Male in the aquarium
A male of Astatheros margaritifer from Lake Peten-Itza [Guatemala] in the aquarium of Don Conkel [USA].Foto von Donald Conkel.

Familie
Cichlidae

Unterfamilie
Cichlinae

Tribus
Therapsini

Gattung
Astatheros

Status
valide


Verwalter

Veröffentlicht:

Zuletzt aktualisiert am :
14-Juni-2015

Astatheros margaritifer (Günther, 1862)


Erstbeschreibung als Heros margaritifer:

ZooBank:D4F7CFC5-4390-4B8E-83B5-8DF304267D05.

  • Günther, Albert C. L. G. 1862. "Catalogue of the fishes in the British Museum. Catalogue of the Acanthopterygii, Pharyngognathi and Anacanthini in the collection of the British Museum". Catalogue of the fishes in the British Museum London. Vol 4; i-xxi + 1-534 (crc00035)

Nomenklatur Geschichte:

Bewohnte Länder:

Etymologie: margaritifer = pearl-bearer, from margarita = pearl (Latin) and ferre = to bear (Latin); in allusion to the peral-colored spots on body shown by the type specimen. The specific name has to be treated as a noun in apposition according to Article 31.2.2 of the Code (ICZN 1999), i.e. it must not be changed to margaritiferum or -us as frequently seen.

Typusmaterial: holotype: BMNH 1.26.62.

The original description is based on a single specimen, collected in March or April 1862 by Osbert Salvin. The holotype is stored in the Natural History Museum, London under the catalog number BMNH 1.26.62. The specimen has been figured trice in the literature: 1) a lithograph in Günther (1868), reproduced here; 2) a monochrome photo in Bussing & Martin (1975); a) color photo in Morgenstern (2015).

Diagnose: Astatheros margaritifer may be distinguished from all other Astatheros species by a the coarse, anteriorly enlarged jaw dentition (vs. teeth fine, needle-like and scarcely increasing in size towards symphysis), five sensory pores on mandible (vs. four), an indistinct midlateral blotch (vs. usually prominent), caudal blotch elongated onto peduncle (vs. confined to caudal fin base). Astatheros margaritifer has been confused with A. longimanus, A. robertsoni and A. macracanthus, from which it may be additionally distinguished as follows: by a well-marked frontal gibbosity (vs. indistinct or absent except in a few exceptional specimens of a single, geographically remote population of A. longimanus), caudal fin emarginate with rounded corners (vs. subtruncate in A. robertsoni, sub-truncate to rounded in A. macracanthus), dorsal fin formula XVII.11 (vs. XIV-XV, rarely XVI.12-15 in A. macracanthus), seven anal spines (vs. invariably five in A. macracanthus), fold of lower lip interrupted (vs. sub-continuous to continuous in adult A. macracanthus), lack of a longitudinal stripe (vs. present in A. robertsoni and A. longimanus), caudal fin completely covered with indistinct light spots (vs. unspotted or only near base in A. macracanthus and A. longimanus), absence of a black axillar spot (vs. present in A. robertsoni) (compiled from Regan, 1905, Bussing et al., 1975 and Morgenstern, 2015).

Größe: The type specimen measures 16.7 mm SL and 164 mm TL; Conkel (1993) gives a maximum length (presumably TL) of 235 mm.

Geschlechtsdimorphismus: According to Conkel (1993), adult males are bronze-colored with conspicuous pearly white spots, while females are bright yellow and lack an intense spotting.

Typusfundort: Lago Petén, Guatemala.

Verbreitung: Astatheros margaritifer is only known from Lake Petén Itzá, Guatemala. All other locality records in literature or collection databases are based on misidentifications.

Fundorte: Lake Petén-Itza (Guatemala, type locality).

