A new species of the genus Gammarus (Crustacea: Amphipoda: Gammaridae) from the low salinity habitats in the northern Gulf of Mexico

In the northern Gulf of Mexico, Gammarus mucronatus sensu lato is represented by at least two forms, G. mucronatus sensu stricto and a less common “macromucronate” form, which appears to be restricted to low salinity habitats. These two forms have traditionally been separated using the size or angle of projection of the dorsal mucronations (processes). However, because of variability in the development of the processes, it is unclear whether this and other morphological differences between G. mucronatus sensu stricto and the “macromucronate” form are ecophenotypic or reflect distinct and separate species. Detailed morphological analyses indicate that these two forms represent distinct species; Gammarus lecroyae, new species, is described in detail and a key to the marine and estuarine Gammarus species from the northern Gulf of Mexico is provided.

Reproduction and food habits of the lined seahorse, Hippocampus erectus (Teleostei: Syngnathidae) of Chesapeake Bay, Virginia

The reproductive and feeding biology of the lined seahorse, Hippocampus erectus, was studied in Chesapeake Bay. Seahorses are monogamous, and males incubate the eggs received from females in a closed brood pouch (= marsupium). Females do not play any parental care after mating. Total sex ratio and the operational sex ratio was strongly skewed toward females. Males and females had similar number of eggs/embryos and hydrated oocytes, respectively. The number of eggs/embryos found in the male brood pouch varied from 97 to 1,552 (fish from 80 to 126 mm TL), whereas the number of hydrated oocytes in female varied from 90 to 1,313 (fish from 60 to 123 mm TL). Both, the number of eggs/embryos and hydrated oocytes were better linearly correlated to total weight than to total length. The small snout and mouth size limits the feeding of the lined seahorse to small prey size. Amphypods were the predominant food items found in the guts, especially Ampithoe longimana, Gammarus mucronatus, and Caprella penantis. The lined seahorse is not abundant in Chesapeake Bay, but keeps a breeding population which is probably brought inside the bay by currents on drifting vegetation. Chances to find a partner may be difficult because of its low abundance, due to turbid waters, and its sedentary behavior.

The biology of Gammarus (Crustacea, Amphipoda) in the northwestern Atlantic. IX. Gammarus wilkitzkii Birula, Gammarus stoerensis Reid, and Gammarus mucronatus Say

Gammarus wilkitzkii is a circumpolar, arctic species found from the Arctic Ocean south to Newfoundland. Females produce a single large brood of large eggs in the autumn or early winter which hatches and is released from April to July. The species matures at a relatively large size.Gammarus stoerensis is an Atlantic amphiboreal species found from eastern Nova Scotia south to Rhode Island. It is a small species and females produce a series of small broods of small eggs between the spring and autumn, but are in the resting stage between then and late winter.Gammarus mucronatus is found from southwestern Newfoundland south to the Gulf of Mexico. It is a small species and produces a low number of small eggs in each of several summer broods.