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Thorichthys pasionis (Rivas 1962), the yellow meeki

 Juan Miguel Artigas Azas, 2010
作者 , 1995.
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(This article was originally published in Cichlid News Magazine, Oct-99 pp. 06-15).
Thorichthys pasionis male

Thorichthys pasionis male from laguna Noh in the Southern Part of the Yucatán peninsula, in the aquarium. Photo by Juan Miguel Artigas Azas.

Introduction

The ancient Mayans were indeed a lucky civilization, for they lived in a land gifted by nature. From the blue skies to the beautiful clear Caribbean seas, they had color all around. The contrast of the forest land with its green cover and dashing feathered inhabitants was breathtaking and teemed with unique animal life. All this natural wealth was not limited to the jungles and seas, but also embodied in the plentiful surfaces of freshwater rivers and lagoons. The wealth extended to unbelievable extremes.

One of the living jewels found in these ancient waters is Thorichthys. This suggested monophyletic assemblage (Miller, 1996) of beautiful cichlid species inhabiting rivers and lagoons in the lowlands of the Atlantic slope in Northern Central America, from the city of Veracruz to the Northern part of Guatemala and Honduras. There are currently eight recognized species of this genus, forming two natural groups. All of them is holding a unique beauty.

As described by Seth Eugene Meek (1904), the genus Thorichthys is defined by a combination of features: "Body deep, much compressed; mouth rather small; caudal fin Iunate, its outer rays produced into a filament; pectoral fin long and pointed, about as long or longer than head; subopercle with a black blotch, otherwise as in Cichlasoma". For Cichlasoma, Meek understood the Genus that comprised what were now defined as Heroine cichlids by the Swedish ichthyologist Sven Kullander (Kullander, 1997).

The eight recognized Thorichthys species form two natural groups (Miller, 1984). The first group is characterized by species with a slightly rounded head profile, isognathous jaws (equally long the lower and upper jaw) and a black blotch on the dorsal fin, normally held only by the females. This group enjoys a wider geographical distribution and comprises five recognized species: Thorichthys aureus (Günther 1862), maculipinnis (Steindachner 1864), helleri (Steindachner 1864), callolepis (Regan 1904) (which lacks the dorsal blotch), and socolofi (Miller & Taylor 1984). The second group is comprised of species with a rather straight frontal profile, a longer snout, prognathous jaws (longer in ,the lower than the upper jaw) and the absence of the black blotch on the dorsal fin. It includes three recognized species: Thorichthys meeki (Brind 1918), affinis (Günther 1862), and pasionis (Rivas 1862), the subject of this writing.

Species of the first group normally inhabit sandy bottomed rivers, while the second group prefer softer substrates, such as mud or detritus, which may be the causative factor leading to the need for a longer snout to penetrate deeper into the susbtrate looking for food.

The best known of the Thorichthys species is undoubtedly T. meeki, the firemouth, which is popular worldwide as an aquarium fish. T. meeki inhabits lowland affluents of the Grijalva-Usumacinta river system as well as water bodies east to the southern part of the Yucatán peninsula, in the northern half of Belize, in the easternmost part of its range.

Part of the firemouth range is shared with a congener of delicate beauty and discrete number, Thorichthys pasionis, also known as the "Yellow meeki". Unfortunately aquarists often neglect this beautiful cichlid and thus accounts on its keeping are scarce. Besides holding the beauty title of the Thorichthys genus, this fish has a unique coloration complemented by a mellow temperament, which couples with a hardy nature. These traits provide both advanced and beginner cichlid aquarists with a fascinating experience.

With the exception of the referenced material, the information written here is my own, obtained by observation in many locales of the natural habitat of the Yellow meeki. Underwater observations were done in places where this was feasible, as well as observations in my own aquariums where I currently keep a colony of this fish, having bred them on several occasions.

