Blastocrithidia

Blastocrithidia is a genus of parasitic flagellate protist belonging to the family Trypanosomatidae.^[2] It is a monoxenous parasite of heteropteran insects,^[3] mainly inhabiting their hindgut and glands.^[4]

Blastocrithidia
A species of Blastocrithidia, B. papi (vertical scale bar = 10 μm).[1]
Scientific classification
Domain:	Eukaryota
Clade:	Discoba
Phylum:	Euglenozoa
Class:	Kinetoplastea
Order:	Trypanosomatida
Family:	Trypanosomatidae
Genus:	Blastocrithidia Laird 1959 [2]
Type species
Blastocrithidia gerridis (Patton 1908) Laird 1959
Species
See text

Characteristics

In addition to Blastocrithidia, one-host trypanosomatids from hemipteran and dipteran insects have been traditionally placed in genera Crithidia, Leptomonas, Herpetomonas, Rhynchoidomonas, and Wallaceina.^[5][6] Blastocrithidia is characterized by epimastigote morphological forms, whereas opisthomastigotes and endomastigotes are exclusive features of the genera Herpetomonas and Wallaceina, respectively.^[6] Blastocrithidia is also able to produce resistant cysts.^[7]

Systematics

The etymology of the genus name Blastocrithidia derives from the two Ancient Greek words βλαστός (blastós), meaning "sprout, scion, child or descendant", and κριθίδιον (krithídion), meaning "small grain of barley".^[8][9]

The genus includes the following species.

• Blastocrithidia caliroae Lipa, Carl & Valentine 1977
• Blastocrithidia cyrtomeni Caicedo et al. 2011
• Blastocrithidia euschisti Hanson & McGhee
• Blastocrithidia familiaris Tieszen et al. 1986
• Blastocrithidia gerridis (Patton 1908) Laird 1959
• Blastocrithidia largi Maslov and Lukes 2010
• Blastocrithidia leptocoridis (McCulloch 1915)
• Blastocrithidia miridarum Podlipaev & Frolov 1987
• Blastocrithidia papi Frolov and Kostygov, 2016
• Blastocrithidia raabei Lipa 1966
• Blastocrithidia triatomae Cerisola et al. 1971
• Blastocrithidia vagoi Tuzet & Laporte 1965
• Blastocrithidia nonstop Votýpka & Lukeš, sp. nov.

Genomics

Genetic code

Blastocrithidia uses in its nuclear genome an alternative genetic code characterized by all three canonical stop codons reassigned to sense codons.^[10]

Table of alternative codons in Blastocrithidia and comparison with the standard genetic code

Genetic code	Translation table	DNA codon	RNA codon	Conditional translation				Standard translation
Blastocrithidia nuclear	31	TAA	UAA	Ter (*)	or	Glu (E)		Ter (*)
		TAG	UAG	Ter (*)	or	Glu (E)		Ter (*)
		TGA	UGA	Trp (W)				Ter (*)

Amino acids biochemical properties

nonpolar

polar

basic

acidic

Termination: stop codon