Lebensraum: Lake Petén Itzá is situated roughly in the middle of Petén district, Guatemala. Its endorheic basin occupies a large karst depression and is subdivided into a major northern basin (about 30 km long and 5 km wide) and a much smaller and shallower southern basin (14 km long, up to 1.5 km wide), which probably fell dry during the lowest water levels. With a surface area of about 100 km², L. Petén Itzá is the third-largest Guatemalan lake. The surface elevation is about 110 m above sea level. It is the deepest lowland lake of Central America, the maximum depth is 165 m (a fact only discovered in 1999, records from 1969 indicate a depth of only 32 m). The northern shore is marked by a steep karst ridge, while the southern shore is shelving and partly margined by poorly drained seasonal swamps. During the last decades, the lake level has undergone fluctuations of 5-6 m. A rising water level, which caused the flooding of streets and buildings in Flores, was already observed in 1862 by Salvin (in Günther, 1868). The water of the lake is rather clear (transparency 4.25 m) very warm, surface temperature is about 30°C or more, but Mendéz & al. (2011) recorded only 24.9-25.2°C at two locations in the southern basin in January 2009. A thermocline with the temperature dropping to 26°C has been recorded at 20 m depth. Conductivity ranges from 485-550 µS/cm, pH from 7.7 - 8.3, dissolved oxygen near surface from 5-8.5 mg/l (data compiled from Brezonik et al., 1974, Basterrechea Díaz, 1988, Anselmetti et al., 2006, Hoddell et al., 2006 and Méndez et al., 2011).

23 fish species have been recorded from L. Petén Itzá so far, among them nine cichlids. Little is known about their ecology and biology in the lake, there is much work to be done.

Ernährung: No data available. Astatheros margaritifer has been traditionally placed along with substrate-sifting species, but does not fully comply with that trophic type in habitus and, moreover, differs considerably in jaw dentition.

Fortpflanzung: No data available, but Astatheros margaritifer is not expected to depart from the usual reproductive behavior of Central American cichlids.

Aquaristik: Six specimens of what is likely this species (but see comments below) have been collected and brought home alive in 1983 by Conkel and party. According to his e-mails circulating in the www, he bred the fish at his farm in Florida and sold the offspring for a couple of years, but I am not aware of any published reports of maintenance or reproduction. According to Conkel (1993), they were very sensitive, and he lost his stock in 1989 due to a cold wave.

Artenschutz: Astatheros margaritifer wurde durch die Internationale Union für die Erhaltung der Natur (IUZN) in der Roten Liste bedrohter Arten bewertet als (EN) stark gefährdet (2009).

Bemerkungen: The status and ID of Astatheros margaritifer remains a mystery, although the amount of information provided by early workers was by no means inferior to that on many other species: The original description (Günther, 1862) was comprehensive by the standards of time, a sufficiently precise type locality was given, and a good figure has been published soon afterwards (Günther, 1868). The fact that Astatheros margaritifer was known from a single specimen was not unusual at that time. The data available allowed the conclusion that it was a species from Lake Petén distinct from any other nominal species described then.

The ‘mystification’ arose from the fact that the species could not be identified in subsequent collections from the lake or from elsewhere (the specimens reported by Pellegrin, 1904 were Astatheros robertsoni, see Bussing et al., 1975), and especially from a supposedly unknown type locality: Peter Hymphry Greenwood notified Bussing & Martin (1975) of the fact that in the register of the British Museum no locality was given for Heros margaritifer, but Lake Petén was stated for the subsequent entry. Greenwood concluded that Günther either knew where the type had been collected or misread the register. Unfortunately, most subsequent authors ignored the first possibility. Therefore, Greenwood’s observation became a trigger for various speculations about the origin and identity of the type, which led to almost crypto-zoological approaches to find the species.

