Richard Evans-Gowing

Energy-dispersive X-ray analysis of the extracellular cadmium sulfide crystallites of Klebsiella aerogenes.

Klebsiella aerogenes forms electron-dense partieles on the cell surface in response to the presence of cadmium ions in the growth medium. These particles ranged from 20 to 200 nm in size, and quantitative energy dispersive X-ray analysis established that they comprise cadmium and sulfur in a 1:1 ratio. This observation leads to the conclusion that the particles are cadmium sulfide crystallites. A combination of atomic absorption spectroscopy, inductively coupled plasma mass spectrometry, and acid-labile sulfide analysis revealed that the total intracellular and bound extracellular cadmium:sulfur ratio is also 1:1, which suggests that the bulk of the cadmium is fixed as extracellular cadmium sulfide. The tolerance of K. acrogenes to cadmium ions and the formation of the cadmium sulfide crystallites were dependent on the buffer composition of the growth medium. The addition of cadmium ions to phosphate-buffered media resulted in cadmium phosphate precipitates that remove the potentially toxic cadmium ions from the growth medium. Electrondense particles formed on the surfaces of bacteria grown under these conditions were a combination of cadmium sulfide and cadmium phosphates. The specific bacterial growth rate in the exponential phase of batch cultures was not affected by up to 2mM cadmium in Tricine-buffered medium, but formation of cadmium sulfide crystallites was maximal during the stationary phase of batch culture. Cadmium tolerance was much lower (10 to 150 μM) in growth media buffered with Tris, Bistris propane, Bes, Tes, or Hepes. These results illustrate the importance of considering medium composition when comparing levels of bacterial cadmium tolerance.

Attachment and detachment of the anterior adhesive pads of the monogenean (platyhelminth) parasite Entobdella soleae from the skin of the common sole (Solea solea).

By preserving specimens of the monogenean (platyhelminth) parasite Entobdella soleae at intervals during locomotion and processing these parasites for transmission and scanning electron microscopy, evidence was found to suggest that adhesion of the anterior pads to the skin of the host, the sole Solea solea, is brought about by interaction between the two kinds of glandular secretion supplied to the pads. It is suggested that the specialised pad tegument through which the gland cell ducts pass may be instrumental in severing the adhesive bond by dissolving the cement immediately adjacent to this tegumental surface.

BACTERIAL PHOTOPROTECTION THROUGH EXTRACELLULAR CADMIUM SULFIDE CRYSTALLITES

Ultraviolet light and the heavy metal, cadmium, both have toxic effects on many microorganisms. In this communication we describe a method by which the bacterium Klebsiella aerogenes surmounts both problems using one biological process: the synthesis of cadmium sulfide (CdS) crystallites. These semiconductor particles absorb radiation in the UV spectral region and therefore, when K. aerogenes produces extracellular CdS material in response to environments containing cadmium ions, a photoprotective layer is formed. The effect of UVA radiation on cultures of Klebsiella aerogenes was monitored using electron microscopy, energy‐dispersive X‐ray analysis and electronic spectroscopy. The results show that at wavelengths 320 nm Λ 400 nm, a photoprotection period of between 4 and 6 h is induced, which eventually fails due to photodegradation of the semiconductor layer to metallic cadmium and elemental sulfur.

Use of cement for attachment in Neocalceostomoides brisbanensis, a calceostomatine monogenean from the gill chamber of the blue catfish, Arius graeffei

The thin, weakly muscular, disc-shaped haptor of the calceostomatine monogenean Neocalceostomoides brisbanensis is attached to surfaces in the gill chamber of its catfish host by cement. It is unlikely that any suction is generated (there are no muscular loculi) and the hooks are reduced in size. Two distinctive secretions are associated with the haptor: a finely granular secretion from glandular tissue within the haptor and anterior to it, which enters the dorsal haptor tegument near the periphery of the disc and spreads throughout the ventral haptor tegument; a coarser secretion produced in the peduncle and posterior region of the body, which finds its way to gland openings near the hamuli via centrally situated large and small haptor reservoirs. It seems most likely that the tegumentary secretion is the cement, but other possibilities are discussed. It is suggested that the increasing importance of cement for haptor attachment in calceostomatines has led to the development of a weakly muscular, foliaceous haptor and a progressive reduction of the hooks.

