Parastenocaris

Parastenocaris brevipes, copyright A. Hobaek.

It's time for another consideration of the overwhelming diversity of stygofaunal copepods. Parastenocaris is a genus of copepods found on almost all the landmasses of the world except, presumably, Antarctica (New Zealand also stands out as an intriguing void in the genus' distribution). The majority of species in this genus are insterstitial, mostly found in soils saturated with fresh water; a small number of species are found in brackish habitats such as estuaries. A few species have also been found above ground, particularly in the tropics (Galasi & Laurentiis 2004). The type species of the genus, P. brevipes, has been found in sphagnum bogs (Karanovic 2005).

As commonly recognised, Parastenocaris is a pretty huge genus, with well over 200 species having been assigned to it over the years. However, the genus has been poorly defined and many authors have questioned its integrity. Galasi & Laurentiis (2004) suggested that Parastenocaris should be restricted to those species most closely related to the type species, P. brevipes. Such a group would still be pretty cosmopolitan; indeed, P. brevipes itself has a Holarctic distribution and is known from both Europe and North America (this stands in pretty stark contrast to the super-short ranges of some stygofaunal copepods). Distinctive features of this restricted P. brevipes group include a characteristic endopodal complex on leg 4 of the male, with the endopod hyaline and with one or two large claws. In contrast, the leg IV endopod in females is long and distally serrate.

Parastenocaris lacustris, from here

Members of the Parastenocaris brevipes groups are found closer to the soil surface than many other members of their family (Karanovic 2005). They are also relatively large, reaching the absolutely monstrous size (I'm sure) of half a millimetre or more. Karanovic (2005) suggested that this larger size could reflect the larger size of the sand grains they live among closer to the surface, or it could simply reflect their access to more reliable food sources that are available to their more deeply buried relatives.

REFERENCES

Galasi, D. M. P., & P. de Laurentiis. 2004. Towards a revision of the genus Parastenocaris Kessler, 1913: establishment of Simplicaris gen. nov. from groundwaters in central Italy and review of the P. brevipes-group (Copepoda, Harpacticoida, Parastenocarididae). Zoological Journal of the Linnean Society 140: 417–436.

Karanovic, T. 2005. Two new subterranean Parastenocarididae (Crustacea, Copepoda, Harpacticoida) from Western Australia. Records of the Western Australian Museum 22: 353–374.

Small Waters

Female Bryocamptus minutus, from here.

For this week's semi-random post topic, I drew the copepod genus Bryocamptus. Copepods have made an appearance on this site before (see here, here and here), seeing as these minute crustaceans inhabit almost all the world's waters. Bryocamptus belongs within the harpacticoids, one of the three main groups of free-living copepods (the others are the calanoids and cyclopoids), and like other harpacticoids members of this genus have a more-or-less parallel-sided, somewhat wormlike form, though Bryocamptus species are shorter than some. Within the harpacticoids, this genus belongs to the family Canthocamptidae, members of which have the first segment of the body bearing swimming legs fused to the cephalothorax (Caramujo & Boavida 2009).

There are over 100 recognised species of Bryocamptus, found in a wide range of fresh-watery habitats (Lee & Chang 2006). They may be found in mountain streams, in springs and temporary pools, or in subterranean groundwaters. Some may even be found 'terrestrially', living in the water film around leaf-litter, mosses or within the soil (Fiers 2013). One type of habitat that I haven't found reference to Bryocamptus living in is larger water bodies such as lakes. This is not particularly unusual: nutrients and micro-organisms tend to accumulate along boundaries, so habitats with a high proportion of edges tend to attract a higher diversity than the relative deserts that are larger water bodies.

Sometimes these habitats can be very small indeed. Groundwater species, for instance, may be restricted to the cracks within formations only some tens of metres in extent. Cottarelli et al. (2012) described Bryocamptus stillae from Conza Cave near Palermo in Sicily. This species was found in seasonal rimstone pools within the cave: temporary pools that would be filled by water dripping from the ceiling during the winter, only to dry up in the summer. However, the copepods are unable to survive out of water, and canthocamptids do not have a resistant phase in their life cycle that could survive the ppols drying out. Cottarelli et al. therefore inferred that the pools were not the copepods' primary habitat; rather, the copepods normally lived in the epikarst, the layer of limestone above the cave. Despite being only a few metres thick, this limestone layer retained enough pockets of moisture to provide a home for the copepods. During the rainy season, when water was more actively flowing through the epikarst, some of the more unfortunate copepods would be carried by the water as it dripped through the cave ceiling into the pools below. They would survive (and even breed) so long as the pools remained wet but they would be doomed to die off over the summer, with the following year's copepods representing an entirely new batch. Interestingly, though, Cottarelli et al. found B. stillae in only one group of pools in the cave. In a second group of pools, only about ten or fifteen metres away, an entirely different copepod species was found. Cottarelli et al. collected in the cave over three separate seasons, and each time the same species was found in the same pools. The evidence indicated that, even though these pools were so close, the water dripping into them came from separate, isolated epikarst formations, each one home to its own species of highly localised copepods.

