Tim M. Berra

Burrowing, Emergence, Behavior, and Functional Morphology of the Australian Salamanderfish, Lepidogalaxias salamandroides

Abstract The salamanderfish is a small endemic salmoniform that inhabits acidic, ephemeral freshwater in southwestern Australia. This paper documents that L. salamandroides burrows into damp sand to avoid the desiccation of its habitat and that it can emerge after an overnight rainfall of 8 mm. When dry pools were flooded by the release of water from a fire truck, fish were caught within 10 minutes. In captivity, the salamanderfish was observed to bend its head at right angles to the body. This is possible because of the wide gaps between the skull and first vertebra and between adjacent vertebrae. Reduced ribs also result in a very flexible body. These features and the robust, wedge-shaped skull are probably adaptations to burrowing. Scanning electron microscopy revealed cycloid scales and a formidable dentition.

Temporal characteristics of fish assemblage structure in an Ohio stream

We examined persistence (constancy of species composition) and stability (constancy of relative species abundances) of a fish assemblage at one site on a fourthorder stream in north-central Ohio. Thirty-eight quantitative samples taken over a 9 yr period indicate that the assemblage was both persistent and stable over that period. Analysis of trophic composition of the assemblage supports the same conclusion. Five groups of species were clearly identified based on clustering of persistence and numerical abundance patterns: permanent/high density, permanent/moderate density, frequent/moderate density, infrequent/low density, and transients. Although the assemblage has some degree of predictability, the mechanisms responsible must be evaluated through other than documentation of long-term pattern.

Gross Anatomy and Histology of the Hook and Skin of Forehead Brooding Male Nurseryfish, Kurtus Gulliveri, From Northern Australia

Mature males of nurseryfish have a hook on their head to which the eggs become attached and are carried like a bunch of grapes. This paper examines the anatomy and histology of the hook. The osteological basis of the hook is shown to be a modification of the supraoccipital crest of the skull covered by typical teleost skin. The integument in the cleft of the hook, where the eggs are attached, is considerably different from ordinary fish skin. The stratified epidermis is devoid of secretory mucus and neurosensory cells and is folded into crypts that extend deeply into the dermis. This may be a specialization that facilitates adhesion of the sticky egg mass. Field observations show that this cleft area of the hook is edematous, and histology confirms that the area is highly vascularized. We speculate that this may facilitate gas exchange and/or nutrition between the male and the egg mass, but this can only be confirmed by physiological experiments with ‘pregnant males’ in captivity. Engorgement with blood in the highly vascularised dermis of the hook may help hold the egg mass in place.

A Greenland Shark from the Wreck of the SS Central America at 2,200 Meters

Abstract The three-masted, wooden-hulled steamship Central America sank in 1857 during a hurricane 370 km east of Savannah, Georgia. During a recovery project begun in 1988, the unmanned research submersible Nemo equipped with video and still cameras filmed a 6-m-long, male Greenland shark Somniosus microcephalus at the 2,200-m-deep wreck site. The depth is 1,000 m deeper than the maximum reported depth for this species. The Savannah location is 440 km further south than the previously known North Carolina records for the Greenland shark.

Incidence of fin erosion and anomalous fishes in a polluted stream and a nearby clean stream

This study documents the incidence of fin erosion and deformed (anomalous) fishes in two adjacent midwestern streams, north-central Ohio, U.S.A. Clear Fork stream flows through agricultural and forested areas, whereas Rocky Fork stream flows through industrialized Mansfield, Ohio, where it receives industrial and municipal effluents. Four sites on each stream were sampled monthly for fishes during July, 1982 through August, 1983. Incidence of fin erosion was significantly greater (P<0.01) at polluted sites compared to unpolluted sites; incidence did not differ among unpolluted sites (P>0.05). Incidence of fin erosion in fish from polluted sites was inversely correlated with water temperature (P<0.002). Severity of fin erosion was greater in fishes collected from polluted sites.Interspecific differences in the location of fin erosion were observed. Creek chubs, white suckers, and stone-rollers had the highest incidence of external deformities. Statistical differences in the incidence of deformed fish between combined polluted sites and combined unpolluted sites were not evident (P>0.05). Nevertheless, total incidence of deformed fishes at polluted sites (0.53%) seemed to be elevated compared to total incidence at unpolluted sites (0.28%). Comparative studies between fish from streams suspected of being polluted and fish from nearby unpolluted, reference streams should be used to define effects of chronic pollution.

Comparison of fish communities in a clean-water stream and an adjacent polluted stream

Fish populations were studied in two parallel tributaries of the Mohican River, Ohio: Clear Fork, relatively undisturbed; and Rocky Fork, which receives industrial discharges and sewage effluent. Water quality in Rocky Fork was significantly worse than the control stream with respect to heavy metals (Cr, Cu, Fe, Ni, and Zn) and ammonia concentrations. Fish species richness and diversity increased downstream in Clear Fork but decreased downstream in Rocky Fork. Pollution-intolerant species were present in the headwaters of Rocky Fork and at all sites of Clear Fork. Fish community similarity of fish communities between corresponding headwater sites was significantly greater than similarity of corresponding downstream reaches, using polluted and unpolluted sites for comparison. Both headwater sites were dominated numerically by generalized invertebrate-feeding fish. At downstream sites in Clear Fork benthic insectivores became dominant in Rocky Fork, generalized invertebrate-feeding fish were present. Fish communities at polluted sites had comparatively lower variability of both trophic structure rank and relative abundance. The smaller populations of fish in these sites were dominated by a few pollution-tolerant species.