Effect of total lens epithelial cell destruction on intraocular lens fixation in the human capsular bag

Purpose To evaluate the effect of complete destruction of lens epithelial cells (LECs) in the capsular bag on intraocular lens (IOL) stability. Setting School of Biological Sciences, University of East Anglia, Norwich, United Kingdom. Design Comparative evaluation. Methods An in vitro organ culture model using the bag–zonule–ciliary body complex isolated from fellow human donor eyes was prepared. A capsulorhexis and fiber extraction were performed, and an Acrysof IOL was implanted. Preparations were secured by pinning the ciliary body to a silicone ring and maintaining it in 6 mL Eagle minimum essential medium supplemented with 5% v/v fetal calf serum and 10 ng/mL transforming growth factor‐&bgr;2 for 3 weeks or more. One bag of each pair was treated with 1 &mgr;M thapsigargin to destroy all LECs. Observations of LEC growth were captured by phase‐contrast microscopy, IOL stability by video microscopy, and endpoint analysis through scanning electron microscopy and immunocytochemistry. Results The LECs in control capsular bags migrated centrally, closing the bag and fixating the IOL between the anterior and posterior capsules, as seen clinically. These events were not observed in the thapsigargin‐treated group. After a period of controlled orbital movement, the IOL in the control group stabilized quicker than in the treated bags. There was no IOL rotation in the bag; however, the IOLs in the treated group rocked with axial movement. Conclusions The LECs appeared to aid stabilization of current IOL designs in the capsular bag. The results have clinical implications for IOL design and for strategies to prevent posterior capsule opacification. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

A new genus and new species of microbothriid monogenean (Platyhelminthes) with a functionally enigmatic reproductive system, parasitic on the skin and mouth lining of the largetooth sawfish, Pristis microdon, in Australia

Dermopristis paradoxus gen. et sp. nov., a microbothriid monogenean parasite from the skin and mouth lining of the largetooth sawfish, Pristis microdon (Elasmobranchii, Pristidae) in Australia, is described. The parasite has 2 juxtaposed testes and differs from other microbothriids in possessing a unique and unusual terminal male reproductive tract comprising a proximal and a distal tube, the latter with a conspicuous opening on the ventral surface and lacking a recognisable male copulatory organ. The smalltooth sawfish, P. pectinata, also has a skin-parasitic microbothriid, Dermophthirioides pristidis Cheung et Nigrelli, 1983, but this parasite species has a prominent copulatory papilla. Dermopristis paradoxus also has parallel ridges with broad tops running in a roughly transverse direction across the ventral surface of the body. The ventral ridges are prominent from the level of the pharynx to the posterior region of the body. The function of the ridges is unknown. Reproductive biology, attachment and feeding in D. paradoxus are discussed. In the absence of unmounted parasite specimens for sectioning, a mounted specimen of D. paradoxus was released from the slide and successfully processed to provide serial, stained, resin sections. This useful technique is recommended to provide anatomical information in situations where only specimens on slides are available for study.

Spermatophores in Dermopristis cairae Whittington et Kearn, 2011 (Monogenea, Microbothriidae)

Spermatophores are described in the microbothriid monogenean Dermopristis cairae from the giant shovel-nosed ray, Glaucostegus typus (Elasmobranchii, Rhinobatidae). Each spermatophore consists of a fusiform capsule containing sperm and a hollow stalk. The proximal ends of the stalks of fully formed spermatophores were open and located in a recess on the ventral surface close to, but not inside, the vagina and the male reproductive opening. Three adult parasites carried spermatophores attached externally to the ventral surface. One individual carried 3 spermatophores and 2 others a single spermatophore. In addition, in 2 adults, short lengths of what appeared to be stalk remnants were observed attached near the reproductive openings. With regard to spermatophore exchange, the evidence in support of the following 2 possibilities is discussed. (1) Adult specimens of D. cairae carrying fully formed spermatophores ventrally are recipients not donors, having received their spermatophores singly during mating events. (2) Spermatophore carrying adults are donors, their spermatophores being freshly made and on offer to a potential mate. The evidence points to the first of these alternatives as the most likely but this is not conclusive and requires observations on mating between living parasites.

