance variables including thrust, drag and propulsive efficiency. Locomotion by all species investigated was achieved via vortex ring propulsion. The slow-swimming P. confoederata produced the highest weight-specific thrust (T=53 N kg(-1)) and swam with the highest whole-cycle propulsive efficiency (eta(wc)=55%). The fast-swimming W. cylindrica had the most streamlined body shape but produced an intermediate weight-specific thrust (T=30 N kg(-1)) and swam with an intermediate whole-cycle propulsive efficiency (eta(wc)=52%). Weak swimming performance variables in the slow-swimming C. affinis, including the lowest weight-specific thrust (T=25 N kg(-1)) and lowest whole-cycle propulsive efficiency (eta(wc)=47%), may be compensated by low energetic requirements. Swimming performance variables are considered in the context of ecological roles and evolutionary relationships.

Grazing impact of salp (Tunicata, Thaliacea) assemblages in the eastern tropical North Pacific

Salps are gelatinous filter-feeders that can intermittently contribute significantly to the cycling of organic matter in the world’s oceans. We estimated the grazing impact of salp assemblages on phytoplankton biomass and rates of primary production (PP) in the eastern tropical North Pacific off Mexico during two cruises in February and November of 2003. Salp biomass comprised a large proportion of the preserved zooplankton biomass (21‐525 mL per 10 3 m 3 ) at stations where large salps were present. Of the 19 species found in the area, Thalia democratica (and closely related species) comprised 11‐100% of total salp abundance but were surpassed in dominance at some locations by Metcalfina hexagona (49%) and an unidentified Cyclosalpa (29%). In February, salp abundance ranged from 6 to 1901 salps m 22 (0.1‐13.5 mg C m 22 ); in November, values ranged from 54 to 631 salps m 22 (1‐193 mg C m 22 ). Ingestion rates by the salp assemblage, estimated from gut pigment content, were moderate and highly variable. Thalia exerted a low impact on phytoplankton stocks and PP, whereas moderate aggregations of cooccurring M. hexagona, Cyclosalpa sp. and Pegea confoederata exerted a higher impact when present. Salp assemblages ingested 0.01‐3.5% of chlorophyll standing stock daily. The proportion of PP removed by salps was estimated to range from 0.1 to 24.5% day 21 , suggesting a significant role for salps in the grazing mediated

The endostyle and the feeding filter in salps (Tunicata)

This note examines the way the pharyngeal feeding filter is constructed within the salp endostyle. Three salp species (Pegea confoederata, Thalia democratica and Salpa fusiformis) have been examined: results from each are essentially similar. The endostyle is a deep ventral groove in the pharynx, divided by a line of long basal cilia. These are flanked by gland cells which secrete the ‘mucus” which forms one of the sets of filaments of the filter. Beside the openings of this basal row of gland cells (marked by bumps of curious ‘mucus’ rodlets), there is a fence of two adjacent rows of cilia. The first of these two rows, (nearest the basal mid-line), whose tips lie next to the rodlet bumps, are regularly spaced 1.0 μm apart along the endostyle, whilst the cilia of the second row are at around half this spacing. Passing upwards in the endostylar groove, this first ciliary fence is followed by a ciliated zone, and then a second row of glandular cells is linked to a second ciliary fence with a single row of cilia only.Filaments derived from the first set of gland cells pass obliquely over the ciliated zone, and continue over the second ciliary fence. The cilia of the second fence are often surrounded by very striking borders or curtains of rodlets which appear to dissolve, run down the cilia and pass off the tips as filaments, when they are joined by the first set of filaments to form a net with an elongate rhomboidal mesh. As this passes upwards, the mesh changes to become more or less square by the time it comes to overlie a striking asymmetrical band of cilia arranged in columns, when it is now composed of two sets of filaments running vertically and horizontally, spaced some 1.3 μm apart.Various aspects of the formation of this filter net are considered.

Thraustochytrid fungoid protists in faecal pellets of the tunicate Pegea confoederata, their tolerance to deep-sea conditions and implication in degradation processes

During a swarm of the tunicate Pegea confoederata (salp) in the northern Arabian Sea, we examined their faecal pellets for thraustochytrid protists and bacteria to understand the role of the former in decomposition processes in the sea. Fresh faecal pellets from surface waters contained on average 6.58 × 10 6 thraustochytrids g -1 dry wt, while bacterial numbers were about 3 orders of magnitude higher. Highest numbers of thraustochytrids were observed when the faecal pellets were incubated at 25°C for 6 d using unsterilized surface sea water, as compared to 10°C using sterilized or unsterilized water collected from 100 m depth. Our results indicate that thraustochytrids in the water column may further colonize faecal pellets. A thraustochytrid isolate cultured from such faecal pellets grew on pine pollen, Artemia larvae and nutrient broth, when subjected to 10°C and a pressure of 10 MPa, corresponding to 1000 m depth. It also produced proteases when subjected to combinations of 2 pressures, 0.1 (1 atm) and 10 MPa (100 atm), and 2 temperature conditions, 30 and 10°C. The results suggest that thraustochytrids found in such particulate organic matter may actively contribute to decomposition processes not only in the surface waters, but also under deep-sea conditions.

Two functionally different muscle fibre types in some salps?

