PYROSOMA

Contents hide

1) Introduction

2) Classification of Pyrosoma

3) Geographical distribution

4) Habit and habitat

5) Comments on Pyrosoma

6) Ecological Importance

7) Conservation Status

8) Special features

9) Identification

Introduction

Pyrosoma is a genus of free-floating colonial tunicates belonging to the subphylum Tunicata (Urochordata) in the phylum Chordata. These fascinating marine organisms form tubular colonies composed of hundreds to thousands of individual zooids embedded in a gelatinous matrix. Often referred to as “sea pickles” due to their shape and texture, Pyrosoma colonies are bioluminescent, emitting a mesmerizing glow in the dark ocean waters.

These creatures are found primarily in open ocean environments, drifting with currents and feeding on microscopic plankton. Pyrosoma is of ecological significance due to its role in nutrient cycling and as part of the marine food web. Its bioluminescence, produced by symbiotic bacteria, has intrigued scientists and sailors for centuries.

Classification of Pyrosoma

Phylum :- Chordata (Dorsal tubular nerve cord, notochord and gill-slits present.)
Group :- Acraniata (No head, cranium or brain)
Sub phylum :- Urochordata (Marine. Body covered by a thick test. Notochord present only in larval tail.)
Class :- Thaliacea (Test with circular muscle bands. Free-living, pelagic.)
Order :- Pyrosomatida (Compact tubular colony. No larva. Muscle bands at end of body.)
Family :- Pyrosomatidae
Genus :- Pyrosoma

Geographical distribution

Found in temperate, tropical, and subtropical oceans worldwide.
Often observed in pelagic zones, from surface waters to mid-ocean depths.
Occasionally sighted near coastlines due to currents and tides.

Habit and habitat

Pyrosoma is pelagic, marine, colonial and bioluminescent urochordate, found at a depth of 500 meters. A few forms are abyssal.

Habit:
- Colonial, with individual zooids working collectively for feeding, movement, and reproduction.
- Free-floating and carried by ocean currents.
Habitat:
- Inhabit open ocean waters, often in the epipelagic and mesopelagic zones.
- Thrive in nutrient-rich areas where plankton is abundant.

Comments on Pyrosoma

It is a thimble-shaped hypopleustonic colony, 25 cm to 1 meter in length and consists of several individuals, called blastozooids, embedded in a common test having test processes and terminal opening.
Colony floats horizontally and is like a balloon cylinder. Zooids are arranged in the wall of the cylinder.
Branchial and atrial apertures are at opposite ends. Branchial openings or mouths of individuals or zooids open to the outside, while atria open into a common cloaca with a terminal outlet, from which a continuous jet emerges.
Colony moves by a jet propulsion. Rhythmic contractions of muscular bands in the body wall cause ejection of water through pharynx and atrium with sufficient force to propel the organism.
Each zooid consists of a large branchial sac with endostyle and dorsal lamina, neural complex, heart and atrium.
Branchial sac contains 50 gill-slits divided by internal longitudinal bars. Endostyle communicates with peripharyngeal band, retropharyngeal band and dorsal lamina. Intestine makes a loop around stomach and ends into atrium. Heart is ventral. Lobed testis is found behind ovary.
Close to the mouth of each zooid arises a tongue-like process of the test, called as buccal appendage. Other structures seen are testes, anus, stomach, oesophagus intestine, atrial muscles, stigmata, mass of mesodermal cells, dorsal tubericle, muscle fibers, luminous organs and tentacles.
Hermaphroditic. Reproduction sexual and asexual.
A single fertilized egg develops within blastozooid and gives rise to asexual oozooid. It gives stolon that forms 4 ascidiozooids or tetrazooid which degenerates and gives rise to cyathozooid. It is enclosed in a test and by repeated budding forms a colony.
Asexually colony multiplies the number of zooids by direct stolon budding, producing blastozooids.

Ecological Importance

Nutrient Cycling: Feed on microscopic plankton, contributing to the cycling of nutrients in the marine ecosystem.
Marine Food Web: Serve as prey for various marine species, including fish, sea turtles, and larger tunicates.
Carbon Sequestration: Contribute to the biological pump by transporting carbon to the deep sea through fecal pellets.
Bioluminescence: Their light-emitting ability aids in communication, predator deterrence, and mating

Conservation Status

Pyrosoma species are not listed as threatened or endangered.
Their populations are influenced by environmental changes such as water temperature and nutrient availability.
Localized threats may include pollution and climate change, which could affect plankton availability.

Special features

Bioluminescence
- Animal produces light on stimulation and when all colonies produce light, the entire area is illuminated as much as one can read the book. Light is produced by bioluminescent cells, which contain curved inclusions.
- According to some, these bioluminescent cells contain luminescent symbiotic bacteria. However, in any case, light is emitted by the chemical interaction between two compounds, luciferin and luciferase, in the presence of moisture
- Emit blue-green light visible at night, created by symbiotic bacteria within their tissues.
Colonial Structure: Tubular colonies can reach several meters in length, with coordinated movement and feeding mechanisms.
Efficient Filter Feeding: Remove significant amounts of plankton from the water, enhancing water clarity.
Rapid Growth: Colonies can grow quickly in favorable conditions, responding dynamically to nutrient availability.
Unique Reproduction: Exhibit both sexual and asexual reproduction, contributing to their rapid population growth.