However, there is one important detail that has been hitherto overlooked (Morgenstern, 2015): The type material of this and other species described by Günther (1862) has been registered only after publication of the original description. The fourth volume of Günther’s “Catalogue of the fishes in the British Museum” has been published on November 8, 1862, and a foreword dated June 15, 1862 indicates that the manuscript was largely finished already at that time, but the date of registration is January 26, 1864! The possibility that Günther misread the register can therefore definitely be ruled out. He must have obtained the locality data directly from the collector Osbert Salvin, and this either by the original label of the specimen or by a letter accompanying the shipment, since Salvin was still in Guatemala at that time. A reconstruction of itinerary and timing of Salvin’s travels makes it also very unlikely that the collector himself could have given a wrong locality, see Morgenstern (2015) for details. We, therefore, must conclude that Lake Petén Itzá is really the type locality of Heros margaritifer.

Rusty Wessel (1996:6) published a photo of Astatheros longimanus under the name Astatheros margaritifer. It was identified as such by Robert Rush Miller, who considered (like Reeve M. Bailey as well) the two nominal species synonymous. However, their distinctness has been convincingly demonstrated by Bussing & Martin (1975) and is also supported by additional characters. Furthermore, A. longimanus is restricted in Guatemala to some rivers of the Pacific slope, where Salvin collected only after the original description of Astatheros margaritifer was completed (Morgenstern, 2015). It should be noted that most museum records of Astatheros margaritifer are attributable to that misidentification and refer actually to A. longimanus.

In the European hobby literature, another cichlid from Honduras was misidentified as Astatheros margaritifer, which is actually either a distinctive geographical variant of or a new species closely related to A. robertsoni. It was first linked with the name of Astatheros margaritifer by Buchhauser (2005). This fish differs considerably from the holotype in body and fin shape, as well as color pattern, its distinctness from Astatheros margaritifer was demonstrated by Schindler & Krahnefeld (2015). A population of A. robertsoni corresponding to those found in South Mexico and Belize is known to occur in L. Petén Itzá, but its conspecificity with Astatheros margaritifer can be ruled out for the same reasons.

Eric Hanneman (2012) found what he believes to be Astatheros margaritifer on the Pacific slope of Guatemala, namely in a tributary to Rio Maria Linda and in Lago Amatitlán. However, what he and his companions collected is clearly A. macracanthus, a species readily distinguished by body and fin shape, fin counts, dentition, color pattern, etc.. Interestingly, they found two different ‘types’ of macracanthus-like fishes in the region, those identified as possible margaritifer being very deep-bodied, but this applies to the type series of A. macracanthus as well. Although Hanneman may well be right in assuming that Salvin and Godman may have obtained specimens sold as food fish in Guatemala City (namely those from L. Amatitlán), the possibility that the holotype of Heros margaritifer was among them can be ruled out as the collections from that area, too, arrived too late to have been taken into consideration for Volume IV of Günther’s Catalogue.

Several authors have argued that Astatheros margaritifer cannot be from L. Petén because no fish fitting the description has been subsequently collected there. But this applies to any other presumed localities as well, and it is possibly not true: Conkel (1993) presented photos of a fish said to have been found in the lake, which may very well correspond to the one found in 1862 by Salvin. Unfortunately, many people did not believe that the fish was really from L. Peten, because the book contains a few photos of obvious hybrid specimens of doubtful origin. However, in 2010, John Heaton, then a resident of San Andres, Lake Petén Itzá, was able to recollect exactly that fish (link) The origin of Conkel’s fish is therefore confirmed. Arguments against its identification as Astatheros margaritifer summarized by Hanneman (2012) can be readily rejected. Conkel’s photos show life, obviously well-doing fish in aquarium, the length of the pectoral fin (Miller’s argument, expressly based on Conkel’s slides) is not exactly determinable from such photos due to the permanent movement of the fins. One of Heaton’s photos of the fish on hook show that the length of the pectoral corresponds very well to that in the holotype. The lack of a well-marked frontal gibbosity in Heaton’s fish (present in Conkel’s) is easily explained by their smaller size (indeed, one of the specimens shows an incipient gibbosity), and the slightly more pronounced concavity before the eye, producing a more prominent snout (or “bird beak-like” mouth, as Hanneman calls it) can be attributed to shrinkage caused by dehydration, an effect frequently seen in specimens not fixed in formalin before ethanol preservation.

