Thorichthys aureus (Günther, 1862)

Etymology: aureus = golden (Latin: adjective); The name selection is not explained in the original description, but Günther describes a yellow longitudinal band running from above the pectoral fin to the lower half of the base of the caudal fin. Specimens from the type locality at Lake Izabal show gold in the opercular area and the anterior part of the flanks.

Common names: United States: Golden firemouth cichlid, Super meeki.

Types: holotype: BMNH 1864.1.26.51 (1).

Holotype, and specimen of 108 mm collected by Osbert Salvin in Lake Izabal [Guatemala]. It is stored in the National History Museum [London] with registration BMNH 1864.1.26.51.

Diagnosis: Thorichthys aureus can be told apart from its closets relative: T. helleri because both males and females of T. aureus do not show conspicuous black markings in the dorsal fin, which are translucent with a red margin and a blue sub-margin in T. aureus — some individuals, particularly females, may show a faint black area above the second and sometimes third vertical bars, reminiscent of T. panchovillae females. In life coloration T. helleri and T. aureus can be extremely similar but T. aureus has a strong iridescent light blue coloration that extends well on the scales of the mid and upper areas of the flanks. In T. helleri this pattern is replaced by blue dots and it is absent in T. maculipinnis. This blue iridescence extends and fuses as specimens mature. The dorsal fin markings further separate T. aureus from T. socolofi and T. panchovillae. T. callolepis, besides being more elongated, with shorter dorsal fin spines and larger scales, lacks the opercular black blotches present in T. aureus.

Size: The holotype of the species is 108 mm in total length. Newton Miller (1907:121) misidentifying Thorichthys aureus as both T. helleri and T. ellioti, reports an specimen of 16.6 cm of total length which should be as large as they get. Stawikowski and Werner (Stawikowski et al., 1998:499) also report specimens of 15 cm in the Tunico River around Lake Izabal. Most individuals I have seen however are less than 12 cm in total length. They should have a life span or approximately seven years.

Sex dimorphism: There is no obvious sexual dimorphism in Thorichthys aureus. Males have longer threads in the dorsal and anal fins and are larger than females, which often are slightly duller in coloration. As in other cichlid species, examination of the genital papillae, which is blunt in females with a larger opening at the tip and pointed in males, is the surest way to tell sexes apart. In doing this kind of examination, be sure to use a soft net to hold the fish and wet hands to touch them to avoid damaging their protective mucous.

Type locality: Guatemala [Lago Yzabal].

Distribution: Thorichthys aureus is distributed in lakes and rivers flowing to the Gulf of Honduras, from the slope from the Rio Grande in Belize (Greenfield et al., 1997:195) in Belize to the Motagua River basin in Honduras (Stawikowski et al., 1998:498). In the Sarstoon River in Guatemala, it shares the flow with T. helleri apparently separated by some rapids and waterfalls in Rio Gracias a Dios around the town of Las Conchas (Artigas Azas, 2017). It seems that some hybridization between the two species has happened in the area.

Habitat: Thorichthys aureus is mostly found in areas of clear water, in main channels and pools of oxygenated rivers and creeks with moderate flow within its range. T. aureus is normally associated with jungle bordered sandy bottomed courses of water, with or without aquatic vegetation, boulders and driftwood. Water is normally clear or very clear, but can also be murky. Thorichthys aureus can be found over a bottom of sand, silt, and mud, preferring shallow (no deeper than 1.5 meters) areas with sunken leaf beds and driftwood.

In Rio Cahabon near Cahaboncito [Guatemala] in the spring of 2016 and 2017 I was able to observe Thorichthys aureus in fast flowing areas of the main channel of the large river; T. aureus would avoid with the strong current by staying among the rocks in shallow areas, where they also had established breeding pairs.

Water in the T. aureus habitat is always alkaline with a pH over 7.5 and hardness from 2 to 10 ° dGH (Stawikowski et al., 1998:499). Temperature in my experience ranges mostly from 24 to 28 °C. In Agua Caliente creek in Guatemala, a thermal flow running into Lake Izabal, the water however could reach over 40°C, only a few T. aureus would remain in areas with no more than an estimated of 32°C.

Localities:

Dulce

Agua Caliente

...

Cahabon River

...

Ciénegas River

...

Lake Izabal

Moho

Blue Creek

Sarstoon

Gracias a Dios River

Conservation: Thorichthys aureus is evaluated by the international union for the conservation of nature in the iucn red list of threatened species as (DD) data deficient (2018). Pollution by agro-chemicals used in the growth of the introduced Cajun palm in Guatemala plus run-offs of the mining industry around Lake Izabal and the heavy pollution in the Motagua River basin pose a threat to this species, currently widely distributed in its range.

