SALP

Contents hide

1) Introduction

2) Classification of Salp

3) Geographical distribution

4) Habit and habitat

5) Comments on Salp

6) Ecological Importance

7) Conservation Status

8) Special features

9) Identification

Introduction

Salp is a genus of free-floating, barrel-shaped tunicates belonging to the class Thaliacea within the subphylum Tunicata (Urochordata). These fascinating marine organisms are pelagic, found drifting in oceans worldwide, particularly in temperate and tropical regions. Known for their remarkable transparency and bioluminescence, Salp species play a vital role in the marine ecosystem as filter feeders.

What makes Salp unique is their life cycle, which alternates between solitary (asexual) and chain-forming colonial (sexual) phases. This dual mode of reproduction allows them to adapt rapidly to changes in food availability, enabling population explosions in nutrient-rich environments.

Classification of Salp

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 :- Salpida (Incomplete muscle bands. No larva.)
Family :- Salpinae
Genus :- Salp

Geographical distribution

Found in all oceans, with a preference for temperate and tropical waters.
Often observed in nutrient-rich areas such as upwelling zones.
Distributed widely in the epipelagic and mesopelagic zones.

Habit and habitat

Salpians are highly modified and peculiar tunicates, living in open sea with specialized reproduction. They are found on surface and down to depths of 200 meters.

Habit:
- Free-floating and planktonic.
- Exhibits both solitary and colonial forms during its life cycle.
Habitat:
- Lives in open ocean waters, thriving in regions with abundant plankton.
- Can be found at various depths, primarily in the upper water column.

Comments on Salp

Body of the animal is cask-shaped, measuring 1 to 8 cm in length and covered by a thick test. The branchial and atrial apertures are at opposite ends. Posteriorly the test in produced into two tail processes. Below test in mantle.
Salp exhibits polymorphism and exists in two phases : (i) oozooid or asexual phase, and (ii) blastozooid or sexual phase or aggregate type.
Two phases are very much alike, but oozooids aresmaller in size and having lesser number of muscle bands. Sexually produced Salp is called as solitary type or oozooid, while alternate generation produced by budding is called as aggregate type or blastozooid.
Typical oozooid consists of branchial and atrial apertures at opposite ends. A ciliated funnel is present on dorsal side. Nerve ganglion, dorsal lamina and pharynx which has endostyle, peripharyngeal band gill present.
Oesophagus, stomach, intestine and gonad constitute a compact mass along the postero-ventral side which is called as visceral nucleus. Muscle bands incomplete.
A stolon originates from ventral side and it carries endostylic and mesenchymal extensions. Stolon produces buds or blastozooids.
Blastozooid is a sexual phase, having paired testes and a single ovary.
Blastozooid is protogynous. Fertilization is internal. Ovum gives rise to a single sexless free oozooid.
Important character of the animal is locomotion by propelling mechanism in which active muscle bands contract and inturned water is ejected through atrial pore.

Ecological Importance

Plankton Control: Consumes phytoplankton, contributing to the balance of microscopic algae populations.
Carbon Sequestration: Plays a role in the biological carbon pump by producing fast-sinking fecal pellets, which transport carbon to the deep sea.
Food Web Support: Serves as prey for marine organisms such as fish, turtles, and larger filter feeders.
Nutrient Cycling: Helps recycle nutrients in the marine ecosystem by feeding on suspended particles and plankton.

Conservation Status

Salp species are not considered endangered or threatened.
Their populations are sensitive to environmental changes, such as water temperature and nutrient availability.

Special features

Sexual and asexual generations alternate a single adult asexually produces several hundred individuals connected to one another. Small fragments of such a chain consisting of several animals, sometimes break loose from parent. Both connected and separated individuals reproduce sexually.
Each individual produces one or several eggs that remain connected to parent by a placenta like structure, analogous to that of higher chordates where the maternal and embryonic circulation are closely related during development. The hatching egg becomes asexual form.
Bioluminescence: Produces light through symbiotic bacteria, which aids in communication and predator deterrence.
Dual Reproduction: Alternates between solitary and colonial phases, enabling rapid adaptation to environmental conditions.
Efficient Filter Feeding: Processes large volumes of water, removing plankton and organic particles.
Transparency: Almost completely transparent, making them nearly invisible to predators.
Rapid Growth: Exhibits exponential growth in favorable conditions, with colonies forming quickly.