Caprellidae is a family of amphipods commonly known as skeleton shrimps. Their common name denotes the threadlike slender body which allows them to virtually disappear among the fine filaments of seaweed, hydroids and bryozoans. They are sometimes also known as ghost shrimps.
Description
Caprellids are easily distinguishable from other amphipods because of their slender elongated bodies. Their bodies can be divided into three parts: the cephalon (head), the pereon (thorax) and the abdomen. The pereon comprises most of the length of the body. It is divided into seven segments known as pereonites. The cephalon is usually fused to the first pereonite; while the highly reduced and almost invisible abdomen is attached to the posterior of the seventh pereonite. They possess two pairs of antennae, with the first pair usually longer than the second pair. The cephalon contains mandibles, maxillae and maxillipeds which function as mouthparts.
Each pereonite has a pair of appendages known as pereopods. The first two pairs are modified into raptorial appendages known as gnathopods. These are used for feeding and defence, as well as locomotion. The third and fourth pair of pereopods are usually reduced or absent altogether. In the third and fourth pereonites are two pairs of gills. Sometimes a third pair of gills may also be present on the second pereonite. In mature females, brood pouches formed by extensions of the coxae (oostegites) are present on the third and fourth pereonites. The fifth to seventh pair of pereopods are smaller than the gnathopods and are used for clasping objects the animals anchor themselves upon.
Most caprellids are highly sexually dimorphic, with the males usually being far larger than the females.
Ecology
Caprellids are exclusively marine and are found in oceans worldwide. A few species are found in the ocean depths, but most prefer low intertidal zones and subtidal waters among eelgrass, hydroids and bryozoans. They are typically seen attached to substrate by their grasping appendages called the pereopods.
Caprellids are omnivorous, feeding on diatoms, detritus, protozoans, smaller amphipods and crustacean larvae. Some species are filter feeders, using their antennae to filter food from the water or scrape it off the substrate. Most species are predators that sit and wait like a praying mantis, with their gnathopods ready to snatch any smaller invertebrates which come along. They accentuate their adaptive form and colouration by assuming an angular pose, resembling that of the fronds among which they live.Encarta Reference Library Premium 2005 DVD. Article – Skeleton Shrimp They remain motionless for long periods of time while waiting to ambush their prey, often protozoa or small worms.
Caprellids are typically preyed upon by surf perch, shrimp, nudibranchs such as the lion nudibranch Melibe leonina and brooding anemones (Epiactis prolifera). Since they often inhabit eelgrass beds with sessile jellyfish, (Haliclystus and Thaumatoscyphus), the caprellids frequently become jellyfish food. Caprellids are not normally considered a main source of food for fish, but when shiner perch (Cymatogaster aggregata) migrate into the eelgrass beds for reproduction, they target caprellids.
Reproduction and growth Mating can only occur when the female is between the new and hardened exoskeletons, which both male and female molt in order to grow. After mating the female will brood the fertilised eggs within her brood pouch. The young will hatch and emerge as juvenile adults. After mating, the female in some species have been known to kill the males by injecting venom from a claw within their gnathopod.
Taxonomy Caprellidae is classified under the superfamily Caprelloidea which belongs to the parvorder Caprellidira of the infraorder Corophiida and the suborder Senticaudata. Caprellidae contains 1345 genera in three subfamilies.
Caprellinae
Abyssicaprella McCain, 1966 Aciconula Mayer, 1903 Aeginella Boeck, 1861 Aeginellopsis Arimoto, 1970 Aeginina Norman, 1905 Caprella Lamarck, 1801 Caprellaporema Guerra-García, 2003 Cubadeutella Ortiz et al., 2009 Deutella Mayer, 1890 Eupariambus K. H. Barnard, 1957 Hemiaegina Mayer, 1890 Heterocaprella Arimoto, 1976 Liriopes Arimoto, 1978 Liropropus Laubitz, 1995 Liropus Mayer, 1890 Mayerella Huntsman, 1915 Metacaprella Mayer, 1903 Metaprotella Mayer, 1890 Monoliropus Mayer, 1903 Noculacia Mayer, 1903 Orthoprotella Mayer, 1903 Paracaprella Mayer, 1890 Paradeutella Mayer, 1890 Paradicaprella Hirayama, 1990 Paraprotella Mayer, 1903 Pariambus Stebbing, 1888 Parvipalpina Stephensen, 1944 Parvipalpus Mayer, 1890 Pedoculina Carausu, 1941 Pedonculocaprella Kaim-Malka, 1983 Pedotrina Arimoto, 1978 Postoparacaprella Arimoto, 1981 Premohemiaegina Arimoto, 1978 Pretritella Arimoto, 1980 Proaeginina Stephensen, 1940 Proliropus Mayer, 1903 Propodalirius Mayer, 1903 Protella Dana, 1853 Protellina Stephensen, 1944 Protellopsis Stebbing, 1888 Protoaeginella Laubitz & Mills, 1972 Prototritella Arimoto, 1977 Pseudaeginella Mayer, 1890 Pseudolirius Mayer, 1890 Pseudoliropus Laubitz, 1970 Pseudoprotella Mayer, 1890 Tanzacaprella Guerra-García, 2001 Thorina Stephensen, 1944 Triantella Mayer, 1903 Triliropus Mayer, 1903 Triperopus Mayer, 1903 Triprotella Arimoto, 1970 Tritella Mayer, 1890 Tropicaprella Guerra-García & Takeuchi, 2003 Verrucaprella Laubitz, 1995
Paracercopinae
Cercops Krøyer, 1843 Paracercops Vassilenko, 1972 Pseudocercops Vassilenko, 1972
Phtisicinae
Aeginoides Schellenberg, 1926 Caprellina Thomson, 1879 Caprellinoides Stebbing, 1888 Chaka Griffiths, 1974 Dodecas Stebbing, 1883 Dodecasella K. H. Barnard, 1931 Hemiproto McCain, 1968 Hircella Mayer, 1882 Jigurru Guerra-García, 2006 Liriarchus Mayer, 1912 Mayericaprella Guerra-García, 2006 Metaproto Mayer, 1903 Paedaridium Mayer, 1903 Paraproto Mayer, 1903 Perotripus Dougherty & Steinberg, 1953 Phtisica Slabber, 1769 Prellicana Mayer, 1903 Protogeton Mayer, 1903 Protomima Mayer, 1903 Protoplesius Mayer, 1903 Pseudocaprellina Sundara Raj, 1927 Pseudododecas McCain & Gray, 1971 Pseudoprellicana Guerra-García, 2006 Pseudoproto Mayer, 1903 Pseudoprotomima McCain, 1969 Quadrisegmentum Hirayama, 1988 Semidodecas Laubitz, 1995 Symmetrella Laubitz, 1995
References
External links
Some information on Caprella bathytatos Photos of skeleton shrimp