Lawrence M. Page

Morphological correlates of ecological specialization in darters

Darters feed on small benthic organisms, primarily insects, and evolutionarily have become increasingly small and benthic; most species are less than 80 mm in standard length. Constraints on decreasing body size include living in midwater and territoriality. Lineages of darters have arisen as new habitats were invaded. Consequently, members of different lineages often vary in characteristics correlated with specific habitat variables. While competition from established taxa undoubtedly has prevented additional habitat invasions, some darters appear to have overcome these barriers through feeding site diversification. Living in various habitats has lead to a variety of reproductive strategies, termed egg-burying, -attaching, -clumping, and -clustering. Sexually selective characteristics, correlated with type of reproductive behavior and habitat, often make the male more conspicuous and therefore are constrained by predation.

Intraspecific phylogeography of Percina evides (Percidae: Etheostomatinae): an additional test of the Central Highlands pre‐Pleistocene vicariance hypothesis

North America exhibits the most diverse freshwater fish fauna among temperate regions of the world. Species diversity is concentrated in the Central Highlands, drained by the Mississippi, Gulf Slope and Atlantic Slope river systems. Previous investigations of Central Highlands biogeography have led to conflicting hypotheses involving dispersal and vicariance to explain the diversity and distribution of the freshwater fish fauna. In this investigation predictions of the Central Highlands pre‐Pleistocene vicariance hypothesis are tested with a phylogeographic analysis of the percid species Percina evides, which is widely distributed in several disjunct areas of the Central Highlands. Phylogenetic analysis of complete gene sequences of mitochondrially encoded cytochrome b recover three phylogroups, with very low levels of sequence polymorphism within groups. The two western phylogroups are monophyletic with respect to the eastern phylogroup. The recovery of two monophyletic lineages with an eastern and western distribution in the disjunct highland areas is a pattern expected from vicariance, but is not predicted by the Central Highlands pre‐Pleistocene vicariance hypothesis. The recovery of very limited mitochondrial DNA polymorphism and lack of phylogeographic structuring across the entire range of the eastern clade, very shallow polymorphism between the disjunct Missouri River and upper Mississippi River populations, and lack of sequence polymorphism in the upper Mississippi River populations, support a hypothesis of dispersal during or following the Pleistocene. The present distribution of P. evides is best explained by both vicariant and dispersal events.

Convergence of a cryptic saddle pattern in benthic freshwater fishes

SynopsisMany North American stream fishes have a similar color pattern of four dark saddles against a light background. An interesting feature of the pattern, in addition to its widespread taxonomic distribution, is its consistent configuration. The interval between the first and second saddle is usually the largest, and the last (third) interval is the smallest. All saddled North American freshwater fishes live on uneven, rocky substrates, and nearly all live in flowing water. It is hypothesized that these fishes achieve crypsis through disruptive coloration; the light spaces between the saddles mimic rocks and the dark saddles appear as shadows or gaps between rocks. Saddles are spaced unevenly because rocks in streams are a mixture of sizes; a fish that mimics a series of rocks of similar sizes is more conspicuous than one that mimics rocks of different sizes. The placement of saddles was measured on five North American species. In four of five North American species measured (a sculpin and three darters), the longest spaces are towards the head where the body is also the widest, this is thought to enhance crypsis because pieces of gravel tend to be round or square. In the madtom, the saddle pattern tends more towards even spacing. The madtom may not rely on camouflage to the same extent as other species examined because of decreased predation pressure associated with being nocturnal and possessing sharp spines and venom glands.

Spawning in the creek chubsucker,Erimyzon oblongus, with a review of spawning behavior in suckers (Catostomidae)

SynopsisErimyzon oblongus was observed spawning in small ditches in central Illinois in 1986, 1987, and 1988. Males defended territories over beds of gravel or near pits that had been constructed byCampostoma anomalum orSemotilus atromaculatus. Females were located upstream in quiet water and drifted downstream tail first into the territory of a male. After a female entered a males territory, she dug in the gravel with her snout, an action which appeared to signal the male that she was ready to spawn. Of the 22 spawns observed in 1986–1988, 18 involved one male and one female, and four involved two males and one female; 19 were over pits constructed by other fishes, and three were over gravel runs; eight were interrupted by other males. Published descriptions suggest relatively little variation in behavior associated with reproduction in suckers. Spawning characteristics ofE. oblongus that appear to be derived within Catostomidae are small size, males as large as females, strongly territorial males, large head tubercles, and pair spawning.

The Food of Spotted Base in Streams of the Wabash River Drainage

Abstract Analysis of stomach and intestinal contents of 114 spotted bass 23 to 320 mm total length, collected from March through November in tributaries of the middle Wabash River, revealed that immatures of aquatic insects were the principal items of food. In bass less than 75 mm, aquatic insects were supplemented by plankton; in bass more than 150 mm, by crayfish and fish. Spotted bass in a stream environment are more insectivorous and less piscivorous than in impoundments.

Distribution and Relative Size of the Swim Bladder in Percina, With Comparisons to Etheostoma, Crystallaria, and Ammocrypta (Teleostei: Percidae)

The distribution of the swim bladder was examined in 20 species representing all four genera (Percina, Etheostoma, Crystallaria, and Ammocrypta) of darters (Etheostomatini). Including data on species examined in other studies, swim bladders have been found in 15 of 17 species of Percina, but were absent in Crystallaria asprella, Ammocrypta pellucida, and the 18 species of Etheostoma examined. Relative swim bladder length in Percina was shown to be positively correlated with body size. Although not statistically significant, swim bladder size also correlates with habitat (riffle, run, or pool) and swimming behavior (midwater or benthic).

The function of the caudal keel inPercina (Percidae)

SynopsisUnique to darters of the subgenusOdontopholis ofPercina andPercina (Imostoma)antesella is the development of a caudal keel in breeding males. The keel is a semicircular extension of the ventral surface of the caudal peduncle and anterior lower caudal fin. The reproductive behavior of species ofPercina implies an adaptive function related to the burial and fertilization of eggs. The caudal keel appears to serve as a plow-share which, in conjunction with an elongated anal fin, facilitates the transfer of sperm from the males genital opening to eggs buried in the substrate by the female.

A portable camera box for photographing small fishes

Fishes are difficult to photograph for a variety of reasons. Ideally, they should be photographed alive and in their natural environments. However, few of us can manage the time and aquatic skills necessary to accomplish that. Also, many species live in turbid water or at insufficient depths to accommodate underwater photography. Live fishes in aquary often are frightened into only a pale reminder of their former selves, and settings seldom simulate natural conditions. The third alternative is to preserve the fishes and photograph them. With proper controls good life-like images can result. The apparatus described below works well for small fishes and is portable. Photos in the ‘Handbook of Darters’ (T.F.H. Publications, Inc., Neptune City, NJ 07753) were taken with this procedure.