Academic literature on the topic 'Pristiophoridae'

A well-known characteristic of chondrichthyans (e.g. sharks, rays) is their covering of external skin denticles (placoid scales), but less well understood is the wide morphological diversity that these skin denticles can show. Some of the more unusual of these are the tooth-like structures associated with the elongate cartilaginous rostrum ‘saw’ in three chondrichthyan groups: Pristiophoridae (sawsharks; Selachii), Pristidae (sawfish; Batoidea) and the fossil Sclerorhynchoidea (Batoidea). Comparative topographic and developmental studies of the ‘saw-teeth’ were undertaken in adults and embryos of these groups, by means of three-dimensional-rendered volumes from X-ray computed tomography. This provided data on development and relative arrangement in embryos, with regenerative replacement in adults. Saw-teeth are morphologically similar on the rostra of the Pristiophoridae and the Sclerorhynchoidea, with the same replacement modes, despite the lack of a close phylogenetic relationship. In both, tooth-like structures develop under the skin of the embryos, aligned with the rostrum surface, before rotating into lateral position and then attaching through a pedicel to the rostrum cartilage. As well, saw-teeth are replaced and added to as space becomes available. By contrast, saw-teeth in Pristidae insert into sockets in the rostrum cartilage, growing continuously and are not replaced. Despite superficial similarity to oral tooth developmental organization, saw-tooth spatial initiation arrangement is associated with rostrum growth. Replacement is space-dependent and more comparable to that of dermal skin denticles. We suggest these saw-teeth represent modified dermal denticles and lack the ‘many-for-one’ replacement characteristic of elasmobranch oral dentitions.

The onchobothriid tetraphyllidean cestode genus Acanthobothrium van Beneden, 1849, parasitic in the spiral intestine of elasmobranch fishes, was investigated in the Australian region. Thirty-three species are recognised, including 27 that are new. Diagnoses compare the morphological taxonomic characters of all congeners. New species are: Acanthobothrium adlardi; A. angelae; A. arlenae; A. bartonae; A. blairi; A. brayi; A. cannoni; A. chisholmae; A. clarkeae; A. cribbi; A. edmondsi; A. gasseri; A. gibsoni; A. gloveri; A. jonesi; A. lasti; A. laurenbrownae; A. martini; A. mooreae; A. ocallaghani; A. odonoghuei; A. pichelinae; A. robertsoni; A. rohdei; A. stevensi; A. thomasae; and A. walkeri. Additional morphological data are provided for A. australe Robinson, 1965, A. pearsoni Williams, 1962, A. heterodonti Drummond, 1937 and A. urolophi Schmidt, 1973, reported previously from Australia. Acanthobothrium rhynchobatidis Subhapradha, 1955 and A. semnovesiculum Verma, 1928 are reported from Australia for the first time and are redescribed. Additional morphological details are provided for A. ijimae Yoshida, 1917 and A. grandiceps Yamaguti, 1952. Acanthobothrium wedli Robinson, 1959 is redescribed from the type host from New Zealand waters and considered a sister species of A. blairi from Tasmania. Seven new host genera for Acanthobothrium are reported: Hypnos Duméril, 1852 (Hypnidae); Pristiophorus MÜller & Henle, 1837 (Pristiophoridae); Sutorectus Whitley, 1939 (Orectolobidae); Aptychotrema Norman, 1926 and Trygonorrhina MÜller & Henle, 1838 (Rhinobatidae); Parascyllium Gill, 1862 (Parascylliidae); and Aetomylaeus Garman, 1908 (Myliobatididae). Species of Acanthobothrium are reported from the families Hypnidae, Pristiophoridae and Parascylliidae for the first time. New host species for Acanthobothrium are: Pristiophorus cirratus (Latham, 1794); Parascyllium ferrugineum McCulloch, 1911; Sutorectus tentaculatus (Peters, 1865); Aptychotrema vincentiana (Haacke, 1885); Trygonorrhina fasciata MÜller & Henle, 1841; Raja whitleyi Iredale, 1938; Raja cerva Whitley, 1939; Hypnos monopterygium (Shaw & Nodder, 1795); Dasyatis annotata Last, 1987; Urolophus cruciatus (Lacépède, 1804); Urolophus expansus McCulloch, 1916; Urolophus lobatus McKay, 1966; Urolophus paucimaculatus Dixon, 1969; Gymnura australis (Ramsay & Ogilby, 1886); Aetomylaeus nicofii (Schneider, 1801); and Myliobatis australis Macleay, 1881 (Myliobatididae). New host records for Australia include the above 16 elasmobranch species and the following three host species also known to harbour Acanthobothrium in other geographic localities: Rhynchobatis djiddensis (Forsskål, 1775) (Rhynchobatidae); Himantura uarnak (Forsskål, 1775); and Pastinachus sephen (Forsskål, 1775) (Dasyatidae). Four additional records for hosts previously reported for Acanthobothrium from Australian waters are Squalus megalops (Macleay, 1881) (Squalidae), Heterodontus portusjacksoni (Meyer, 1793) (Heterodontidae), Orectolobus maculatus (Bonnaterre, 1788) (Orectolobidae) and Trygonoptera ‘testacea’ MÜller & Henle, 1841 (Urolophidae). An emended diagnosis of the genus, key to Australian species, host-parasite checklist, phylogenetic analysis of the Australian species and an updated world list of all species of Acanthobothrium are provided.

