Two new European species of the marine genus Tubificoides (Annelida: Clitellata: Naididae) with notes on the morphology of T. pseudogaster (Dahl, 1960)

Two new species of Tubificoides (subfamily Tubificinae), T. charlotteae n. sp. and T. mackiei n. sp., are described based on morphological analyses. Both species were flagged as potentially cryptic in a previous investigation, based on both mitochondrial and nuclear sequence data. Tubificoides charlotteae n. sp., known only from an intertidal site in southern Spain, is characterized by the lack of cuticular papillation, the possession of several needle-like hair chaetae in dorsal bundles, a cone-shaped penis sheath, and a rather large, muscular penial sac. It strongly resembles the north-west European, largely sublittoral species T. amplivasatus, but differs from this species in terms of body size, width of vas deferens, and the shape and size of both the ejaculatory duct and penial sac. Tubificoides mackiei n. sp., collected from the southeast coast of Norway and the west coast of Sweden, is characterized by the lack of cuticular papillae and hair chaetae, and the possession of a rather long penis sheath with a wide terminal opening. It shares several morphological features with the sympatric species Tubificoides pseudogaster, but is distinguished from the latter by the detailed morphology and length of the penis sheaths, the width of the atrium, and the lower maximal number of bifid chaetae in dorsal preclitellar bundles. The utility of an integrative comparative approach, combining molecules and morphology, for the identification and delineation of new taxa within Tubificoides is briefly discussed.

Larval digenean preferences in two sympatric snail species at differing tidal levels off the Atlantic coast of Patagonia

Larval stages of the trematodesMaritrema madrynenseand Hemiuroidea fam. gen. et sp. differentially parasitizedSiphonaria lessoniiandS. lateralis, two sympatric pulmonate snail species on the rocky intertidal shore at Puerto Deseado, south-western Atlantic coast of Patagonia, Argentina. Snail specimens were collected at two sampling sites with contrasting physical–chemical characteristics. One site, in the upper intertidal, was exposed to sewage from fish-processing plants, greater hydrodynamic forcing and desiccation, a wider temperature range, longer exposure to ultraviolet radiation and higher abundance of birds. The second site, in the lower intertidal, was generally characterized by less stressful environmental conditions. At both sites,S. lateralisshowed a markedly higher density thanS. lessonii(55.13 vs. 5.87 snails/m2, respectively). Despite this, the prevalence of both digeneans was higher inS. lessonii(17.37% and 3.52% forM. madrynenseand Hemiuroidea, respectively) than inS. lateralis(0.09% and 0% forM. madrynenseand Hemiuroidea, respectively). This study demonstrates high parasite specificity for the host. Low densities ofS. lessoniiare attributed to castration of parasitized hosts and reduction of their physiological condition. The prevalence and intensity of infection of both digenean parasites were higher at the more stressful, upper intertidal site, thus suggesting that a higher abundance of birds and exposure to sewage pollution may promote the transmission of trematodes.

Temporal variation in prevalence and cercarial development of Echinostephilla patellae (Digenea, Philophthalmidae) in the intertidal gastropod Patella vulgata

The trematode Echinostephilla patellae is an abundant but scarcely investigated parasite found in coastal ecosystems of the British Isles. Redial and cercarial stages of the digenean occur in the digestive gland and gonads of common limpets Patella vulgata. Here, we present data on the temporal distribution of E. patellae infections in P. vulgata from an intertidal site on the Irish south coast as well as on the intramolluscan development of the cercariae over a period of one year. Prevalence of infection showed temporal variation with a distinct peak in September, possibly related to an increase in the abundance of bird final hosts coinciding with comparatively high temperatures at the study locality during the summer months. Maturation of cercarial stages was strongly correlated with water temperature. Whilst fully developed cercariae were present in the rediae from May to November, large numbers of infective stages occurred in the limpets’ mantle blood vessels — where they accumulate prior to release — between June and September, suggesting this period of time to be the main transmission window for E. patellae cercariae.

Ecology of Pinna bicolor gmelin (Mollusca : Bivalvia) in Gulf St Vincent, South Australia: density, reproductive cycle, recruitment, growth and mortality at three sites

Random samples of P. bicolor were taken from one intertidal and two subtidal sites over 3 years and tagged individuals of P. bicolor were followed for up to 6 years at two other sites. P. bicolor is dioecious. Mature gonads were observed in early summer (November-January) with a peak in December each year. The pattern appeared to differ little between years or sites but the period of maximum gonad activity was shorter at the intertidal site. Growth was slower at the intertidal site and animals reached a smaller maximum size there than at the subtidal sites, which differed slightly. It is concluded that P. bicolor can reach reproductive size (15 cm shell length) in little more than a year but, at least subtidally, have a low mortality rate (less than 0.1 year-1) thereafter. Recruitment is variable and it is argued that at some sites superficially 'stable' densities of P. bicolor are maintained by occasional strong recruitments, which are 'stored' in the population because of low adult mortality. The implications of this for management and for the use of P. bicolor as a biological monitor are discussed.

Growth and reproduction of the red alga Rhodomela larix

Components of the growth and life history of the red alga Rhodomela larix (Turner) C. Agardh were studied during an 18-month period at a high intertidal and a low intertidal site on the central Oregon coast. Growth was measured by following (i) individually marked upright axes, (ii) clumps of axes thought to represent individual plants, and (iii) large patches of R. larix. Variation in size and growth was common among axes, and portions of some axes were clearly perennial. Plants grew most rapidly in the spring and summer (up to 1.2 mm/day) with a large amount of variation occurring between and within zones and among seasons. Overall, plants at the higher site were shorter and had fewer branches during most of the year than plants at the lower site. Gametophytes were more common in the higher site, while tetrasporophytes predominated at both sites. Reproductive axes were present throughout the observation period, although little recruitment of sexual propagules was seen, implying that populations may be maintained by vegetative perennation of individual plants.