Theodore W. Pietsch

Evolution of the salmonid mitochondrial control region

To explore the evolutionary nature of the salmonid mitochondrial DNA (mtDNA) control region (D-loop) and its utility for inferring phylogenies, the entire region was sequenced from all eight species of anadromous Pacific salmon, genus Oncorhynchus; the Atlantic salmon, Salmo salar; and the Arctic grayling, Thymallus arcticus. A comparison of aligned sequences demonstrates that the generally conserved sequence elements that have been previously reported for other vertebrates are maintained in these primitive teleost fishes. Results reveal a significantly nonrandom distribution of nucleotide substitutions, insertions, and deletions that suggests that portions of the salmonid D-loop may be under differential selective constraints and that most of the control region of these fishes may evolve at a rate similar to that of the remainder of their mtDNA genomes. Maximum likelihood and Fitch parsimony analyses of 9 kb of aligned salmonid sequence data give evolutionary trees of identical topology. These results are consistent with previous molecular studies of a limited number of salmonid taxa and with more comprehensive, classical analyses of salmonid evolution. Predictions from these data, based on a molecular clock assumption for the mtDNA control region, are also consistent with fossil evidence that suggests that species of Oncorhynchus could be as old as the Middle Pliocene and would have thus given rise to the extant Pacific salmon prior to about 5 or 6 million years ago.

Dimorphism, parasitism, and sex revisited: modes of reproduction among deep-sea ceratioid anglerfishes (Teleostei: Lophiiformes)

Sexual parasitism, a remarkable mode of reproduction unique to some members of the deep-sea anglerfish suborder Ceratioidei, in which males are dwarfed and become permanently attached to much larger females, is described in a number of previously unreported specimens and taxa. Although generally attributed to all ceratioids, and despite more than a sevenfold increase in the number of known parasitized females in collections throughout the world in the past 50 years, the phenomenon is surprisingly confined to few taxa within the suborder. To date, permanently attached males have been found in only 5 of the 11 ceratioid families, 10 of the 35 genera, and 23 of the 160 recognized species. Notes on taxonomic content, available material, occurrence of sexual parasitism, gravid females and ripe males, the development of eyes and nostrils of the males, the ability of males to capture and ingest food independently of the female, occurrences of multiple attachments of males to a single female, and the nature of the fusion between coupled males and females are given for each ceratioid family. This information is then summarized and discussed. Evidence is presented to reaffirm the presence of three reproductive modes: obligatory parasitism, facultative parasitism, and temporary nonparasitic attachment. Additional evidence is provided to reaffirm the hypothesis that sexual parasitism has evolved separately at least three and perhaps five or more times within the suborder.

High-Speed Cinematographic Evidence for Ultrafast Feeding in Antennariid Anglerfishes

Analyses by means of high-speed, light cinematography at 800 and 1000 frames per second have shown that members of the shallow-water anglerfish genus Antennarius are capable of producing an enormous suction pressure for prey capture by means of an extraordinarily rapid expansion of the buccal and opercular cavities. Prey is totally engulfed at speeds considerably greater than those recorded for any other fish. The structural adaptations responsible for this rapid prey engulfment provide anglerfishes with one of the fastest known vertebrate feeding mechanisms.

Evolutionary Relationships of the Sea Moths (Teleostei: Pegasidae) with a Classification of Gasterosteiform Families

Members of the currently recognized acanthopterygian order Pegasiformes have an unusual feeding mechanism in which enlarged maxillovomerine cartilages are closely associated with the maxillae, premaxillae and dentaries forming a highly protrusible mouth. This is a unique mechanism among living teleosts, but apparently present in the Lower Eocene Ramphosidae, currently placed among the aulostomoid gasterosteiforms. This and other evidence support a gasterosteiform ancestry for the Pegasidae. The Pegasiformes are synonymized with the Gasterosteiformes. The fossil Ramphosidae are resurrected from the synonymy of the Macrorhamphosidae and placed with the Pegasidae in a new superfamily, the Pegasoidea. The Pegasoidea are proposed as the primitive sister-group of the Solenostomidae and Syngnathidae. The Solenostomidae and Syngnathidae are included in a new superfamily, the Syngnathoidea, which together with the Pegasoidea form the primitive sister-group of the Macrorhamphosidae, Centriscidae, Aulostomidae and Fistulariidae.