The squaliform sharks represent one of the most speciose shark clades. Many adult squaliforms have blade-like teeth, either on both jaws or restricted to the lower jaw, forming a continuous, serrated blade along the jaw margin. These teeth are replaced as a single unit and successor teeth lack the alternate arrangement present in other elasmobranchs. Micro-CT scans of embryos of squaliforms and a related outgroup (Pristiophoridae) revealed that the squaliform dentition pattern represents a highly modified version of tooth replacement seen in other clades. Teeth of Squalus embryos are arranged in an alternate pattern, with successive tooth rows containing additional teeth added proximally. Asynchronous timing of tooth production along the jaw and tooth loss prior to birth cause teeth to align in oblique sets containing teeth from subsequent rows; these become parallel to the jaw margin during ontogeny, so that adult Squalus has functional tooth rows comprising obliquely stacked teeth of consecutive developmental rows. In more strongly heterodont squaliforms, initial embryonic lower teeth develop into the oblique functional sets seen in adult Squalus , with no requirement to form, and subsequently lose, teeth arranged in an initial alternate pattern.

Abstract Background Understanding movement patterns of a species is vital for optimising conservation and management strategies. This information is often difficult to obtain in the marine realm for species that regularly occur at depth. The common sawshark (Pristiophorus cirratus) is a small, benthic-associated elasmobranch species that occurs from shallow to deep-sea environments. No information is known regarding its movement ecology. Despite this, P. cirrata are still regularly landed as nontargeted catch in the south eastern Australian fisheries. Three individuals were tagged with pop-up satellite archival tags (PSATs) off the coast of Tasmania, Australia, to test the viability of satellite tagging on these small elasmobranchs and to provide novel insights into their movement. Results Tags were successfully retained for up to 3 weeks, but movement differed on an individual basis. All three individuals displayed a post-release response to tagging and limited vertical movement was observed for up to 5–7 days post-tagging. Temperature loggers on the tags suggest the animals were not stationary but moved horizontally during this time, presumably in a flight response. After this response, continuous wavelet transformations identified diel vertical movements in one individual at cyclical intervals of 12- and 24-hour periods; however, two others did not display as clear a pattern. Temperature was not significantly correlated with movement in the study period. The deepest depths recorded during the deployments for all individuals was approximately 120 m and the shallowest was 5 m. Conclusions This study demonstrates that sawsharks can be successfully tagged by pop-up satellite archival tags. The data presented here show that sawsharks regularly move both horizontally and vertically in the water column, which was an unexpected result for this small benthic species. Additional research aimed at resolving the trophic ecology will help identify the drivers of these movements and help to better define the ecological, behavioural and physiological roles of these sharks in their ecosystems. These data describe a substantial ability to move in the common sawshark that was previously unknown and provides the first account of movement ecology on the family of sawsharks: Pristiophoridae.