Sphaeroma papillae hunt

Marine Isopods seem to be a poorly represented group on iNat, especially along the east coast of North America. Some species are also very poorly known despite being suprisingly common in some places. One of those species is Sphaeroma papillae, a Sphaeromatid that until a few days ago was only known from Cold Spring Harbor, Long Island and one spot somewhere on the north shore of Cape Cod. Some observations of them were made in Cold Spring Harbor in the past year, one which I used to find a population along the east side of the harbor to get a good idea where they like. Using that I managed to find a third population about 10min away in Oyster Bay under some rocks in a popular park, so now not only can I use that to help locate more populations of this species but I can also help others try to find this obscure but common species.

Sphaeroma papillae [Nassaquatuck Seapill]
Known range: Cold Spring Harbor, NY; Oyster Bay, NY; Cape Cod's northern coast
Theoretical range: Long Island Sound to Cape Cod, possibly further north
Habitat: under mid-sized dark rocks in areas of the intertidal zone that are directily influenced by any sort of freshwater. The two spots I saw the isopods had a salinity between 6-8ppt, while the nearby bays had much higher salinities (12-21ppt). They also appear to be obligate to this habitat, since rocks only a few feet away from the influence of the freshwater streams completely lacked them. Other than the freshwater requirement and their preference for dark rocks, they don't seem to be picky at all; the first spot I checked was a freshwater seepage coming from a wooden seawall and the second was next to a freshwter creek on a popular beach in the middle of a heavily developed town

How to identify: The uropod branches being the same length as each other rules out the only other Sphaeromatid genus in the area (Cassidinidea, which has the outer uropod branch less than half as long as the inner one) and the outer branch of the uropods being unserrated + the prescense of two linear tubercles on the telson rules out the only other Sphaeroma in the area (S. quadridentatum)

“Sphaeroma

If anyone on the coast of Southern New England and the north shore of Long Island knows of places that seem to match the habitat description, please check them for this species!

Posted by astrobirder astrobirder, January 04, 2021 01:08 AM

Observations

Photos / Sounds

What

Nassaquatuck Seapill (Sphaeroma papillae)

Observer

astrobirder

Date

January 1, 2021 08:36 AM EST

Description

Under a rock next to a very low salinity creek (second photo showing the measurement). Better photos coming soon

Photos / Sounds

What

Nassaquatuck Seapill (Sphaeroma papillae)

Observer

astrobirder

Date

January 1, 2021 08:47 AM EST

Description

Under a rock in a low salinity creek (sixth photo shows the measurements). Better photos coming soon

Photos / Sounds

What

Nassaquatuck Seapill (Sphaeroma papillae)

Observer

astrobirder

Date

January 1, 2021 07:32 AM EST

Description

Last shot shows identification features for this species

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