Species Introductions and Potential for Marine Pest Invasions into Tropical Marine Communities, with Special Reference to the Indo-Pacific

Introductions of marine species by hull fouling or ballast water have occurred extensively in temperate areas, often with substantial deleterious impacts. However, current information suggests that marine introductions potentially able to achieve pest species status have been fewer in tropical regions. A 1997 risk assessment examining introductions to 12 tropical ports in Queensland (Australia) concluded that far fewer marine species appeared to have been introduced, even at major bulk export ports where the number of ship visits and volume of discharged ballast water are more than at most of Australia's cooler water ports. Results from recent surveys looking for introduced species in tropical ports across northern Australia are beginning to support this conclusion, although the lack of historic baseline surveys and the poor taxonomic status of many tropical groups are preventing a precise picture. The 1997 report also concluded that, apart from pathogens and parasites of warm-water species, the potential for marine pest invasions in Queensland tropical ports appeared to be low, and not only because much of the discharged ballast water originates from temperate ports in North Asia. In contrast, recent surveys of harbors in Hawai'i have found over 110 introduced species (including 23 cryptogenic species), the majority in the estuarine embayments of Pearl Harbor and O'ahu's commercial harbors. We suggest that the biogeographically isolated and less diverse marine communities of Hawaiian ports have been more susceptible to introductions than those of tropical Australia for several reasons, including the closeness of Australia to the central Indo-Pacific "triangle" of megadiversity (Indonesia-Philippines- Papua New Guinea) and consequent high biodiversity and low endemicity, hence offering fewer niches for nonindigenous species to become established. The isolated central Pacific position of Hawai'i and its long history of receiving worldwide commercial and naval shipping (including more heavily fouled vessels than contemporary merchant ships) is another key factor, although the estuarine warm-water ports of Townsville, Brisbane, and Darwin also provided anchorages for military units during World War n. Hull fouling remains an important vector, as it is the most likely cause of the recent transfer of the highly invasive Caribbean black-striped mussel (Mytilopsis sallei) to enclosed (lock-gate) marinas in Darwin by international cruising yachts arriving via the Panama Canal. The cost of eliminating this pest (>US$1.6 million) underscores the importance of managing not just commercial shipping but also pleasure craft, fishing boats, and naval ships as vectors of exotic species to ports, harbors, and marinas in coral reef areas

The Work of the Course: validity and reliability in assessing English Literature

© 2017 National Association for the Teaching of English This article reflects on the values and practices of a revolutionary UK A level (senior secondary) course that achieved a high degree of validity and reliability in assessing the study of English literature. John Hodgson and Bill Greenwell were involved in its teaching and assessment from an early stage, and Greenwell's comments on an early draft of the article have been incorporated. The practice of literary response enshrined in the course was based on a striking application of “personal response” to literature, gave students opportunities to show capability in studying and writing a range of literary styles and genres, and engaged teachers regionally and nationally in a developed professional community of practice. It remains a touchstone of quality as well as of innovation in English curriculum and assessment

A proposal for the functional and phylogenetic significance of differences in the dentition of lampreys (Agnatha: Petromyzontiformes)

