Crangonyx richmondensis

Ellis, 1941

Ellis Bog Crangonyctid

A small freshwater amphipod crustacean to North America. The exhibits an with distinct seasonal breeding patterns. are restricted to specific freshwater with particular substrate and vegetation characteristics. Two have been described: C. r. richmondensis and C. r. laurentianus, with the latter studied in detail in Algonquin Park, Ontario.

Pronunciation

How to pronounce Crangonyx richmondensis: /kræŋˈɡoʊnɪks rɪtʃməndˈɛnsɪs/

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Identification

Distinguished from other Crangonyx by subtle morphological features; differentiation requires examination of specific body proportions and setation patterns. The subspecies C. r. laurentianus was originally described based on characteristics of the gnathopods and uropods.

Habitat

Small acid lakes of the Precambrian Shield; restricted to shallow waters where vegetation is scarce and sediment contains clay. The C. r. laurentianus occurs in small acid lakes with specific substrate requirements.

Distribution

North America; specifically recorded from Ontario (Algonquin Park region for C. r. laurentianus) and presumably the eastern United States for the nominate based on the specific epithet.

Seasonality

Breeding occurs in late April in Little Minnow Lake, Algonquin Park. Juveniles released from female marsupium in mid-June. die shortly after release. Immatures peak in mid-July, declining to constant levels by October. The summer overwinters and matures the following spring.

Life Cycle

with single breeding season per year. Females carry and embryos in a pouch (marsupium). Development includes multiple instars with linear growth in length during the growing season. Sex ratio appears displaced toward males. Egg numbers increase faster than female body volume.

Similar Taxa

Crangonyx pseudogracilisAn North American amphipod in Europe; distinguished by preferences and invasion , though morphological differentiation requires detailed examination
Gammarus pulexEuropean native amphipod that has been observed to prey on Crangonyx ; differs in geographic distribution and ecological interactions
Gammarus duebeniEuropean native amphipod with predatory toward ; less effective than G. pulex