Evolutionary history of anglerfishes (Teleostei: Lophiiformes): a mitogenomic perspective

BackgroundThe teleost order Lophiiformes, commonly known as the anglerfishes, contains a diverse array of marine fishes, ranging from benthic shallow-water dwellers to highly modified deep-sea midwater species. They comprise 321 living species placed in 68 genera, 18 families and 5 suborders, but approximately half of the species diversity is occupied by deep-sea ceratioids distributed among 11 families. The evolutionary origins of such remarkable habitat and species diversity, however, remain elusive because of the lack of fresh material for a majority of the deep-sea ceratioids and incompleteness of the fossil record across all of the Lophiiformes. To obtain a comprehensive picture of the phylogeny and evolutionary history of the anglerfishes, we assembled whole mitochondrial genome (mitogenome) sequences from 39 lophiiforms (33 newly determined during this study) representing all five suborders and 17 of the 18 families. Sequences of 77 higher teleosts including the 39 lophiiform sequences were unambiguously aligned and subjected to phylogenetic analysis and divergence time estimation.ResultsPartitioned maximum likelihood analysis confidently recovered monophyly for all of the higher taxa (including the order itself) with the exception of the Thaumatichthyidae (Lasiognathus was deeply nested within the Oneirodidae). The mitogenomic trees strongly support the most basal and an apical position of the Lophioidei and a clade comprising Chaunacoidei + Ceratioidei, respectively, although alternative phylogenetic positions of the remaining two suborders (Antennarioidei and Ogcocephaloidei) with respect to the above two lineages are statistically indistinguishable. While morphology-based intra-subordinal relationships for relatively shallow, benthic dwellers (Lophioidei, Antennarioidei, Ogcocephaloidei, Chaunacoidei) are either congruent with or statistically indistinguishable from the present mitogenomic tree, those of the principally deep-sea midwater dwellers (Ceratioidei) cannot be reconciled with the molecular phylogeny. A relaxed molecular-clock Bayesian analysis of the divergence times suggests that all of the subordinal diversifications have occurred during a relatively short time period between 100 and 130 Myr ago (early to mid Cretaceous).ConclusionsThe mitogenomic analyses revealed previously unappreciated phylogenetic relationships among the lophiiform suborders and ceratioid familes. Although the latter relationships cannot be reconciled with the earlier hypotheses based on morphology, we found that simple exclusion of the reductive or simplified characters can alleviate some of the conflict. The acquisition of novel features, such as male dwarfism, bioluminescent lures, and unique reproductive modes allowed the deep-sea ceratioids to diversify rapidly in a largely unexploited, food-poor bathypelagic zone (200-2000 m depth) relative to the other lophiiforms occurring in shallow coastal areas.

Cyanine Blue: A Versatile and Harmless Stain for Specimen Observation

A staining technique for small fluid-preserved specimens, widely used by Japanese ichthyologists, is described. This technique is so widespread and popular in Japan that it is the ichthyological equivalent of eosin-hematoxylin staining in histology, for which almost every researcher has designed his or her own protocol (Akihito et al., 1993). Despite its widespread popularity as a technique for specimen observation, it is not available in published Western literature. There are two advantages in using this technique. First, the contrast of anatomical features (e.g., cephalic sensory pores and canals, pores on lateral-line scales, gillrakers, fin rays, myomeres, and nares) is greatly enhanced. Second, and more important, the stain is soluble in both water and ethanol (EtOH). Thus, once the specimen is returned to the original preservation fluid, the stain comes off, leaving no permanent effect on the specimen. This feature makes the stain ideal for use in fluid-preserved museum specimens regardless of taxon. Cyanine Blue 5R is listed as either Acid Blue 113, C.I. (Colour Index; Society of Dyers and Colourists, 1956) Acid Blue 113, or CI 26360. Cyanine Blue 5R is soluble in water (violet), ethanol (violet Blue), and cellosolve and is slightly soluble in acetone. It should be stored in a cool