Feeding: In spite of all the papers where T. aureus is mentioned over the years (mostly with a taxonomic character) there are not stomach examination to this day to my knowledge, so we know little about this. In my observations however they do not differ in their feeding behavior from other Thorichthys species.

Thorichthys ssp. feed in loose groups in shallow areas of the habitat. They wanders facing downwards and picking on the substrate, creating small pits in it, more than sifters Thorichthys are pickers, they do not systematically pick on every area of the substrate like sifter cichlid species (e.g. Cribroheros robertsoni) do, the way they locate their preys has not been studied to my knowledge. Material picked up is scrupulously examined in the mouth and inedible matter expelled through mouth and gills, while softer material is filtered by gill rakes. Thorichthys are carnivorous and I have never seen them collecting vegetable matter, although it may be ingested as a sub-product of the picking process.

Breeding: I have been able to observe Thorichthys aureus breeding in natural habitat and in the aquarium a number of times, I report here what I have been able to observe.

Thorichthys aureus starts breeding efforts in the last months of the dry season around March, when the water is clearer, warmer and the flow is slower. In my observations T. aureus normally selects territories in slower flow shallow areas, in many occasions over accumulations of fallen leaves that seem to hide their color pattern from above, some structure in the form or rocks or sunken wood is always selected for their territories. Suitable areas may be occupied by many pairs, separated on occasion by no more than one meter. A solid surface in the form of a rock, wood or sunken leaf with surrounding cover is a valuable asset for a territory and males fight for such areas.

At one point the territory is defended by the new pair. They defend their territory by making small frontal runs towards neighboring pairs with their gular pouches and opercular plates extended. In this situation the black blotches on the extended operculum give them the appearance of bigger fish, and other fish are normally intimidated without a fight. On a few occasions pairs get to their counterparts mouths and bite them, but without any damage being produced.

T. aureus cleans the spawning surface vigorously with their mouths prior to depositing their ovoid yellowish translucent eggs in tight circles. I would estimate spawns of about 100 to 200 eggs, depending on the size of the female. Females watch over their spawn, circulating water among eggs with their pectoral fins, while males chase intruders away from the territory.

Eggs hatch in about 48 hours under aquarium conditions at 26-28 °C. Small pits in the substrate are excavated by the pair where they place the newly hatched wrigglers; subsequently wrigglers are transported by the female from one pit to another several times a day. Five to six days later the yolk sac, with which the babies are born, is fully consumed and the little babies start making swimming attempts inside their pits. The next day, with all the wriggler now swimming, the pairs school them around the territory.

I have followed pairs and have seen that they always circle the same area around the nest, not venturing more than a few meters away, and it is probable that they use the same pits for night cover. Herding their babies the pair behaves as other Central American cichlids do: the females closely guarding the babies and guiding them. Signaling is achieved with spasmodic body shakes and with rapid opening and closing of the fins. Males, also signaling, take the lead.

Babies seem to feed picking on the surfaces that they pass, and females don’t seem to make any special effort (unlike other Central American cichlids) to provide food for their babies.

When babies abandon their parents at a little over a centimeter and half in length (about two months post spawning) they congregate in covered shallow areas of the habitat, where they are seen in the company of many other young fish.

Aquaristics: According to Arnold (1911) Thorichthys aureus was first introduced (from Puerto Barrios, Guatemala) to Germany in the spring of 1910. Another import from May 1911 was said to contain specimens from the same place as well as from southern México (if so possibly from Puerto México, now Coatzacoalcos). The latter must then have been T. panchovillai but it cannot be ruled out that a few Cribroheros robertsoni were among them. In 1926, Brumann reports of the breeding of T. aureus in the home aquarium in Germany.

In 1985, Stawikowski and Werner (1985:228) show color photographs of T. aureus in aquarium, which stem from earlier introductions. In the early 80s, several species including T. aureus, T. helleri and (in France) even T. pasionis had been confused under the name Cichlasoma aureum. In 1985, Stawikowski and Werner found the species in Guatemala and could thus show which one is the real T. aureus (Rico Morgenstern, personal communication).

In the United States of America, Ross Socolof (Socolof, 1971:11) refers that the fish was imported by him and other people in April 1970 from Belize or Guatemala, it was first known as the "Super Meeki" until Robert Rush Miller from the University of Michigan correctly identified it. Axelrod & Vorderwinkler (1974:384,386) show what they call Cichlasoma aureum. The picture on page 384 apparently depicts a dead female of T. aureus, while the picture on page 386 shows instead two individuals of Thorichthys meeki in black and white. They make the annotation (p. 383) that T. aureus is a good parent under the right conditions.