Of course, the identification needs to be confirmed on the basis of examination of fresh material, but with the confirmation of the type locality and the proof that such a fish actually occurs in L. Petén Itzá, it seems more than likely that Conkel and Heaton have rediscovered Heros margaritifer. Nevertheless, there are several open questions to resolve. While the species is placed here tentatively (and largely for technical reasons) within Astatheros, the generic assignment is actually unresolved. It was placed within the longimanus complex (then a subgroup of Amphilophus) by Bussing & Martin (1975) but the grouping was based expressly on “admittedly superficial criteria”, and all their groups turned out to be polyphyletic. Our current understanding of the genera Amphilophus and Astatheros is largely based on the results of DNA analyses, in which Astatheros margaritifer could not be included so far; and useful diagnoses are yet lacking for both. Nevertheless, judging from comparison of species’ characters, there is nothing that would link Astatheros margaritifer unambiguously to any of them. Furthermore, the impression of several people that this fish could be a natural hybrid (in which case the name Heros margaritifer would be invalid) cannot be dismissed. The scarcity in collections, the peculiar admixture of characters and the apparent lack of similar forms in adjacent systems would support that view. Several potential parental species have been discussed based on superficial resemblance, but consideration of all characters would leave only two: Thorichthys affinis and Paratheraps melanurus. However, the ‘hybrid theory’, too, remains to be tested, Astatheros margaritifer could equally be simply a rare or elusive species. The criteria mentioned above would, for example, also apply to 'Theraps' wesseli, of which we know that it is no hybrid. Such species, however, may well have evolved from hybrid forms, which would explain their peculiar characters, inconsistent position in molecular phylogenies, etc.

Therefore, everyone who plans collecting in Lake Petén Itzá is appealed to keep an eye out for this cichlid, there is still much to learn!.

Literatur (23):

