The Tale of Paracladotricha salina

How a Tiny Ciliate Required Two Attempts to Officially Exist

Microbiology Taxonomy Scientific Discovery

Introduction

Imagine spending years discovering a new life form, documenting its every detail, and giving it a name, only to discover it doesn't officially exist.

This isn't science fiction—it's exactly what happened to a team of ciliate researchers who discovered a microscopic organism in a hypersaline pond in China 1 4 .

Their story reveals the intricate dance between scientific discovery and the bureaucratic rules that govern biological names, culminating in a taxonomic mystery that required a "corrigendum"—an official correction—to resolve.

The protagonist of our story is Paracladotricha salina, a hypotrichous ciliate barely visible to the naked eye, yet possessing a unique combination of biological features that fascinated scientists.

Meet Paracladotricha Salina: A Strange New Microbe

Physical Characteristics
  • Size: 50-120 micrometers long
  • Shape: Teardrop-like with pointed posterior
  • Nuclear Features: Four macronuclear nodules
  • Movement: Complex cirri arrangements
Habitat Details
  • Location: Abandoned offshore mollusc-farming pond
  • Salinity: 80‰ (twice as salty as seawater)
  • Temperature: 17°C at discovery
  • pH: 8.0

What Makes This Ciliate Unusual?

Paracladotricha salina exhibits a remarkable example of evolutionary reduction. While its ancestors likely possessed a full complement of ciliary structures, this species has dispensed with several features 4 :

  • No paroral membrane
  • No buccal cirri
  • No postoral cirri
  • No pretransverse ventral cirri
  • No transverse cirri
  • No caudal cirri

Highly reduced dorsal kineties - only 1-2 basal body pairs each 1 4

The Scientific Discovery: From Pond to Publication

Morphology

Bright field and differential interference contrast microscopy

Staining

Protargol staining method for infraciliature visualization

Genetics

SSU rRNA gene sequencing for phylogenetic analysis

Morphometric Characteristics

Characteristic Details
Body size in vivo 50-120 × 20-35 μm
Body shape Slender, flexible with narrowly rounded anterior and pointed posterior
Macronuclear nodules 4
Adoral zone About 37% of body length, composed of 23 membranelles on average
Frontoventral rows 3 rows with varying numbers of cirri each
Marginal rows Right row: 26 cirri average; Left row: 18 cirri average
Dorsal kineties 1-3, highly reduced to just 1-2 basal body pairs each
Habitat Hypersaline waters (about 80‰ salinity)

Key Steps in the Research Process

Sample Collection

Glass slides suspended in hypersaline pond to collect ciliates without sediment disturbance 2

Cultivation

Water from sampling site with added rice grains to maintain and multiply specimens

Live Observation

Bright field and differential interference contrast microscopy to study natural appearance

Staining

Protargol method to reveal infraciliature and nuclear apparatus 2

Morphogenesis

Observation of dividing cells using staining methods to understand developmental patterns 2 4

DNA Sequencing

SSU rRNA gene amplification and analysis to determine evolutionary relationships 2 4

The Naming Puzzle: A Tale of Two Publications

Taxonomic Dilemma: When Shao and colleagues first discovered and characterized the ciliate in 2014, they followed standard scientific practice—but encountered an unexpected bureaucratic hurdle 1 4 .
2006

Sample Collection

First discovery in hypersaline pond
2014

Original Publication

Detailed description but names not ICZN-compliant
2017

Corrigendum Publication

Names made official through proper registration
The Problem

According to Articles 8.5 and 9.11 of the ICZN code, electronic-only publications must meet specific criteria to be considered valid for naming purposes 1 .

The original 2014 electronic publication lacked ZooBank registration, a requirement for electronic publications to make names available.
The Solution

To fix this problem, the same team published a corrigendum in 2017—an official correction to the original paper 1 .

  • Formal diagnosis of genus and species
  • Designation of type material
  • Clear statement of ICZN compliance
  • Explicit ZooBank registration

The Scientist's Toolkit: Key Research Reagents and Methods

Protargol Solution

Silver-based staining reagent that highlights ciliary structures and nuclear apparatus 2 .

Glass Slide Substrates

Artificial substrates placed in aquatic environments for clean sample collection 2 .

PCR Reagents

Universal primers Eukaryotic A and B for SSU rRNA gene amplification 2 .

BioEdit & SeaView

Software for sequence alignment and phylogenetic analysis 2 .

MrBayes & PhyML

Statistical packages for Bayesian inference and maximum likelihood analysis 2 .

Rice Grains

Used to enrich bacterial food sources in culture media 2 .

Broader Implications: Why a Tiny Ciliate Matters

Evolutionary Reduction

Helps scientists understand how organisms simplify structures over time 2 4 .

Morphological Importance

Highlights ongoing relevance of traditional morphology alongside molecular biology 2 4 .

Scientific Rigor

Illustrates that scientific rigor extends beyond the laboratory to naming conventions 1 .

The remarkable loss of multiple ciliary structures in P. salina represents an extreme example of morphological simplification. By studying such organisms, scientists can identify which structures are essential for survival and which can be dispensed with under certain environmental conditions 4 .

A Name Earned, A Mystery Revealed

The story of Paracladotricha salina embodies the dynamic, sometimes messy process of scientific discovery. From its initial observation in a hypersaline pond to the careful documentation of its unique biology, and through the bureaucratic maze of taxonomic rules, this microscopic organism has earned its place in the scientific record 1 2 4 .

Discovery

Documentation

Naming

Communication

The next time you look at a pond, remember that it may hold microscopic mysteries waiting to be discovered, named, and understood—each with its own unique story to tell about the evolutionary pathways that shape the living world.

References