Gnathia pilosus
Encyclopedia
Gnathia pilosus is the eighth gnathiid
species to be described from South Africa
. It occurs on the warmer east coast compared to the other seven gnathiids found on the colder west and south coasts of South Africa. Gnathiids have a polymorphic and biphasic life cycle
(reproductive stage and ectoparasite larval stage). There are three larval stages with each stage having two forms, namely praniza and zuphea. The praniza is usually a replete, haematophagous phase while the zuphea is an unfed benthic dweller phase. Adults can be found in groups with a single male and up to 43 females and immature specimens. The free-living adults do not feed and are usually hidden in a cavity or sponge where reproduction will occur. The larvae of gnathiid isopods are known to parasitise a large variety of intertidal fish worldwide. The taxonomic classification of gnathiids is usually based on the morphological characteristics of the adult male. The detailed descriptions of the female and larva, however, are also important for identifying these life stages to species level when collected in the absence of males.
may be the cause of slower moulting
in the winter months. The zuphea 1 is released from the female marsupium in the autumn months and subsequently attaches to their host fish. During feeding, the zuphea 1 transform into the praniza 1. The praniza 1 detaches from the host and rests on the bottom substrate, utilising the blood meal
to sustain itself until moulting into the zuphea 2 after 35 days. The zuphea 2 feeds on a host to become the praniza 2 and moults into a zuphea 3 which will also feed to become the very swollen praniza 3. Within a few weeks, the sex of the praniza 3 can be determined by the presence of either the testes in the male larva or thin ovary
strands in the female larvae. The male praniza 3 moults before the female praniza 3 in order to be ready for reproduction as soon as the females mature. This is important as the female requires fertilisation immediately after completing its moult. The larvae increase in length and width with each moult. Embryos develop in the female marsupium until released from the oostegite openings as zuphea 1 larvae. The life cycle from zuphea 1 to adult female fertilization ranges between 125 and 140 days.
Gnathiidae
Gnathiidae is a family of isopod crustaceans. They occur in a wide range of depths, from the littoral zone to the deep sea. The adults are associated with sponges and may not feed...
species to be described from South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
. It occurs on the warmer east coast compared to the other seven gnathiids found on the colder west and south coasts of South Africa. Gnathiids have a polymorphic and biphasic life cycle
Biological life cycle
A life cycle is a period involving all different generations of a species succeeding each other through means of reproduction, whether through asexual reproduction or sexual reproduction...
(reproductive stage and ectoparasite larval stage). There are three larval stages with each stage having two forms, namely praniza and zuphea. The praniza is usually a replete, haematophagous phase while the zuphea is an unfed benthic dweller phase. Adults can be found in groups with a single male and up to 43 females and immature specimens. The free-living adults do not feed and are usually hidden in a cavity or sponge where reproduction will occur. The larvae of gnathiid isopods are known to parasitise a large variety of intertidal fish worldwide. The taxonomic classification of gnathiids is usually based on the morphological characteristics of the adult male. The detailed descriptions of the female and larva, however, are also important for identifying these life stages to species level when collected in the absence of males.
Life cycle
Gnathia pilosus is capable of breeding throughout the year, but with majority of the gnathiids breeding in summer and releasing their young in autumn. Gnathia pilosus larvae show decrease in growth over colder months. A decrease in water temperatureTemperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
may be the cause of slower moulting
Ecdysis
Ecdysis is the moulting of the cuticula in many invertebrates. This process of moulting is the defining feature of the clade Ecdysozoa, comprising the arthropods, nematodes, velvet worms, horsehair worms, rotifers, tardigrades and Cephalorhyncha...
in the winter months. The zuphea 1 is released from the female marsupium in the autumn months and subsequently attaches to their host fish. During feeding, the zuphea 1 transform into the praniza 1. The praniza 1 detaches from the host and rests on the bottom substrate, utilising the blood meal
Blood meal
Blood meal is a dry, inert powder made from blood used as a high-nitrogen fertilizer and a high protein animal feed. N= 13.25%, P = 1.0%, K = 0.6%. It is one of the highest non-synthetic sources of nitrogen. Blood meal is completely soluble and can be mixed with water to be used as a liquid...
to sustain itself until moulting into the zuphea 2 after 35 days. The zuphea 2 feeds on a host to become the praniza 2 and moults into a zuphea 3 which will also feed to become the very swollen praniza 3. Within a few weeks, the sex of the praniza 3 can be determined by the presence of either the testes in the male larva or thin ovary
Ovary
The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...
strands in the female larvae. The male praniza 3 moults before the female praniza 3 in order to be ready for reproduction as soon as the females mature. This is important as the female requires fertilisation immediately after completing its moult. The larvae increase in length and width with each moult. Embryos develop in the female marsupium until released from the oostegite openings as zuphea 1 larvae. The life cycle from zuphea 1 to adult female fertilization ranges between 125 and 140 days.