Tritella pilimana Mayer 1890

Length: 3-8.3mm. Body smooth dorsally, with laterally pointing spines antero-laterally on pereonites 2, 3 and 4 and medially over gills. Antenna 1 nearly as long as cephalon plus pereonites 2 and 3. Antenna 2 shorter than peduncle of antenna 1, slender with long swimming setae. Propodus of gnathopod 2 twice as long as it is broad, palm slightly concave, densely setose with proximal grasping spine and poison spine. Dactylus with distal and slight proximal thickening, gently tapering distally, densely setose along inner margin. Basis attached anteriorly on pereonite 2. Pereopods 3 and 4 one-segmented with three apical setae; pereopods 5,6 and 7 six-segmented, propodus with proximal grasping spines; palmar knobs supporting grasping spines may be present on pereopod 7. Female differs in showing no lengthening of pereonite 1 with maturity; gnathopod 2 with heavier propodus, median minute poison spine.

California, Washington, Oregon, British Columbia, Alaska; Pacific North-west

Caprellid, "Ghost" or "Skeleton" shrimps, so called for their skeletal appearance. Amphipod crustaceans, easily distinguished by the elongate stick-like body form and reduction of the abdominal appendages. Head is generally fused with pereonite 1. Pereopods on first 2 segments (pereonites) are most flexible and called gnathopods; gnathopods 2 being the largest, used in defense, feeding and substrate attachment. In many species pereopods 3 and 4 may also be reduced or absent. Gills on pereonites 3 + 4, rarely on pereonite 2. Pereopods 5 - 7 much smaller than 1 + 2, used for clinging to the substratum. In females, brood plates (öostegites) develop on pereonites 3 + 4. Much remains to be learnt about their biology, ecology and in many cases changing distributions.

9- 145m. Found on many substrates on open intertidal coasts (hydroids, bryozoans, coralline algae, algae, eelgrass, compound ascidians, tubes of sabellid worms), subtidally on crab pots. Zostera and coralline algae.

1 female ‘intersex’ specimen found- possessing male gnathopod 2, an abdomen with penes, female brood plates, and genital openings on posterior ventral surface of pereonite 5.

How to Distinguish from Similar Species: Tritella laevis has a next-to-last article of antenna 2 only 4x as long as wide and its setae are not much longer than the article is wide. Mayerella banksia has 2 articles on its vestigialpereopods on pereonites 3 and 4.

Biology/Natural History: : Caprellid amphipods such as this species appear to be fearsome predators for their size. They hold onto substrates such as eelgrass or hydroids with their posterior appendages and wave their bodies around looking for prey to grab. They can move from place to place by grabbing the new place with their anterior gnathopods, then loosening their posterior legs and moving them up to the new object to reattach..

Can be found on eelgrass

As with all caprellid amphipods, the pereon has only 6 visible pereonites, some of which have only vestigialpereopods; the abdomen is vestigial; and the body is slender and sticklike, somewhat resembling a praying mantis. Tritella pilimana has gnathopods but no gills on pereonites 1 and 2. It has flat, leaflike gills and vestigialpereopods on pereonites 3 and 4. The vestigialpereopods on pereonites 3 and 4 have only 1 article. The mandible has a palp. The second antennae have long setae on the longer articles, and the next to the last article of antenna 2 is about 6x as long as wide and has setae about 2x as long as the article is wide.