Was the Darwin/Wedgwood Dynasty Adversely Affected by Consanguinity?

Charles Darwin, who was married to his first cousin, Emma Wedgwood, was one of the first experimentalists to demonstrate the adverse effects of inbreeding and to question the consequences of consanguineous mating. He documented the phenomenon of inbreeding depression for numerous plant species, and this caused him to worry about the health of his own children, who were often ill. To determine whether Darwins fears were justified, we constructed a pedigree of the Darwin/Wedgwood dynasty from the large quantity of genealogical information published on these families. The inbreeding coefficients (F) computed from the pedigree show that Darwins children were subject to a moderate level of inbreeding (F = 0.0630), and the progeny of related families had still higher inbreeding values (e.g., F = 0.1255 for the progeny of Henry Wedgwood, Emma Wedgwoods brother). The analysis of a sample of 25 Darwin/Wedgwood families belonging to four consecutive generations shows a statistically significant positive association between child mortality (death at or before the age of 10 years) and inbreeding coefficient detected by means of nonparametric tests (&tgr; = 0.309, P = 0.040). Our findings suggest that the high childhood mortality experienced by the Darwin progeny (3 of his 10 children died at age 10 or younger) might be a result of increased homozygosity of deleterious recessive alleles produced by the consanguineous marriages within the Darwin/Wedgwood dynasty.

Gross and Histological Morphology of the Swimbladder and Lack of Accessory Respiratory Structures in Lepidogalaxias salamandroides, an Aestivating Fish from Western Australia

The swimbladder morphology of Lepidogalaxias salamandroides was investigated. This small (maximum size is 67 mm SL) freshwater fish is endemic to southwestern Australia. It apparently survives droughts by aestivating in the bottom mud. The physostomous swimbladder is poorly developed, consisting of a thin serous membrane that extends from the dorsal body wall to the gut. It does not have the tissue normally associated with a teleost swimbladder. Instead, it is composed of a double-layered membrane that consists of squamous epithelium with a thin basement layer of collagen fibers. It appears more like dorsal mesentery, and almost certainly cannot be used in aerial respiration. Comparisons were made with Australian galaxiids and an American umbrid fish all of which possess a well-developed physostomous swimbladder. The skin of L. salamandroides contains numerous goblet (mucous) cells, and the opercular chamber lacks adaptations for air breathing. We suggest four hypotheses whereby L. salamandroides can survive the desiccation of its habitat without air breathing.

Some 20th century fish discoveries

Of the approximately 1.5 million species described to date, about 48 170 (3.2%) are vertebrates. Of these 24 618 (51%) are fishes. Amazingly, 41% of fishes are found in fresh water which makes up a negligible percentage of the water on earth. The sea accounts for 97% of all water on the planet and contains 58% of the fish species, mostly from shallow, warm-coastal areas. The families Cichlidae, Cyprinidae, Characidae, Loricariidae, and Cyprinodontidae constitute about half of all the recently described new freshwater fish species named in the period 1978–1993. The Gobiidae and Serranidae are the marine families with the largest number of recently described new species. The most new freshwater teleost names came from South America (39%), Africa (32%) and Asia (17%). New fish species continue to be described at the rate of roughly 130–160 each year. An estimated 13 775 new fish names have been proposed in this century, representing about 56% of all currently known fish species. Three species are discussed in detail to represent remarkable examples of 20th century fish discoveries: the coelacanth Latimeria chalumnae, the salamanderfish Lepidogalaxias salamandroides of Western Australia, and the megamouth shark Megachasma pelagios.

Early life history of the nurseryfish, Kurtus gulliveri (Perciformes : Kurtidae), from northern Australia

Abstract Eggs and larvae of nurseryfish, Kurtus gulliveri, one of two known species of Kurtidae, are described and illustrated for the first time using material collected in two rivers of Australias Northern Territory. Nurseryfish are unique among fishes in that males carry a cluster of fertilized eggs on a bony hook projecting from their foreheads. No brooding males were captured during this study, although one partial egg cluster was found adjacent to a male caught in a gill net. Three clusters found attached to gill nets without associated males had approximately 900–1300, slightly elliptical, 2.1–2.5 mm diameter, eggs, each with multiple oil droplets and a single, relatively thick chorionic filamentous strand at opposite poles. Larvae are pelagic and hatch at approximately 5-mm body length (BL) at the flexion stage possessing a large yolk sac, forming dorsal, caudal, and anal fins, and little pigment. Notochord flexion and yolk-sac resorption are complete by 6.9 mm. Post–yolk-sac larvae resemble adults in having a hatchet-shaped body that is almost transparent in life, including a large head with relatively small eyes, preopercular spines and a prominent, inflated gas bladder. Larval length data obtained fortnightly from August to November 2001 suggests that breeding occurs during northern Australias dry season (May to November) and that larvae leave the pelagic environment at about 25 mm.