Taxonomy

Although its famous and more much abundant syntopic (inhabiting together) congener, Thorichthys meeki, the firemouth, was described as early as 1918, it was not until 1962 that Luis Rene Rivas named Thorichthys pasionis. The reason for this is that Walter Lannoy Brind (a north American aquarist with no ichthyological background but with a sharp eye and deep knowledge of aquarium species), who recognized the species as new and published its description, obtained its type material in New York. The provenience of the type material was stated as the shallow reaches of a river near the port of Progreso, in the northwestern part of the Yucatán peninsula. The specimens (265) were captured and transported by a French sailor to New York city for sale to aquarium stores and wholesalers, a common practice in the time (Socolof, 1996). We should note here that the area where Thorichthys meeki was captured is well north outside the range of Thorichthys pasionis.

The noted ichthyologist Carl L. Hubbs described Cichlasoma champotonis (a synonym of Thorichthys helleri) among several other species after an ichthyological survey of the fishes of the Yucatan peninsula in 1935; no mention of anything like Thorichthys pasionis was made in his report (Hubbs, 1936).

Thorichthys pasionis is one of the more recently described Thorichthys. In 1962 Rivas published the formal description of Thorichthys pasionis in the Quarterly Journal of the Florida Academy of Sciences. Described from specimens collected by Rivas himself, which were collected from Rio de la Pasión at Sayaxche in the northern Guatemalan Petén county during an expedition conducted in June, 1961 by the Ichthyological Laboratory and Museum of the University of Miami. The holotype is housed in the U. S. National Museum (USNM 203156). It is from this collecting locale, a tributary of the mighty Usumacinta, that the specific name was taken.

Thorichthys pasionis was found to have a more elevated number of gill rakers than the rest of the species of the Thorichthys genus. It is also further distinguished from T. aureus, helleri and maculipinnis by the absence of supplementary lateral lines on the caudal fin, the more numerous pectoral rays, and the longer anal base. From its closer relatives, T. meeki and T. affine, the differences include a less numerous anal fin spine count, and greater number of gill rakers. This of course refers to preserved specimens, as differences in live coloration are striking.

Distribution and Habitat

Thorichthys pasionis habitat
Left: Laguna del camarón outside Villahermosa, Tabasco, besides Grijalva river. Right: Laguna Noh in the Southern Part of the Yucatán peninsula. Photo by Juan Miguel Artigas Azas.

Thorichthys pasionis is always found sympatrically with Thorichthys meeki, as it inhabits a great part of the range of the latter. The yellow meeki has its westernmost range in México in rivers and lagoons in the lower Grijalva river around the city of Villahermosa, north to the mouth of the Grijalva-Usumacinta system. The yellow meeki range extends eastwards reaching the Rio Usumacinta affluents in the Petén area in northern Guatemala, where it seems to be especially abundant. T. pasionis range includes Rio Usumacinta affluents San Pedro and la Pasión. The species is also found in the basin of the rivers Chompán and Candelaria, all these rivers flowing to the gulf of México. Thorichthys pasionis is absent in the north and south-eastern parts of the Yucatán peninsula and in Belize, in the basin of the rivers Hondo, New River, Belize, and Sibún, where Thorichthys meeki extends his companion range and Thorichthys affinis is found in replacement.

Thorichthys pasionis seems to be especially fond of lagoons rather than rivers, and it is found in abundance in these bodies of water. Soft muddy bottoms and slow flow to stagnant water characterize the habitat where Thorichthys pasionis dwells. As all Thorichthys species, they are inhabitants of the shallow parts of rivers and lagoons, where they are normally found in groups of all ages.

The water in the yellow meeki habitat is normally characterized by low visibility, although not murky, which is not surprising considering the nature of the sediment. Temperature ranges between 25° to 30° Celsius and the pH is always on the alkaline side, from 7.5 and up to 8.5 are the measurements I have obtained in several parts of the cichlids range. Water temperature is normally higher in the Thorichthys pasionis habitat than in that of the species of the T. helleri group. Hardness is more variable with measurements of 8 and up of General Hardness German degrees.

Low flat lands, no higher than 300 meters of altitude and either covered by tropical or dry jungle characterize the area T. pasionis inhabits. Air temperature during the spring and summer can easily go up to 40° Celsius during the day. Winter temperatures are still in the tropical range, with lows approximately 15° Celsius, according to statistics of weather information systems.