REFERENCES

Caramujo, M.-J., & M.-J. Boavida. 2009. The practical identification of harpacticoids (Copepoda, Harpacticoida) in inland waters of central Portugal for applied studies. Crustaceana 82 (4): 385–409.

Cottarelli, V., M. C. Bruno, M. T. Spena & R. Grasso. 2012. Studies on subterranean copepods from Italy, with descriptions of two new epikarstic species from a cave in Sicily. Zoological Studies 51 (4): 556–582.

Fiers, F. 2013. Bryocamptus (Bryocamptus) gauthieri (Roy, 1924): a Mediterranean edaphic specialist (Crustacea: Copepoda: Harpacticoida). Revue Suisse de Zoologie 120 (3): 357–371.

Lee, J. M., & C. Y. Chang. 2006. Taxonomy on freshwater canthocamptid harpacticoids from South Korea V. Genus Bryocamptus. Korean J. Syst. Zool. 22 (2): 195–208.

Amphiascus: Can a Copepod be a Friend of Mine?

Amphiascus sp., copyright Alexandra.

The animal shown in the image above is a member of Amphiascus, a cosmopolitan genus of about thirty known species of benthic harpacticoid copepods. Amphiascus is a genus of the family Miraciidae; in older texts, you will find it referred to the Diosaccidae, but this family is now regarded as a synonym of the former. Miraciids are somewhat elongate harpacticoids generally with a fusiform body shape and females with paired egg sacs; as with other copepod taxa, their specific characterisation depends on fairly fine characters of the appendage setation (Willen 2002). Wells et al. (1982) placed Amphiascus in association with a group of related genera in the miraciid family tree on the basis of its retention of a fairly extensive setation on the pereiopods, two inner setae on the endopod of pereiopod II in females, and two articulated claws on that segment in males. However, the proposed phylogeny of Wells et al. provides no apomorphies for Amphiascus itself, implying that it is characterised only by plesiomorphies relative to related genera.

The title of this post refers to the circumstances surrounding the discovery of a relatively recently described Amphiascus species, A. kawamurai Ueda & Nagai 2005. In the cultivation in Japan of nori, the edible alga used (among other things) in wrapping sushi rolls, the conchocelis phase of the life cycle is grown on oyster shells in outdoor tanks of seawater (like many algae, nori goes through an alternation of generations, with its life cycle including two very distinct forms; as well as the familiar large flat alga, the life cycle of nori includes a small filamentous shell-boring stage, initially mistaken for a distinct organism and called Conchocelis). Unfortunately, the oyster shells may also become overgrown with diatoms, retarding the growth of conchocelis. As a result, nori growers may be required to laboriously scrub the shells of diatoms several times over the conchocelis growth period. However, it was noticed in Ariake Bay in Kyushu that some form of copepod would sometimes appear in the nori tanks, presumably brought in with seawater from the bay. When this copepod was present, it would graze on the diatoms, reducing the need for other controls. Study of the nori-tank copepod revealed it to be a previously undescribed species, revealing once more that even the species we are not aware of have the potential to directly improve our lives.

REFERENCES

Ueda, H., & H. Nagai. 2005. Amphiascus kawamurai, a new harpacticoid copepod (Crustacea: Harpacticoida: Miraciidae) from nori cultivation tanks in Japan, with a redescription of the closely related A. parvus. Species Diversity 10: 249–258.

Wells, J. B. J., G. R. F. Hicks & B. C. Coull. 1982. Common harpacticoid copepods from New Zealand harbours and estuaries. New Zealand Journal of Zoology 9 (2): 151–184.

Willen, E. 2002. Notes on the systematic position of the Stenheliinae (Copepoda, Harpacticoida) within the Thalestridimorpha and description of two new species from Motupore Island, Papua New Guinea. Cah. Biol. Mar. 43: 27–42.