The shape and arrangement of the teeth and multicuspid laminae of the oral disc and tongue-like piston are described for parasitic lampreys representing the six holarctic genera (Petromyzonli-dae) and each of the monogeneric Southern Hemisphere families (Mordaciidae and Geotriidae). Particular attention is paid to describing the divergent dentitional characters, the location of attack and the size of the oral disc and buccal glands of the blood-feeding Petromyzon marinus and the flesh-feeding Lampetra (Lampetra) fluviatilis and Lampetra (Lampelra) ayresii. The conclusions drawn from these comparisons are used to make suggestions regarding the feeding biology of other parasitic species of lamprey for which less comprehensive data are available. Compared with P. marinus, the flesh-feeding L.fiuviatilis and L. fluviatils have fewer and smaller oral disc teeth between the circumoral and marginal teeth, a much wider and deeper supraoral. a far larger central cusp on the transverse lingual lamina (which in turn is convex rather than V-shaped) and a smaller oral disc and buccal glands. It is proposed that in the two Lampetra species, the central cusp on the transverse lingual lamina and the interaction of this lamina with the supraoral are adaptations for gouging and cutting out pieces of host tissue. By contrast, the serrated edges of the lingual laminae in P. marinus are used to create a small but deep wound through which a stream of blood is then drawn. This mode of feeding is facilitated by the ability of P. marinus to remain attached for long periods at a single location on the host and to secrete a flow of anticoagulant ‘saliva’ from its relatively large buccal glands. Since the characteristics of the feeding structures in the parasitic members of the genera lchthyomyzon and Mordacia resemble more closely those of P. marinus than L. fluviutilis and L. ayresii, they would appear to be adapted primarily for the extraction of blood. On the other hand, the reverse is true of Lampetra (Lethenleron) japoniea and Geotria auslralis, indicating that these species ingest predominantly muscle tissue. Species such as Lampetra (Entosphenus) tridentata have an intermediate type of dentition and are apparently more versatile in their feeding habits. It is concluded that: (i) blood-feeding preceded flesh-feeding in ‘modern’ lampreys; (ii) endemic freshwater parasitic species typically ingest blood; (iii) the ability to feed on flesh developed in populations which had access to estuarine and marine hosts; and (iv) pre-Tertiary forms resembling contemporary lehthyomyzon unicuspsis could have given rise independently to both of the divergent and specialized genera of Southern Hemisphere lampreys (Mordacia and Geolria)

Morphology of the exocrine pancreas of the Southern Hemisphere lamprey,Geotria australis, and changes during metamorphosis

The distribution and histology of zymogen cells and the activity of digestive enzymes have been examined in the alimentary canal of larval, metamorphosing (stages 1–7), and adult Geotria australis (Geotriidae). Comparisons of the arrangement of the larval and adult zymogen cells are made with those observed in Mordacia mordax, a representative of the other Southern Hemisphere lamprey family (Mordaciidae), and with those reported elsewhere for holarctic lampreys (Petromyzontidae). In larval G. australis, epithelial zymogen cells are mainly restricted to the prominent pair of tubular diverticula which project forward from the oesophageal/intestinal junction. By contrast, zymogen cells of adults are present in the epithelium of both the anterior intestine and the intestinal caecum, a structure located at the new and more anterior oesophageal/intestinal junction which forms during metamorphosis. Amylolytic activity was greater in the larval divrticula than in the adult caecum, whereas the reverse was true for tryptic activity. This feature presumably reflects the high dietary contribution made by detritus and algae during the filter-feeding larval phase and by host muscle tissue during the predatory adult phase. The high tryptic activity in the caecum must promote the early breakdown of host tissue and thereby facilitate the digestion of lipids in the anterior intestine where lipolytic activity is high. At the commencement of metamorphosis, digestive activity and the number of zymogen cells declines markedly. By stage 4 the intestine has rotated anticlockwise almost 360°; the two larval diverticula have disappeared; and the new exocrine caecum of the adult has started to develop from a forward proliferation of intestinal mucosal cells. While the exocrine pancreatic tissue of larval M. mordax is unique amongst lampreys in its location within a single, large diverticulum containing an extensive network of mucosal folds, that of the adult is found in the same position as in G. australis and holarctic lampreys

Growth and the average duration of larval life in the southern hemisphere lamprey, Geotria australis Gray

The average duration of larval life in the anadromous lamprey, Geotria australis (the sole representative of the Geotriidae) is estimated as 41/4 years. Compared with other lampreys, the ammocoetes of G. australis have a slow growth rate, increase in length during the year preceding metamorphosis and typically enter metamorphosis at a small mean length (<100 mm) and weight (<1.2 g)

