Typhlichthys eigenmanni Hubbs

Lynne R. Parenti, 2006, Typhlichthys eigenmanni Charlton, 1933, an available name for a blind cavefish (Teleostei: Amblyopsidae), differentiated on the basis of characters of the central nervous system., Zootaxa 1374, pp. 55-59 : 55-57

“ Typhlichthys eigenmanni Hubbs ,” with no year of description and no characters distinguishing it from other blind cavefishes of the family Amplyopsidae from Missouri, was listed by Hubbs (1938:265) in a table. Typhlichthys eigenmanni Hubbs 1938 has subsequently been treated as a nomen nudum by Woods & Inger (1957), Pfleiger (1971), Eschmeyer (1998, 2006), Poly & Proudlove (2004), among others. The purpose of this paper is to demonstrate that Typhlichthys eigenmanni Charlton , 1933 is an available name for a blind cavefish, and to draw attention to comparative anatomical characters of the central nervous system that may be used to distinguish among blind cavefish species and by which this name was made available.

Harry Hayward Charlton was a professor in the Department of Anatomy, University of Missouri, Columbia, in the early 20th century. In 1933, he published a paper on the comparative anatomy of the optic tectum, the primary visual center of the brain, of two Missouri blind cavefish species that he referred to by the names Troglichthys rosae and Typhlichthys eigenmanni . The first species, the Ozark Cavefish, was described in the genus Typhlichthys and is now classified as Amplyopsis rosae (Eigenmann , 1898). Charlton was an unintentional author of the binominal Typhlichthys eigenmanni which he credited to Hubbs (Charlton, 1933:287, footnote 1): “The description of this new subspecies has not yet been published, but Dr. Carl L. Hubbs, curator of fishes at the University of Michigan, in a personal communication, states that a full description will appear shortly, as indicated in the list of literature cited, and that he has named it Typhlichthys eigenmanni in honor of the late Doctor [Carl] Eigenmann.” The literature cited by Charlton (1933) includes the following entry: “Hubbs, Carl L. 1932. Studies of the fishes of the order Cyprinidontes [sic]. X. A new blind cave fish from Missouri. Occ. Pap. Mus. Zool. Univ. Mich. (in press).” Hubbs’s numbered series on cyprinodontiform fishes appeared in a variety of publication outlets (see Miller, 1981), but none with this title. Hubbs never described Typhlichthys eigenmanni , but Charlton did, unintentionally, using comparative neuroanatomical characters.

Characters

“The optic tectum and its related fiber tracts in blind fishes. A. Troglichthys rosae and Typhlichthys eigenmanni ” is the title of Charlton’s (1933) paper on the comparison of the central nervous system of two species of blind cavefishes. Brains of eleven specimens identified as Typhlichthys eigenmanni were serially sectioned and stained with methylene blue, neutral red, and haematoxylin (for cells), and silver-stained (for nerves). Size of all of the specimens of both species that Charlton (1933:287) examined were approximately 30 to 65 mm in [total] length, “… with Typhlichthys eigenmanni running just a little smaller on the average than Troglichthys rosae .” Throughout the text, he used one or the other species as an example to describe certain characteristics which I interpret as general statements about blind cavefishes of the family Amblyopsidae. At least four explicit statements were made, however, that serve to distinguish Typhlichthys eigenmanni from other amblyopsids:

1) Optic Nerve

With regard to the diameter of the optic nerve, Charlton (1933:292) noted that: “In Amblyopsis spelaeus …the optic nerve appears quite similar to that of Troglichthys rosae … In Typhlichthys eigenmanni , a comparable nerve is found. It is, however, somewhat smaller.”

2) Tractus mesenchephalo-cerebellaris anterior

The bundle of nerve fibers identified as the tractus mesencephalo-cerebellaris anterior “…arises not only from the optic tectum, but from the geniculate ganglion and pretectal nucleus…” (Charlton, 1933:300). The size of this tract was compared among blind fishes and other taxa by Charlton (1933:301) who reported that “…The largest tract studied was in Monocanthus [sic], while that of Microgadus and Anableps were only slightly smaller. Next came the two blind fishes, Typhlichthys having a tract somewhat larger than Troglichthys , and finally Clarius , where the cerebellar tract is about the same size or slightly smaller than in the blind forms.”

3) Fibrae tectales nervi optici

Charlton (1933:308) described the complex path of these fiber bundles: “The caudal ascending bundle is accompanied by fibers…which turn caudally into the [optic] bulb at the point where the fibrae tectales nervi optici turn rostrally to join the anterior bundle. This description applies to both the blind fishes; the rostral bundle in Typhlichthys eigenmanni , however, seems to ascend in front of the nucleus dorsalis thalami instead of bending around its anterior pole.”

4) Brachia tecti

The brachia tecti are bundles of myelinated fibers that connect the corpus geniculatum laterale with the optic tectum (Meader, 1934:386). Charlton (1933:312) noted that “The brachia are quite prominent in the blind fishes, being somewhat larger, however, in Troglichthys than in Typhlichthys .”

Thus, four characters were discussed that may be used to distinguish among blind cavefish species and by which Typhlichthys eigenmanni Charlton , 1933 was made available: 1) a relatively narrow optic nerve; 2) a relatively large tractus mesencephalocerebellaris anterior; 3) the rostral bundle of the fibrae tectales nervi optici ascending in front of the nucleus dorsali thalami as opposed to coursing around its anterior pole; and, 4) relatively small brachia tecti.

Specimens

Limited data on the eleven specimens of Typhlichthys eigenmanni used by Charlton (1933) was provided in his comparative brain study. Charlton (1933: 287) acknowledged a debt to “…Robert M. Snyder, Jr., who graciously permitted collections of Typhlichthys eigenmanni to be made in a cave situated upon his property.” Snyder (1876-1937) was a well-known Kansas City businessman who lived in a mansion, known as Ha Ha Tonka Castle, Camden County, Missouri, now the site of a state park. Current location of the putative syntypes, histological preparations and the specimens from which they were prepared, if they are still extant, is unknown. Ralph G. Meader, studying the optic system of the soldierfish, Sargocentron vexillarium , for his Ph.D. at Yale in the early 1930s, may have used the specimens (Meader, 1934:365): "An opportunity has been afforded for comparison with many other species of teleosts through the deposit of Dr. Harry H. Charlton's collection of prepared teleost brains with the Department of Anatomy of the Yale School of Medicine." Efforts to date to locate the slides at Yale have been unsuccessful, however. This is not due to poor curatorial practices, but to the failure of authors to recognize the value of voucher material and to have it catalogued in appropriate repositories. Systematists have long recognized the value of voucher material, of course, and have encouraged colleagues to deposit material in museum collections. Unfortunately, the current trend, even in systematics journals, is to not publish this information, which some erroneously consider to be supplementary (see discussion in Funk, Hoch, Prather & Wagner, 2005).