Showing papers in "Veliger in 2006"

Two introduced pest slugs: Tandonia budapestensis new to the Americas, and Deroceras panormitanum new to the Eastern USA

Abstract: A study about the natural history of the slug Rathouisia leonina Heude, 1882 was carried out both in the field and in the laboratory. The external morphology, distribution, habitat, food range and preference, predatory behavior and reproduction were studied. Adult slugs were up to 1.02 g in weight and 35 mm long when kept inactive. They always preyed upon eggs, juveniles and adults of snails, rather than those of slugs of other families. Smaller individuals (0.18—0.55 g) showed preferences for feeding on bradybaenid snails Trichobradybaena siibmissa with larger diameter and larger apertural opening, while larger slugs (0.63—1.02 g) showed no such preference. The slugs also showed a preference for the eggs of Acusta ravida over those of Bradybaena similaris and T. siibmissa. The length of feeding scars on snail eggs made by infant slugs measured 0.24-0.47 mm, and those made by adult slugs 0.41-0.62 mm. After copulation adult slugs laid 10—49 eggs per clutch. The number of eggs was not correlated with their parent slugs' weight but the diameter of the eggs (1.88-3.09 mm) showed a positive correlation to the parent slugs' weight. It took 25-29 days for the eggs to hatch at 17.5-23.5°C, 86% ± 5% RH in the laboratory.

Habitat usage by the page springsnail, pyrgulopsis morrisoni (Gastropoda

Abstract: We measured habitat variables and the occurrence and density of the Page springsnail, Pyrgulopsis morrisoni (Hershler & Landye, 1988), in the Oak Creek Springs Complex of central Arizona during the spring and summer of 2001. Occurrence and high density of P. morrisoni were associated with gravel and pebble substrates, and absence and low density with silt and sand. Occurrence and high density were also associated with lower levels of dissolved oxygen and low conductivity. Occurrence was further associated with shallower water depths. Water velocity may play an important role in maintaining springsnail habitat by influencing substrate composition and other physico-chemical variables. Our study constitutes the first empirical effort to define P. morrisoni habitat and should be useful in assessing the relative suitability of spring environments for the species. The best approach to manage springsnail habitat is to maintain springs in their natural state.

Cretaceous Acila (Truncacila) (Bivalvia : Nuculidae) from the Pacific slope of North America

Abstract: The Cretaceous record of the nuculid bivalve Acila (Truncacila) Grant & Gale, 1931, is established for the first time in the region extending from the Queen Charlotte Islands, British Columbia, southward to Baja California, Mexico. Its record is represented by three previously named species, three new species, and one possible new species. The previously named species are reviewed and refined. The cumulative geologic range of all these species is Early Cretaceous (late Aptian) to Late Cretaceous (early late Maastrichtian), with the highest diversity (four species) occurring in the latest Campanian to early Maastrichtian. Acila (T.) allisoni, sp. nov., known only from upper Aptian strata of northern Baja California, Mexico, is one of the earliest confirmed records of this subgenus. \"Aptian\" reports of Truncacila in Tunisia, Morocco, and possibly eastern Venzeula need confirmation. Specimens of the study area Acila are most abundant in sandy, shallow-marine deposits that accumulated under warmwater conditions. Possible deeper water occurrences need critical evaluation.

Growth and activity patterns in a backyard population of the banana slug, Ariolimax columbianus

Abstract: The study was carried out on and around a redwood deck in a suburban area of central California, using bait-plates to attract nearby banana slugs. Over a period of two years 150 individual Ariolimax columbianus weighing between 0.4 and 75.4 g were identified using photographs of the patterns on their maculated bodies. In many subsequent sightings of these slugs, we recorded their weight, their appearance, the time and location, and their activity. In both 1999 and 2000, slugs weighing less than a gram appeared in January and, feeding both day and night, gained weight at an average rate of 0.11 g/day. The weight of individual slugs fluctuates widely, and only below 20 g does weight correlate with the age of a slug. Maximal weights are reached in summer. In the following autumn months, slugs may lose up to 50% of their maximal weight. Within one day, feeding slugs showed an average weight increase of 10.12%. Slugs over 20 grams appeared at the bait-plates during early morning hours and towards dusk; they did not feed during the night. Slugs frequented specific sites, usually appearing at the same or nearby bait-plates, or repeatedly selecting the same night roosting site, and little long distance movement was seen. Slugs recorded on the deck did not cross the grass to bait-plates 4.8 m away. They displayed a cyclic behavior, appearing at a bait-plate for one or two days followed by an absence of an equal or longer period before reappearing. Adult slugs did not feed at bait-trays with many young slugs. On a July day, 46 individual slugs weighing a total of 750 g were recorded in an area of approximately 60 square meters. Our evidence indicates that these slugs do not live much longer than two years. The number of slugs on the deck was highest with temperatures between 8

New Late Cretaceous mytilid and tellinoidean bivalves from California

Abstract: One new subfamily, one new genus, and two new species of Late Cretaceous warm-water, shallow-marine bivalves from California are described and named. The mytilid Xenomytilus fons, gen. et sp. nov., from middle to uppermost Maastrichtian strata in central and southern California, represents the type genus of Xenomytilinae, subfamily nov. This new subfamily is comprised of Lycettia Cox, 1937, and Xenomytilus. Lycettia is an Old World Tethyan bivalve that ranges from the late Early Jurassic (Toarcian) to the Late Cretaceous (Campanian). Xenomytilus is known only from California, but future studies might reveal it to be more widespread. Xenomytilus fons is from Maastrichtian strata in central and southern California and is locally moderately common. It inhabited siliciclastic nearshore, warm waters and most likely had an epifaunal mode of life, with attachment by byssus to hard substrate. Specimens were commonly transported by turbidity currents into deeper waters. The other new species is the tellinoidean Icanotia californica, sp. nov., from the upper Turonian upper part of the Baker Canyon Member and lower part of the Holz Shale Member of the Ladd Formation in the Santa Ana Mountains, Orange County, southern California. It lived in inner shelf waters and was infaunal in silts and very fine sands. Icanotia is a relatively rare, warm temperate and Tethyan, Cretaceous (Valanginian to Maastrichtian) bivalve known predominantly from Europe. Rare dispersals of Icanotia into the New World were, most likely, by westward-flowing equatorial currents that coincided with high stands of sea level. Its occurrence in southern California is its only record on the Pacific slope of North America.

Additions and Refinements to Aptian to Santonian (Cretaceous) Turritella (Mollusca: Gastropoda) from the Pacific Slope of North America

Abstract: This paper presents the first detailed paleontologic study of pre-Campanian (pre-late Late Cretaceous) Turritella sensu lato from the Pacific slope of North America, mainly from outcrops in California. Seven species, two of which are new, have a cumulative chronologic range of late Aptian to Santonian, an interval of 30 million years that coincides with much of Chron C34, the long-normal interval. One of the new species, Turritella xylina, is only the second known Cenomanian Turritella from the study area, and the other new species, Turritella encina, is the first Santonian Turritella reported from the study area. The previously named species are redescribed and are refined in their stratigraphic distributions. They are: Turritella seriatimgranulata Roemer, 1849, of late Aptian age; Turritella infralineata Gabb, 1864, of late early Albian age; Turritella petersoni Merriam, 1941, Cenomanian to early Turonian age; Turritella hearni Merriam, 1941, of Turonian and probably Coniacian age; and Turritella iota Popenoe, 1937, of late Turonian age. Turritella seriatimgranulata is also known from Albian strata in Sonora, Mexico, New Mexico, and Texas.