Baraminology of Goodeidae

As I’ve previously written, I’ve gotten back into the fishkeeping hobby on the side of my writing. One of the fish I am keeping currently is a member of a very special family of fish known as the Goodeidae family, or the Goodeids in the aquarist jargon.  Goodeids are mostly livebearing fish found largely in Mexico and the United States. Most species stay small, around two inches, though a few species reach a maximum of eight inches. The family is small, with around fifty species depending on what source you use. This article will examine the Goodeids and see whether they are their own baramin or whether they should be folded into another baramin.

The primary consideration of the enhanced cognitum concept of baraminology is hybridization, based on the Biblical understanding of kinds. However, in this instance, there is very little information available. The only scientific reports I could find were between two species of genus Xenotaca, X. melanosoma and X. eiseni[1]. Since this is expected under the enhanced cognitum model, more hybrid data is needed. This is something that can be tested. However, as most goodeids are considered endangered species, most aquarium hobbyists who keep them, do so in species only aquariums for the purpose of breeding and perpetuating the species.  Thus, for the moment, hybridization data cannot be used to determine whether goodeids are their own kind.

Since hybridization data is unavailable currently, cognitive methods must be used to determine whether the goodeids are their own baramin.  In order to determine whether the goodeids are their own baramin, the large livebearing family Poeciliidae will be used as a cognitive outgroup. The Poecilids are the much more well known Guppies, Swordtails, Mollies and so on.  Within Goodeidae, there are two subfamilies, Goodeinae and Empetrichthyinae. The Goodeinae are all livebearers, while the Empetrichthyinae are egg layers.  Based on this, there appears to be a discontinuity within the family. However, the overall bodyplan within the family is very similar. All share a single, rearward dorsal fin, of varying size and shape.  In some species, it is sail like, while in others is smaller and protrudes further from the body.  The anal fin is slightly pronounced and often colorful. The caudal fin is rounded and oftenat least slightly colored.  The pelvic fins are paired and, at least in Goodeinae has a special extension called an andropodium which the males use to pass gametes to the females. Females lack this special structure. Goodeinae femalse give birth to live young who are born attached to an umbilical cord-like structure called a trophotaeniae. Every member of the Goodeinae subfamily has this special structure.  Empertrichthys, as egg layers, lack this structure, as to the Poeciliidae. Therefore it seems likely that these three groups are all discontinuous from one another.

This discontinuity is borne out in part by evolutionary phylogenetic studies.  Every phylogentic study I examined on Goodeidae places Crenichthys as distant from the Goodeinae subfamily[2][3]. Given it is in the subfamily Empetrichthyinae, this is hardly surprising, as its reproductive systems are completely different from the members of Goodeinae. Interestingly, an examination of unfertilized embryos in Poeciliids and Goodeids revealed significant discontinuity in the form and development of the embryo[4]. This being the case, the Goodeids can be regarded as distinct from the Poeciliids.

Genomic evidence is very limited within the Goodeid family. Some full mitochondrial genomes are available, but even there it is limited and, mitochondrial DNA is generally nunreliable. However, BLAST alignment of the mtDNA of Xenotoca eiseni and Empetrichthys latos reveals only an 85.75% similarity[5]. However, between Empetrichthys latos and Crenichthys baileyi  is 92.31%[6].

 

Whole genome analysis is much to be preferred to mtDNA analysis but such is not available. However, a few genes have been at least partially sequenced. The RAG1 gene in Ameca splendens and Ataeniobius toweri are 98.98%  similar[7]. In Chapalichthys pardalis and A. toweri, the similarity is 98.91%[8]. However, between A. toweri and Crenichthys baileyi  the similarity is 98.4%[9]. Results like this are the reason whole genome information is vital when performing genomic comparisons.  Genes which perform similar functions are usually fairly similar in different organisms.  Since genomic information is lacking and what little we have serves only to muddie the waters, genomics will be ignored for the moment, though it certainly should be considered once it becomes available.

 

Based on this, we can deduce that subfamily Goodinae is its own separate baramin. Empetrichthyinae may be its own baramin or may be placed into another baramin.  Further study would be required to determine which option is accurate.   The below chart shows what genera are classified in the Goodinae baramin. This classification is tentative as hybridization data is completely lacking, but until such time as hybridization data is available, this classification will give a foundation upon which to base future baraminology studies.

Goodeid

 

 

[1] John Michael Fitzsimons “Morphological and Behavioral Intermediacy in Hybrids of Two Species of Goodeid Fishes (Cyprinodontiformes: Osteichthyes) from Mexico.” Copeia Volume 1974, no. 4 (1974) Pages 848-855. https://www.jstor.org/stable/1442581

 

[2] Ignacio Doadrio and Omar Dominguez. “Phylogenetic relationships within the fish family Goodeidae based on cytochrome b sequence data.” Molecular Phylogenetics and Evolution Volume 31 (2004) Pages 416-430. https://www.sciencedirect.com/science/article/pii/S1055790303003324

[3] Shane A. Webb “Molecular systematics of the genus Allodontichthys (Cyprinodontiformes: Goodeidae.)” Reviews in Fish Biology and Fisheries Volume 12 (2002) Pages 193-205. https://www.researchgate.net/profile/Shane_Webb/publication/227033898_Molecular_systematics_of_the_genus_Allodontichthys_Cyprinodontiformes_Goodeidae/links/53d6b2b90cf220632f3dcd23/Molecular-systematics-of-the-genus-Allodontichthys-Cyprinodontiformes-Goodeidae.pdf

[4] Britta Gravemeier and Hartmut Greven “The envelope of fully grown, unfertilized oocytes in Heterandria formosa (Poeciliidae) and Xenotoca eiseni (Goodeidae)” Verhandlungen der Gesellschaft fur Ichthyologie Band Volume 5 (2006) Pages 7-11. http://www.biologie.hhu.de/fileadmin/redaktion/Fakultaeten/Mathematisch-Naturwissenschaftliche_Fakultaet/Biologie/Institute/weitere_und_ehemalige_Dozenten/weitere_Dozenten/Prof._Dr._Hartmut_Greven_i._R/2006_05_Gravemeier-Greven-GfI-Bd-5_7-11.pdf

[5] Accession numbers: AP006777.1 KY014102.1

[6] Accession number: KY014104.1

[7] Accession numbers: KJ697267.1 KJ697275.1

[8] Accession numbers KJ697276.1

[9] Accession number KJ697278.1

 

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s