Thorichthys pasionis is found together with two other Thorichthys species. As mentioned, Thorichthys meeki, but also with T. helleri. This latter species differs in that it seems to prefer riverine habitats and it is found in small densities in the yellow meeki company. Other cichlid species include the substrate sifter Amphilophus robertsoni, also known as the "mojarra zacatera", Paratheraps bifasciatus and P. synspilus. 'Cichlasoma' octofaciatus (which will be probably assigned to the genus Archocentrus). Parachromis friedrichsthali, P. managuensis and Petenia splendida include the cichlid predators also found together with the yellow meeki, and which probably prey on its young. Other cichlid species are 'Cichlasoma' salvini and 'Cichlasoma' urophthalmus, which are found in good numbers, and 'Cichlasoma' heterospilum and 'Cichlasoma' pearsei, which also seem to prefer riverine habitats.

Other fish families and species found in good numbers in the lagoons where Thorichthys pasionis inhabit include: Poecilidae: represented at least by Belonesox belicianus, Poecilia petenense, Carlhubbsia kidderi, Phallichthys fairweatheri (In the Petén Area), Gambusia yucatana and Gambusia sexradiata. Clupeidae: Dorosoma petensisis and Dorosoma anale. Characidae; Astyanax aeneus and Hyphessobrycon compressus. Lepisosteidae; Lepisosteus tropicus, Pimelodidae; Rhamdia guatemalensis and Rhamdia laticauda. Ariidae; Arius aguadulce. Atherinidae; Atherinella alvarezi and Symbranchidae: Ophisternon aenigmaticum. Riverine habitats include several more species.

Thorichthys pasionis habitat

Right: Thorichthys pasionis male from laguna Noh in the Southern Part of the Yucatán peninsula. Left: Thorichthys pasionis male from Nakajuca lagoon in the State of Tabasco, México. Photo by Juan Miguel Artigas Azas.

Biology

Thorichthys pasionis tends to live in extremely high densities in the lagoons within its natural range, and although normally outnumbered by Thorichthys meeki, it is a plentiful species as well. A throw of a casting net at the shores of the lagoons where it inhabits often produces an incredible number of both Thorichthys species, plus many other fish, cichlids and non-cichlids. The densities in which these fish live in the wild always amaze me. In the aquarium I have observed that a good number of specimens do fairly well, as they tend to establish small territories and live happily with it. Pairs establish their territory marks with any object present in the aquarium in as little as 30 centimeters square. A good amount of interaction is constantly present, but rarely is any fish injured. The interaction among Thorichthys pasionis pairs is normally limited to facing each other, making small frontal runs in which the individuals put their gill covers forward and extend their gular pouches (which in the case of the yellow meeki are of an attractive black coloration) in an attempt to intimidate each other. For this purpose as the gill covers are projected forward, their black subopercular blotches or "eyespots" separate resembling eyes more widely placed. After a brief advance pair retrocede and repeat this behavior a few times before returning to their respective territories. In this regard they behave much like their cousin the firemouth, in which Radeater and Ferro (1979) have studied this behavior with the aforementioned conclusions.

Juveniles and non-breeding individuals gather together among any driftwood present, picking on the substrate in search of food. All non-edible material is expelled through the gills, where their numerous gill rakers filter it. Although I am not aware of stomach content examinations on wild specimens of Thorichthys pasionis, it is not unreasonable to assume that they are invertebrate eaters in the wild, taking advantage of the organisms living in the upper layer of the soft substrate. Plant material is completely absent in the murky water of their habitat.