  • Anselmetti, F.S & D. Ariztegui, D.A. Hodell, M.B. Hillesheim, M. Brenner, A. Gilli, J.A. McKenzie & A.D. Mueller. 2006. "Late Quaternary climate-induced lake level variations in Lake Pete´n Itza´, Guatemala, inferred from seismic stratigraphic analysis". Palaeogeography, Palaeoclimatology, Palaeoecology. (n. 230), pp. 52–69 (crc06763)
  • Basterrechea Díaz, Manuel. 1988. "Limnología del Lago Petén Itzá, Guatemala". Revista de Biologia Tropical. v. 36(n. 1), pp. 123-127 (crc06765)
  • Brezonik, P. L & J.L. Fox. 1974. "The Limnology of Selected Guatemalan Lakes". Hydrobiologia. v. 45(n. 4), pp. 467-487 (crc06766)
  • Buchhauser, P. 2005. "Zum Fischfang nach Honduras". Deutsche Cichliden Gesellschaft- Informationen. v. 36(no. 6); pp. 126-131 (crc01107)
  • Bussing, William & M. Martin. 1975. "Systematic status, variation and distribution of four Middle American cichlid fishes belonging to the Amphilophus species group, genus Cichlasoma". Natural History Museum L.A. County Contributions of Science. n. 269; pp. 1-41 (crc01108) (Kurzfassung)
  • Conkel, Donald. 1993. "Cichlids of North & Central America". TFH Publications. pp. 1-191 (crc00971)
  • Eigenmann, Carl H. 1893. "Catalogue of the fresh-water fishes of Central America and Southern Mexico". Proceeding of the United States National Museum. vol. 16 (n. 925): pp53-60 (crc02506)
  • Fernández-Yépez, Agustín. 1969. "Contribución al conocimiento de los cíclidos". Evencias. (n. 22) pp. unnumbered); Pls. 1-1 (crc00247)
  • Günther, Albert C. L. G. 1868. "An account of the fishes of the states of Central America, based on collections made by Capt. J. M. Dow, F. Godman, Esq., and O. Salvin, Esq". Transactions of the Zoological Society of London. v. 6(n. 7), pp. 377-494, Pls. 63-87 (crc06106)
  • Günther, Albert C. L. G. 1862. "Catalogue of the fishes in the British Museum. Catalogue of the Acanthopterygii, Pharyngognathi and Anacanthini in the collection of the British Museum". Catalogue of the fishes in the British Museum London. Vol 4; i-xxi + 1-534 (crc00035)
  • Hanneman, Eric. 2012. "The Enigmatic Amphilophus margaritifer. Tasting Good for Over 3500 Years". Cichlid News Magazine. v. 21(n. 2), pp. 26-33 (crc04215)
  • Hoddell, D & F. Anselmetti, M. Brenner & D. Ariztegui. 2006. "The Lake Petén Itzá Scientifi c Drilling Project". Scientific Drilling. (n. 3), pp. 25-29 (crc06764)
  • ICZN. 1999. "International Code of Zoological Nomenclature, 4th edition". International Trust for Zoological Nomenclature, Natural History Museum London (crc03781)
  • Jordan, David Starr & B.W. Evermann & H.W. Clark. 1930. "Checklist of the fishes and fishlike vertebrates of North and Middle America. Appendix X". Report of the US Commissioner of Fisheries. 416-424 (crc02509)
  • Jordan, David Starr & B.W. Evermann. 1896. "Checklist of the fishes and fish like vertebrates of North and Middle America". Report of the Commissioner of Fish and Fisheries. XXI: 207-584 (crc02517)
  • Kullander, Sven. 1996. "Heroina isonycterina, a new species of cichlid fish from Western Amazonia, with comments on cichlasomine systematics". Ichthyological Explorations of Freshwaters. v. 7(n. 2), pp. 149-172 (crc01223) (Kurzfassung)
  • Miller, Robert Rush. 1966. "Geographical distribution of Central American freshwater fishes". Copeia. v. 1966 (n. 4); pp. 773-802 (crc01105)
  • Morgenstern, Rico. 2015. "Anmerkungen zur Herkunft und Identität von Heros margaritifer Günther, 1862". Deutsche Cichliden Gesellschaft- Informationen. v. 46(n. 1), pp. 2-9 (crc06614)
  • Méndez, Anaitté & García, María-Elena, Lozano, Lourdes. 2011. "Sistemática del pez Petenia splendida (Perciformes: Cichlidae) en el lago Petén Itzá, Guatemala". Revista de Biologia Tropical. v. 59(n. 3), pp. 1205-1216 (crc04962) (Kurzfassung)
  • Pellegrin, Jacques. 1904. "Contribution à l'étude anatomique, biologique et taxinomique des poissons de la famille des Cichlidés - Taxinomie". Bulletin de la Société Zoologique de France. pp 121-400 (crc00027) (Kurzfassung)
  • Regan, Charles Tate. 1905. "A revision of the fishes of the American cichlid genus Cichlosoma and of the allied genera". Annals and Magazine of Natural History. (Ser. 7) vol. 16; pp 60-77; 225-243; 316-340; 433-445 (crc00042)
  • Schindler, Ingo & Lutz Krahnefeld. 2015. "Es ist nicht margaritifer - Zur Bestimmung von Astatheros sp. 'Honduras'". Deutsche Cichliden Gesellschaft- Informationen. v. 46(n. 2), pp. 34-41 (crc06767)
  • Wessel, Rusty. 1996. "A "Top Ten" List of the Cichlids of Honduras". Cichlid News Magazine (crc00479)

Externe Kataloge: Catalog of Fishes, Encyclopedia of Life, FishBase, ZooBank.

Anführung:

Morgenstern, Rico. (Juni 14, 2015). "Astatheros margaritifer (Günther, 1862)". Cichlid Room Companion. Abgerufen am Dezember 13, 2019, von: https://cichlidae.com/species.php?id=486&lang=de.