Phylogenetic Relationships of Esocoid Fishes (Teleostei) Based on Partial Cytochrome b and 16S Mitochondrial DNA Sequences

Abstract The phylogenetic systematics of esocoid fishes are examined using comparisons of partial DNA sequences of the mitochondrial genes coding for the transmembrane protein cytochrome b and the 16S RNA ribosomal subunit. Nucleotide sequences from all species of umbrids, three species of esocids, and salmonid, osmerid, cypriniform, and neoteleostean outgroups were compared to determine patterns of molecular evolution and uncover evidence of phylogenetic relationships. Multiple sequence alignments for each of the two DNA regions examined were used to characterize the amount and type of change shown by the data. The sequences were analyzed under different models of molecular evolution using maximum-parsimony and maximum-likelihood optimality criteria of phylogenetic reconstruction. The phylogenetic analyses revealed previously undiscovered affinities between species of umbrids and esocids that imply the paraphyly of the Umbridae as currently defined. The following set of esocoid interrelationships is proposed: (((Esox, Novumbra), Dallia), Umbra). Esocoid classification is revised based on present findings.

The feeding mechanism of Stylephorus chordatus (Teleostei : Lampridiformes) : functional and ecological implications

The unique feeding mechanism of Stylephorus chordatus depends on negative pressure created by the expansion of a membranous pouch that connects the cranium to an elongate, tubular mouth. Volume enlargement produced by this expansion may be as great as 38 times the volume of the closed buccal cavity. The tremendous, apparently rapid increase in volume provides for a high rate of water flow into the mouth cavity and thus an efficient sucking device for prey capture. Evidence is provided to indicate that Stylephorus hangs, head-up in the water column, feeding on small planktonic organisms, mainly copepods.

Dimorphism, Parasitism and Sex: Reproductive Strategies among Deepsea Ceratioid Anglerfishes

Knowledge of the reproductive biology of the Ceratioidei is reviewed and new and scattered evidence is brought together in an attempt to reevaluate some previously accepted ideas concerning the unique sexual habits of these fishes. Notes on taxonomic content, available material, occurrence of parasitism, gravid females and ripe males and the ability of males to ingest food independently of the female are given for each ceratioid family, after which this information is summarized and discussed. Data are presented to support at least three reproductive strategies utilized by ceratioid anglerfishes: sexually mature males of the Ceratiidae, Linophrynidae and perhaps the Neoceratiidae, are obligatory sexual parasites; those of the Caulophrynidae and the oneirodid genus Leptacanthichthys are probably facultative sexual parasites; and those of the Melanocetidae, Himantolophidae, Gigantactinidae and at least some oneirodid genera, are non-parasitic and perhaps spawn during a nonparasitic, temporary attachment. The four ceratioid families in which sexual parasitism has been previously recorded appear to form a highly specialized, monophyletic group, most likely derived from some oneirodid-like ancestor. If a facultative sexual parasitism exists for some ceratioids, particularly some oneirodid genera, it would form a convenient evolutionary intermediate between those ceratioids with obligatory sexual parasitism and those whose males never become parasitic.

A Review of the Monotypic Deep-Sea Anglerfish Family Centrophrynidae: Taxonomy, Distribution and Osteology

Centrophryne spinulosa, the only member of the deep-sea anglerfish family Centrophrynidae, is redescribed on the basis of new material recently collected from the eastern north Pacific Ocean. The distribution of C. spinulosa is world-wide in tropical and subtropical waters. A complete osteological description is presented with some comparative aspects discussed. Otoliths of C. spinulosa are compared with those of some members of the families Caulophrynidae, Gigantactinidae, and Oneirodidae. A revised key to the females of the families of the suborder Ceratioidei is included.