Morphological and molecular characterization of two new species ofAndracantha(Acanthocephala: Polymorphidae) from New Zealand shags (Phalacrocoracidae) and penguins (Spheniscidae) with a key to the species

Two new species ofAndracantha(Polymorphidae) are described from the intestine of the shagsLeucocarbo chalconotus(Gray) andPhalacrocorax punctatus(Sparrman), and the penguinEudyptula minor(Forster) from southern South Island, New Zealand.Andracantha leucocarboin. sp. is distinguished from its congeners by having no genital or ventral trunk spines, but possessing a scattering of small spines between the anterior fields of spines. This is the first record of a species ofAndracanthafrom a penguin. Circumbursal papillae are illustrated in a scanning electron micrograph for the first time in the polymorphids.Andracantha sigman. sp. is distinguished by the sigmoid shape of its largest proboscis hook, hook VIII, and having the ventral field separated from the posterior disc field by an aspinous gap. A Maximum Likelihood tree fromcox1 and large ribosomal subunit (LSU) data showsA. leucocarboin. sp. to be more closely related toA. gravidathanA. sigman. sp. and the genusAndracanthaas sister toCorynosomaspp. Genetic distances between species ofAndracanthaare comparatively large. A key to the species ofAndracanthais provided.

Polymorphism and specificity of positioning of contractile vacuole pores in a ciliate, Chilodonella steini

The unicellular ciliate Chilodonella steini has a well-defined flat and ciliated ventral field. During divisional morphogenesis two sets of new contractile vacuole pores (CVPs) are formed on this field. During final pattern formation some of these CVP primordia and the old parental set of CVPs are completely resorbed. Primary pattern of distribution of the CVP primoidia and final pattern of distribution of the matured CVPs manifest an intraclonal polymorphism. From analysis of this polymorphism some features of mechanism(s) of CVP pattern determination are deduced: 1. There is a strict, short-distance negative control of appearance of CVP primordia at sites of oral morphogenesis and around the ventral field. 2. Certain indeterminacy of large-scale patterning of CVP primordia is observed over the area competent to yield CVP formation. However, within this area three longitudinal sectors with a high probability of occurrence of CVP primordia are alternated with sectors nearly deprived of their occurrence. 3. Positive control of probability of occurrence and of specificity of location is found for certain CVP primordia. An interaction of mechanism of positioning on cellular longitudes and latitudes is proposed to account for these facts. 4. The resorption of supernumerary CVP primordia does not alter the character of the global map of distribution of CVP primordia achieved during primary pattern formation. The primordia located at some latitudes persist, whereas others are resorbed at random. It is suggested that all CVP primordia which do not mature at the time of stabilization of divisional morphogenesis are resorbed. Thus the global map of CVPs distribution would result from the sum of the individual determinations of the fates of each CVP primordium, superimposed on an initial spatially non-uniform distribution of CVP primordia.

Reflectivity of the Chorioidal Tapeta of Selachians

The reflecting layer or chorioidal tapetum in the eye of many selachians was examined to determine, especially, whether it is a set feature or whether it can be occluded.Many selachians have a tapetum under the entire fundus of the eye. It consists of highly reflecting cells, towards the outer ends of which there is a layer of melanophores. In active pelagic sharks of the neritic zone (e.g. Squalus, Mustelus), the melanophores send out pigment over the reflecting cells so as to conceal them when the fish is illuminated; the pigment retreats in darkness. In benthic species of the neritic zone, notably Scyliorhinus, the fundus has a black ventral area; a tapetum occurs elsewhere and is not occlusible. The eyes of rays have a black ventral field, and pigment migration over the tapetum is slight. The tapetum is not occlusible in deep-sea squaloids and a chimaerid Hydrolagus affinis.Reflectivity of the dark-adapted tapetum of Squalus acanthias amounts to about 85%. Full expansion of pigment in the light and retreat in darkness occupy about 2 hr in this fish.Pieces of tapeta, freed of retinae, were mounted in Ringer solution, observed, and photographed by oblique illumination from above. The tapetal pigment migrates inwards over the reflecting plates in such preparations of tapeta from fishes that have occlusible tapeta.The suggestion is offered that the tapetum is concealed, either by closure of the pupil or by migration of pigment, so as to avoid displaying eye-shine. Deep-sea squaloids, living in dimly lit environments, do neither.

The Tapetum in Scyliorhinus Canicula

Tapeta were examined of light- and dark-adapted dogfish. Scyliorhinus canicula. The tapetum in the eye of this fish is fixed; pigment processes in the tapetum do not move when a fish is changed from dark to light and vice versa. A black ventral field and a bright dorsal fundus are always present.

Memoirs: On Benhamia cœcifera, n. sp., from the Gold Coast

Benhamia cœcifera is, then, characterised (1) by the number and arrangement of the peculiar copulatory pits on the ventral field; (2) by the possession of a number of peculiar finger-shaped cæca arising from the intestine; (3) by the form of the foldings of the wall of the calciferous glands, and possibly (4) by the termination of the dorsal vessel in Segment VIII ; (5) by the extent of the clitellum ; (6) by the position of the first dorsal pore between Segments iv and v.