Swallowing of sea water and its role in egestion in the monogenean Entobdella Soleae, a skin parasite of the common sole (Solea solea), with observations on other monogeneans and on a freshwater temnocephalan

Swallowing sea water plays an important part in the process of egestion in several, epidermis-feeding, monogenean parasites from the skin and gills of fishes. In Entobdella soleae, from the skin of the common sole, Solea solea, the retracted pharynx acts as a peristaltic pump, forcing sea water into the branched and blind-ending intestine, inflating the gut diverticula and providing a suspension medium for debris from the digestive process. This secondary role for the pharynx has not previously been recorded. Inflation of the gut extends the muscles lying beneath the gastrodermis, and possibly neighbouring parenchymal muscles, permitting them to contract. This expels the sea water and flushes out the debris from the gut via the mouth. In E. soleae, the myofibrils associated with the gastrodermis appear to have narrower thick filaments than nearby parenchymal myofibrils. A similar series of swallowing movements, involving consecutive contractions of the pharynx followed by an egestion event, has been obser...

A new species of Acanthocotyle Monticelli, 1888 (Platyhelminthes: Monogenea: Acanthocotylidae) from the ventral skin of the banded stingaree, Urolophus cruciatus (Lacépède, 1804), from Tasmania, Australia.

Acanthocotyle urolophi sp. nov. is described from the skin of the banded stingaree, Urolophus cruciatus (Lacepede, 1804). This is the first acanthocotylid to be described from Australian waters. Acanthocotyle urolophi sp. nov. is distinguished from other species of Acanthocotyle by a combination of the number of vitelline follicles 38 (33–46) and the number of rows 35 (32–37) of sclerites on the pseudohaptor. In addition, Acanthocotyle urolophi sp. nov. has no germarial appendix and no uterine “arm”. A uterine receptaculum seminis was not identified in whole mounts. There is no penis papilla and no penis sclerite associated with the male reproductive opening. A brief description of the larva is provided. The diagnosis of the Acanthocotylidae Price, 1936 is amended and we review the Allacanthocotylinae Yamaguti, 1963, Lophocotylinae Yamaguti, 1963 and Pseudacanthocotylinae Yamaguti, 1963. We deem that these subfamilies are invalid and that the family now comprises only the subfamily Acanthocotylinae and the genus Acanthocotyle. The validity of species previously assigned to the Acanthocotylidae (sensu Yamaguti, 1963) is discussed and a key to what we consider to be the valid species in the family is also provided.

A new species of Entobdella Blainville in Lamarck, 1818 (Monogenea: Capsalidae: Entobdellinae) from the Greenland halibut, Reinhardtius hippoglossoides.

Abstract A previously undescribed species of Entobdella is reported from the skin of the Greenland halibut, Reinhardtius hippoglossoides (Pleuronectiformes, Pleuronectidae). Entobdella whittingtoni sp. nov. differs from other species of Entobdella, including skin parasites of the related pleuronectids Hippoglossus hippoglossus (Atlantic halibut) and H. stenolepis (Pacific halibut), in lacking papillae on the ventral surface of the haptor. Other characteristics of E. whittingtoni are as follows: the absence of vitelline follicles lateral to the pharynx thereby exposing gut caeca in this region of whole mounts; the presence of a circular feature of unknown function, resembling a rosette in sections, attached to the wall of the internal male accessory reservoir; the lack of eyes. Papillae are also absent from the ventral surface of the haptor of the gill-parasitic entobdelline Branchobdella pugetensis, a gill parasite of the pleuronectid Atheresthes stomias. This raises the question as to whether this gill parasite has evolved from a skin-parasitic ancestor similar to E. whittingtoni. An answer to this question requires a more detailed study of the male reproductive apparatus of B. pugetensis and the use of molecular techniques to explore the relationship between B. pugetensis and E. whittingtoni