When keeping T. aureus, remember its habitat preferences. Unlike T. meeki, T. aureus cannot successfully thrive in low oxygen, bad quality or warm water (over 28 ̊C) conditions. It likes cool and oxygenated water, within its natural parameters. If water loses quality, bacterial infections and hole-in-the-head are likely to strike.

Although not very aggressive and hardly ever damaging each other, I would not recommend anything less than 300 liters for housing a group of Thorichthys aureus and a group of them to dilute aggressiveness. As for decoration, I prefer natural looking aquariums with rocks and driftwood, with a fine sand substrate that allows them (and me) to enjoy their natural picking behavior. You can then notice that at feeding time many small pits are dug on the sandy surface of the aquarium.

Natural shyness is easily overcome with dither fish. I have used large Poecilia species, naturally occurring with T. aureus in some areas of the habitat. Any other large Poeciliids (or other large dither fish) would do just fine. Just try to avoid fish that bite on the fins, as they can produce a counter effect to what you are looking for. Small dither fish may be eaten by adult T. aureus.

Providing for food is no problem; they are eager eaters when conditions are right. I consider Thorichthys of the T. helleri group a delicate fish in terms of diet, and although they are carnivorous in nature, I suggest to avoid diets with terrestrial animal proteins to avoid bloat. It worked well for me.

As for breeding, if conditions are right, nothing will stop them from trying. I use inverted flower pots with the bottom opened as nest possibilities and they love them and readily use them, but readily spawn in open areas as well. They do not become too aggressive in breeding time and in fact you can raise a group of babies in the home aquarium, again, if conditions are right. Fry can be easily fed with brine shrimp nauplii. You may however fail the first few occasions as they are quite shy and nervous but you will eventually succeed, and it is wonderful to observe their full pattern behavior in the home aquarium!.

Comments: After the original description of Heros aureus in 1862, Günther reviews his description (1868:455) and lists two specimens: the holotype (BMNH 1864.1.26.51) and one more specimen from the Osbert Salvin collection present in the BMNH (BMNH 1865.4.29.73) from the Motagua River [Guatemala]. He drops a second specimen (BMNH 1857.7.31.17) which he had marked with an interrogation mark in the original description: a 44 mm (From Regan, 1905:321) specimen obtained by the British Museum from Mr. Sallé’s collection through Mr. Cuming (a dealer of natural history objects), deciding it is not the same species.

When Regan made his revision of Cichlasoma (Regan, 1905) he placed T. aureus in the section Thorichthys (Regan, 1905:321). He examined nine specimens other than the types, of which just two (BMNH 1864.1.26.51 and BMNH 1865.4.29.73) could be attributable to T. aureus if we take into consideration their collecting locations.

Since two types were used in the description, Regan (1905:320) named a lectotype for T. aureus, this is however not applicable since one of the specimens listed by Günther in the original description (BMNH 1857.7.31.17) with a question mark invalidates it as syntype, effectively making BMNH 1864.1.26.51 the holotype of the species. According to the International Code of Zoological Nomenclature (Article 72.4.1), specimens that are doubtfully attributed to a new taxon are excluded from the type series (Rico Morgenstern, personal communication).

Regan (1905:320) named in synonymy of Thorichthys aureus T. helleri (referred as H. helleri), T. maculipinnis (referred as Heros maculipinnis and Thorichthys ellioti) and Thorichthys panchovillae, the latter not specifically referred but specimens from Rio de Sarabia and Santo Domingo de Guzman (both in the basin of the Coatzacoalcos River) comprise part of the 11 specimens he examined.

You cannot blame Regan for considering all these species in synonymy, members of the Thorichthys helleri group are very closely related and in some cases it is very difficult to tell them apart, even having access to their live coloration. Regan did not have this luxury so the challenge was not small. The taxonomic differences among these group of species overlap (Miller et al., 1961:6) and even today we cannot have a good diagnosis based on morphology alone. The species in this group have been confused with each other several times in scientific literature (Meek, 1907:142; Miller, 1907:121; Hubbs, 1936:257).

Hubbs (1936:257), having access to live specimens, reverts Regan’s action (1905:320) and establishes morphological differences between T. aureus and T. helleri (described as Cichlasoma champotonis) and T. ellioti (junior synonym of T. maculipinnis). The differences offered probably would not hold for a generally applicable diagnosis though.

In Honduras, the population in Rio Copan is reported (Stawikowski et al., 1998:499) to be metallic golden (honoring their name) with only a small blue area at the back, this population is referred as the “gold aureus”, in contrast with the Belizean and Guatemalan populations which are referred as the “blue aureus”.