I have not been able to determine any difference in the feeding preferences of the syntopic Thorichthys meeki and T. pasions. The deeper layers of the lagoons which T. pasions inhabits are sifted by Amphilophus robertsoni, while fallen fruits or soft leaves are taken by Paratheraps bifasciatus or P. synspillus, which can often be observed in this behavior. 'Cichlasoma' salvini seems to take advantage or arthropods falling into the water. The small algae and associated animal life that grows covering solid surfaces in the shallows is grazed constantly by specimens of Poecilia petenensis. For any unattended fry, there is always the danger of becoming a meal. With the opportunistic Astyanax aeneus's effective attacks during the day, and the catfishes Arius aguadulce, Rhamdia laticauda and R. guatemalensis night time prowls, it is very important that the fry stick close by their parents. Small fish hiding among vegetation are often hunted by Belonesox belicianus. Dorosoma anale and D. petenensis, plentiful in the lagoons, are known to feed on small mollusks. Small cichlids, Poeciilids and characinids are preyed upon by the larger predators, like Petenia splendida, Parachromis managuensis and P. friedrichsthali. As a whole, the lagoons that house Thorichthys pasionis are a rich and complex community.

Males of Thorichthys pasionis grow to about 15 centimeters in standard length, with females staying smaller at around 12 centimeters. Sexual dimorphism is not striking although sometimes females show a slightly less yellow suffusion on the anterior part of their flanks, as well as shorter fin threads and a slightly rounded frontal profile.

Pairs seem to form during the dry season between February and May, as it is around this time that I have been able to collect individuals in breeding coloration. In this phase the yellow color intensifies and it is further adorned by a deepening of the black vertical lateral bars from the dorsal region to mid-flanks. The black color of gular pouches also intensifies. In the aquarium this fish looks for a vertical surface or crevice to place their eggs. I wouldn't be surprised if this cichlid acts in the same manner in the wild, given the abundance of dust that could otherwise settle on the eggs. I have found the greater densities of breeding individuals around driftwood, in very shallow areas. Here I would assume the stronger light provides more available food for the fry.

The eggs are yellowish, adhesive, and rather small in size with a maximum length of 1.7 mm (Coleman and Galvani, 1998). They are placed slightly apart from one another, which I presume is due to the low oxygen content in the water. This helps to increase the circulation and oxygen to each egg. Each spawning effort produces normally around three hundred eggs, although in exceptional cases, I have had captive pairs producing over five hundred fry, but not consistently. However, I have noticed that T. pasionis tend to produce way more eggs than T. meeki. Eggs hatch around two days under aquarium conditions at 26° celsius and the fry are free swimming about five days later, after they have consumed their heavy yolk sac. Several times during the period from hatching to free swimming, the fry are taken into the parents' mouths and moved to small pre-dug pits in the substrate. In order to duplicate this behavior in the aquarium, it is necessary to provide very fine sand as substratum, as otherwise this won't be observed. When sand is not available the fish will clean an entire area of gravel and place the wrigglers directly on the bottom of the tank (or the fry-sucking underwater filter plate!).

It is the female that takes care of the eggs and wrigglers, although the male hovers close by to drive intruders away. The female constantly fans the eggs with her pectoral fins to keep dust and small bits of debris off of them, a behavior that extends to care for the wrigglers. Occasionally the male will take over care of the pre-swimming fry so that the female can leave the territory, presumably in search of food, after which she returns a couple of minutes later and normal pair positioning is resumed. During the breeding periods the antagonistic behavior towards other Thorichthys pairs increases significantly, although as common, rarely any damage is done.

At the free-swimming stage both parents must closely protect the fry. On many occasions I have observed a breeding pair loose coordination because of a disturbance and immediately witness part (or many times all) of their fry (and breeding effort) subject to the fast, coordinated, and savage attacks of the opportunistic Astyanax aeneus. Fry feed from edible matter on the bottom of the habitat while guided by the female who always positions herself above them, calling their attention with fast shakes of her fins. The father always stays close, no more than twenty centimeters away from the fry, keeping potential predators at distance. The fry abandon the parents at around 1 cm. of length (which is attained after three weeks in the aquarium if well fed), as this is the size I have been able to collect them hiding under the shore vegetation where they live out their first stage of their life. Thorichthys pasions pairs caring for their fry never seem to venture far away from the original spawning site.

Thorichthys have a number of potential predators such as the gar Lepisosteus tropicus, as well as an abundance of fish eating birds, reptiles and otters, while fry is preyed upon by Astyanax aeneus and the various catfishes.

Thorichthys pasionis

Thorichthys pasionis female from laguna Noh in the Southern Part of the Yucatán peninsula, with her fry in the aquarium. Photo by Juan Miguel Artigas Azas.