Oral papillae of adults of the southern hemisphere lamprey Geotria australis

The morphology, cell types, and innervation of the several small papillae (x̄ = 17) and two larger papillae, which together form a ring just outside the fimbriae surrounding the suctorial disc of adult Geotria australis, have been studied using various histological stains, including silver impregnation, and scanning and transmission electron microscopy. The epithelium of all papillae consists almost entirely of mucigenic cells. The multivillous and oligovillous cells, which are found elsewhere in the lamprey epidermis, were not observed, and Merkel and polyvillous cells are rare. Free nerve endings are common, however, in the basal layers of the epidermis. Unlike the small papillae, the two large papillae contain a core of skeletal muscle and a prominent layer of dermal collagen. In the submucosa of these large papillae, the nerves form a dense, compact layer that contains many large and probably sensory axons. It is suggested that the oral disc papillae of adult G. australis are encapsulated mechanosensory structures that play a role in enabling the animal to locate and attach to a suitable point on host fishes or other surfaces

Morphology and innervation of the buccal glands of the southern hemisphere lamprey,Geotria australis

The buccal glands of adults of the Southern Hemisphere lamprey Geotria australis consist of a pair of small, bean-shaped, hollow sacs, embedded within the basilaris muscle in the region below the eyes and to either side of the piston cartilage. Each gland, which is lined by a simple columnar epithelium and surrounded by an incomplete layer of skeletal muscle, discharges its contents into the oral cavity via a long, narrow duct. In downstream migrating young adults, the epithelial cells are low columnar, intermediate in electron density, and contain dark-staining inclusions and numerous lipid-like droplets. After saltwater acclimation, the epithelial cells become taller and the numbers of dark-staining inclusions increase whereas those of lipid-like droplets decline. By the end of the marine phase, the epithelium is more folded and now also contains dark and light cells. The ultrastructure of the epithelium shows the characteristics of both apocrine and merocrine secretion. Although intra-epithelial nerve endings were not observed, axons and occasional neurons are present in the lamina propria. Since the skeletal muscle capsule is also well innervated and contains neurons, a local feed-back mechanism may regulate the release of buccal gland fluid by monitoring the luminal pressure. Contractions of the skeletal muscle capsule and movements of the basilaris muscle during feeding would presumably assist the movement of secretion along the duct. The secretion possesses anticoagulating and haemolytic properties

Physiological adaptations of the living agnathans

The modes of life and environments of the extant agnathans (cyclostomes) are discussed in relation to their adaptations to temperature, light, oxygen and salinity. As their antitropical distribution indicates, both hagfishes and lampreys are cold water groups. Since hagfishes live in deeper waters than lampreys, they are not exposed to the marked seasonal changes in temperature and light which influence major events in the lamprey life cycle. Both groups tend to be nocturnally active, either burrowing during daylight as in the case of larval lampreys (ammocoetes) and most hagfishes, or showing cryptic behaviour as in the case of adult lampreys. Olfaction plays a major part in the location of prey, presumably aided in adult lampreys by their eyes and sensitive electrosensory system. Rates of standard oxygen consumption, ventilatory frequency and heart rate of adult lampreys increase at night. Standard oxygen consumption is relatively low in ammocoetes (as it also is in hagfishes) but increases markedly during metamorphosis into the adult lamprey. Ammocoetes and hagfishes, and to a lesser extent adult lampreys, are resistant to reduced environmental oxygen tensions. Differences in the oxygen dissociation curves of ammocoetes, adult lampreys and hagfishes can be related to differences in the characteristics of their monomeric haemoglobins and their environments and modes of life. The extraordinary tolerance of the hagfish heart to hypoxia is a reflection of a robust capacity for glycolysis, an LDH isozyme geared towards anaerobic functioning and a low work output. The hagfishes, which are restricted to marine waters, are osmoconformers. The osmolality of their blood, which is almost wholly attributable to inorganic ions, is virtually identical to that of full strength sea water (c. 1000 mOsmkg−1). By contrast, the osmolality of the blood of larval and adult lampreys when in fresh water is only 205-260 mOsm kg−1, i.e. about one quarter to one fifth of those of hagfish, and these rise only to 240-270 mOsm kg−1 in the adults of anadromous lampreys in sea water. The regulation of ions by adult lampreys is achieved by mechanisms similar to those adopted by teleosts. The implications of the contrasting ionic and osmotic physiology of the two living groups of agnathans are discussed in relation to their possible environmental history and against the background of their Carboniferous fossil representatives