This paper describes the structure and operation of the fibres in the locomotor muscle bands of several salp species. In many species, for example Thalia democratica or Pegea confoederata , all the muscle fibres of the locomotor muscle bands are similar in width and structure. In others, for example Salpa fusiformis and S. maxima, although fibre structure is similar, the marginal fibres edging the bands may be some 3-4 times the width of those in the centre of the band. In Ihlea punctata , not only is there a more striking difference in width between the marginal and central fibres of the bands, but also the two differ in structure. The marginal fibres are up to 10 times the width of the central fibres and the two differ in myofibrillar and mitochondrial content. Intracellular recordings from the fibres show that the normally compound spike potentials do not overshoot resting potentials (up to -70 mV), and are decremental. The two types of fibre may be separately activated. It is suggested that in Ihlea punctata , the wide marginal fibres may be involved in slow swimming, the central narrow fibres in `escape´ swimming.

Degradation of faecal pellets in Pegea confoederata (Salpidae, Thaliacea) and its implication in the vertical flux of organic matter

Faecal pellets of P. confoederata were maintained in suspension for 10 days and changes in their morphological, microbiological and fatty acid characteristics as well as their resulting sinking rates were followed during this period. Among the morphological characteristics measured, the perimeter, the surface area and the longest dimension decreased linearly with time but their form remained unchanged. The weight decreased. Microbiological concentrations showed three stages, a rapid increase was followed by a rapid decrease and then finally a small re-increase for heterotroph populations and stabilization for autotrophs. Total fatty acid concentration followed a similar pattern to that of microbial concentrations with some exceptions for individual fatty acids. These three stages in degradation were attributed to incubation conditions as well as to trophic relationships. The sinking rates, measured in different turbulent conditions, varied from 2706 to 3646 m day −1 for the fresh faecal pellets and decreased 30% after 10 days incubation whatever the turbulent kinetic energy dissipation rate. For fresh faecal pellets, the observed sinking rates were greater in highly turbulent conditions than in moderately turbulent or in calm conditions. At the beginning of incubation, minimal sinking rates were observed in moderately turbulent conditions and after four days in calm conditions. This was attributed to the state of degradation of the faecal pellets. Considering the wind induced turbulence for the 0 to 200 m layer, high wind speeds delay sinking rates and increase residence times when compared to moderate or low wind speeds. According to our calculations, the residence times in this superficial layer of faecal pellets of P. confoederata, an oceanic salp species, never exceed 100 min (calculated for wind speeds varying from 0 to 24 m s −1).

The response of the salp, Pegea confoederata, to high levels of particulate material: Starvation in the midst of plenty1

When the pelagic tunicate Pegea confoederata is presented with concentrations of particulate material equivalent to levels found in neritic areas, its feeding mechanism is disrupted. A bolus is formed that blocks the esophagus, dramatically decreasing the amount of material that enters the stomach. This bolus never occurs at particle concentrations &lt;0.5 ppm, and always forms at particle concentrations &gt; 5.0 ppm. For oceanic waters, 0.5 ppm lies in the upper range of values, so that it appears that P. confoederata is adapted for feeding on average concentrations of particulate material in the open sea. These results are in contrast to those with most of the calanoid copepods that have been studied. Because P. confoederata feeds on oceanic average amounts of food, it can be more evenly distributed throughout the great oceanic central water masses, decreasing the likelihood of its discovery by predators.

The sterol chemistry of salps: the occurrence and distribution of saturated sterols

Three species of salps(Pegea confoederata, Salpa maxima,and S.fusiformis)from the Western Mediterranean have been analysed for their general biochemical composition and their detailed sterol chemistry. In particular the distribution of saturated sterols in various tissues of the salps has been studied. The results suggests that dietary phytoplankton exerts a major influence on the tissue sterol composition of the salps, although the presence of occelesterol and saturated sterols in the salps cannot be explained on the basis of diet. Possible explanations for the occurrence and distribution of the saturated sterols are considered.

Chromosomes of Thaliaceans

SUMMARYThe chromosomes of six species of thaliaceans have been examined. The haploid number 11 was determined for Pyrosoma atlanticum and Doliolum denticolatum; the haploid number 12 was found for Pegea confoederata, Salpa fusiformis, Thalia democratica; the haploid number 13 was found in Salpa maxima.Salpa fusiformis and Thalia democratica are strikingly akin with respect to both number and morphology of diakinetic chromosomes whereas the other species of Salpida all possess distinguishing peculiarities. Pegea confoederata takes a place apart among the thaliaceans by virtue of the minute dimension of its chromosomes.The karyology of thaliaceans appears to be well differenciated from that of other tunicates and, although ascidians and thaliaceans are the most akin to each other, it is not possible to establish a meaningful probable relationship between their chromosomes.

Geographic Distribution and Relative Abundance of Salpidae off the Oregon Coast

Six species of salps were identified from 437 midwater trawl and 202 plankton net collections off Oregon from 1961 to 1964: Helicosalpa virgula, Iasis zonaria, Salpa fusiformis, Pegea confoederata, Thalia democratica, and Thetys vagina. Relative abundance of the species varied in time and space and few distributional patterns were evident. Salpa fusiformis and I. zonaria, the most common species, were found during all seasons of the year, the highest numbers usually during the summer, the upwelling season. Thalia democratica, H. virgula, and T. vagina were found only during 1963, and P. confoederata was most common during 1963. This was an abnormally warm year and the presence of these species off Oregon may have been related to advection from the south or west and the lack of upwelling.