Aquarium considerations

When given the correct conditions, Thorichthys pasions can be easily kept and bred in the aquarium. A tank size of at least 250 liters is my first recommendation (I use 400 liters). I am aware of aquarists who have successfully kept and bred this fish in smaller quarters, although I doubt any normal behavior can be observed there.

T. pasionis seem to do very well when kept in a group of at least eight individuals, preferably of several sizes. The yellow meeki is not a very active cichlid and prefers to move slowly and stay close to their preferred spot or territory in the lower thirty centimeters of the tank.

Companions for Thorichthys pasionis are not difficult to choose, and for this purpose one can take a look at the fish species found syntopically to get an idea of what to keep together (of course you won't think about keeping the Mexican gar with them). However, one should also consider that it is impossible to expect a fish community to behave as it would in nature when in the confined space of our aquariums. Some species can't be expected to successfully cohabitate in an aquarium with the yellow meeki, even if in nature they share a habitat. Poecilia petenense makes a wonderful choice even for the smaller tanks, as it is ignored by T. pasionis and it is peaceful enough not to bother the cichlids or fry. It is also large enough not to perish on the attacks of a breeding pair of T. pasions. Rhamdia species are also a good choice for the yellow meeki tank provided hiding places for them. Astyanax aeneus makes another good choice although in smaller tanks without much cover they tend to nip the threads of the dorsal and anal fins of males of yellow meeki, and also tend to get to the food much faster than the cichlids. This can make it difficult to feed the fry in a community tank. Of course you can also keep non-syntopic species, and Rainbow fishes would then make a perfect choice.

In my tanks I use external trickle filters, but any good filtration method would be sufficient for their well-being. Water in my area has a Ph 7.8 and a general and carbonate hardness value of 9 German. Unlike the Thorichthys species of the helleri group, which require that the water temperature does not exceed 28° celsius, T. pasions seems to tolerate higher temperatures, as high as 30°C without any problem. This is consistent with their natural habitat. Temperatures should not be kept below 22°C, as growth and coloring slow and any breeding activity is stopped. Lower temperatures for a prolonged period lead to stress, loss of appetite, and eventually thinness, diseases, and death.

For decoration I use a thin layer of fine sand, which they love, as I see them sifting through it a good deal of the time. I also keep an abundance of driftwood and some rocks. For breeding I have found nothing better than up-turned flowerpots with the top opened to the proper size for them to fit. The yellow meeki as well as all Thorichthys really love the pots and can't resist placing their eggs on the walls inside. Even though this is very different from the way they spawn in the natural habitat, which is generally over open surfaces on small rocks, or drift leaves.

Thorichthys and many other cichlids are afraid of bright lights and open ceilings, as in nature, often death comes from above. Given this, you should take care of these needs in their captive keeping. They will only show their best colors when this consideration is taken into account.

Food it is not a problem, they will eagerly take anything you offer. Thorichthys pasionis are particularly fond of frozen red worms, but I normally feed them my own "concoction" made out of raw shrimp, oysters, saltwater fish, oatmeal, and usually some vegetables such as lettuce. Flake foods are greedily accepted as well. These fish are real gluttons and will eat anything you offer. It is better to give them carotene rich foods to keep their yellow coloration at a good level. Fry can be easily offered brine shrimp nauplii and they grow quite fast, reaching ca. 1 cm after three weeks of free swimming time.

Taking the above considerations into account, I can assure you there will be no problems in keeping one of the most beautiful cichlids that you can have.

Thorichthys pasionis

Thorichthys pasionis from laguna Noh in the Southern Part of the Yucatán peninsula, two pairs facing each other defending their territories. Photo by Juan Miguel Artigas Azas.

References

© Copyright 1995 Juan Miguel Artigas Azas, all rights reserved

引語:

Artigas Azas, Juan Miguel. (十月 18, 2000). "Thorichthys pasionis (Rivas 1962), the yellow meeki". 慈鯛魚室同好網. 檢索 五月 25, 2013, 來自: http://www.cichlidae.com/article.php?id=148&lang=zh.


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