Showing papers in "Veliger in 2000"

Sex change, reproduction, and development of Crepidula adunca and Crepidula lingulata (Gastropoda : Calyptraeidae)

Abstract: This paper describes the reproduction and development of Crepidula adunca and Crepidula lingulata from San Juan Island, Washington, USA. Both species were sampled every 2 months to determine the reproductive season and to measure the relationship between adult size and sex, capsule number, egg number, and brood weight. Development of each species is described briefly based on the broods obtained from these samples. As expected for protandrous hermaphrodites, females were larger than males, in both species. Crepidula adunca is an intertidal species that is usually found in stacks of two animals. This species reproduces all year, and embryos develop directly into crawl-away juveniles. Crepidula lingulata is a solitary subtidal species that produces planktotrophic veliger larvae in the summer. These veligers have distinctive pigmentation on the velum and settle 4 weeks after hatching at a shell length of 750 |im. Experiments show that associations with conspecifics do influence sex change in C. lingulata: males kept with females were less likely to change sex than those kept alone or with other males.

Development and Anatomy of Nitidiscala tincta (Carpenter, 1865) (Gastropoda : Epitoniidae)

Abstract: The epitoniids (Gastropoda: Ptenoglossa) are one group for which there are no current well-supported hypotheses of relationships. Herein I describe the development and adult anatomy of an epitoniid, Nitidiscala tincta, and discuss intra-familial variation in characters used for higher level systematics. Female N. tincta lay 75 u,m eggs in clusters in sand-covered capsules connected together along a mucus strand. The first two cleavages are synchronous, appear equal, and produce a polar lobe. Gastrulation is by epiboly and produces a trochophorelike stage with embryonic kidneys. At hatching the larvae are 125 u,m long and have a small velum, heart, eyes, and a well-developed, black pigmented mantle organ. The shell is right-handed and slightly hydrophobia The mantle cavity contains a gill with triangular lamellae, purple hypobranchial gland, and a triple-ridged osphradium. The acrembolic probosis ends in a robust pair or jaws slightly anterior to the split odontophore, a ptenoglossan radula, and two pairs of salivary glands. The presence of both caenogastropod and heterobranch developmental synapomorphies suggests that ideas about the evolution of development among gastropods may need to be reevaluated.

A new species of hydrobiid snail of the genus Pyrgulopsis from northwestern Nevada

Abstract: Pyrgulopsis bruesi new species, from northwest Nevada, differs from closely similar P. augustae on the basis of its higher-spired shell, larger penial filament, and more ventrally positioned seminal receptacle. This species is endemic to a thermal spring area in a small basin which was inundated by pluvial Lake Lahontan.